Provided by: gcc-5-alpha-linux-gnu_5.3.1-14ubuntu2cross1_amd64 bug

NAME

       gcc - GNU project C and C++ compiler

SYNOPSIS

       gcc [-c|-S|-E] [-std=standard]
           [-g] [-pg] [-Olevel]
           [-Wwarn...] [-Wpedantic]
           [-Idir...] [-Ldir...]
           [-Dmacro[=defn]...] [-Umacro]
           [-foption...] [-mmachine-option...]
           [-o outfile] [@file] infile...

       Only the most useful options are listed here; see below for the remainder.  g++ accepts
       mostly the same options as gcc.

DESCRIPTION

       When you invoke GCC, it normally does preprocessing, compilation, assembly and linking.
       The "overall options" allow you to stop this process at an intermediate stage.  For
       example, the -c option says not to run the linker.  Then the output consists of object
       files output by the assembler.

       Other options are passed on to one stage of processing.  Some options control the
       preprocessor and others the compiler itself.  Yet other options control the assembler and
       linker; most of these are not documented here, since you rarely need to use any of them.

       Most of the command-line options that you can use with GCC are useful for C programs; when
       an option is only useful with another language (usually C++), the explanation says so
       explicitly.  If the description for a particular option does not mention a source
       language, you can use that option with all supported languages.

       The gcc program accepts options and file names as operands.  Many options have multi-
       letter names; therefore multiple single-letter options may not be grouped: -dv is very
       different from -d -v.

       You can mix options and other arguments.  For the most part, the order you use doesn't
       matter.  Order does matter when you use several options of the same kind; for example, if
       you specify -L more than once, the directories are searched in the order specified.  Also,
       the placement of the -l option is significant.

       Many options have long names starting with -f or with -W---for example,
       -fmove-loop-invariants, -Wformat and so on.  Most of these have both positive and negative
       forms; the negative form of -ffoo is -fno-foo.  This manual documents only one of these
       two forms, whichever one is not the default.

OPTIONS

   Option Summary
       Here is a summary of all the options, grouped by type.  Explanations are in the following
       sections.

       Overall Options
           -c  -S  -E  -o file  -no-canonical-prefixes -pipe  -pass-exit-codes -x language  -v
           -###  --help[=class[,...]]  --target-help --version -wrapper @file -fplugin=file
           -fplugin-arg-name=arg -fdump-ada-spec[-slim] -fada-spec-parent=unit
           -fdump-go-spec=file

       C Language Options
           -ansi  -std=standard  -fgnu89-inline -aux-info filename
           -fallow-parameterless-variadic-functions -fno-asm  -fno-builtin  -fno-builtin-function
           -fhosted  -ffreestanding -fopenacc -fopenmp -fopenmp-simd -fms-extensions
           -fplan9-extensions -trigraphs -traditional -traditional-cpp -fallow-single-precision
           -fcond-mismatch -flax-vector-conversions -fsigned-bitfields  -fsigned-char
           -funsigned-bitfields  -funsigned-char

       C++ Language Options
           -fabi-version=n  -fno-access-control  -fcheck-new -fconstexpr-depth=n
           -ffriend-injection -fno-elide-constructors -fno-enforce-eh-specs -ffor-scope
           -fno-for-scope  -fno-gnu-keywords -fno-implicit-templates
           -fno-implicit-inline-templates -fno-implement-inlines  -fms-extensions
           -fno-nonansi-builtins  -fnothrow-opt  -fno-operator-names -fno-optional-diags
           -fpermissive -fno-pretty-templates -frepo  -fno-rtti -fsized-deallocation -fstats
           -ftemplate-backtrace-limit=n -ftemplate-depth=n -fno-threadsafe-statics
           -fuse-cxa-atexit -fno-weak  -nostdinc++ -fvisibility-inlines-hidden
           -fvtable-verify=[std|preinit|none] -fvtv-counts -fvtv-debug -fvisibility-ms-compat
           -fext-numeric-literals -Wabi=n  -Wabi-tag  -Wconversion-null  -Wctor-dtor-privacy
           -Wdelete-non-virtual-dtor -Wliteral-suffix -Wnarrowing -Wnoexcept -Wnon-virtual-dtor
           -Wreorder -Weffc++  -Wstrict-null-sentinel -Wno-non-template-friend  -Wold-style-cast
           -Woverloaded-virtual  -Wno-pmf-conversions -Wsign-promo

       Objective-C and Objective-C++ Language Options
           -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime -fno-nil-receivers
           -fobjc-abi-version=n -fobjc-call-cxx-cdtors -fobjc-direct-dispatch -fobjc-exceptions
           -fobjc-gc -fobjc-nilcheck -fobjc-std=objc1 -fno-local-ivars
           -fivar-visibility=[public|protected|private|package] -freplace-objc-classes
           -fzero-link -gen-decls -Wassign-intercept -Wno-protocol  -Wselector
           -Wstrict-selector-match -Wundeclared-selector

       Language Independent Options
           -fmessage-length=n -fdiagnostics-show-location=[once|every-line]
           -fdiagnostics-color=[auto|never|always] -fno-diagnostics-show-option
           -fno-diagnostics-show-caret

       Warning Options
           -fsyntax-only  -fmax-errors=n  -Wpedantic -pedantic-errors -w  -Wextra  -Wall
           -Waddress  -Waggregate-return -Waggressive-loop-optimizations -Warray-bounds
           -Warray-bounds=n -Wbool-compare -Wno-attributes -Wno-builtin-macro-redefined
           -Wc90-c99-compat -Wc99-c11-compat -Wc++-compat -Wc++11-compat -Wc++14-compat
           -Wcast-align  -Wcast-qual -Wchar-subscripts -Wclobbered  -Wcomment
           -Wconditionally-supported -Wconversion -Wcoverage-mismatch -Wdate-time
           -Wdelete-incomplete -Wno-cpp -Wno-deprecated -Wno-deprecated-declarations
           -Wno-designated-init -Wdisabled-optimization -Wno-discarded-qualifiers
           -Wno-discarded-array-qualifiers -Wno-div-by-zero -Wdouble-promotion -Wempty-body
           -Wenum-compare -Wno-endif-labels -Werror  -Werror=* -Wfatal-errors  -Wfloat-equal
           -Wformat  -Wformat=2 -Wno-format-contains-nul -Wno-format-extra-args
           -Wformat-nonliteral -Wformat-security  -Wformat-signedness  -Wformat-y2k
           -Wframe-larger-than=len -Wno-free-nonheap-object -Wjump-misses-init
           -Wignored-qualifiers  -Wincompatible-pointer-types -Wimplicit
           -Wimplicit-function-declaration  -Wimplicit-int -Winit-self  -Winline
           -Wno-int-conversion -Wno-int-to-pointer-cast -Wno-invalid-offsetof -Winvalid-pch
           -Wlarger-than=len  -Wunsafe-loop-optimizations -Wlogical-op -Wlogical-not-parentheses
           -Wlong-long -Wmain -Wmaybe-uninitialized -Wmemset-transposed-args -Wmissing-braces
           -Wmissing-field-initializers -Wmissing-include-dirs -Wno-multichar  -Wnonnull
           -Wnormalized=[none|id|nfc|nfkc]
            -Wodr  -Wno-overflow  -Wopenmp-simd -Woverlength-strings  -Wpacked
           -Wpacked-bitfield-compat  -Wpadded -Wparentheses  -Wpedantic-ms-format
           -Wno-pedantic-ms-format -Wpointer-arith  -Wno-pointer-to-int-cast -Wredundant-decls
           -Wno-return-local-addr -Wreturn-type  -Wsequence-point  -Wshadow  -Wno-shadow-ivar
           -Wshift-count-negative -Wshift-count-overflow -Wsign-compare  -Wsign-conversion
           -Wfloat-conversion -Wsizeof-pointer-memaccess  -Wsizeof-array-argument
           -Wstack-protector -Wstack-usage=len -Wstrict-aliasing -Wstrict-aliasing=n
           -Wstrict-overflow -Wstrict-overflow=n -Wsuggest-attribute=[pure|const|noreturn|format]
           -Wsuggest-final-types  -Wsuggest-final-methods  -Wsuggest-override
           -Wmissing-format-attribute -Wswitch  -Wswitch-default  -Wswitch-enum -Wswitch-bool
           -Wsync-nand -Wsystem-headers  -Wtrampolines  -Wtrigraphs  -Wtype-limits  -Wundef
           -Wuninitialized  -Wunknown-pragmas  -Wno-pragmas -Wunsuffixed-float-constants
           -Wunused  -Wunused-function -Wunused-label  -Wunused-local-typedefs -Wunused-parameter
           -Wno-unused-result -Wunused-value  -Wunused-variable -Wunused-but-set-parameter
           -Wunused-but-set-variable -Wuseless-cast -Wvariadic-macros
           -Wvector-operation-performance -Wvla -Wvolatile-register-var  -Wwrite-strings
           -Wzero-as-null-pointer-constant

       C and Objective-C-only Warning Options
           -Wbad-function-cast  -Wmissing-declarations -Wmissing-parameter-type
           -Wmissing-prototypes  -Wnested-externs -Wold-style-declaration  -Wold-style-definition
           -Wstrict-prototypes  -Wtraditional  -Wtraditional-conversion
           -Wdeclaration-after-statement -Wpointer-sign

       Debugging Options
           -dletters  -dumpspecs  -dumpmachine  -dumpversion -fsanitize=style -fsanitize-recover
           -fsanitize-recover=style -fasan-shadow-offset=number
           -fsanitize-undefined-trap-on-error -fcheck-pointer-bounds -fchkp-check-incomplete-type
           -fchkp-first-field-has-own-bounds -fchkp-narrow-bounds
           -fchkp-narrow-to-innermost-array -fchkp-optimize -fchkp-use-fast-string-functions
           -fchkp-use-nochk-string-functions -fchkp-use-static-bounds
           -fchkp-use-static-const-bounds -fchkp-treat-zero-dynamic-size-as-infinite
           -fchkp-check-read -fchkp-check-read -fchkp-check-write -fchkp-store-bounds
           -fchkp-instrument-calls -fchkp-instrument-marked-only -fchkp-use-wrappers
           -fdbg-cnt-list -fdbg-cnt=counter-value-list -fdisable-ipa-pass_name
           -fdisable-rtl-pass_name -fdisable-rtl-pass-name=range-list -fdisable-tree-pass_name
           -fdisable-tree-pass-name=range-list -fdump-noaddr -fdump-unnumbered
           -fdump-unnumbered-links -fdump-translation-unit[-n] -fdump-class-hierarchy[-n]
           -fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline -fdump-passes -fdump-statistics
           -fdump-tree-all -fdump-tree-original[-n] -fdump-tree-optimized[-n] -fdump-tree-cfg
           -fdump-tree-alias -fdump-tree-ch -fdump-tree-ssa[-n] -fdump-tree-pre[-n]
           -fdump-tree-ccp[-n] -fdump-tree-dce[-n] -fdump-tree-gimple[-raw] -fdump-tree-dom[-n]
           -fdump-tree-dse[-n] -fdump-tree-phiprop[-n] -fdump-tree-phiopt[-n]
           -fdump-tree-forwprop[-n] -fdump-tree-copyrename[-n] -fdump-tree-nrv -fdump-tree-vect
           -fdump-tree-sink -fdump-tree-sra[-n] -fdump-tree-forwprop[-n] -fdump-tree-fre[-n]
           -fdump-tree-vtable-verify -fdump-tree-vrp[-n] -fdump-tree-storeccp[-n]
           -fdump-final-insns=file -fcompare-debug[=opts]  -fcompare-debug-second
           -feliminate-dwarf2-dups -fno-eliminate-unused-debug-types
           -feliminate-unused-debug-symbols -femit-class-debug-always -fenable-kind-pass
           -fenable-kind-pass=range-list -fdebug-types-section -fmem-report-wpa -fmem-report
           -fpre-ipa-mem-report -fpost-ipa-mem-report -fprofile-arcs -fopt-info
           -fopt-info-options[=file] -frandom-seed=number -fsched-verbose=n -fsel-sched-verbose
           -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose -fstack-usage  -ftest-coverage
           -ftime-report -fvar-tracking -fvar-tracking-assignments
           -fvar-tracking-assignments-toggle -g  -glevel  -gtoggle  -gcoff  -gdwarf-version -ggdb
           -grecord-gcc-switches  -gno-record-gcc-switches -gstabs  -gstabs+  -gstrict-dwarf
           -gno-strict-dwarf -gvms  -gxcoff  -gxcoff+ -gz[=type] -fno-merge-debug-strings
           -fno-dwarf2-cfi-asm -fdebug-prefix-map=old=new -femit-struct-debug-baseonly
           -femit-struct-debug-reduced -femit-struct-debug-detailed[=spec-list] -p  -pg
           -print-file-name=library  -print-libgcc-file-name -print-multi-directory
           -print-multi-lib  -print-multi-os-directory -print-prog-name=program
           -print-search-dirs  -Q -print-sysroot -print-sysroot-headers-suffix -save-temps
           -save-temps=cwd -save-temps=obj -time[=file]

       Optimization Options
           -faggressive-loop-optimizations -falign-functions[=n] -falign-jumps[=n]
           -falign-labels[=n] -falign-loops[=n] -fassociative-math -fauto-profile
           -fauto-profile[=path] -fauto-inc-dec -fbranch-probabilities
           -fbranch-target-load-optimize -fbranch-target-load-optimize2 -fbtr-bb-exclusive
           -fcaller-saves -fcheck-data-deps -fcombine-stack-adjustments -fconserve-stack
           -fcompare-elim -fcprop-registers -fcrossjumping -fcse-follow-jumps -fcse-skip-blocks
           -fcx-fortran-rules -fcx-limited-range -fdata-sections -fdce -fdelayed-branch
           -fdelete-null-pointer-checks -fdevirtualize -fdevirtualize-speculatively
           -fdevirtualize-at-ltrans -fdse -fearly-inlining -fipa-sra -fexpensive-optimizations
           -ffat-lto-objects -ffast-math -ffinite-math-only -ffloat-store
           -fexcess-precision=style -fforward-propagate -ffp-contract=style -ffunction-sections
           -fgcse -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity -fgcse-sm
           -fhoist-adjacent-loads -fif-conversion -fif-conversion2 -findirect-inlining
           -finline-functions -finline-functions-called-once -finline-limit=n
           -finline-small-functions -fipa-cp -fipa-cp-clone -fipa-cp-alignment -fipa-pta
           -fipa-profile -fipa-pure-const -fipa-reference -fipa-icf -fira-algorithm=algorithm
           -fira-region=region -fira-hoist-pressure -fira-loop-pressure -fno-ira-share-save-slots
           -fno-ira-share-spill-slots -fira-verbose=n -fisolate-erroneous-paths-dereference
           -fisolate-erroneous-paths-attribute -fivopts -fkeep-inline-functions
           -fkeep-static-consts -flive-range-shrinkage -floop-block -floop-interchange
           -floop-strip-mine -floop-unroll-and-jam -floop-nest-optimize -floop-parallelize-all
           -flra-remat -flto -flto-compression-level -flto-partition=alg -flto-report
           -flto-report-wpa -fmerge-all-constants -fmerge-constants -fmodulo-sched
           -fmodulo-sched-allow-regmoves -fmove-loop-invariants -fno-branch-count-reg
           -fno-defer-pop -fno-function-cse -fno-guess-branch-probability -fno-inline
           -fno-math-errno -fno-peephole -fno-peephole2 -fno-sched-interblock -fno-sched-spec
           -fno-signed-zeros -fno-toplevel-reorder -fno-trapping-math
           -fno-zero-initialized-in-bss -fomit-frame-pointer -foptimize-sibling-calls
           -fpartial-inlining -fpeel-loops -fpredictive-commoning -fprefetch-loop-arrays
           -fprofile-report -fprofile-correction -fprofile-dir=path -fprofile-generate
           -fprofile-generate=path -fprofile-use -fprofile-use=path -fprofile-values
           -fprofile-reorder-functions -freciprocal-math -free -frename-registers
           -freorder-blocks -freorder-blocks-and-partition -freorder-functions
           -frerun-cse-after-loop -freschedule-modulo-scheduled-loops -frounding-math
           -fsched2-use-superblocks -fsched-pressure -fsched-spec-load
           -fsched-spec-load-dangerous -fsched-stalled-insns-dep[=n] -fsched-stalled-insns[=n]
           -fsched-group-heuristic -fsched-critical-path-heuristic -fsched-spec-insn-heuristic
           -fsched-rank-heuristic -fsched-last-insn-heuristic -fsched-dep-count-heuristic
           -fschedule-fusion -fschedule-insns -fschedule-insns2 -fsection-anchors
           -fselective-scheduling -fselective-scheduling2 -fsel-sched-pipelining
           -fsel-sched-pipelining-outer-loops -fsemantic-interposition -fshrink-wrap
           -fsignaling-nans -fsingle-precision-constant -fsplit-ivs-in-unroller
           -fsplit-wide-types -fssa-phiopt -fstack-protector -fstack-protector-all
           -fstack-protector-strong -fstack-protector-explicit -fstdarg-opt -fstrict-aliasing
           -fstrict-overflow -fthread-jumps -ftracer -ftree-bit-ccp -ftree-builtin-call-dce
           -ftree-ccp -ftree-ch -ftree-coalesce-inline-vars -ftree-coalesce-vars -ftree-copy-prop
           -ftree-copyrename -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop
           -ftree-fre -ftree-loop-if-convert -ftree-loop-if-convert-stores -ftree-loop-im
           -ftree-phiprop -ftree-loop-distribution -ftree-loop-distribute-patterns
           -ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize -ftree-loop-vectorize
           -ftree-parallelize-loops=n -ftree-pre -ftree-partial-pre -ftree-pta -ftree-reassoc
           -ftree-sink -ftree-slsr -ftree-sra -ftree-switch-conversion -ftree-tail-merge
           -ftree-ter -ftree-vectorize -ftree-vrp -funit-at-a-time -funroll-all-loops
           -funroll-loops -funsafe-loop-optimizations -funsafe-math-optimizations
           -funswitch-loops -fipa-ra -fvariable-expansion-in-unroller -fvect-cost-model -fvpt
           -fweb -fwhole-program -fwpa -fuse-linker-plugin --param name=value -O  -O0  -O1  -O2
           -O3  -Os -Ofast -Og

       Preprocessor Options
           -Aquestion=answer -A-question[=answer] -C  -dD  -dI  -dM  -dN -Dmacro[=defn]  -E  -H
           -idirafter dir -include file  -imacros file -iprefix file  -iwithprefix dir
           -iwithprefixbefore dir  -isystem dir -imultilib dir -isysroot dir -M  -MM  -MF  -MG
           -MP  -MQ  -MT  -nostdinc -P  -fdebug-cpp -ftrack-macro-expansion -fworking-directory
           -remap -trigraphs  -undef  -Umacro -Wp,option -Xpreprocessor option -no-integrated-cpp

       Assembler Option
           -Wa,option  -Xassembler option

       Linker Options
           object-file-name  -fuse-ld=linker -llibrary -nostartfiles  -nodefaultlibs  -nostdlib
           -pie -rdynamic -s  -static -static-libgcc -static-libstdc++ -static-libasan
           -static-libtsan -static-liblsan -static-libubsan -static-libmpx -static-libmpxwrappers
           -shared -shared-libgcc  -symbolic -T script  -Wl,option  -Xlinker option -u symbol -z
           keyword

       Directory Options
           -Bprefix -Idir -iplugindir=dir -iquotedir -Ldir -specs=file -I- --sysroot=dir
           --no-sysroot-suffix

       Machine Dependent Options
           AArch64 Options -mabi=name  -mbig-endian  -mlittle-endian -mgeneral-regs-only
           -mcmodel=tiny  -mcmodel=small  -mcmodel=large -mstrict-align -momit-leaf-frame-pointer
           -mno-omit-leaf-frame-pointer -mtls-dialect=desc  -mtls-dialect=traditional
           -mfix-cortex-a53-835769  -mno-fix-cortex-a53-835769 -mfix-cortex-a53-843419
           -mno-fix-cortex-a53-843419 -march=name  -mcpu=name  -mtune=name

           Adapteva Epiphany Options -mhalf-reg-file -mprefer-short-insn-regs -mbranch-cost=num
           -mcmove -mnops=num -msoft-cmpsf -msplit-lohi -mpost-inc -mpost-modify
           -mstack-offset=num -mround-nearest -mlong-calls -mshort-calls -msmall16 -mfp-mode=mode
           -mvect-double -max-vect-align=num -msplit-vecmove-early -m1reg-reg

           ARC Options -mbarrel-shifter -mcpu=cpu -mA6 -mARC600 -mA7 -mARC700 -mdpfp
           -mdpfp-compact -mdpfp-fast -mno-dpfp-lrsr -mea -mno-mpy -mmul32x16 -mmul64 -mnorm
           -mspfp -mspfp-compact -mspfp-fast -msimd -msoft-float -mswap -mcrc -mdsp-packa -mdvbf
           -mlock -mmac-d16 -mmac-24 -mrtsc -mswape -mtelephony -mxy -misize -mannotate-align
           -marclinux -marclinux_prof -mepilogue-cfi -mlong-calls -mmedium-calls -msdata
           -mucb-mcount -mvolatile-cache -malign-call -mauto-modify-reg -mbbit-peephole -mno-brcc
           -mcase-vector-pcrel -mcompact-casesi -mno-cond-exec -mearly-cbranchsi -mexpand-adddi
           -mindexed-loads -mlra -mlra-priority-none -mlra-priority-compact mlra-priority-
           noncompact -mno-millicode -mmixed-code -mq-class -mRcq -mRcw -msize-level=level
           -mtune=cpu -mmultcost=num -munalign-prob-threshold=probability

           ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name -mapcs-stack-check
           -mno-apcs-stack-check -mapcs-float  -mno-apcs-float -mapcs-reentrant
           -mno-apcs-reentrant -msched-prolog  -mno-sched-prolog -mlittle-endian  -mbig-endian
           -mfloat-abi=name -mfp16-format=name -mthumb-interwork  -mno-thumb-interwork -mcpu=name
           -march=name  -mfpu=name -mtune=name -mprint-tune-info -mstructure-size-boundary=n
           -mabort-on-noreturn -mlong-calls  -mno-long-calls -msingle-pic-base
           -mno-single-pic-base -mpic-register=reg -mnop-fun-dllimport -mpoke-function-name
           -mthumb  -marm -mtpcs-frame  -mtpcs-leaf-frame -mcaller-super-interworking
           -mcallee-super-interworking -mtp=name -mtls-dialect=dialect -mword-relocations
           -mfix-cortex-m3-ldrd -munaligned-access -mneon-for-64bits -mslow-flash-data
           -masm-syntax-unified -mrestrict-it

           AVR Options -mmcu=mcu -maccumulate-args -mbranch-cost=cost -mcall-prologues -mint8
           -mn_flash=size -mno-interrupts -mrelax -mrmw -mstrict-X -mtiny-stack -nodevicelib
           -Waddr-space-convert

           Blackfin Options -mcpu=cpu[-sirevision] -msim -momit-leaf-frame-pointer
           -mno-omit-leaf-frame-pointer -mspecld-anomaly  -mno-specld-anomaly  -mcsync-anomaly
           -mno-csync-anomaly -mlow-64k -mno-low64k  -mstack-check-l1  -mid-shared-library
           -mno-id-shared-library  -mshared-library-id=n -mleaf-id-shared-library
           -mno-leaf-id-shared-library -msep-data  -mno-sep-data  -mlong-calls  -mno-long-calls
           -mfast-fp -minline-plt -mmulticore  -mcorea  -mcoreb  -msdram -micplb

           C6X Options -mbig-endian  -mlittle-endian -march=cpu -msim -msdata=sdata-type

           CRIS Options -mcpu=cpu  -march=cpu  -mtune=cpu -mmax-stack-frame=n
           -melinux-stacksize=n -metrax4  -metrax100  -mpdebug  -mcc-init  -mno-side-effects
           -mstack-align  -mdata-align  -mconst-align -m32-bit  -m16-bit  -m8-bit
           -mno-prologue-epilogue  -mno-gotplt -melf  -maout  -melinux  -mlinux  -sim  -sim2
           -mmul-bug-workaround  -mno-mul-bug-workaround

           CR16 Options -mmac -mcr16cplus -mcr16c -msim -mint32 -mbit-ops -mdata-model=model

           Darwin Options -all_load  -allowable_client  -arch  -arch_errors_fatal -arch_only
           -bind_at_load  -bundle  -bundle_loader -client_name  -compatibility_version
           -current_version -dead_strip -dependency-file  -dylib_file  -dylinker_install_name
           -dynamic  -dynamiclib  -exported_symbols_list -filelist  -flat_namespace
           -force_cpusubtype_ALL -force_flat_namespace  -headerpad_max_install_names -iframework
           -image_base  -init  -install_name  -keep_private_externs -multi_module
           -multiply_defined  -multiply_defined_unused -noall_load
           -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs  -noprebind
           -noseglinkedit -pagezero_size  -prebind  -prebind_all_twolevel_modules -private_bundle
           -read_only_relocs  -sectalign -sectobjectsymbols  -whyload  -seg1addr -sectcreate
           -sectobjectsymbols  -sectorder -segaddr -segs_read_only_addr -segs_read_write_addr
           -seg_addr_table  -seg_addr_table_filename  -seglinkedit -segprot  -segs_read_only_addr
           -segs_read_write_addr -single_module  -static  -sub_library  -sub_umbrella
           -twolevel_namespace  -umbrella  -undefined -unexported_symbols_list
           -weak_reference_mismatches -whatsloaded -F -gused -gfull -mmacosx-version-min=version
           -mkernel -mone-byte-bool

           DEC Alpha Options -mno-fp-regs  -msoft-float -mieee  -mieee-with-inexact
           -mieee-conformant -mfp-trap-mode=mode  -mfp-rounding-mode=mode -mtrap-precision=mode
           -mbuild-constants -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix
           -mfloat-vax  -mfloat-ieee -mexplicit-relocs  -msmall-data  -mlarge-data -msmall-text
           -mlarge-text -mmemory-latency=time

           FR30 Options -msmall-model -mno-lsim

           FRV Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float  -msoft-float
           -malloc-cc  -mfixed-cc  -mdword  -mno-dword -mdouble  -mno-double -mmedia  -mno-media
           -mmuladd  -mno-muladd -mfdpic  -minline-plt -mgprel-ro  -multilib-library-pic
           -mlinked-fp  -mlong-calls  -malign-labels -mlibrary-pic  -macc-4  -macc-8 -mpack
           -mno-pack  -mno-eflags  -mcond-move  -mno-cond-move -moptimize-membar
           -mno-optimize-membar -mscc  -mno-scc  -mcond-exec  -mno-cond-exec -mvliw-branch
           -mno-vliw-branch -mmulti-cond-exec  -mno-multi-cond-exec  -mnested-cond-exec
           -mno-nested-cond-exec  -mtomcat-stats -mTLS -mtls -mcpu=cpu

           GNU/Linux Options -mglibc -muclibc -mbionic -mandroid -tno-android-cc -tno-android-ld

           H8/300 Options -mrelax  -mh  -ms  -mn  -mexr -mno-exr  -mint32  -malign-300

           HPPA Options -march=architecture-type -mdisable-fpregs  -mdisable-indexing
           -mfast-indirect-calls  -mgas  -mgnu-ld   -mhp-ld -mfixed-range=register-range
           -mjump-in-delay -mlinker-opt -mlong-calls -mlong-load-store  -mno-disable-fpregs
           -mno-disable-indexing  -mno-fast-indirect-calls  -mno-gas -mno-jump-in-delay
           -mno-long-load-store -mno-portable-runtime  -mno-soft-float -mno-space-regs
           -msoft-float  -mpa-risc-1-0 -mpa-risc-1-1  -mpa-risc-2-0  -mportable-runtime
           -mschedule=cpu-type  -mspace-regs  -msio  -mwsio -munix=unix-std  -nolibdld  -static
           -threads

           IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as  -mgnu-ld  -mno-pic
           -mvolatile-asm-stop  -mregister-names  -msdata -mno-sdata -mconstant-gp  -mauto-pic
           -mfused-madd -minline-float-divide-min-latency -minline-float-divide-max-throughput
           -mno-inline-float-divide -minline-int-divide-min-latency
           -minline-int-divide-max-throughput -mno-inline-int-divide -minline-sqrt-min-latency
           -minline-sqrt-max-throughput -mno-inline-sqrt -mdwarf2-asm -mearly-stop-bits
           -mfixed-range=register-range -mtls-size=tls-size -mtune=cpu-type -milp32 -mlp64
           -msched-br-data-spec -msched-ar-data-spec -msched-control-spec -msched-br-in-data-spec
           -msched-ar-in-data-spec -msched-in-control-spec -msched-spec-ldc
           -msched-spec-control-ldc -msched-prefer-non-data-spec-insns
           -msched-prefer-non-control-spec-insns -msched-stop-bits-after-every-cycle
           -msched-count-spec-in-critical-path -msel-sched-dont-check-control-spec
           -msched-fp-mem-deps-zero-cost -msched-max-memory-insns-hard-limit
           -msched-max-memory-insns=max-insns

           LM32 Options -mbarrel-shift-enabled -mdivide-enabled -mmultiply-enabled
           -msign-extend-enabled -muser-enabled

           M32R/D Options -m32r2 -m32rx -m32r -mdebug -malign-loops -mno-align-loops
           -missue-rate=number -mbranch-cost=number -mmodel=code-size-model-type -msdata=sdata-
           type -mno-flush-func -mflush-func=name -mno-flush-trap -mflush-trap=number -G num

           M32C Options -mcpu=cpu -msim -memregs=number

           M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune -m68000  -m68020  -m68020-40
           -m68020-60  -m68030  -m68040 -m68060  -mcpu32  -m5200  -m5206e  -m528x  -m5307  -m5407
           -mcfv4e  -mbitfield  -mno-bitfield  -mc68000  -mc68020 -mnobitfield  -mrtd  -mno-rtd
           -mdiv  -mno-div  -mshort -mno-short  -mhard-float  -m68881  -msoft-float  -mpcrel
           -malign-int  -mstrict-align  -msep-data  -mno-sep-data -mshared-library-id=n
           -mid-shared-library  -mno-id-shared-library -mxgot -mno-xgot

           MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div  -mrelax-immediates
           -mno-relax-immediates  -mwide-bitfields  -mno-wide-bitfields -m4byte-functions
           -mno-4byte-functions  -mcallgraph-data -mno-callgraph-data  -mslow-bytes
           -mno-slow-bytes  -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340
           -mstack-increment

           MeP Options -mabsdiff -mall-opts -maverage -mbased=n -mbitops -mc=n -mclip
           -mconfig=name -mcop -mcop32 -mcop64 -mivc2 -mdc -mdiv -meb -mel -mio-volatile -ml
           -mleadz -mm -mminmax -mmult -mno-opts -mrepeat -ms -msatur -msdram -msim -msimnovec
           -mtf -mtiny=n

           MicroBlaze Options -msoft-float -mhard-float -msmall-divides -mcpu=cpu -mmemcpy
           -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift -mxl-pattern-compare -mxl-stack-check
           -mxl-gp-opt -mno-clearbss -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt
           -mbig-endian -mlittle-endian -mxl-reorder -mxl-mode-app-model

           MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2  -mips3  -mips4
           -mips32  -mips32r2  -mips32r3  -mips32r5 -mips32r6  -mips64  -mips64r2  -mips64r3
           -mips64r5  -mips64r6 -mips16  -mno-mips16  -mflip-mips16 -minterlink-compressed
           -mno-interlink-compressed -minterlink-mips16  -mno-interlink-mips16 -mabi=abi
           -mabicalls  -mno-abicalls -mshared  -mno-shared  -mplt  -mno-plt  -mxgot  -mno-xgot
           -mgp32  -mgp64  -mfp32  -mfpxx  -mfp64  -mhard-float  -msoft-float -mno-float
           -msingle-float  -mdouble-float -modd-spreg -mno-odd-spreg -mabs=mode  -mnan=encoding
           -mdsp  -mno-dsp  -mdspr2  -mno-dspr2 -mmcu -mmno-mcu -meva -mno-eva -mvirt -mno-virt
           -mxpa -mno-xpa -mmicromips -mno-micromips -mfpu=fpu-type -msmartmips  -mno-smartmips
           -mpaired-single  -mno-paired-single  -mdmx  -mno-mdmx -mips3d  -mno-mips3d  -mmt
           -mno-mt  -mllsc  -mno-llsc -mlong64  -mlong32  -msym32  -mno-sym32 -Gnum
           -mlocal-sdata  -mno-local-sdata -mextern-sdata  -mno-extern-sdata  -mgpopt  -mno-gopt
           -membedded-data  -mno-embedded-data -muninit-const-in-rodata
           -mno-uninit-const-in-rodata -mcode-readable=setting -msplit-addresses
           -mno-split-addresses -mexplicit-relocs  -mno-explicit-relocs -mcheck-zero-division
           -mno-check-zero-division -mdivide-traps  -mdivide-breaks -mmemcpy  -mno-memcpy
           -mlong-calls  -mno-long-calls -mmad -mno-mad -mimadd -mno-imadd -mfused-madd
           -mno-fused-madd  -nocpp -mfix-24k -mno-fix-24k -mfix-r4000  -mno-fix-r4000
           -mfix-r4400  -mno-fix-r4400 -mfix-r10000 -mno-fix-r10000  -mfix-rm7000 -mno-fix-rm7000
           -mfix-vr4120  -mno-fix-vr4120 -mfix-vr4130  -mno-fix-vr4130  -mfix-sb1  -mno-fix-sb1
           -mflush-func=func  -mno-flush-func -mbranch-cost=num  -mbranch-likely
           -mno-branch-likely -mfp-exceptions -mno-fp-exceptions -mvr4130-align -mno-vr4130-align
           -msynci -mno-synci -mrelax-pic-calls -mno-relax-pic-calls -mmcount-ra-address

           MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon  -mabi=gnu
           -mabi=mmixware  -mzero-extend  -mknuthdiv  -mtoplevel-symbols -melf  -mbranch-predict
           -mno-branch-predict  -mbase-addresses -mno-base-addresses  -msingle-exit
           -mno-single-exit

           MN10300 Options -mmult-bug  -mno-mult-bug -mno-am33 -mam33 -mam33-2 -mam34 -mtune=cpu-
           type -mreturn-pointer-on-d0 -mno-crt0  -mrelax -mliw -msetlb

           Moxie Options -meb -mel -mmul.x -mno-crt0

           MSP430 Options -msim -masm-hex -mmcu= -mcpu= -mlarge -msmall -mrelax -mhwmult= -minrt

           NDS32 Options -mbig-endian -mlittle-endian -mreduced-regs -mfull-regs -mcmov -mno-cmov
           -mperf-ext -mno-perf-ext -mv3push -mno-v3push -m16bit -mno-16bit -misr-vector-size=num
           -mcache-block-size=num -march=arch -mcmodel=code-model -mctor-dtor -mrelax

           Nios II Options -G num -mgpopt=option -mgpopt -mno-gpopt -mel -meb -mno-bypass-cache
           -mbypass-cache -mno-cache-volatile -mcache-volatile -mno-fast-sw-div -mfast-sw-div
           -mhw-mul -mno-hw-mul -mhw-mulx -mno-hw-mulx -mno-hw-div -mhw-div -mcustom-insn=N
           -mno-custom-insn -mcustom-fpu-cfg=name -mhal -msmallc -msys-crt0=name -msys-lib=name

           Nvidia PTX Options -m32 -m64 -mmainkernel

           PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0  -m40  -m45  -m10 -mbcopy
           -mbcopy-builtin  -mint32  -mno-int16 -mint16  -mno-int32  -mfloat32  -mno-float64
           -mfloat64  -mno-float32  -mabshi  -mno-abshi -mbranch-expensive  -mbranch-cheap
           -munix-asm  -mdec-asm

           picoChip Options -mae=ae_type -mvliw-lookahead=N -msymbol-as-address
           -mno-inefficient-warnings

           PowerPC Options See RS/6000 and PowerPC Options.

           RL78 Options -msim -mmul=none -mmul=g13 -mmul=rl78 -m64bit-doubles -m32bit-doubles

           RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model
           -mpowerpc64 -maltivec  -mno-altivec -mpowerpc-gpopt  -mno-powerpc-gpopt
           -mpowerpc-gfxopt  -mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopcntb  -mno-popcntb
           -mpopcntd -mno-popcntd -mfprnd  -mno-fprnd -mcmpb -mno-cmpb -mmfpgpr -mno-mfpgpr
           -mhard-dfp -mno-hard-dfp -mfull-toc   -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc
           -m64  -m32  -mxl-compat  -mno-xl-compat  -mpe -malign-power  -malign-natural
           -msoft-float  -mhard-float  -mmultiple  -mno-multiple -msingle-float -mdouble-float
           -msimple-fpu -mstring  -mno-string  -mupdate  -mno-update -mavoid-indexed-addresses
           -mno-avoid-indexed-addresses -mfused-madd  -mno-fused-madd  -mbit-align
           -mno-bit-align -mstrict-align  -mno-strict-align  -mrelocatable -mno-relocatable
           -mrelocatable-lib  -mno-relocatable-lib -mtoc  -mno-toc  -mlittle  -mlittle-endian
           -mbig  -mbig-endian -mdynamic-no-pic  -maltivec -mswdiv  -msingle-pic-base
           -mprioritize-restricted-insns=priority -msched-costly-dep=dependence_type
           -minsert-sched-nops=scheme -mcall-sysv  -mcall-netbsd -maix-struct-return
           -msvr4-struct-return -mabi=abi-type -msecure-plt -mbss-plt
           -mblock-move-inline-limit=num -misel -mno-isel -misel=yes  -misel=no -mspe -mno-spe
           -mspe=yes  -mspe=no -mpaired -mgen-cell-microcode -mwarn-cell-microcode -mvrsave
           -mno-vrsave -mmulhw -mno-mulhw -mdlmzb -mno-dlmzb -mfloat-gprs=yes  -mfloat-gprs=no
           -mfloat-gprs=single -mfloat-gprs=double -mprototype  -mno-prototype -msim  -mmvme
           -mads  -myellowknife  -memb  -msdata -msdata=opt  -mvxworks  -G num  -pthread -mrecip
           -mrecip=opt -mno-recip -mrecip-precision -mno-recip-precision -mveclibabi=type -mfriz
           -mno-friz -mpointers-to-nested-functions -mno-pointers-to-nested-functions
           -msave-toc-indirect -mno-save-toc-indirect -mpower8-fusion -mno-mpower8-fusion
           -mpower8-vector -mno-power8-vector -mcrypto -mno-crypto -mdirect-move -mno-direct-move
           -mquad-memory -mno-quad-memory -mquad-memory-atomic -mno-quad-memory-atomic
           -mcompat-align-parm -mno-compat-align-parm -mupper-regs-df -mno-upper-regs-df
           -mupper-regs-sf -mno-upper-regs-sf -mupper-regs -mno-upper-regs

           RX Options -m64bit-doubles  -m32bit-doubles  -fpu  -nofpu -mcpu= -mbig-endian-data
           -mlittle-endian-data -msmall-data -msim  -mno-sim -mas100-syntax -mno-as100-syntax
           -mrelax -mmax-constant-size= -mint-register= -mpid -mno-warn-multiple-fast-interrupts
           -msave-acc-in-interrupts

           S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type -mhard-float  -msoft-float
           -mhard-dfp -mno-hard-dfp -mlong-double-64 -mlong-double-128 -mbackchain
           -mno-backchain -mpacked-stack  -mno-packed-stack -msmall-exec  -mno-small-exec
           -mmvcle -mno-mvcle -m64  -m31  -mdebug  -mno-debug  -mesa  -mzarch -mtpf-trace
           -mno-tpf-trace  -mfused-madd  -mno-fused-madd -mwarn-framesize  -mwarn-dynamicstack
           -mstack-size -mstack-guard -mhotpatch=halfwords,halfwords

           Score Options -meb -mel -mnhwloop -muls -mmac -mscore5 -mscore5u -mscore7 -mscore7d

           SH Options -m1  -m2  -m2e -m2a-nofpu -m2a-single-only -m2a-single -m2a -m3  -m3e
           -m4-nofpu  -m4-single-only  -m4-single  -m4 -m4a-nofpu -m4a-single-only -m4a-single
           -m4a -m4al -m5-64media  -m5-64media-nofpu -m5-32media  -m5-32media-nofpu -m5-compact
           -m5-compact-nofpu -mb  -ml  -mdalign  -mrelax -mbigtable -mfmovd -mhitachi -mrenesas
           -mno-renesas -mnomacsave -mieee -mno-ieee -mbitops  -misize  -minline-ic_invalidate
           -mpadstruct -mspace -mprefergot  -musermode -multcost=number -mdiv=strategy
           -mdivsi3_libfunc=name -mfixed-range=register-range -mindexed-addressing
           -mgettrcost=number -mpt-fixed -maccumulate-outgoing-args -minvalid-symbols
           -matomic-model=atomic-model -mbranch-cost=num -mzdcbranch -mno-zdcbranch
           -mcbranch-force-delay-slot -mfused-madd -mno-fused-madd -mfsca -mno-fsca -mfsrra
           -mno-fsrra -mpretend-cmove -mtas

           Solaris 2 Options -mclear-hwcap -mno-clear-hwcap -mimpure-text  -mno-impure-text
           -pthreads -pthread

           SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -mmemory-model=mem-
           model -m32  -m64  -mapp-regs  -mno-app-regs -mfaster-structs  -mno-faster-structs
           -mflat  -mno-flat -mfpu  -mno-fpu  -mhard-float  -msoft-float -mhard-quad-float
           -msoft-quad-float -mstack-bias  -mno-stack-bias -munaligned-doubles
           -mno-unaligned-doubles -muser-mode  -mno-user-mode -mv8plus  -mno-v8plus  -mvis
           -mno-vis -mvis2  -mno-vis2  -mvis3  -mno-vis3 -mcbcond -mno-cbcond -mfmaf  -mno-fmaf
           -mpopc  -mno-popc -mfix-at697f -mfix-ut699

           SPU Options -mwarn-reloc -merror-reloc -msafe-dma -munsafe-dma -mbranch-hints
           -msmall-mem -mlarge-mem -mstdmain -mfixed-range=register-range -mea32 -mea64
           -maddress-space-conversion -mno-address-space-conversion -mcache-size=cache-size
           -matomic-updates -mno-atomic-updates

           System V Options -Qy  -Qn  -YP,paths  -Ym,dir

           TILE-Gx Options -mcpu=CPU -m32 -m64 -mbig-endian -mlittle-endian -mcmodel=code-model

           TILEPro Options -mcpu=cpu -m32

           V850 Options -mlong-calls  -mno-long-calls  -mep  -mno-ep -mprolog-function
           -mno-prolog-function  -mspace -mtda=n  -msda=n  -mzda=n -mapp-regs  -mno-app-regs
           -mdisable-callt  -mno-disable-callt -mv850e2v3 -mv850e2 -mv850e1 -mv850es -mv850e
           -mv850 -mv850e3v5 -mloop -mrelax -mlong-jumps -msoft-float -mhard-float -mgcc-abi
           -mrh850-abi -mbig-switch

           VAX Options -mg  -mgnu  -munix

           Visium Options -mdebug -msim -mfpu -mno-fpu -mhard-float -msoft-float -mcpu=cpu-type
           -mtune=cpu-type -msv-mode -muser-mode

           VMS Options -mvms-return-codes -mdebug-main=prefix -mmalloc64 -mpointer-size=size

           VxWorks Options -mrtp  -non-static  -Bstatic  -Bdynamic -Xbind-lazy  -Xbind-now

           x86 Options -mtune=cpu-type  -march=cpu-type -mtune-ctrl=feature-list
           -mdump-tune-features -mno-default -mfpmath=unit -masm=dialect  -mno-fancy-math-387
           -mno-fp-ret-in-387  -msoft-float -mno-wide-multiply  -mrtd  -malign-double
           -mpreferred-stack-boundary=num -mincoming-stack-boundary=num -mcld -mcx16 -msahf
           -mmovbe -mcrc32 -mrecip -mrecip=opt -mvzeroupper -mprefer-avx128 -mmmx  -msse  -msse2
           -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -mavx -mavx2 -mavx512f -mavx512pf -mavx512er
           -mavx512cd -msha -maes -mpclmul -mfsgsbase -mrdrnd -mf16c -mfma -mprefetchwt1
           -mclflushopt -mxsavec -mxsaves -msse4a -m3dnow -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop
           -mlzcnt -mbmi2 -mfxsr -mxsave -mxsaveopt -mrtm -mlwp -mmpx -mmwaitx -mthreads
           -mno-align-stringops  -minline-all-stringops -minline-stringops-dynamically
           -mstringop-strategy=alg -mmemcpy-strategy=strategy -mmemset-strategy=strategy
           -mpush-args  -maccumulate-outgoing-args  -m128bit-long-double -m96bit-long-double
           -mlong-double-64 -mlong-double-80 -mlong-double-128 -mregparm=num  -msseregparm
           -mveclibabi=type -mvect8-ret-in-mem -mpc32 -mpc64 -mpc80 -mstackrealign
           -momit-leaf-frame-pointer  -mno-red-zone -mno-tls-direct-seg-refs -mcmodel=code-model
           -mabi=name -maddress-mode=mode -m32 -m64 -mx32 -m16 -mlarge-data-threshold=num
           -msse2avx -mfentry -mrecord-mcount -mnop-mcount -m8bit-idiv
           -mavx256-split-unaligned-load -mavx256-split-unaligned-store -malign-data=type
           -mstack-protector-guard=guard

           x86 Windows Options -mconsole -mcygwin -mno-cygwin -mdll -mnop-fun-dllimport -mthread
           -municode -mwin32 -mwindows -fno-set-stack-executable

           Xstormy16 Options -msim

           Xtensa Options -mconst16 -mno-const16 -mfused-madd  -mno-fused-madd -mforce-no-pic
           -mserialize-volatile  -mno-serialize-volatile -mtext-section-literals
           -mno-text-section-literals -mtarget-align  -mno-target-align -mlongcalls
           -mno-longcalls

           zSeries Options See S/390 and zSeries Options.

       Code Generation Options
           -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions -fnon-call-exceptions
           -fdelete-dead-exceptions  -funwind-tables -fasynchronous-unwind-tables -fno-gnu-unique
           -finhibit-size-directive  -finstrument-functions
           -finstrument-functions-exclude-function-list=sym,sym,...
           -finstrument-functions-exclude-file-list=file,file,...  -fno-common  -fno-ident
           -fpcc-struct-return  -fpic  -fPIC -fpie -fPIE -fno-jump-tables -frecord-gcc-switches
           -freg-struct-return  -fshort-enums -fshort-double  -fshort-wchar -fverbose-asm
           -fpack-struct[=n]  -fstack-check -fstack-limit-register=reg  -fstack-limit-symbol=sym
           -fno-stack-limit -fsplit-stack -fleading-underscore  -ftls-model=model
           -fstack-reuse=reuse_level -ftrapv  -fwrapv  -fbounds-check
           -fvisibility=[default|internal|hidden|protected] -fstrict-volatile-bitfields
           -fsync-libcalls

   Options Controlling the Kind of Output
       Compilation can involve up to four stages: preprocessing, compilation proper, assembly and
       linking, always in that order.  GCC is capable of preprocessing and compiling several
       files either into several assembler input files, or into one assembler input file; then
       each assembler input file produces an object file, and linking combines all the object
       files (those newly compiled, and those specified as input) into an executable file.

       For any given input file, the file name suffix determines what kind of compilation is
       done:

       file.c
           C source code that must be preprocessed.

       file.i
           C source code that should not be preprocessed.

       file.ii
           C++ source code that should not be preprocessed.

       file.m
           Objective-C source code.  Note that you must link with the libobjc library to make an
           Objective-C program work.

       file.mi
           Objective-C source code that should not be preprocessed.

       file.mm
       file.M
           Objective-C++ source code.  Note that you must link with the libobjc library to make
           an Objective-C++ program work.  Note that .M refers to a literal capital M.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.h
           C, C++, Objective-C or Objective-C++ header file to be turned into a precompiled
           header (default), or C, C++ header file to be turned into an Ada spec (via the
           -fdump-ada-spec switch).

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
           C++ source code that must be preprocessed.  Note that in .cxx, the last two letters
           must both be literally x.  Likewise, .C refers to a literal capital C.

       file.mm
       file.M
           Objective-C++ source code that must be preprocessed.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.hh
       file.H
       file.hp
       file.hxx
       file.hpp
       file.HPP
       file.h++
       file.tcc
           C++ header file to be turned into a precompiled header or Ada spec.

       file.f
       file.for
       file.ftn
           Fixed form Fortran source code that should not be preprocessed.

       file.F
       file.FOR
       file.fpp
       file.FPP
       file.FTN
           Fixed form Fortran source code that must be preprocessed (with the traditional
           preprocessor).

       file.f90
       file.f95
       file.f03
       file.f08
           Free form Fortran source code that should not be preprocessed.

       file.F90
       file.F95
       file.F03
       file.F08
           Free form Fortran source code that must be preprocessed (with the traditional
           preprocessor).

       file.go
           Go source code.

       file.ads
           Ada source code file that contains a library unit declaration (a declaration of a
           package, subprogram, or generic, or a generic instantiation), or a library unit
           renaming declaration (a package, generic, or subprogram renaming declaration).  Such
           files are also called specs.

       file.adb
           Ada source code file containing a library unit body (a subprogram or package body).
           Such files are also called bodies.

       file.s
           Assembler code.

       file.S
       file.sx
           Assembler code that must be preprocessed.

       other
           An object file to be fed straight into linking.  Any file name with no recognized
           suffix is treated this way.

       You can specify the input language explicitly with the -x option:

       -x language
           Specify explicitly the language for the following input files (rather than letting the
           compiler choose a default based on the file name suffix).  This option applies to all
           following input files until the next -x option.  Possible values for language are:

                   c  c-header  cpp-output
                   c++  c++-header  c++-cpp-output
                   objective-c  objective-c-header  objective-c-cpp-output
                   objective-c++ objective-c++-header objective-c++-cpp-output
                   assembler  assembler-with-cpp
                   ada
                   f77  f77-cpp-input f95  f95-cpp-input
                   go
                   java

       -x none
           Turn off any specification of a language, so that subsequent files are handled
           according to their file name suffixes (as they are if -x has not been used at all).

       -pass-exit-codes
           Normally the gcc program exits with the code of 1 if any phase of the compiler returns
           a non-success return code.  If you specify -pass-exit-codes, the gcc program instead
           returns with the numerically highest error produced by any phase returning an error
           indication.  The C, C++, and Fortran front ends return 4 if an internal compiler error
           is encountered.

       If you only want some of the stages of compilation, you can use -x (or filename suffixes)
       to tell gcc where to start, and one of the options -c, -S, or -E to say where gcc is to
       stop.  Note that some combinations (for example, -x cpp-output -E) instruct gcc to do
       nothing at all.

       -c  Compile or assemble the source files, but do not link.  The linking stage simply is
           not done.  The ultimate output is in the form of an object file for each source file.

           By default, the object file name for a source file is made by replacing the suffix .c,
           .i, .s, etc., with .o.

           Unrecognized input files, not requiring compilation or assembly, are ignored.

       -S  Stop after the stage of compilation proper; do not assemble.  The output is in the
           form of an assembler code file for each non-assembler input file specified.

           By default, the assembler file name for a source file is made by replacing the suffix
           .c, .i, etc., with .s.

           Input files that don't require compilation are ignored.

       -E  Stop after the preprocessing stage; do not run the compiler proper.  The output is in
           the form of preprocessed source code, which is sent to the standard output.

           Input files that don't require preprocessing are ignored.

       -o file
           Place output in file file.  This applies to whatever sort of output is being produced,
           whether it be an executable file, an object file, an assembler file or preprocessed C
           code.

           If -o is not specified, the default is to put an executable file in a.out, the object
           file for source.suffix in source.o, its assembler file in source.s, a precompiled
           header file in source.suffix.gch, and all preprocessed C source on standard output.

       -v  Print (on standard error output) the commands executed to run the stages of
           compilation.  Also print the version number of the compiler driver program and of the
           preprocessor and the compiler proper.

       -###
           Like -v except the commands are not executed and arguments are quoted unless they
           contain only alphanumeric characters or "./-_".  This is useful for shell scripts to
           capture the driver-generated command lines.

       -pipe
           Use pipes rather than temporary files for communication between the various stages of
           compilation.  This fails to work on some systems where the assembler is unable to read
           from a pipe; but the GNU assembler has no trouble.

       --help
           Print (on the standard output) a description of the command-line options understood by
           gcc.  If the -v option is also specified then --help is also passed on to the various
           processes invoked by gcc, so that they can display the command-line options they
           accept.  If the -Wextra option has also been specified (prior to the --help option),
           then command-line options that have no documentation associated with them are also
           displayed.

       --target-help
           Print (on the standard output) a description of target-specific command-line options
           for each tool.  For some targets extra target-specific information may also be
           printed.

       --help={class|[^]qualifier}[,...]
           Print (on the standard output) a description of the command-line options understood by
           the compiler that fit into all specified classes and qualifiers.  These are the
           supported classes:

           optimizers
               Display all of the optimization options supported by the compiler.

           warnings
               Display all of the options controlling warning messages produced by the compiler.

           target
               Display target-specific options.  Unlike the --target-help option however, target-
               specific options of the linker and assembler are not displayed.  This is because
               those tools do not currently support the extended --help= syntax.

           params
               Display the values recognized by the --param option.

           language
               Display the options supported for language, where language is the name of one of
               the languages supported in this version of GCC.

           common
               Display the options that are common to all languages.

           These are the supported qualifiers:

           undocumented
               Display only those options that are undocumented.

           joined
               Display options taking an argument that appears after an equal sign in the same
               continuous piece of text, such as: --help=target.

           separate
               Display options taking an argument that appears as a separate word following the
               original option, such as: -o output-file.

           Thus for example to display all the undocumented target-specific switches supported by
           the compiler, use:

                   --help=target,undocumented

           The sense of a qualifier can be inverted by prefixing it with the ^ character, so for
           example to display all binary warning options (i.e., ones that are either on or off
           and that do not take an argument) that have a description, use:

                   --help=warnings,^joined,^undocumented

           The argument to --help= should not consist solely of inverted qualifiers.

           Combining several classes is possible, although this usually restricts the output so
           much that there is nothing to display.  One case where it does work, however, is when
           one of the classes is target.  For example, to display all the target-specific
           optimization options, use:

                   --help=target,optimizers

           The --help= option can be repeated on the command line.  Each successive use displays
           its requested class of options, skipping those that have already been displayed.

           If the -Q option appears on the command line before the --help= option, then the
           descriptive text displayed by --help= is changed.  Instead of describing the displayed
           options, an indication is given as to whether the option is enabled, disabled or set
           to a specific value (assuming that the compiler knows this at the point where the
           --help= option is used).

           Here is a truncated example from the ARM port of gcc:

                     % gcc -Q -mabi=2 --help=target -c
                     The following options are target specific:
                     -mabi=                                2
                     -mabort-on-noreturn                   [disabled]
                     -mapcs                                [disabled]

           The output is sensitive to the effects of previous command-line options, so for
           example it is possible to find out which optimizations are enabled at -O2 by using:

                   -Q -O2 --help=optimizers

           Alternatively you can discover which binary optimizations are enabled by -O3 by using:

                   gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
                   gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
                   diff /tmp/O2-opts /tmp/O3-opts | grep enabled

       -no-canonical-prefixes
           Do not expand any symbolic links, resolve references to /../ or /./, or make the path
           absolute when generating a relative prefix.

       --version
           Display the version number and copyrights of the invoked GCC.

       -wrapper
           Invoke all subcommands under a wrapper program.  The name of the wrapper program and
           its parameters are passed as a comma separated list.

                   gcc -c t.c -wrapper gdb,--args

           This invokes all subprograms of gcc under gdb --args, thus the invocation of cc1 is
           gdb --args cc1 ....

       -fplugin=name.so
           Load the plugin code in file name.so, assumed to be a shared object to be dlopen'd by
           the compiler.  The base name of the shared object file is used to identify the plugin
           for the purposes of argument parsing (See -fplugin-arg-name-key=value below).  Each
           plugin should define the callback functions specified in the Plugins API.

       -fplugin-arg-name-key=value
           Define an argument called key with a value of value for the plugin called name.

       -fdump-ada-spec[-slim]
           For C and C++ source and include files, generate corresponding Ada specs.

       -fada-spec-parent=unit
           In conjunction with -fdump-ada-spec[-slim] above, generate Ada specs as child units of
           parent unit.

       -fdump-go-spec=file
           For input files in any language, generate corresponding Go declarations in file.  This
           generates Go "const", "type", "var", and "func" declarations which may be a useful way
           to start writing a Go interface to code written in some other language.

       @file
           Read command-line options from file.  The options read are inserted in place of the
           original @file option.  If file does not exist, or cannot be read, then the option
           will be treated literally, and not removed.

           Options in file are separated by whitespace.  A whitespace character may be included
           in an option by surrounding the entire option in either single or double quotes.  Any
           character (including a backslash) may be included by prefixing the character to be
           included with a backslash.  The file may itself contain additional @file options; any
           such options will be processed recursively.

   Compiling C++ Programs
       C++ source files conventionally use one of the suffixes .C, .cc, .cpp, .CPP, .c++, .cp, or
       .cxx; C++ header files often use .hh, .hpp, .H, or (for shared template code) .tcc; and
       preprocessed C++ files use the suffix .ii.  GCC recognizes files with these names and
       compiles them as C++ programs even if you call the compiler the same way as for compiling
       C programs (usually with the name gcc).

       However, the use of gcc does not add the C++ library.  g++ is a program that calls GCC and
       automatically specifies linking against the C++ library.  It treats .c, .h and .i files as
       C++ source files instead of C source files unless -x is used.  This program is also useful
       when precompiling a C header file with a .h extension for use in C++ compilations.  On
       many systems, g++ is also installed with the name c++.

       When you compile C++ programs, you may specify many of the same command-line options that
       you use for compiling programs in any language; or command-line options meaningful for C
       and related languages; or options that are meaningful only for C++ programs.

   Options Controlling C Dialect
       The following options control the dialect of C (or languages derived from C, such as C++,
       Objective-C and Objective-C++) that the compiler accepts:

       -ansi
           In C mode, this is equivalent to -std=c90. In C++ mode, it is equivalent to
           -std=c++98.

           This turns off certain features of GCC that are incompatible with ISO C90 (when
           compiling C code), or of standard C++ (when compiling C++ code), such as the "asm" and
           "typeof" keywords, and predefined macros such as "unix" and "vax" that identify the
           type of system you are using.  It also enables the undesirable and rarely used ISO
           trigraph feature.  For the C compiler, it disables recognition of C++ style //
           comments as well as the "inline" keyword.

           The alternate keywords "__asm__", "__extension__", "__inline__" and "__typeof__"
           continue to work despite -ansi.  You would not want to use them in an ISO C program,
           of course, but it is useful to put them in header files that might be included in
           compilations done with -ansi.  Alternate predefined macros such as "__unix__" and
           "__vax__" are also available, with or without -ansi.

           The -ansi option does not cause non-ISO programs to be rejected gratuitously.  For
           that, -Wpedantic is required in addition to -ansi.

           The macro "__STRICT_ANSI__" is predefined when the -ansi option is used.  Some header
           files may notice this macro and refrain from declaring certain functions or defining
           certain macros that the ISO standard doesn't call for; this is to avoid interfering
           with any programs that might use these names for other things.

           Functions that are normally built in but do not have semantics defined by ISO C (such
           as "alloca" and "ffs") are not built-in functions when -ansi is used.

       -std=
           Determine the language standard.   This option is currently only supported when
           compiling C or C++.

           The compiler can accept several base standards, such as c90 or c++98, and GNU dialects
           of those standards, such as gnu90 or gnu++98.  When a base standard is specified, the
           compiler accepts all programs following that standard plus those using GNU extensions
           that do not contradict it.  For example, -std=c90 turns off certain features of GCC
           that are incompatible with ISO C90, such as the "asm" and "typeof" keywords, but not
           other GNU extensions that do not have a meaning in ISO C90, such as omitting the
           middle term of a "?:" expression. On the other hand, when a GNU dialect of a standard
           is specified, all features supported by the compiler are enabled, even when those
           features change the meaning of the base standard.  As a result, some strict-conforming
           programs may be rejected.  The particular standard is used by -Wpedantic to identify
           which features are GNU extensions given that version of the standard. For example
           -std=gnu90 -Wpedantic warns about C++ style // comments, while -std=gnu99 -Wpedantic
           does not.

           A value for this option must be provided; possible values are

           c90
           c89
           iso9899:1990
               Support all ISO C90 programs (certain GNU extensions that conflict with ISO C90
               are disabled). Same as -ansi for C code.

           iso9899:199409
               ISO C90 as modified in amendment 1.

           c99
           c9x
           iso9899:1999
           iso9899:199x
               ISO C99.  This standard is substantially completely supported, modulo bugs and
               floating-point issues (mainly but not entirely relating to optional C99 features
               from Annexes F and G).  See <http://gcc.gnu.org/c99status.html> for more
               information.  The names c9x and iso9899:199x are deprecated.

           c11
           c1x
           iso9899:2011
               ISO C11, the 2011 revision of the ISO C standard.  This standard is substantially
               completely supported, modulo bugs, floating-point issues (mainly but not entirely
               relating to optional C11 features from Annexes F and G) and the optional Annexes K
               (Bounds-checking interfaces) and L (Analyzability).  The name c1x is deprecated.

           gnu90
           gnu89
               GNU dialect of ISO C90 (including some C99 features).

           gnu99
           gnu9x
               GNU dialect of ISO C99.  The name gnu9x is deprecated.

           gnu11
           gnu1x
               GNU dialect of ISO C11.  This is the default for C code.  The name gnu1x is
               deprecated.

           c++98
           c++03
               The 1998 ISO C++ standard plus the 2003 technical corrigendum and some additional
               defect reports. Same as -ansi for C++ code.

           gnu++98
           gnu++03
               GNU dialect of -std=c++98.  This is the default for C++ code.

           c++11
           c++0x
               The 2011 ISO C++ standard plus amendments.  The name c++0x is deprecated.

           gnu++11
           gnu++0x
               GNU dialect of -std=c++11.  The name gnu++0x is deprecated.

           c++14
           c++1y
               The 2014 ISO C++ standard plus amendments.  The name c++1y is deprecated.

           gnu++14
           gnu++1y
               GNU dialect of -std=c++14.  The name gnu++1y is deprecated.

           c++1z
               The next revision of the ISO C++ standard, tentatively planned for 2017.  Support
               is highly experimental, and will almost certainly change in incompatible ways in
               future releases.

           gnu++1z
               GNU dialect of -std=c++1z.  Support is highly experimental, and will almost
               certainly change in incompatible ways in future releases.

       -fgnu89-inline
           The option -fgnu89-inline tells GCC to use the traditional GNU semantics for "inline"
           functions when in C99 mode.

           Using this option is roughly equivalent to adding the "gnu_inline" function attribute
           to all inline functions.

           The option -fno-gnu89-inline explicitly tells GCC to use the C99 semantics for
           "inline" when in C99 or gnu99 mode (i.e., it specifies the default behavior).  This
           option is not supported in -std=c90 or -std=gnu90 mode.

           The preprocessor macros "__GNUC_GNU_INLINE__" and "__GNUC_STDC_INLINE__" may be used
           to check which semantics are in effect for "inline" functions.

       -aux-info filename
           Output to the given filename prototyped declarations for all functions declared and/or
           defined in a translation unit, including those in header files.  This option is
           silently ignored in any language other than C.

           Besides declarations, the file indicates, in comments, the origin of each declaration
           (source file and line), whether the declaration was implicit, prototyped or
           unprototyped (I, N for new or O for old, respectively, in the first character after
           the line number and the colon), and whether it came from a declaration or a definition
           (C or F, respectively, in the following character).  In the case of function
           definitions, a K&R-style list of arguments followed by their declarations is also
           provided, inside comments, after the declaration.

       -fallow-parameterless-variadic-functions
           Accept variadic functions without named parameters.

           Although it is possible to define such a function, this is not very useful as it is
           not possible to read the arguments.  This is only supported for C as this construct is
           allowed by C++.

       -fno-asm
           Do not recognize "asm", "inline" or "typeof" as a keyword, so that code can use these
           words as identifiers.  You can use the keywords "__asm__", "__inline__" and
           "__typeof__" instead.  -ansi implies -fno-asm.

           In C++, this switch only affects the "typeof" keyword, since "asm" and "inline" are
           standard keywords.  You may want to use the -fno-gnu-keywords flag instead, which has
           the same effect.  In C99 mode (-std=c99 or -std=gnu99), this switch only affects the
           "asm" and "typeof" keywords, since "inline" is a standard keyword in ISO C99.

       -fno-builtin
       -fno-builtin-function
           Don't recognize built-in functions that do not begin with __builtin_ as prefix.

           GCC normally generates special code to handle certain built-in functions more
           efficiently; for instance, calls to "alloca" may become single instructions which
           adjust the stack directly, and calls to "memcpy" may become inline copy loops.  The
           resulting code is often both smaller and faster, but since the function calls no
           longer appear as such, you cannot set a breakpoint on those calls, nor can you change
           the behavior of the functions by linking with a different library.  In addition, when
           a function is recognized as a built-in function, GCC may use information about that
           function to warn about problems with calls to that function, or to generate more
           efficient code, even if the resulting code still contains calls to that function.  For
           example, warnings are given with -Wformat for bad calls to "printf" when "printf" is
           built in and "strlen" is known not to modify global memory.

           With the -fno-builtin-function option only the built-in function function is disabled.
           function must not begin with __builtin_.  If a function is named that is not built-in
           in this version of GCC, this option is ignored.  There is no corresponding
           -fbuiltin-function option; if you wish to enable built-in functions selectively when
           using -fno-builtin or -ffreestanding, you may define macros such as:

                   #define abs(n)          __builtin_abs ((n))
                   #define strcpy(d, s)    __builtin_strcpy ((d), (s))

       -fhosted
           Assert that compilation targets a hosted environment.  This implies -fbuiltin.  A
           hosted environment is one in which the entire standard library is available, and in
           which "main" has a return type of "int".  Examples are nearly everything except a
           kernel.  This is equivalent to -fno-freestanding.

       -ffreestanding
           Assert that compilation targets a freestanding environment.  This implies
           -fno-builtin.  A freestanding environment is one in which the standard library may not
           exist, and program startup may not necessarily be at "main".  The most obvious example
           is an OS kernel.  This is equivalent to -fno-hosted.

       -fopenacc
           Enable handling of OpenACC directives "#pragma acc" in C/C++ and "!$acc" in Fortran.
           When -fopenacc is specified, the compiler generates accelerated code according to the
           OpenACC Application Programming Interface v2.0 <http://www.openacc.org/>.  This option
           implies -pthread, and thus is only supported on targets that have support for
           -pthread.

           Note that this is an experimental feature, incomplete, and subject to change in future
           versions of GCC.  See <https://gcc.gnu.org/wiki/OpenACC> for more information.

       -fopenmp
           Enable handling of OpenMP directives "#pragma omp" in C/C++ and "!$omp" in Fortran.
           When -fopenmp is specified, the compiler generates parallel code according to the
           OpenMP Application Program Interface v4.0 <http://www.openmp.org/>.  This option
           implies -pthread, and thus is only supported on targets that have support for
           -pthread. -fopenmp implies -fopenmp-simd.

       -fopenmp-simd
           Enable handling of OpenMP's SIMD directives with "#pragma omp" in C/C++ and "!$omp" in
           Fortran. Other OpenMP directives are ignored.

       -fcilkplus
           Enable the usage of Cilk Plus language extension features for C/C++.  When the option
           -fcilkplus is specified, enable the usage of the Cilk Plus Language extension features
           for C/C++.  The present implementation follows ABI version 1.2.  This is an
           experimental feature that is only partially complete, and whose interface may change
           in future versions of GCC as the official specification changes.  Currently, all
           features but "_Cilk_for" have been implemented.

       -fgnu-tm
           When the option -fgnu-tm is specified, the compiler generates code for the Linux
           variant of Intel's current Transactional Memory ABI specification document (Revision
           1.1, May 6 2009).  This is an experimental feature whose interface may change in
           future versions of GCC, as the official specification changes.  Please note that not
           all architectures are supported for this feature.

           For more information on GCC's support for transactional memory,

           Note that the transactional memory feature is not supported with non-call exceptions
           (-fnon-call-exceptions).

       -fms-extensions
           Accept some non-standard constructs used in Microsoft header files.

           In C++ code, this allows member names in structures to be similar to previous types
           declarations.

                   typedef int UOW;
                   struct ABC {
                     UOW UOW;
                   };

           Some cases of unnamed fields in structures and unions are only accepted with this
           option.

           Note that this option is off for all targets but x86 targets using ms-abi.

       -fplan9-extensions
           Accept some non-standard constructs used in Plan 9 code.

           This enables -fms-extensions, permits passing pointers to structures with anonymous
           fields to functions that expect pointers to elements of the type of the field, and
           permits referring to anonymous fields declared using a typedef.    This is only
           supported for C, not C++.

       -trigraphs
           Support ISO C trigraphs.  The -ansi option (and -std options for strict ISO C
           conformance) implies -trigraphs.

       -traditional
       -traditional-cpp
           Formerly, these options caused GCC to attempt to emulate a pre-standard C compiler.
           They are now only supported with the -E switch.  The preprocessor continues to support
           a pre-standard mode.  See the GNU CPP manual for details.

       -fcond-mismatch
           Allow conditional expressions with mismatched types in the second and third arguments.
           The value of such an expression is void.  This option is not supported for C++.

       -flax-vector-conversions
           Allow implicit conversions between vectors with differing numbers of elements and/or
           incompatible element types.  This option should not be used for new code.

       -funsigned-char
           Let the type "char" be unsigned, like "unsigned char".

           Each kind of machine has a default for what "char" should be.  It is either like
           "unsigned char" by default or like "signed char" by default.

           Ideally, a portable program should always use "signed char" or "unsigned char" when it
           depends on the signedness of an object.  But many programs have been written to use
           plain "char" and expect it to be signed, or expect it to be unsigned, depending on the
           machines they were written for.  This option, and its inverse, let you make such a
           program work with the opposite default.

           The type "char" is always a distinct type from each of "signed char" or "unsigned
           char", even though its behavior is always just like one of those two.

       -fsigned-char
           Let the type "char" be signed, like "signed char".

           Note that this is equivalent to -fno-unsigned-char, which is the negative form of
           -funsigned-char.  Likewise, the option -fno-signed-char is equivalent to
           -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
           These options control whether a bit-field is signed or unsigned, when the declaration
           does not use either "signed" or "unsigned".  By default, such a bit-field is signed,
           because this is consistent: the basic integer types such as "int" are signed types.

   Options Controlling C++ Dialect
       This section describes the command-line options that are only meaningful for C++ programs.
       You can also use most of the GNU compiler options regardless of what language your program
       is in.  For example, you might compile a file firstClass.C like this:

               g++ -g -frepo -O -c firstClass.C

       In this example, only -frepo is an option meant only for C++ programs; you can use the
       other options with any language supported by GCC.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
           Use version n of the C++ ABI.  The default is version 0.

           Version 0 refers to the version conforming most closely to the C++ ABI specification.
           Therefore, the ABI obtained using version 0 will change in different versions of G++
           as ABI bugs are fixed.

           Version 1 is the version of the C++ ABI that first appeared in G++ 3.2.

           Version 2 is the version of the C++ ABI that first appeared in G++ 3.4, and was the
           default through G++ 4.9.

           Version 3 corrects an error in mangling a constant address as a template argument.

           Version 4, which first appeared in G++ 4.5, implements a standard mangling for vector
           types.

           Version 5, which first appeared in G++ 4.6, corrects the mangling of attribute
           const/volatile on function pointer types, decltype of a plain decl, and use of a
           function parameter in the declaration of another parameter.

           Version 6, which first appeared in G++ 4.7, corrects the promotion behavior of C++11
           scoped enums and the mangling of template argument packs, const/static_cast, prefix ++
           and --, and a class scope function used as a template argument.

           Version 7, which first appeared in G++ 4.8, that treats nullptr_t as a builtin type
           and corrects the mangling of lambdas in default argument scope.

           Version 8, which first appeared in G++ 4.9, corrects the substitution behavior of
           function types with function-cv-qualifiers.

           See also -Wabi.

       -fabi-compat-version=n
           On targets that support strong aliases, G++ works around mangling changes by creating
           an alias with the correct mangled name when defining a symbol with an incorrect
           mangled name.  This switch specifies which ABI version to use for the alias.

           With -fabi-version=0 (the default), this defaults to 2.  If another ABI version is
           explicitly selected, this defaults to 0.

           The compatibility version is also set by -Wabi=n.

       -fno-access-control
           Turn off all access checking.  This switch is mainly useful for working around bugs in
           the access control code.

       -fcheck-new
           Check that the pointer returned by "operator new" is non-null before attempting to
           modify the storage allocated.  This check is normally unnecessary because the C++
           standard specifies that "operator new" only returns 0 if it is declared "throw()", in
           which case the compiler always checks the return value even without this option.  In
           all other cases, when "operator new" has a non-empty exception specification, memory
           exhaustion is signalled by throwing "std::bad_alloc".  See also new (nothrow).

       -fconstexpr-depth=n
           Set the maximum nested evaluation depth for C++11 constexpr functions to n.  A limit
           is needed to detect endless recursion during constant expression evaluation.  The
           minimum specified by the standard is 512.

       -fdeduce-init-list
           Enable deduction of a template type parameter as "std::initializer_list" from a brace-
           enclosed initializer list, i.e.

                   template <class T> auto forward(T t) -> decltype (realfn (t))
                   {
                     return realfn (t);
                   }

                   void f()
                   {
                     forward({1,2}); // call forward<std::initializer_list<int>>
                   }

           This deduction was implemented as a possible extension to the originally proposed
           semantics for the C++11 standard, but was not part of the final standard, so it is
           disabled by default.  This option is deprecated, and may be removed in a future
           version of G++.

       -ffriend-injection
           Inject friend functions into the enclosing namespace, so that they are visible outside
           the scope of the class in which they are declared.  Friend functions were documented
           to work this way in the old Annotated C++ Reference Manual.  However, in ISO C++ a
           friend function that is not declared in an enclosing scope can only be found using
           argument dependent lookup.  GCC defaults to the standard behavior.

           This option is for compatibility, and may be removed in a future release of G++.

       -fno-elide-constructors
           The C++ standard allows an implementation to omit creating a temporary that is only
           used to initialize another object of the same type.  Specifying this option disables
           that optimization, and forces G++ to call the copy constructor in all cases.

       -fno-enforce-eh-specs
           Don't generate code to check for violation of exception specifications at run time.
           This option violates the C++ standard, but may be useful for reducing code size in
           production builds, much like defining "NDEBUG".  This does not give user code
           permission to throw exceptions in violation of the exception specifications; the
           compiler still optimizes based on the specifications, so throwing an unexpected
           exception results in undefined behavior at run time.

       -fextern-tls-init
       -fno-extern-tls-init
           The C++11 and OpenMP standards allow "thread_local" and "threadprivate" variables to
           have dynamic (runtime) initialization.  To support this, any use of such a variable
           goes through a wrapper function that performs any necessary initialization.  When the
           use and definition of the variable are in the same translation unit, this overhead can
           be optimized away, but when the use is in a different translation unit there is
           significant overhead even if the variable doesn't actually need dynamic
           initialization.  If the programmer can be sure that no use of the variable in a non-
           defining TU needs to trigger dynamic initialization (either because the variable is
           statically initialized, or a use of the variable in the defining TU will be executed
           before any uses in another TU), they can avoid this overhead with the
           -fno-extern-tls-init option.

           On targets that support symbol aliases, the default is -fextern-tls-init.  On targets
           that do not support symbol aliases, the default is -fno-extern-tls-init.

       -ffor-scope
       -fno-for-scope
           If -ffor-scope is specified, the scope of variables declared in a for-init-statement
           is limited to the "for" loop itself, as specified by the C++ standard.  If
           -fno-for-scope is specified, the scope of variables declared in a for-init-statement
           extends to the end of the enclosing scope, as was the case in old versions of G++, and
           other (traditional) implementations of C++.

           If neither flag is given, the default is to follow the standard, but to allow and give
           a warning for old-style code that would otherwise be invalid, or have different
           behavior.

       -fno-gnu-keywords
           Do not recognize "typeof" as a keyword, so that code can use this word as an
           identifier.  You can use the keyword "__typeof__" instead.  -ansi implies
           -fno-gnu-keywords.

       -fno-implicit-templates
           Never emit code for non-inline templates that are instantiated implicitly (i.e. by
           use); only emit code for explicit instantiations.

       -fno-implicit-inline-templates
           Don't emit code for implicit instantiations of inline templates, either.  The default
           is to handle inlines differently so that compiles with and without optimization need
           the same set of explicit instantiations.

       -fno-implement-inlines
           To save space, do not emit out-of-line copies of inline functions controlled by
           "#pragma implementation".  This causes linker errors if these functions are not
           inlined everywhere they are called.

       -fms-extensions
           Disable Wpedantic warnings about constructs used in MFC, such as implicit int and
           getting a pointer to member function via non-standard syntax.

       -fno-nonansi-builtins
           Disable built-in declarations of functions that are not mandated by ANSI/ISO C.  These
           include "ffs", "alloca", "_exit", "index", "bzero", "conjf", and other related
           functions.

       -fnothrow-opt
           Treat a "throw()" exception specification as if it were a "noexcept" specification to
           reduce or eliminate the text size overhead relative to a function with no exception
           specification.  If the function has local variables of types with non-trivial
           destructors, the exception specification actually makes the function smaller because
           the EH cleanups for those variables can be optimized away.  The semantic effect is
           that an exception thrown out of a function with such an exception specification
           results in a call to "terminate" rather than "unexpected".

       -fno-operator-names
           Do not treat the operator name keywords "and", "bitand", "bitor", "compl", "not", "or"
           and "xor" as synonyms as keywords.

       -fno-optional-diags
           Disable diagnostics that the standard says a compiler does not need to issue.
           Currently, the only such diagnostic issued by G++ is the one for a name having
           multiple meanings within a class.

       -fpermissive
           Downgrade some diagnostics about nonconformant code from errors to warnings.  Thus,
           using -fpermissive allows some nonconforming code to compile.

       -fno-pretty-templates
           When an error message refers to a specialization of a function template, the compiler
           normally prints the signature of the template followed by the template arguments and
           any typedefs or typenames in the signature (e.g. "void f(T) [with T = int]" rather
           than "void f(int)") so that it's clear which template is involved.  When an error
           message refers to a specialization of a class template, the compiler omits any
           template arguments that match the default template arguments for that template.  If
           either of these behaviors make it harder to understand the error message rather than
           easier, you can use -fno-pretty-templates to disable them.

       -frepo
           Enable automatic template instantiation at link time.  This option also implies
           -fno-implicit-templates.

       -fno-rtti
           Disable generation of information about every class with virtual functions for use by
           the C++ run-time type identification features ("dynamic_cast" and "typeid").  If you
           don't use those parts of the language, you can save some space by using this flag.
           Note that exception handling uses the same information, but G++ generates it as
           needed. The "dynamic_cast" operator can still be used for casts that do not require
           run-time type information, i.e. casts to "void *" or to unambiguous base classes.

       -fsized-deallocation
           Enable the built-in global declarations

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           as introduced in C++14.  This is useful for user-defined replacement deallocation
           functions that, for example, use the size of the object to make deallocation faster.
           Enabled by default under -std=c++14 and above.  The flag -Wsized-deallocation warns
           about places that might want to add a definition.

       -fstats
           Emit statistics about front-end processing at the end of the compilation.  This
           information is generally only useful to the G++ development team.

       -fstrict-enums
           Allow the compiler to optimize using the assumption that a value of enumerated type
           can only be one of the values of the enumeration (as defined in the C++ standard;
           basically, a value that can be represented in the minimum number of bits needed to
           represent all the enumerators).  This assumption may not be valid if the program uses
           a cast to convert an arbitrary integer value to the enumerated type.

       -ftemplate-backtrace-limit=n
           Set the maximum number of template instantiation notes for a single warning or error
           to n.  The default value is 10.

       -ftemplate-depth=n
           Set the maximum instantiation depth for template classes to n.  A limit on the
           template instantiation depth is needed to detect endless recursions during template
           class instantiation.  ANSI/ISO C++ conforming programs must not rely on a maximum
           depth greater than 17 (changed to 1024 in C++11).  The default value is 900, as the
           compiler can run out of stack space before hitting 1024 in some situations.

       -fno-threadsafe-statics
           Do not emit the extra code to use the routines specified in the C++ ABI for thread-
           safe initialization of local statics.  You can use this option to reduce code size
           slightly in code that doesn't need to be thread-safe.

       -fuse-cxa-atexit
           Register destructors for objects with static storage duration with the "__cxa_atexit"
           function rather than the "atexit" function.  This option is required for fully
           standards-compliant handling of static destructors, but only works if your C library
           supports "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
           Don't use the "__cxa_get_exception_ptr" runtime routine.  This causes
           "std::uncaught_exception" to be incorrect, but is necessary if the runtime routine is
           not available.

       -fvisibility-inlines-hidden
           This switch declares that the user does not attempt to compare pointers to inline
           functions or methods where the addresses of the two functions are taken in different
           shared objects.

           The effect of this is that GCC may, effectively, mark inline methods with
           "__attribute__ ((visibility ("hidden")))" so that they do not appear in the export
           table of a DSO and do not require a PLT indirection when used within the DSO.
           Enabling this option can have a dramatic effect on load and link times of a DSO as it
           massively reduces the size of the dynamic export table when the library makes heavy
           use of templates.

           The behavior of this switch is not quite the same as marking the methods as hidden
           directly, because it does not affect static variables local to the function or cause
           the compiler to deduce that the function is defined in only one shared object.

           You may mark a method as having a visibility explicitly to negate the effect of the
           switch for that method.  For example, if you do want to compare pointers to a
           particular inline method, you might mark it as having default visibility.  Marking the
           enclosing class with explicit visibility has no effect.

           Explicitly instantiated inline methods are unaffected by this option as their linkage
           might otherwise cross a shared library boundary.

       -fvisibility-ms-compat
           This flag attempts to use visibility settings to make GCC's C++ linkage model
           compatible with that of Microsoft Visual Studio.

           The flag makes these changes to GCC's linkage model:

           1.  It sets the default visibility to "hidden", like -fvisibility=hidden.

           2.  Types, but not their members, are not hidden by default.

           3.  The One Definition Rule is relaxed for types without explicit visibility
               specifications that are defined in more than one shared object: those declarations
               are permitted if they are permitted when this option is not used.

           In new code it is better to use -fvisibility=hidden and export those classes that are
           intended to be externally visible.  Unfortunately it is possible for code to rely,
           perhaps accidentally, on the Visual Studio behavior.

           Among the consequences of these changes are that static data members of the same type
           with the same name but defined in different shared objects are different, so changing
           one does not change the other; and that pointers to function members defined in
           different shared objects may not compare equal.  When this flag is given, it is a
           violation of the ODR to define types with the same name differently.

       -fvtable-verify=[std|preinit|none]
           Turn on (or off, if using -fvtable-verify=none) the security feature that verifies at
           run time, for every virtual call, that the vtable pointer through which the call is
           made is valid for the type of the object, and has not been corrupted or overwritten.
           If an invalid vtable pointer is detected at run time, an error is reported and
           execution of the program is immediately halted.

           This option causes run-time data structures to be built at program startup, which are
           used for verifying the vtable pointers.  The options std and preinit control the
           timing of when these data structures are built.  In both cases the data structures are
           built before execution reaches "main".  Using -fvtable-verify=std causes the data
           structures to be built after shared libraries have been loaded and initialized.
           -fvtable-verify=preinit causes them to be built before shared libraries have been
           loaded and initialized.

           If this option appears multiple times in the command line with different values
           specified, none takes highest priority over both std and preinit; preinit takes
           priority over std.

       -fvtv-debug
           When used in conjunction with -fvtable-verify=std or -fvtable-verify=preinit, causes
           debug versions of the runtime functions for the vtable verification feature to be
           called.  This flag also causes the compiler to log information about which vtable
           pointers it finds for each class.  This information is written to a file named
           vtv_set_ptr_data.log in the directory named by the environment variable VTV_LOGS_DIR
           if that is defined or the current working directory otherwise.

           Note:  This feature appends data to the log file. If you want a fresh log file, be
           sure to delete any existing one.

       -fvtv-counts
           This is a debugging flag.  When used in conjunction with -fvtable-verify=std or
           -fvtable-verify=preinit, this causes the compiler to keep track of the total number of
           virtual calls it encounters and the number of verifications it inserts.  It also
           counts the number of calls to certain run-time library functions that it inserts and
           logs this information for each compilation unit.  The compiler writes this information
           to a file named vtv_count_data.log in the directory named by the environment variable
           VTV_LOGS_DIR if that is defined or the current working directory otherwise.  It also
           counts the size of the vtable pointer sets for each class, and writes this information
           to vtv_class_set_sizes.log in the same directory.

           Note:  This feature appends data to the log files.  To get fresh log files, be sure to
           delete any existing ones.

       -fno-weak
           Do not use weak symbol support, even if it is provided by the linker.  By default, G++
           uses weak symbols if they are available.  This option exists only for testing, and
           should not be used by end-users; it results in inferior code and has no benefits.
           This option may be removed in a future release of G++.

       -nostdinc++
           Do not search for header files in the standard directories specific to C++, but do
           still search the other standard directories.  (This option is used when building the
           C++ library.)

       In addition, these optimization, warning, and code generation options have meanings only
       for C++ programs:

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
           When an explicit -fabi-version=n option is used, causes G++ to warn when it generates
           code that is probably not compatible with the vendor-neutral C++ ABI.  Since G++ now
           defaults to -fabi-version=0, -Wabi has no effect unless either an older ABI version is
           selected (with -fabi-version=n) or an older compatibility version is selected (with
           -Wabi=n or -fabi-compat-version=n).

           Although an effort has been made to warn about all such cases, there are probably some
           cases that are not warned about, even though G++ is generating incompatible code.
           There may also be cases where warnings are emitted even though the code that is
           generated is compatible.

           You should rewrite your code to avoid these warnings if you are concerned about the
           fact that code generated by G++ may not be binary compatible with code generated by
           other compilers.

           -Wabi can also be used with an explicit version number to warn about compatibility
           with a particular -fabi-version level, e.g. -Wabi=2 to warn about changes relative to
           -fabi-version=2.  Specifying a version number also sets -fabi-compat-version=n.

           The known incompatibilities in -fabi-version=2 (which was the default from GCC 3.4 to
           4.9) include:

           *   A template with a non-type template parameter of reference type was mangled
               incorrectly:

                       extern int N;
                       template <int &> struct S {};
                       void n (S<N>) {2}

               This was fixed in -fabi-version=3.

           *   SIMD vector types declared using "__attribute ((vector_size))" were mangled in a
               non-standard way that does not allow for overloading of functions taking vectors
               of different sizes.

               The mangling was changed in -fabi-version=4.

           *   "__attribute ((const))" and "noreturn" were mangled as type qualifiers, and
               "decltype" of a plain declaration was folded away.

               These mangling issues were fixed in -fabi-version=5.

           *   Scoped enumerators passed as arguments to a variadic function are promoted like
               unscoped enumerators, causing "va_arg" to complain.  On most targets this does not
               actually affect the parameter passing ABI, as there is no way to pass an argument
               smaller than "int".

               Also, the ABI changed the mangling of template argument packs, "const_cast",
               "static_cast", prefix increment/decrement, and a class scope function used as a
               template argument.

               These issues were corrected in -fabi-version=6.

           *   Lambdas in default argument scope were mangled incorrectly, and the ABI changed
               the mangling of "nullptr_t".

               These issues were corrected in -fabi-version=7.

           *   When mangling a function type with function-cv-qualifiers, the un-qualified
               function type was incorrectly treated as a substitution candidate.

               This was fixed in -fabi-version=8.

           It also warns about psABI-related changes.  The known psABI changes at this point
           include:

           *   For SysV/x86-64, unions with "long double" members are passed in memory as
               specified in psABI.  For example:

                       union U {
                         long double ld;
                         int i;
                       };

               "union U" is always passed in memory.

       -Wabi-tag (C++ and Objective-C++ only)
           Warn when a type with an ABI tag is used in a context that does not have that ABI tag.
           See C++ Attributes for more information about ABI tags.

       -Wctor-dtor-privacy (C++ and Objective-C++ only)
           Warn when a class seems unusable because all the constructors or destructors in that
           class are private, and it has neither friends nor public static member functions.
           Also warn if there are no non-private methods, and there's at least one private member
           function that isn't a constructor or destructor.

       -Wdelete-non-virtual-dtor (C++ and Objective-C++ only)
           Warn when "delete" is used to destroy an instance of a class that has virtual
           functions and non-virtual destructor. It is unsafe to delete an instance of a derived
           class through a pointer to a base class if the base class does not have a virtual
           destructor.  This warning is enabled by -Wall.

       -Wliteral-suffix (C++ and Objective-C++ only)
           Warn when a string or character literal is followed by a ud-suffix which does not
           begin with an underscore.  As a conforming extension, GCC treats such suffixes as
           separate preprocessing tokens in order to maintain backwards compatibility with code
           that uses formatting macros from "<inttypes.h>".  For example:

                   #define __STDC_FORMAT_MACROS
                   #include <inttypes.h>
                   #include <stdio.h>

                   int main() {
                     int64_t i64 = 123;
                     printf("My int64: %"PRId64"\n", i64);
                   }

           In this case, "PRId64" is treated as a separate preprocessing token.

           This warning is enabled by default.

       -Wnarrowing (C++ and Objective-C++ only)
           Warn when a narrowing conversion prohibited by C++11 occurs within { }, e.g.

                   int i = { 2.2 }; // error: narrowing from double to int

           This flag is included in -Wall and -Wc++11-compat.

           With -std=c++11, -Wno-narrowing suppresses the diagnostic required by the standard.
           Note that this does not affect the meaning of well-formed code; narrowing conversions
           are still considered ill-formed in SFINAE context.

       -Wnoexcept (C++ and Objective-C++ only)
           Warn when a noexcept-expression evaluates to false because of a call to a function
           that does not have a non-throwing exception specification (i.e. "throw()" or
           "noexcept") but is known by the compiler to never throw an exception.

       -Wnon-virtual-dtor (C++ and Objective-C++ only)
           Warn when a class has virtual functions and an accessible non-virtual destructor
           itself or in an accessible polymorphic base class, in which case it is possible but
           unsafe to delete an instance of a derived class through a pointer to the class itself
           or base class.  This warning is automatically enabled if -Weffc++ is specified.

       -Wreorder (C++ and Objective-C++ only)
           Warn when the order of member initializers given in the code does not match the order
           in which they must be executed.  For instance:

                   struct A {
                     int i;
                     int j;
                     A(): j (0), i (1) { }
                   };

           The compiler rearranges the member initializers for "i" and "j" to match the
           declaration order of the members, emitting a warning to that effect.  This warning is
           enabled by -Wall.

       -fext-numeric-literals (C++ and Objective-C++ only)
           Accept imaginary, fixed-point, or machine-defined literal number suffixes as GNU
           extensions.  When this option is turned off these suffixes are treated as C++11 user-
           defined literal numeric suffixes.  This is on by default for all pre-C++11 dialects
           and all GNU dialects: -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++14.  This
           option is off by default for ISO C++11 onwards (-std=c++11, ...).

       The following -W... options are not affected by -Wall.

       -Weffc++ (C++ and Objective-C++ only)
           Warn about violations of the following style guidelines from Scott Meyers' Effective
           C++ series of books:

           *   Define a copy constructor and an assignment operator for classes with dynamically-
               allocated memory.

           *   Prefer initialization to assignment in constructors.

           *   Have "operator=" return a reference to *this.

           *   Don't try to return a reference when you must return an object.

           *   Distinguish between prefix and postfix forms of increment and decrement operators.

           *   Never overload "&&", "||", or ",".

           This option also enables -Wnon-virtual-dtor, which is also one of the effective C++
           recommendations.  However, the check is extended to warn about the lack of virtual
           destructor in accessible non-polymorphic bases classes too.

           When selecting this option, be aware that the standard library headers do not obey all
           of these guidelines; use grep -v to filter out those warnings.

       -Wstrict-null-sentinel (C++ and Objective-C++ only)
           Warn about the use of an uncasted "NULL" as sentinel.  When compiling only with GCC
           this is a valid sentinel, as "NULL" is defined to "__null".  Although it is a null
           pointer constant rather than a null pointer, it is guaranteed to be of the same size
           as a pointer.  But this use is not portable across different compilers.

       -Wno-non-template-friend (C++ and Objective-C++ only)
           Disable warnings when non-templatized friend functions are declared within a template.
           Since the advent of explicit template specification support in G++, if the name of the
           friend is an unqualified-id (i.e., friend foo(int)), the C++ language specification
           demands that the friend declare or define an ordinary, nontemplate function.  (Section
           14.5.3).  Before G++ implemented explicit specification, unqualified-ids could be
           interpreted as a particular specialization of a templatized function.  Because this
           non-conforming behavior is no longer the default behavior for G++,
           -Wnon-template-friend allows the compiler to check existing code for potential trouble
           spots and is on by default.  This new compiler behavior can be turned off with
           -Wno-non-template-friend, which keeps the conformant compiler code but disables the
           helpful warning.

       -Wold-style-cast (C++ and Objective-C++ only)
           Warn if an old-style (C-style) cast to a non-void type is used within a C++ program.
           The new-style casts ("dynamic_cast", "static_cast", "reinterpret_cast", and
           "const_cast") are less vulnerable to unintended effects and much easier to search for.

       -Woverloaded-virtual (C++ and Objective-C++ only)
           Warn when a function declaration hides virtual functions from a base class.  For
           example, in:

                   struct A {
                     virtual void f();
                   };

                   struct B: public A {
                     void f(int);
                   };

           the "A" class version of "f" is hidden in "B", and code like:

                   B* b;
                   b->f();

           fails to compile.

       -Wno-pmf-conversions (C++ and Objective-C++ only)
           Disable the diagnostic for converting a bound pointer to member function to a plain
           pointer.

       -Wsign-promo (C++ and Objective-C++ only)
           Warn when overload resolution chooses a promotion from unsigned or enumerated type to
           a signed type, over a conversion to an unsigned type of the same size.  Previous
           versions of G++ tried to preserve unsignedness, but the standard mandates the current
           behavior.

   Options Controlling Objective-C and Objective-C++ Dialects
       (NOTE: This manual does not describe the Objective-C and Objective-C++ languages
       themselves.

       This section describes the command-line options that are only meaningful for Objective-C
       and Objective-C++ programs.  You can also use most of the language-independent GNU
       compiler options.  For example, you might compile a file some_class.m like this:

               gcc -g -fgnu-runtime -O -c some_class.m

       In this example, -fgnu-runtime is an option meant only for Objective-C and Objective-C++
       programs; you can use the other options with any language supported by GCC.

       Note that since Objective-C is an extension of the C language, Objective-C compilations
       may also use options specific to the C front-end (e.g., -Wtraditional).  Similarly,
       Objective-C++ compilations may use C++-specific options (e.g., -Wabi).

       Here is a list of options that are only for compiling Objective-C and Objective-C++
       programs:

       -fconstant-string-class=class-name
           Use class-name as the name of the class to instantiate for each literal string
           specified with the syntax "@"..."".  The default class name is "NXConstantString" if
           the GNU runtime is being used, and "NSConstantString" if the NeXT runtime is being
           used (see below).  The -fconstant-cfstrings option, if also present, overrides the
           -fconstant-string-class setting and cause "@"..."" literals to be laid out as constant
           CoreFoundation strings.

       -fgnu-runtime
           Generate object code compatible with the standard GNU Objective-C runtime.  This is
           the default for most types of systems.

       -fnext-runtime
           Generate output compatible with the NeXT runtime.  This is the default for NeXT-based
           systems, including Darwin and Mac OS X.  The macro "__NEXT_RUNTIME__" is predefined if
           (and only if) this option is used.

       -fno-nil-receivers
           Assume that all Objective-C message dispatches ("[receiver message:arg]") in this
           translation unit ensure that the receiver is not "nil".  This allows for more
           efficient entry points in the runtime to be used.  This option is only available in
           conjunction with the NeXT runtime and ABI version 0 or 1.

       -fobjc-abi-version=n
           Use version n of the Objective-C ABI for the selected runtime.  This option is
           currently supported only for the NeXT runtime.  In that case, Version 0 is the
           traditional (32-bit) ABI without support for properties and other Objective-C 2.0
           additions.  Version 1 is the traditional (32-bit) ABI with support for properties and
           other Objective-C 2.0 additions.  Version 2 is the modern (64-bit) ABI.  If nothing is
           specified, the default is Version 0 on 32-bit target machines, and Version 2 on 64-bit
           target machines.

       -fobjc-call-cxx-cdtors
           For each Objective-C class, check if any of its instance variables is a C++ object
           with a non-trivial default constructor.  If so, synthesize a special "- (id)
           .cxx_construct" instance method which runs non-trivial default constructors on any
           such instance variables, in order, and then return "self".  Similarly, check if any
           instance variable is a C++ object with a non-trivial destructor, and if so, synthesize
           a special "- (void) .cxx_destruct" method which runs all such default destructors, in
           reverse order.

           The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods thusly generated only
           operate on instance variables declared in the current Objective-C class, and not those
           inherited from superclasses.  It is the responsibility of the Objective-C runtime to
           invoke all such methods in an object's inheritance hierarchy.  The "- (id)
           .cxx_construct" methods are invoked by the runtime immediately after a new object
           instance is allocated; the "- (void) .cxx_destruct" methods are invoked immediately
           before the runtime deallocates an object instance.

           As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has support for
           invoking the "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods.

       -fobjc-direct-dispatch
           Allow fast jumps to the message dispatcher.  On Darwin this is accomplished via the
           comm page.

       -fobjc-exceptions
           Enable syntactic support for structured exception handling in Objective-C, similar to
           what is offered by C++ and Java.  This option is required to use the Objective-C
           keywords @try, @throw, @catch, @finally and @synchronized.  This option is available
           with both the GNU runtime and the NeXT runtime (but not available in conjunction with
           the NeXT runtime on Mac OS X 10.2 and earlier).

       -fobjc-gc
           Enable garbage collection (GC) in Objective-C and Objective-C++ programs.  This option
           is only available with the NeXT runtime; the GNU runtime has a different garbage
           collection implementation that does not require special compiler flags.

       -fobjc-nilcheck
           For the NeXT runtime with version 2 of the ABI, check for a nil receiver in method
           invocations before doing the actual method call.  This is the default and can be
           disabled using -fno-objc-nilcheck.  Class methods and super calls are never checked
           for nil in this way no matter what this flag is set to.  Currently this flag does
           nothing when the GNU runtime, or an older version of the NeXT runtime ABI, is used.

       -fobjc-std=objc1
           Conform to the language syntax of Objective-C 1.0, the language recognized by GCC 4.0.
           This only affects the Objective-C additions to the C/C++ language; it does not affect
           conformance to C/C++ standards, which is controlled by the separate C/C++ dialect
           option flags.  When this option is used with the Objective-C or Objective-C++
           compiler, any Objective-C syntax that is not recognized by GCC 4.0 is rejected.  This
           is useful if you need to make sure that your Objective-C code can be compiled with
           older versions of GCC.

       -freplace-objc-classes
           Emit a special marker instructing ld(1) not to statically link in the resulting object
           file, and allow dyld(1) to load it in at run time instead.  This is used in
           conjunction with the Fix-and-Continue debugging mode, where the object file in
           question may be recompiled and dynamically reloaded in the course of program
           execution, without the need to restart the program itself.  Currently, Fix-and-
           Continue functionality is only available in conjunction with the NeXT runtime on Mac
           OS X 10.3 and later.

       -fzero-link
           When compiling for the NeXT runtime, the compiler ordinarily replaces calls to
           "objc_getClass("...")" (when the name of the class is known at compile time) with
           static class references that get initialized at load time, which improves run-time
           performance.  Specifying the -fzero-link flag suppresses this behavior and causes
           calls to "objc_getClass("...")"  to be retained.  This is useful in Zero-Link
           debugging mode, since it allows for individual class implementations to be modified
           during program execution.  The GNU runtime currently always retains calls to
           "objc_get_class("...")"  regardless of command-line options.

       -fno-local-ivars
           By default instance variables in Objective-C can be accessed as if they were local
           variables from within the methods of the class they're declared in.  This can lead to
           shadowing between instance variables and other variables declared either locally
           inside a class method or globally with the same name.  Specifying the -fno-local-ivars
           flag disables this behavior thus avoiding variable shadowing issues.

       -fivar-visibility=[public|protected|private|package]
           Set the default instance variable visibility to the specified option so that instance
           variables declared outside the scope of any access modifier directives default to the
           specified visibility.

       -gen-decls
           Dump interface declarations for all classes seen in the source file to a file named
           sourcename.decl.

       -Wassign-intercept (Objective-C and Objective-C++ only)
           Warn whenever an Objective-C assignment is being intercepted by the garbage collector.

       -Wno-protocol (Objective-C and Objective-C++ only)
           If a class is declared to implement a protocol, a warning is issued for every method
           in the protocol that is not implemented by the class.  The default behavior is to
           issue a warning for every method not explicitly implemented in the class, even if a
           method implementation is inherited from the superclass.  If you use the -Wno-protocol
           option, then methods inherited from the superclass are considered to be implemented,
           and no warning is issued for them.

       -Wselector (Objective-C and Objective-C++ only)
           Warn if multiple methods of different types for the same selector are found during
           compilation.  The check is performed on the list of methods in the final stage of
           compilation.  Additionally, a check is performed for each selector appearing in a
           "@selector(...)"  expression, and a corresponding method for that selector has been
           found during compilation.  Because these checks scan the method table only at the end
           of compilation, these warnings are not produced if the final stage of compilation is
           not reached, for example because an error is found during compilation, or because the
           -fsyntax-only option is being used.

       -Wstrict-selector-match (Objective-C and Objective-C++ only)
           Warn if multiple methods with differing argument and/or return types are found for a
           given selector when attempting to send a message using this selector to a receiver of
           type "id" or "Class".  When this flag is off (which is the default behavior), the
           compiler omits such warnings if any differences found are confined to types that share
           the same size and alignment.

       -Wundeclared-selector (Objective-C and Objective-C++ only)
           Warn if a "@selector(...)" expression referring to an undeclared selector is found.  A
           selector is considered undeclared if no method with that name has been declared before
           the "@selector(...)" expression, either explicitly in an @interface or @protocol
           declaration, or implicitly in an @implementation section.  This option always performs
           its checks as soon as a "@selector(...)" expression is found, while -Wselector only
           performs its checks in the final stage of compilation.  This also enforces the coding
           style convention that methods and selectors must be declared before being used.

       -print-objc-runtime-info
           Generate C header describing the largest structure that is passed by value, if any.

   Options to Control Diagnostic Messages Formatting
       Traditionally, diagnostic messages have been formatted irrespective of the output device's
       aspect (e.g. its width, ...).  You can use the options described below to control the
       formatting algorithm for diagnostic messages, e.g. how many characters per line, how often
       source location information should be reported.  Note that some language front ends may
       not honor these options.

       -fmessage-length=n
           Try to format error messages so that they fit on lines of about n characters.  If n is
           zero, then no line-wrapping is done; each error message appears on a single line.
           This is the default for all front ends.

       -fdiagnostics-show-location=once
           Only meaningful in line-wrapping mode.  Instructs the diagnostic messages reporter to
           emit source location information once; that is, in case the message is too long to fit
           on a single physical line and has to be wrapped, the source location won't be emitted
           (as prefix) again, over and over, in subsequent continuation lines.  This is the
           default behavior.

       -fdiagnostics-show-location=every-line
           Only meaningful in line-wrapping mode.  Instructs the diagnostic messages reporter to
           emit the same source location information (as prefix) for physical lines that result
           from the process of breaking a message which is too long to fit on a single line.

       -fdiagnostics-color[=WHEN]
       -fno-diagnostics-color
           Use color in diagnostics.  WHEN is never, always, or auto.  The default depends on how
           the compiler has been configured, it can be any of the above WHEN options or also
           never if GCC_COLORS environment variable isn't present in the environment, and auto
           otherwise.  auto means to use color only when the standard error is a terminal.  The
           forms -fdiagnostics-color and -fno-diagnostics-color are aliases for
           -fdiagnostics-color=always and -fdiagnostics-color=never, respectively.

           The colors are defined by the environment variable GCC_COLORS.  Its value is a colon-
           separated list of capabilities and Select Graphic Rendition (SGR) substrings. SGR
           commands are interpreted by the terminal or terminal emulator.  (See the section in
           the documentation of your text terminal for permitted values and their meanings as
           character attributes.)  These substring values are integers in decimal representation
           and can be concatenated with semicolons.  Common values to concatenate include 1 for
           bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default foreground color, 30
           to 37 for foreground colors, 90 to 97 for 16-color mode foreground colors, 38;5;0 to
           38;5;255 for 88-color and 256-color modes foreground colors, 49 for default background
           color, 40 to 47 for background colors, 100 to 107 for 16-color mode background colors,
           and 48;5;0 to 48;5;255 for 88-color and 256-color modes background colors.

           The default GCC_COLORS is

                   error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01

           where 01;31 is bold red, 01;35 is bold magenta, 01;36 is bold cyan, 01;32 is bold
           green and 01 is bold. Setting GCC_COLORS to the empty string disables colors.
           Supported capabilities are as follows.

           "error="
               SGR substring for error: markers.

           "warning="
               SGR substring for warning: markers.

           "note="
               SGR substring for note: markers.

           "caret="
               SGR substring for caret line.

           "locus="
               SGR substring for location information, file:line or file:line:column etc.

           "quote="
               SGR substring for information printed within quotes.

       -fno-diagnostics-show-option
           By default, each diagnostic emitted includes text indicating the command-line option
           that directly controls the diagnostic (if such an option is known to the diagnostic
           machinery).  Specifying the -fno-diagnostics-show-option flag suppresses that
           behavior.

       -fno-diagnostics-show-caret
           By default, each diagnostic emitted includes the original source line and a caret '^'
           indicating the column.  This option suppresses this information.  The source line is
           truncated to n characters, if the -fmessage-length=n option is given.  When the output
           is done to the terminal, the width is limited to the width given by the COLUMNS
           environment variable or, if not set, to the terminal width.

   Options to Request or Suppress Warnings
       Warnings are diagnostic messages that report constructions that are not inherently
       erroneous but that are risky or suggest there may have been an error.

       The following language-independent options do not enable specific warnings but control the
       kinds of diagnostics produced by GCC.

       -fsyntax-only
           Check the code for syntax errors, but don't do anything beyond that.

       -fmax-errors=n
           Limits the maximum number of error messages to n, at which point GCC bails out rather
           than attempting to continue processing the source code.  If n is 0 (the default),
           there is no limit on the number of error messages produced.  If -Wfatal-errors is also
           specified, then -Wfatal-errors takes precedence over this option.

       -w  Inhibit all warning messages.

       -Werror
           Make all warnings into errors.

       -Werror=
           Make the specified warning into an error.  The specifier for a warning is appended;
           for example -Werror=switch turns the warnings controlled by -Wswitch into errors.
           This switch takes a negative form, to be used to negate -Werror for specific warnings;
           for example -Wno-error=switch makes -Wswitch warnings not be errors, even when -Werror
           is in effect.

           The warning message for each controllable warning includes the option that controls
           the warning.  That option can then be used with -Werror= and -Wno-error= as described
           above.  (Printing of the option in the warning message can be disabled using the
           -fno-diagnostics-show-option flag.)

           Note that specifying -Werror=foo automatically implies -Wfoo.  However, -Wno-error=foo
           does not imply anything.

       -Wfatal-errors
           This option causes the compiler to abort compilation on the first error occurred
           rather than trying to keep going and printing further error messages.

       You can request many specific warnings with options beginning with -W, for example
       -Wimplicit to request warnings on implicit declarations.  Each of these specific warning
       options also has a negative form beginning -Wno- to turn off warnings; for example,
       -Wno-implicit.  This manual lists only one of the two forms, whichever is not the default.
       For further language-specific options also refer to C++ Dialect Options and Objective-C
       and Objective-C++ Dialect Options.

       Some options, such as -Wall and -Wextra, turn on other options, such as -Wunused, which
       may turn on further options, such as -Wunused-value. The combined effect of positive and
       negative forms is that more specific options have priority over less specific ones,
       independently of their position in the command-line. For options of the same specificity,
       the last one takes effect. Options enabled or disabled via pragmas take effect as if they
       appeared at the end of the command-line.

       When an unrecognized warning option is requested (e.g., -Wunknown-warning), GCC emits a
       diagnostic stating that the option is not recognized.  However, if the -Wno- form is used,
       the behavior is slightly different: no diagnostic is produced for -Wno-unknown-warning
       unless other diagnostics are being produced.  This allows the use of new -Wno- options
       with old compilers, but if something goes wrong, the compiler warns that an unrecognized
       option is present.

       -Wpedantic
       -pedantic
           Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that
           use forbidden extensions, and some other programs that do not follow ISO C and ISO
           C++.  For ISO C, follows the version of the ISO C standard specified by any -std
           option used.

           Valid ISO C and ISO C++ programs should compile properly with or without this option
           (though a rare few require -ansi or a -std option specifying the required version of
           ISO C).  However, without this option, certain GNU extensions and traditional C and
           C++ features are supported as well.  With this option, they are rejected.

           -Wpedantic does not cause warning messages for use of the alternate keywords whose
           names begin and end with __.  Pedantic warnings are also disabled in the expression
           that follows "__extension__".  However, only system header files should use these
           escape routes; application programs should avoid them.

           Some users try to use -Wpedantic to check programs for strict ISO C conformance.  They
           soon find that it does not do quite what they want: it finds some non-ISO practices,
           but not all---only those for which ISO C requires a diagnostic, and some others for
           which diagnostics have been added.

           A feature to report any failure to conform to ISO C might be useful in some instances,
           but would require considerable additional work and would be quite different from
           -Wpedantic.  We don't have plans to support such a feature in the near future.

           Where the standard specified with -std represents a GNU extended dialect of C, such as
           gnu90 or gnu99, there is a corresponding base standard, the version of ISO C on which
           the GNU extended dialect is based.  Warnings from -Wpedantic are given where they are
           required by the base standard.  (It does not make sense for such warnings to be given
           only for features not in the specified GNU C dialect, since by definition the GNU
           dialects of C include all features the compiler supports with the given option, and
           there would be nothing to warn about.)

       -pedantic-errors
           Give an error whenever the base standard (see -Wpedantic) requires a diagnostic, in
           some cases where there is undefined behavior at compile-time and in some other cases
           that do not prevent compilation of programs that are valid according to the standard.
           This is not equivalent to -Werror=pedantic, since there are errors enabled by this
           option and not enabled by the latter and vice versa.

       -Wall
           This enables all the warnings about constructions that some users consider
           questionable, and that are easy to avoid (or modify to prevent the warning), even in
           conjunction with macros.  This also enables some language-specific warnings described
           in C++ Dialect Options and Objective-C and Objective-C++ Dialect Options.

           -Wall turns on the following warning flags:

           -Waddress -Warray-bounds=1 (only with -O2) -Wc++11-compat  -Wc++14-compat
           -Wchar-subscripts -Wenum-compare (in C/ObjC; this is on by default in C++)
           -Wimplicit-int (C and Objective-C only) -Wimplicit-function-declaration (C and
           Objective-C only) -Wcomment -Wformat -Wmain (only for C/ObjC and unless
           -ffreestanding) -Wmaybe-uninitialized -Wmissing-braces (only for C/ObjC) -Wnonnull
           -Wopenmp-simd -Wparentheses -Wpointer-sign -Wreorder -Wreturn-type -Wsequence-point
           -Wsign-compare (only in C++) -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch
           -Wtrigraphs -Wuninitialized -Wunknown-pragmas -Wunused-function -Wunused-label
           -Wunused-value -Wunused-variable -Wvolatile-register-var

           Note that some warning flags are not implied by -Wall.  Some of them warn about
           constructions that users generally do not consider questionable, but which
           occasionally you might wish to check for; others warn about constructions that are
           necessary or hard to avoid in some cases, and there is no simple way to modify the
           code to suppress the warning. Some of them are enabled by -Wextra but many of them
           must be enabled individually.

       -Wextra
           This enables some extra warning flags that are not enabled by -Wall. (This option used
           to be called -W.  The older name is still supported, but the newer name is more
           descriptive.)

           -Wclobbered -Wempty-body -Wignored-qualifiers -Wmissing-field-initializers
           -Wmissing-parameter-type (C only) -Wold-style-declaration (C only) -Woverride-init
           -Wsign-compare -Wtype-limits -Wuninitialized -Wunused-parameter (only with -Wunused or
           -Wall) -Wunused-but-set-parameter (only with -Wunused or -Wall)

           The option -Wextra also prints warning messages for the following cases:

           *   A pointer is compared against integer zero with "<", "<=", ">", or ">=".

           *   (C++ only) An enumerator and a non-enumerator both appear in a conditional
               expression.

           *   (C++ only) Ambiguous virtual bases.

           *   (C++ only) Subscripting an array that has been declared "register".

           *   (C++ only) Taking the address of a variable that has been declared "register".

           *   (C++ only) A base class is not initialized in a derived class's copy constructor.

       -Wchar-subscripts
           Warn if an array subscript has type "char".  This is a common cause of error, as
           programmers often forget that this type is signed on some machines.  This warning is
           enabled by -Wall.

       -Wcomment
           Warn whenever a comment-start sequence /* appears in a /* comment, or whenever a
           Backslash-Newline appears in a // comment.  This warning is enabled by -Wall.

       -Wno-coverage-mismatch
           Warn if feedback profiles do not match when using the -fprofile-use option.  If a
           source file is changed between compiling with -fprofile-gen and with -fprofile-use,
           the files with the profile feedback can fail to match the source file and GCC cannot
           use the profile feedback information.  By default, this warning is enabled and is
           treated as an error.  -Wno-coverage-mismatch can be used to disable the warning or
           -Wno-error=coverage-mismatch can be used to disable the error.  Disabling the error
           for this warning can result in poorly optimized code and is useful only in the case of
           very minor changes such as bug fixes to an existing code-base.  Completely disabling
           the warning is not recommended.

       -Wno-cpp
           (C, Objective-C, C++, Objective-C++ and Fortran only)

           Suppress warning messages emitted by "#warning" directives.

       -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
           Give a warning when a value of type "float" is implicitly promoted to "double".  CPUs
           with a 32-bit "single-precision" floating-point unit implement "float" in hardware,
           but emulate "double" in software.  On such a machine, doing computations using
           "double" values is much more expensive because of the overhead required for software
           emulation.

           It is easy to accidentally do computations with "double" because floating-point
           literals are implicitly of type "double".  For example, in:

                   float area(float radius)
                   {
                      return 3.14159 * radius * radius;
                   }

           the compiler performs the entire computation with "double" because the floating-point
           literal is a "double".

       -Wformat
       -Wformat=n
           Check calls to "printf" and "scanf", etc., to make sure that the arguments supplied
           have types appropriate to the format string specified, and that the conversions
           specified in the format string make sense.  This includes standard functions, and
           others specified by format attributes, in the "printf", "scanf", "strftime" and
           "strfmon" (an X/Open extension, not in the C standard) families (or other target-
           specific families).  Which functions are checked without format attributes having been
           specified depends on the standard version selected, and such checks of functions
           without the attribute specified are disabled by -ffreestanding or -fno-builtin.

           The formats are checked against the format features supported by GNU libc version 2.2.
           These include all ISO C90 and C99 features, as well as features from the Single Unix
           Specification and some BSD and GNU extensions.  Other library implementations may not
           support all these features; GCC does not support warning about features that go beyond
           a particular library's limitations.  However, if -Wpedantic is used with -Wformat,
           warnings are given about format features not in the selected standard version (but not
           for "strfmon" formats, since those are not in any version of the C standard).

           -Wformat=1
           -Wformat
               Option -Wformat is equivalent to -Wformat=1, and -Wno-format is equivalent to
               -Wformat=0.  Since -Wformat also checks for null format arguments for several
               functions, -Wformat also implies -Wnonnull.  Some aspects of this level of format
               checking can be disabled by the options: -Wno-format-contains-nul,
               -Wno-format-extra-args, and -Wno-format-zero-length.  -Wformat is enabled by
               -Wall.

           -Wno-format-contains-nul
               If -Wformat is specified, do not warn about format strings that contain NUL bytes.

           -Wno-format-extra-args
               If -Wformat is specified, do not warn about excess arguments to a "printf" or
               "scanf" format function.  The C standard specifies that such arguments are
               ignored.

               Where the unused arguments lie between used arguments that are specified with $
               operand number specifications, normally warnings are still given, since the
               implementation could not know what type to pass to "va_arg" to skip the unused
               arguments.  However, in the case of "scanf" formats, this option suppresses the
               warning if the unused arguments are all pointers, since the Single Unix
               Specification says that such unused arguments are allowed.

           -Wno-format-zero-length
               If -Wformat is specified, do not warn about zero-length formats.  The C standard
               specifies that zero-length formats are allowed.

           -Wformat=2
               Enable -Wformat plus additional format checks.  Currently equivalent to -Wformat
               -Wformat-nonliteral -Wformat-security -Wformat-y2k.

           -Wformat-nonliteral
               If -Wformat is specified, also warn if the format string is not a string literal
               and so cannot be checked, unless the format function takes its format arguments as
               a "va_list".

           -Wformat-security
               If -Wformat is specified, also warn about uses of format functions that represent
               possible security problems.  At present, this warns about calls to "printf" and
               "scanf" functions where the format string is not a string literal and there are no
               format arguments, as in "printf (foo);".  This may be a security hole if the
               format string came from untrusted input and contains %n.  (This is currently a
               subset of what -Wformat-nonliteral warns about, but in future warnings may be
               added to -Wformat-security that are not included in -Wformat-nonliteral.)

           -Wformat-signedness
               If -Wformat is specified, also warn if the format string requires an unsigned
               argument and the argument is signed and vice versa.

           -Wformat-y2k
               If -Wformat is specified, also warn about "strftime" formats that may yield only a
               two-digit year.

       -Wnonnull
           Warn about passing a null pointer for arguments marked as requiring a non-null value
           by the "nonnull" function attribute.

           -Wnonnull is included in -Wall and -Wformat.  It can be disabled with the -Wno-nonnull
           option.

       -Winit-self (C, C++, Objective-C and Objective-C++ only)
           Warn about uninitialized variables that are initialized with themselves.  Note this
           option can only be used with the -Wuninitialized option.

           For example, GCC warns about "i" being uninitialized in the following snippet only
           when -Winit-self has been specified:

                   int f()
                   {
                     int i = i;
                     return i;
                   }

           This warning is enabled by -Wall in C++.

       -Wimplicit-int (C and Objective-C only)
           Warn when a declaration does not specify a type.  This warning is enabled by -Wall.

       -Wimplicit-function-declaration (C and Objective-C only)
           Give a warning whenever a function is used before being declared. In C99 mode
           (-std=c99 or -std=gnu99), this warning is enabled by default and it is made into an
           error by -pedantic-errors. This warning is also enabled by -Wall.

       -Wimplicit (C and Objective-C only)
           Same as -Wimplicit-int and -Wimplicit-function-declaration.  This warning is enabled
           by -Wall.

       -Wignored-qualifiers (C and C++ only)
           Warn if the return type of a function has a type qualifier such as "const".  For ISO C
           such a type qualifier has no effect, since the value returned by a function is not an
           lvalue.  For C++, the warning is only emitted for scalar types or "void".  ISO C
           prohibits qualified "void" return types on function definitions, so such return types
           always receive a warning even without this option.

           This warning is also enabled by -Wextra.

       -Wmain
           Warn if the type of "main" is suspicious.  "main" should be a function with external
           linkage, returning int, taking either zero arguments, two, or three arguments of
           appropriate types.  This warning is enabled by default in C++ and is enabled by either
           -Wall or -Wpedantic.

       -Wmissing-braces
           Warn if an aggregate or union initializer is not fully bracketed.  In the following
           example, the initializer for "a" is not fully bracketed, but that for "b" is fully
           bracketed.  This warning is enabled by -Wall in C.

                   int a[2][2] = { 0, 1, 2, 3 };
                   int b[2][2] = { { 0, 1 }, { 2, 3 } };

           This warning is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
           Warn if a user-supplied include directory does not exist.

       -Wparentheses
           Warn if parentheses are omitted in certain contexts, such as when there is an
           assignment in a context where a truth value is expected, or when operators are nested
           whose precedence people often get confused about.

           Also warn if a comparison like "x<=y<=z" appears; this is equivalent to "(x<=y ? 1 :
           0) <= z", which is a different interpretation from that of ordinary mathematical
           notation.

           Also warn about constructions where there may be confusion to which "if" statement an
           "else" branch belongs.  Here is an example of such a case:

                   {
                     if (a)
                       if (b)
                         foo ();
                     else
                       bar ();
                   }

           In C/C++, every "else" branch belongs to the innermost possible "if" statement, which
           in this example is "if (b)".  This is often not what the programmer expected, as
           illustrated in the above example by indentation the programmer chose.  When there is
           the potential for this confusion, GCC issues a warning when this flag is specified.
           To eliminate the warning, add explicit braces around the innermost "if" statement so
           there is no way the "else" can belong to the enclosing "if".  The resulting code looks
           like this:

                   {
                     if (a)
                       {
                         if (b)
                           foo ();
                         else
                           bar ();
                       }
                   }

           Also warn for dangerous uses of the GNU extension to "?:" with omitted middle operand.
           When the condition in the "?": operator is a boolean expression, the omitted value is
           always 1.  Often programmers expect it to be a value computed inside the conditional
           expression instead.

           This warning is enabled by -Wall.

       -Wsequence-point
           Warn about code that may have undefined semantics because of violations of sequence
           point rules in the C and C++ standards.

           The C and C++ standards define the order in which expressions in a C/C++ program are
           evaluated in terms of sequence points, which represent a partial ordering between the
           execution of parts of the program: those executed before the sequence point, and those
           executed after it.  These occur after the evaluation of a full expression (one which
           is not part of a larger expression), after the evaluation of the first operand of a
           "&&", "||", "? :" or "," (comma) operator, before a function is called (but after the
           evaluation of its arguments and the expression denoting the called function), and in
           certain other places.  Other than as expressed by the sequence point rules, the order
           of evaluation of subexpressions of an expression is not specified.  All these rules
           describe only a partial order rather than a total order, since, for example, if two
           functions are called within one expression with no sequence point between them, the
           order in which the functions are called is not specified.  However, the standards
           committee have ruled that function calls do not overlap.

           It is not specified when between sequence points modifications to the values of
           objects take effect.  Programs whose behavior depends on this have undefined behavior;
           the C and C++ standards specify that "Between the previous and next sequence point an
           object shall have its stored value modified at most once by the evaluation of an
           expression.  Furthermore, the prior value shall be read only to determine the value to
           be stored.".  If a program breaks these rules, the results on any particular
           implementation are entirely unpredictable.

           Examples of code with undefined behavior are "a = a++;", "a[n] = b[n++]" and "a[i++] =
           i;".  Some more complicated cases are not diagnosed by this option, and it may give an
           occasional false positive result, but in general it has been found fairly effective at
           detecting this sort of problem in programs.

           The standard is worded confusingly, therefore there is some debate over the precise
           meaning of the sequence point rules in subtle cases.  Links to discussions of the
           problem, including proposed formal definitions, may be found on the GCC readings page,
           at <http://gcc.gnu.org/readings.html>.

           This warning is enabled by -Wall for C and C++.

       -Wno-return-local-addr
           Do not warn about returning a pointer (or in C++, a reference) to a variable that goes
           out of scope after the function returns.

       -Wreturn-type
           Warn whenever a function is defined with a return type that defaults to "int".  Also
           warn about any "return" statement with no return value in a function whose return type
           is not "void" (falling off the end of the function body is considered returning
           without a value), and about a "return" statement with an expression in a function
           whose return type is "void".

           For C++, a function without return type always produces a diagnostic message, even
           when -Wno-return-type is specified.  The only exceptions are "main" and functions
           defined in system headers.

           This warning is enabled by -Wall.

       -Wshift-count-negative
           Warn if shift count is negative. This warning is enabled by default.

       -Wshift-count-overflow
           Warn if shift count >= width of type. This warning is enabled by default.

       -Wswitch
           Warn whenever a "switch" statement has an index of enumerated type and lacks a "case"
           for one or more of the named codes of that enumeration.  (The presence of a "default"
           label prevents this warning.)  "case" labels outside the enumeration range also
           provoke warnings when this option is used (even if there is a "default" label).  This
           warning is enabled by -Wall.

       -Wswitch-default
           Warn whenever a "switch" statement does not have a "default" case.

       -Wswitch-enum
           Warn whenever a "switch" statement has an index of enumerated type and lacks a "case"
           for one or more of the named codes of that enumeration.  "case" labels outside the
           enumeration range also provoke warnings when this option is used.  The only difference
           between -Wswitch and this option is that this option gives a warning about an omitted
           enumeration code even if there is a "default" label.

       -Wswitch-bool
           Warn whenever a "switch" statement has an index of boolean type.  It is possible to
           suppress this warning by casting the controlling expression to a type other than
           "bool".  For example:

                   switch ((int) (a == 4))
                     {
                     ...
                     }

           This warning is enabled by default for C and C++ programs.

       -Wsync-nand (C and C++ only)
           Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch" built-in functions are
           used.  These functions changed semantics in GCC 4.4.

       -Wtrigraphs
           Warn if any trigraphs are encountered that might change the meaning of the program
           (trigraphs within comments are not warned about).  This warning is enabled by -Wall.

       -Wunused-but-set-parameter
           Warn whenever a function parameter is assigned to, but otherwise unused (aside from
           its declaration).

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused together with -Wextra.

       -Wunused-but-set-variable
           Warn whenever a local variable is assigned to, but otherwise unused (aside from its
           declaration).  This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused, which is enabled by -Wall.

       -Wunused-function
           Warn whenever a static function is declared but not defined or a non-inline static
           function is unused.  This warning is enabled by -Wall.

       -Wunused-label
           Warn whenever a label is declared but not used.  This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only)
           Warn when a typedef locally defined in a function is not used.  This warning is
           enabled by -Wall.

       -Wunused-parameter
           Warn whenever a function parameter is unused aside from its declaration.

           To suppress this warning use the "unused" attribute.

       -Wno-unused-result
           Do not warn if a caller of a function marked with attribute "warn_unused_result" does
           not use its return value. The default is -Wunused-result.

       -Wunused-variable
           Warn whenever a local variable or non-constant static variable is unused aside from
           its declaration.  This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-value
           Warn whenever a statement computes a result that is explicitly not used. To suppress
           this warning cast the unused expression to "void". This includes an expression-
           statement or the left-hand side of a comma expression that contains no side effects.
           For example, an expression such as "x[i,j]" causes a warning, while "x[(void)i,j]"
           does not.

           This warning is enabled by -Wall.

       -Wunused
           All the above -Wunused options combined.

           In order to get a warning about an unused function parameter, you must either specify
           -Wextra -Wunused (note that -Wall implies -Wunused), or separately specify
           -Wunused-parameter.

       -Wuninitialized
           Warn if an automatic variable is used without first being initialized or if a variable
           may be clobbered by a "setjmp" call. In C++, warn if a non-static reference or non-
           static "const" member appears in a class without constructors.

           If you want to warn about code that uses the uninitialized value of the variable in
           its own initializer, use the -Winit-self option.

           These warnings occur for individual uninitialized or clobbered elements of structure,
           union or array variables as well as for variables that are uninitialized or clobbered
           as a whole.  They do not occur for variables or elements declared "volatile".  Because
           these warnings depend on optimization, the exact variables or elements for which there
           are warnings depends on the precise optimization options and version of GCC used.

           Note that there may be no warning about a variable that is used only to compute a
           value that itself is never used, because such computations may be deleted by data flow
           analysis before the warnings are printed.

       -Wmaybe-uninitialized
           For an automatic variable, if there exists a path from the function entry to a use of
           the variable that is initialized, but there exist some other paths for which the
           variable is not initialized, the compiler emits a warning if it cannot prove the
           uninitialized paths are not executed at run time. These warnings are made optional
           because GCC is not smart enough to see all the reasons why the code might be correct
           in spite of appearing to have an error.  Here is one example of how this can happen:

                   {
                     int x;
                     switch (y)
                       {
                       case 1: x = 1;
                         break;
                       case 2: x = 4;
                         break;
                       case 3: x = 5;
                       }
                     foo (x);
                   }

           If the value of "y" is always 1, 2 or 3, then "x" is always initialized, but GCC
           doesn't know this. To suppress the warning, you need to provide a default case with
           assert(0) or similar code.

           This option also warns when a non-volatile automatic variable might be changed by a
           call to "longjmp".  These warnings as well are possible only in optimizing
           compilation.

           The compiler sees only the calls to "setjmp".  It cannot know where "longjmp" will be
           called; in fact, a signal handler could call it at any point in the code.  As a
           result, you may get a warning even when there is in fact no problem because "longjmp"
           cannot in fact be called at the place that would cause a problem.

           Some spurious warnings can be avoided if you declare all the functions you use that
           never return as "noreturn".

           This warning is enabled by -Wall or -Wextra.

       -Wunknown-pragmas
           Warn when a "#pragma" directive is encountered that is not understood by GCC.  If this
           command-line option is used, warnings are even issued for unknown pragmas in system
           header files.  This is not the case if the warnings are only enabled by the -Wall
           command-line option.

       -Wno-pragmas
           Do not warn about misuses of pragmas, such as incorrect parameters, invalid syntax, or
           conflicts between pragmas.  See also -Wunknown-pragmas.

       -Wstrict-aliasing
           This option is only active when -fstrict-aliasing is active.  It warns about code that
           might break the strict aliasing rules that the compiler is using for optimization.
           The warning does not catch all cases, but does attempt to catch the more common
           pitfalls.  It is included in -Wall.  It is equivalent to -Wstrict-aliasing=3

       -Wstrict-aliasing=n
           This option is only active when -fstrict-aliasing is active.  It warns about code that
           might break the strict aliasing rules that the compiler is using for optimization.
           Higher levels correspond to higher accuracy (fewer false positives).  Higher levels
           also correspond to more effort, similar to the way -O works.  -Wstrict-aliasing is
           equivalent to -Wstrict-aliasing=3.

           Level 1: Most aggressive, quick, least accurate.  Possibly useful when higher levels
           do not warn but -fstrict-aliasing still breaks the code, as it has very few false
           negatives.  However, it has many false positives.  Warns for all pointer conversions
           between possibly incompatible types, even if never dereferenced.  Runs in the front
           end only.

           Level 2: Aggressive, quick, not too precise.  May still have many false positives (not
           as many as level 1 though), and few false negatives (but possibly more than level 1).
           Unlike level 1, it only warns when an address is taken.  Warns about incomplete types.
           Runs in the front end only.

           Level 3 (default for -Wstrict-aliasing): Should have very few false positives and few
           false negatives.  Slightly slower than levels 1 or 2 when optimization is enabled.
           Takes care of the common pun+dereference pattern in the front end:
           "*(int*)&some_float".  If optimization is enabled, it also runs in the back end, where
           it deals with multiple statement cases using flow-sensitive points-to information.
           Only warns when the converted pointer is dereferenced.  Does not warn about incomplete
           types.

       -Wstrict-overflow
       -Wstrict-overflow=n
           This option is only active when -fstrict-overflow is active.  It warns about cases
           where the compiler optimizes based on the assumption that signed overflow does not
           occur.  Note that it does not warn about all cases where the code might overflow: it
           only warns about cases where the compiler implements some optimization.  Thus this
           warning depends on the optimization level.

           An optimization that assumes that signed overflow does not occur is perfectly safe if
           the values of the variables involved are such that overflow never does, in fact,
           occur.  Therefore this warning can easily give a false positive: a warning about code
           that is not actually a problem.  To help focus on important issues, several warning
           levels are defined.  No warnings are issued for the use of undefined signed overflow
           when estimating how many iterations a loop requires, in particular when determining
           whether a loop will be executed at all.

           -Wstrict-overflow=1
               Warn about cases that are both questionable and easy to avoid.  For example,  with
               -fstrict-overflow, the compiler simplifies "x + 1 > x" to 1.  This level of
               -Wstrict-overflow is enabled by -Wall; higher levels are not, and must be
               explicitly requested.

           -Wstrict-overflow=2
               Also warn about other cases where a comparison is simplified to a constant.  For
               example: "abs (x) >= 0".  This can only be simplified when -fstrict-overflow is in
               effect, because "abs (INT_MIN)" overflows to "INT_MIN", which is less than zero.
               -Wstrict-overflow (with no level) is the same as -Wstrict-overflow=2.

           -Wstrict-overflow=3
               Also warn about other cases where a comparison is simplified.  For example: "x + 1
               > 1" is simplified to "x > 0".

           -Wstrict-overflow=4
               Also warn about other simplifications not covered by the above cases.  For
               example: "(x * 10) / 5" is simplified to "x * 2".

           -Wstrict-overflow=5
               Also warn about cases where the compiler reduces the magnitude of a constant
               involved in a comparison.  For example: "x + 2 > y" is simplified to "x + 1 >= y".
               This is reported only at the highest warning level because this simplification
               applies to many comparisons, so this warning level gives a very large number of
               false positives.

       -Wsuggest-attribute=[pure|const|noreturn|format]
           Warn for cases where adding an attribute may be beneficial. The attributes currently
           supported are listed below.

           -Wsuggest-attribute=pure
           -Wsuggest-attribute=const
           -Wsuggest-attribute=noreturn
               Warn about functions that might be candidates for attributes "pure", "const" or
               "noreturn".  The compiler only warns for functions visible in other compilation
               units or (in the case of "pure" and "const") if it cannot prove that the function
               returns normally. A function returns normally if it doesn't contain an infinite
               loop or return abnormally by throwing, calling "abort" or trapping.  This analysis
               requires option -fipa-pure-const, which is enabled by default at -O and higher.
               Higher optimization levels improve the accuracy of the analysis.

           -Wsuggest-attribute=format
           -Wmissing-format-attribute
               Warn about function pointers that might be candidates for "format" attributes.
               Note these are only possible candidates, not absolute ones.  GCC guesses that
               function pointers with "format" attributes that are used in assignment,
               initialization, parameter passing or return statements should have a corresponding
               "format" attribute in the resulting type.  I.e. the left-hand side of the
               assignment or initialization, the type of the parameter variable, or the return
               type of the containing function respectively should also have a "format" attribute
               to avoid the warning.

               GCC also warns about function definitions that might be candidates for "format"
               attributes.  Again, these are only possible candidates.  GCC guesses that "format"
               attributes might be appropriate for any function that calls a function like
               "vprintf" or "vscanf", but this might not always be the case, and some functions
               for which "format" attributes are appropriate may not be detected.

       -Wsuggest-final-types
           Warn about types with virtual methods where code quality would be improved if the type
           were declared with the C++11 "final" specifier, or, if possible, declared in an
           anonymous namespace. This allows GCC to more aggressively devirtualize the polymorphic
           calls. This warning is more effective with link time optimization, where the
           information about the class hierarchy graph is more complete.

       -Wsuggest-final-methods
           Warn about virtual methods where code quality would be improved if the method were
           declared with the C++11 "final" specifier, or, if possible, its type were declared in
           an anonymous namespace or with the "final" specifier.  This warning is more effective
           with link time optimization, where the information about the class hierarchy graph is
           more complete. It is recommended to first consider suggestions of
           -Wsuggest-final-types and then rebuild with new annotations.

       -Wsuggest-override
           Warn about overriding virtual functions that are not marked with the override keyword.

       -Warray-bounds
       -Warray-bounds=n
           This option is only active when -ftree-vrp is active (default for -O2 and above). It
           warns about subscripts to arrays that are always out of bounds. This warning is
           enabled by -Wall.

           -Warray-bounds=1
               This is the warning level of -Warray-bounds and is enabled by -Wall; higher levels
               are not, and must be explicitly requested.

           -Warray-bounds=2
               This warning level also warns about out of bounds access for arrays at the end of
               a struct and for arrays accessed through pointers. This warning level may give a
               larger number of false positives and is deactivated by default.

       -Wbool-compare
           Warn about boolean expression compared with an integer value different from
           "true"/"false".  For instance, the following comparison is always false:

                   int n = 5;
                   ...
                   if ((n > 1) == 2) { ... }

           This warning is enabled by -Wall.

       -Wno-discarded-qualifiers (C and Objective-C only)
           Do not warn if type qualifiers on pointers are being discarded.  Typically, the
           compiler warns if a "const char *" variable is passed to a function that takes a "char
           *" parameter.  This option can be used to suppress such a warning.

       -Wno-discarded-array-qualifiers (C and Objective-C only)
           Do not warn if type qualifiers on arrays which are pointer targets are being
           discarded. Typically, the compiler warns if a "const int (*)[]" variable is passed to
           a function that takes a "int (*)[]" parameter.  This option can be used to suppress
           such a warning.

       -Wno-incompatible-pointer-types (C and Objective-C only)
           Do not warn when there is a conversion between pointers that have incompatible types.
           This warning is for cases not covered by -Wno-pointer-sign, which warns for pointer
           argument passing or assignment with different signedness.

       -Wno-int-conversion (C and Objective-C only)
           Do not warn about incompatible integer to pointer and pointer to integer conversions.
           This warning is about implicit conversions; for explicit conversions the warnings
           -Wno-int-to-pointer-cast and -Wno-pointer-to-int-cast may be used.

       -Wno-div-by-zero
           Do not warn about compile-time integer division by zero.  Floating-point division by
           zero is not warned about, as it can be a legitimate way of obtaining infinities and
           NaNs.

       -Wsystem-headers
           Print warning messages for constructs found in system header files.  Warnings from
           system headers are normally suppressed, on the assumption that they usually do not
           indicate real problems and would only make the compiler output harder to read.  Using
           this command-line option tells GCC to emit warnings from system headers as if they
           occurred in user code.  However, note that using -Wall in conjunction with this option
           does not warn about unknown pragmas in system headers---for that, -Wunknown-pragmas
           must also be used.

       -Wtrampolines
           Warn about trampolines generated for pointers to nested functions.  A trampoline is a
           small piece of data or code that is created at run time on the stack when the address
           of a nested function is taken, and is used to call the nested function indirectly.
           For some targets, it is made up of data only and thus requires no special treatment.
           But, for most targets, it is made up of code and thus requires the stack to be made
           executable in order for the program to work properly.

       -Wfloat-equal
           Warn if floating-point values are used in equality comparisons.

           The idea behind this is that sometimes it is convenient (for the programmer) to
           consider floating-point values as approximations to infinitely precise real numbers.
           If you are doing this, then you need to compute (by analyzing the code, or in some
           other way) the maximum or likely maximum error that the computation introduces, and
           allow for it when performing comparisons (and when producing output, but that's a
           different problem).  In particular, instead of testing for equality, you should check
           to see whether the two values have ranges that overlap; and this is done with the
           relational operators, so equality comparisons are probably mistaken.

       -Wtraditional (C and Objective-C only)
           Warn about certain constructs that behave differently in traditional and ISO C.  Also
           warn about ISO C constructs that have no traditional C equivalent, and/or problematic
           constructs that should be avoided.

           *   Macro parameters that appear within string literals in the macro body.  In
               traditional C macro replacement takes place within string literals, but in ISO C
               it does not.

           *   In traditional C, some preprocessor directives did not exist.  Traditional
               preprocessors only considered a line to be a directive if the # appeared in column
               1 on the line.  Therefore -Wtraditional warns about directives that traditional C
               understands but ignores because the # does not appear as the first character on
               the line.  It also suggests you hide directives like "#pragma" not understood by
               traditional C by indenting them.  Some traditional implementations do not
               recognize "#elif", so this option suggests avoiding it altogether.

           *   A function-like macro that appears without arguments.

           *   The unary plus operator.

           *   The U integer constant suffix, or the F or L floating-point constant suffixes.
               (Traditional C does support the L suffix on integer constants.)  Note, these
               suffixes appear in macros defined in the system headers of most modern systems,
               e.g. the _MIN/_MAX macros in "<limits.h>".  Use of these macros in user code might
               normally lead to spurious warnings, however GCC's integrated preprocessor has
               enough context to avoid warning in these cases.

           *   A function declared external in one block and then used after the end of the
               block.

           *   A "switch" statement has an operand of type "long".

           *   A non-"static" function declaration follows a "static" one.  This construct is not
               accepted by some traditional C compilers.

           *   The ISO type of an integer constant has a different width or signedness from its
               traditional type.  This warning is only issued if the base of the constant is ten.
               I.e. hexadecimal or octal values, which typically represent bit patterns, are not
               warned about.

           *   Usage of ISO string concatenation is detected.

           *   Initialization of automatic aggregates.

           *   Identifier conflicts with labels.  Traditional C lacks a separate namespace for
               labels.

           *   Initialization of unions.  If the initializer is zero, the warning is omitted.
               This is done under the assumption that the zero initializer in user code appears
               conditioned on e.g. "__STDC__" to avoid missing initializer warnings and relies on
               default initialization to zero in the traditional C case.

           *   Conversions by prototypes between fixed/floating-point values and vice versa.  The
               absence of these prototypes when compiling with traditional C causes serious
               problems.  This is a subset of the possible conversion warnings; for the full set
               use -Wtraditional-conversion.

           *   Use of ISO C style function definitions.  This warning intentionally is not issued
               for prototype declarations or variadic functions because these ISO C features
               appear in your code when using libiberty's traditional C compatibility macros,
               "PARAMS" and "VPARAMS".  This warning is also bypassed for nested functions
               because that feature is already a GCC extension and thus not relevant to
               traditional C compatibility.

       -Wtraditional-conversion (C and Objective-C only)
           Warn if a prototype causes a type conversion that is different from what would happen
           to the same argument in the absence of a prototype.  This includes conversions of
           fixed point to floating and vice versa, and conversions changing the width or
           signedness of a fixed-point argument except when the same as the default promotion.

       -Wdeclaration-after-statement (C and Objective-C only)
           Warn when a declaration is found after a statement in a block.  This construct, known
           from C++, was introduced with ISO C99 and is by default allowed in GCC.  It is not
           supported by ISO C90.

       -Wundef
           Warn if an undefined identifier is evaluated in an "#if" directive.

       -Wno-endif-labels
           Do not warn whenever an "#else" or an "#endif" are followed by text.

       -Wshadow
           Warn whenever a local variable or type declaration shadows another variable,
           parameter, type, class member (in C++), or instance variable (in Objective-C) or
           whenever a built-in function is shadowed. Note that in C++, the compiler warns if a
           local variable shadows an explicit typedef, but not if it shadows a struct/class/enum.

       -Wno-shadow-ivar (Objective-C only)
           Do not warn whenever a local variable shadows an instance variable in an Objective-C
           method.

       -Wlarger-than=len
           Warn whenever an object of larger than len bytes is defined.

       -Wframe-larger-than=len
           Warn if the size of a function frame is larger than len bytes.  The computation done
           to determine the stack frame size is approximate and not conservative.  The actual
           requirements may be somewhat greater than len even if you do not get a warning.  In
           addition, any space allocated via "alloca", variable-length arrays, or related
           constructs is not included by the compiler when determining whether or not to issue a
           warning.

       -Wno-free-nonheap-object
           Do not warn when attempting to free an object that was not allocated on the heap.

       -Wstack-usage=len
           Warn if the stack usage of a function might be larger than len bytes.  The computation
           done to determine the stack usage is conservative.  Any space allocated via "alloca",
           variable-length arrays, or related constructs is included by the compiler when
           determining whether or not to issue a warning.

           The message is in keeping with the output of -fstack-usage.

           *   If the stack usage is fully static but exceeds the specified amount, it's:

                         warning: stack usage is 1120 bytes

           *   If the stack usage is (partly) dynamic but bounded, it's:

                         warning: stack usage might be 1648 bytes

           *   If the stack usage is (partly) dynamic and not bounded, it's:

                         warning: stack usage might be unbounded

       -Wunsafe-loop-optimizations
           Warn if the loop cannot be optimized because the compiler cannot assume anything on
           the bounds of the loop indices.  With -funsafe-loop-optimizations warn if the compiler
           makes such assumptions.

       -Wno-pedantic-ms-format (MinGW targets only)
           When used in combination with -Wformat and -pedantic without GNU extensions, this
           option disables the warnings about non-ISO "printf" / "scanf" format width specifiers
           "I32", "I64", and "I" used on Windows targets, which depend on the MS runtime.

       -Wpointer-arith
           Warn about anything that depends on the "size of" a function type or of "void".  GNU C
           assigns these types a size of 1, for convenience in calculations with "void *"
           pointers and pointers to functions.  In C++, warn also when an arithmetic operation
           involves "NULL".  This warning is also enabled by -Wpedantic.

       -Wtype-limits
           Warn if a comparison is always true or always false due to the limited range of the
           data type, but do not warn for constant expressions.  For example, warn if an unsigned
           variable is compared against zero with "<" or ">=".  This warning is also enabled by
           -Wextra.

       -Wbad-function-cast (C and Objective-C only)
           Warn when a function call is cast to a non-matching type.  For example, warn if a call
           to a function returning an integer type is cast to a pointer type.

       -Wc90-c99-compat (C and Objective-C only)
           Warn about features not present in ISO C90, but present in ISO C99.  For instance,
           warn about use of variable length arrays, "long long" type, "bool" type, compound
           literals, designated initializers, and so on.  This option is independent of the
           standards mode.  Warnings are disabled in the expression that follows "__extension__".

       -Wc99-c11-compat (C and Objective-C only)
           Warn about features not present in ISO C99, but present in ISO C11.  For instance,
           warn about use of anonymous structures and unions, "_Atomic" type qualifier,
           "_Thread_local" storage-class specifier, "_Alignas" specifier, "Alignof" operator,
           "_Generic" keyword, and so on.  This option is independent of the standards mode.
           Warnings are disabled in the expression that follows "__extension__".

       -Wc++-compat (C and Objective-C only)
           Warn about ISO C constructs that are outside of the common subset of ISO C and ISO
           C++, e.g. request for implicit conversion from "void *" to a pointer to non-"void"
           type.

       -Wc++11-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 1998 and ISO C++ 2011,
           e.g., identifiers in ISO C++ 1998 that are keywords in ISO C++ 2011.  This warning
           turns on -Wnarrowing and is enabled by -Wall.

       -Wc++14-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 2011 and ISO C++ 2014.
           This warning is enabled by -Wall.

       -Wcast-qual
           Warn whenever a pointer is cast so as to remove a type qualifier from the target type.
           For example, warn if a "const char *" is cast to an ordinary "char *".

           Also warn when making a cast that introduces a type qualifier in an unsafe way.  For
           example, casting "char **" to "const char **" is unsafe, as in this example:

                     /* p is char ** value.  */
                     const char **q = (const char **) p;
                     /* Assignment of readonly string to const char * is OK.  */
                     *q = "string";
                     /* Now char** pointer points to read-only memory.  */
                     **p = 'b';

       -Wcast-align
           Warn whenever a pointer is cast such that the required alignment of the target is
           increased.  For example, warn if a "char *" is cast to an "int *" on machines where
           integers can only be accessed at two- or four-byte boundaries.

       -Wwrite-strings
           When compiling C, give string constants the type "const char[length]" so that copying
           the address of one into a non-"const" "char *" pointer produces a warning.  These
           warnings help you find at compile time code that can try to write into a string
           constant, but only if you have been very careful about using "const" in declarations
           and prototypes.  Otherwise, it is just a nuisance. This is why we did not make -Wall
           request these warnings.

           When compiling C++, warn about the deprecated conversion from string literals to "char
           *".  This warning is enabled by default for C++ programs.

       -Wclobbered
           Warn for variables that might be changed by "longjmp" or "vfork".  This warning is
           also enabled by -Wextra.

       -Wconditionally-supported (C++ and Objective-C++ only)
           Warn for conditionally-supported (C++11 [intro.defs]) constructs.

       -Wconversion
           Warn for implicit conversions that may alter a value. This includes conversions
           between real and integer, like "abs (x)" when "x" is "double"; conversions between
           signed and unsigned, like "unsigned ui = -1"; and conversions to smaller types, like
           "sqrtf (M_PI)". Do not warn for explicit casts like "abs ((int) x)" and "ui =
           (unsigned) -1", or if the value is not changed by the conversion like in "abs (2.0)".
           Warnings about conversions between signed and unsigned integers can be disabled by
           using -Wno-sign-conversion.

           For C++, also warn for confusing overload resolution for user-defined conversions; and
           conversions that never use a type conversion operator: conversions to "void", the same
           type, a base class or a reference to them. Warnings about conversions between signed
           and unsigned integers are disabled by default in C++ unless -Wsign-conversion is
           explicitly enabled.

       -Wno-conversion-null (C++ and Objective-C++ only)
           Do not warn for conversions between "NULL" and non-pointer types. -Wconversion-null is
           enabled by default.

       -Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
           Warn when a literal '0' is used as null pointer constant.  This can be useful to
           facilitate the conversion to "nullptr" in C++11.

       -Wdate-time
           Warn when macros "__TIME__", "__DATE__" or "__TIMESTAMP__" are encountered as they
           might prevent bit-wise-identical reproducible compilations.

       -Wdelete-incomplete (C++ and Objective-C++ only)
           Warn when deleting a pointer to incomplete type, which may cause undefined behavior at
           runtime.  This warning is enabled by default.

       -Wuseless-cast (C++ and Objective-C++ only)
           Warn when an expression is casted to its own type.

       -Wempty-body
           Warn if an empty body occurs in an "if", "else" or "do while" statement.  This warning
           is also enabled by -Wextra.

       -Wenum-compare
           Warn about a comparison between values of different enumerated types.  In C++ enumeral
           mismatches in conditional expressions are also diagnosed and the warning is enabled by
           default.  In C this warning is enabled by -Wall.

       -Wjump-misses-init (C, Objective-C only)
           Warn if a "goto" statement or a "switch" statement jumps forward across the
           initialization of a variable, or jumps backward to a label after the variable has been
           initialized.  This only warns about variables that are initialized when they are
           declared.  This warning is only supported for C and Objective-C; in C++ this sort of
           branch is an error in any case.

           -Wjump-misses-init is included in -Wc++-compat.  It can be disabled with the
           -Wno-jump-misses-init option.

       -Wsign-compare
           Warn when a comparison between signed and unsigned values could produce an incorrect
           result when the signed value is converted to unsigned.  This warning is also enabled
           by -Wextra; to get the other warnings of -Wextra without this warning, use -Wextra
           -Wno-sign-compare.

       -Wsign-conversion
           Warn for implicit conversions that may change the sign of an integer value, like
           assigning a signed integer expression to an unsigned integer variable. An explicit
           cast silences the warning. In C, this option is enabled also by -Wconversion.

       -Wfloat-conversion
           Warn for implicit conversions that reduce the precision of a real value.  This
           includes conversions from real to integer, and from higher precision real to lower
           precision real values.  This option is also enabled by -Wconversion.

       -Wsized-deallocation (C++ and Objective-C++ only)
           Warn about a definition of an unsized deallocation function

                   void operator delete (void *) noexcept;
                   void operator delete[] (void *) noexcept;

           without a definition of the corresponding sized deallocation function

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           or vice versa.  Enabled by -Wextra along with -fsized-deallocation.

       -Wsizeof-pointer-memaccess
           Warn for suspicious length parameters to certain string and memory built-in functions
           if the argument uses "sizeof".  This warning warns e.g.  about "memset (ptr, 0, sizeof
           (ptr));" if "ptr" is not an array, but a pointer, and suggests a possible fix, or
           about "memcpy (&foo, ptr, sizeof (&foo));".  This warning is enabled by -Wall.

       -Wsizeof-array-argument
           Warn when the "sizeof" operator is applied to a parameter that is declared as an array
           in a function definition.  This warning is enabled by default for C and C++ programs.

       -Wmemset-transposed-args
           Warn for suspicious calls to the "memset" built-in function, if the second argument is
           not zero and the third argument is zero.  This warns e.g.@ about "memset (buf, sizeof
           buf, 0)" where most probably "memset (buf, 0, sizeof buf)" was meant instead.  The
           diagnostics is only emitted if the third argument is literal zero.  If it is some
           expression that is folded to zero, a cast of zero to some type, etc., it is far less
           likely that the user has mistakenly exchanged the arguments and no warning is emitted.
           This warning is enabled by -Wall.

       -Waddress
           Warn about suspicious uses of memory addresses. These include using the address of a
           function in a conditional expression, such as "void func(void); if (func)", and
           comparisons against the memory address of a string literal, such as "if (x == "abc")".
           Such uses typically indicate a programmer error: the address of a function always
           evaluates to true, so their use in a conditional usually indicate that the programmer
           forgot the parentheses in a function call; and comparisons against string literals
           result in unspecified behavior and are not portable in C, so they usually indicate
           that the programmer intended to use "strcmp".  This warning is enabled by -Wall.

       -Wlogical-op
           Warn about suspicious uses of logical operators in expressions.  This includes using
           logical operators in contexts where a bit-wise operator is likely to be expected.

       -Wlogical-not-parentheses
           Warn about logical not used on the left hand side operand of a comparison.  This
           option does not warn if the RHS operand is of a boolean type.  Its purpose is to
           detect suspicious code like the following:

                   int a;
                   ...
                   if (!a > 1) { ... }

           It is possible to suppress the warning by wrapping the LHS into parentheses:

                   if ((!a) > 1) { ... }

           This warning is enabled by -Wall.

       -Waggregate-return
           Warn if any functions that return structures or unions are defined or called.  (In
           languages where you can return an array, this also elicits a warning.)

       -Wno-aggressive-loop-optimizations
           Warn if in a loop with constant number of iterations the compiler detects undefined
           behavior in some statement during one or more of the iterations.

       -Wno-attributes
           Do not warn if an unexpected "__attribute__" is used, such as unrecognized attributes,
           function attributes applied to variables, etc.  This does not stop errors for
           incorrect use of supported attributes.

       -Wno-builtin-macro-redefined
           Do not warn if certain built-in macros are redefined.  This suppresses warnings for
           redefinition of "__TIMESTAMP__", "__TIME__", "__DATE__", "__FILE__", and
           "__BASE_FILE__".

       -Wstrict-prototypes (C and Objective-C only)
           Warn if a function is declared or defined without specifying the argument types.  (An
           old-style function definition is permitted without a warning if preceded by a
           declaration that specifies the argument types.)

       -Wold-style-declaration (C and Objective-C only)
           Warn for obsolescent usages, according to the C Standard, in a declaration. For
           example, warn if storage-class specifiers like "static" are not the first things in a
           declaration.  This warning is also enabled by -Wextra.

       -Wold-style-definition (C and Objective-C only)
           Warn if an old-style function definition is used.  A warning is given even if there is
           a previous prototype.

       -Wmissing-parameter-type (C and Objective-C only)
           A function parameter is declared without a type specifier in K&R-style functions:

                   void foo(bar) { }

           This warning is also enabled by -Wextra.

       -Wmissing-prototypes (C and Objective-C only)
           Warn if a global function is defined without a previous prototype declaration.  This
           warning is issued even if the definition itself provides a prototype.  Use this option
           to detect global functions that do not have a matching prototype declaration in a
           header file.  This option is not valid for C++ because all function declarations
           provide prototypes and a non-matching declaration declares an overload rather than
           conflict with an earlier declaration.  Use -Wmissing-declarations to detect missing
           declarations in C++.

       -Wmissing-declarations
           Warn if a global function is defined without a previous declaration.  Do so even if
           the definition itself provides a prototype.  Use this option to detect global
           functions that are not declared in header files.  In C, no warnings are issued for
           functions with previous non-prototype declarations; use -Wmissing-prototypes to detect
           missing prototypes.  In C++, no warnings are issued for function templates, or for
           inline functions, or for functions in anonymous namespaces.

       -Wmissing-field-initializers
           Warn if a structure's initializer has some fields missing.  For example, the following
           code causes such a warning, because "x.h" is implicitly zero:

                   struct s { int f, g, h; };
                   struct s x = { 3, 4 };

           This option does not warn about designated initializers, so the following modification
           does not trigger a warning:

                   struct s { int f, g, h; };
                   struct s x = { .f = 3, .g = 4 };

           In C++ this option does not warn either about the empty { } initializer, for example:

                   struct s { int f, g, h; };
                   s x = { };

           This warning is included in -Wextra.  To get other -Wextra warnings without this one,
           use -Wextra -Wno-missing-field-initializers.

       -Wno-multichar
           Do not warn if a multicharacter constant ('FOOF') is used.  Usually they indicate a
           typo in the user's code, as they have implementation-defined values, and should not be
           used in portable code.

       -Wnormalized[=<none|id|nfc|nfkc>]
           In ISO C and ISO C++, two identifiers are different if they are different sequences of
           characters.  However, sometimes when characters outside the basic ASCII character set
           are used, you can have two different character sequences that look the same.  To avoid
           confusion, the ISO 10646 standard sets out some normalization rules which when applied
           ensure that two sequences that look the same are turned into the same sequence.  GCC
           can warn you if you are using identifiers that have not been normalized; this option
           controls that warning.

           There are four levels of warning supported by GCC.  The default is -Wnormalized=nfc,
           which warns about any identifier that is not in the ISO 10646 "C" normalized form,
           NFC.  NFC is the recommended form for most uses.  It is equivalent to -Wnormalized.

           Unfortunately, there are some characters allowed in identifiers by ISO C and ISO C++
           that, when turned into NFC, are not allowed in identifiers.  That is, there's no way
           to use these symbols in portable ISO C or C++ and have all your identifiers in NFC.
           -Wnormalized=id suppresses the warning for these characters.  It is hoped that future
           versions of the standards involved will correct this, which is why this option is not
           the default.

           You can switch the warning off for all characters by writing -Wnormalized=none or
           -Wno-normalized.  You should only do this if you are using some other normalization
           scheme (like "D"), because otherwise you can easily create bugs that are literally
           impossible to see.

           Some characters in ISO 10646 have distinct meanings but look identical in some fonts
           or display methodologies, especially once formatting has been applied.  For instance
           "\u207F", "SUPERSCRIPT LATIN SMALL LETTER N", displays just like a regular "n" that
           has been placed in a superscript.  ISO 10646 defines the NFKC normalization scheme to
           convert all these into a standard form as well, and GCC warns if your code is not in
           NFKC if you use -Wnormalized=nfkc.  This warning is comparable to warning about every
           identifier that contains the letter O because it might be confused with the digit 0,
           and so is not the default, but may be useful as a local coding convention if the
           programming environment cannot be fixed to display these characters distinctly.

       -Wno-deprecated
           Do not warn about usage of deprecated features.

       -Wno-deprecated-declarations
           Do not warn about uses of functions, variables, and types marked as deprecated by
           using the "deprecated" attribute.

       -Wno-overflow
           Do not warn about compile-time overflow in constant expressions.

       -Wno-odr
           Warn about One Definition Rule violations during link-time optimization.  Requires
           -flto-odr-type-merging to be enabled.  Enabled by default.

       -Wopenmp-simd
           Warn if the vectorizer cost model overrides the OpenMP or the Cilk Plus simd directive
           set by user.  The -fsimd-cost-model=unlimited option can be used to relax the cost
           model.

       -Woverride-init (C and Objective-C only)
           Warn if an initialized field without side effects is overridden when using designated
           initializers.

           This warning is included in -Wextra.  To get other -Wextra warnings without this one,
           use -Wextra -Wno-override-init.

       -Wpacked
           Warn if a structure is given the packed attribute, but the packed attribute has no
           effect on the layout or size of the structure.  Such structures may be mis-aligned for
           little benefit.  For instance, in this code, the variable "f.x" in "struct bar" is
           misaligned even though "struct bar" does not itself have the packed attribute:

                   struct foo {
                     int x;
                     char a, b, c, d;
                   } __attribute__((packed));
                   struct bar {
                     char z;
                     struct foo f;
                   };

       -Wpacked-bitfield-compat
           The 4.1, 4.2 and 4.3 series of GCC ignore the "packed" attribute on bit-fields of type
           "char".  This has been fixed in GCC 4.4 but the change can lead to differences in the
           structure layout.  GCC informs you when the offset of such a field has changed in GCC
           4.4.  For example there is no longer a 4-bit padding between field "a" and "b" in this
           structure:

                   struct foo
                   {
                     char a:4;
                     char b:8;
                   } __attribute__ ((packed));

           This warning is enabled by default.  Use -Wno-packed-bitfield-compat to disable this
           warning.

       -Wpadded
           Warn if padding is included in a structure, either to align an element of the
           structure or to align the whole structure.  Sometimes when this happens it is possible
           to rearrange the fields of the structure to reduce the padding and so make the
           structure smaller.

       -Wredundant-decls
           Warn if anything is declared more than once in the same scope, even in cases where
           multiple declaration is valid and changes nothing.

       -Wnested-externs (C and Objective-C only)
           Warn if an "extern" declaration is encountered within a function.

       -Wno-inherited-variadic-ctor
           Suppress warnings about use of C++11 inheriting constructors when the base class
           inherited from has a C variadic constructor; the warning is on by default because the
           ellipsis is not inherited.

       -Winline
           Warn if a function that is declared as inline cannot be inlined.  Even with this
           option, the compiler does not warn about failures to inline functions declared in
           system headers.

           The compiler uses a variety of heuristics to determine whether or not to inline a
           function.  For example, the compiler takes into account the size of the function being
           inlined and the amount of inlining that has already been done in the current function.
           Therefore, seemingly insignificant changes in the source program can cause the
           warnings produced by -Winline to appear or disappear.

       -Wno-invalid-offsetof (C++ and Objective-C++ only)
           Suppress warnings from applying the "offsetof" macro to a non-POD type.  According to
           the 2014 ISO C++ standard, applying "offsetof" to a non-standard-layout type is
           undefined.  In existing C++ implementations, however, "offsetof" typically gives
           meaningful results.  This flag is for users who are aware that they are writing
           nonportable code and who have deliberately chosen to ignore the warning about it.

           The restrictions on "offsetof" may be relaxed in a future version of the C++ standard.

       -Wno-int-to-pointer-cast
           Suppress warnings from casts to pointer type of an integer of a different size. In
           C++, casting to a pointer type of smaller size is an error. Wint-to-pointer-cast is
           enabled by default.

       -Wno-pointer-to-int-cast (C and Objective-C only)
           Suppress warnings from casts from a pointer to an integer type of a different size.

       -Winvalid-pch
           Warn if a precompiled header is found in the search path but can't be used.

       -Wlong-long
           Warn if "long long" type is used.  This is enabled by either -Wpedantic or
           -Wtraditional in ISO C90 and C++98 modes.  To inhibit the warning messages, use
           -Wno-long-long.

       -Wvariadic-macros
           Warn if variadic macros are used in ISO C90 mode, or if the GNU alternate syntax is
           used in ISO C99 mode.  This is enabled by either -Wpedantic or -Wtraditional.  To
           inhibit the warning messages, use -Wno-variadic-macros.

       -Wvarargs
           Warn upon questionable usage of the macros used to handle variable arguments like
           "va_start".  This is default.  To inhibit the warning messages, use -Wno-varargs.

       -Wvector-operation-performance
           Warn if vector operation is not implemented via SIMD capabilities of the architecture.
           Mainly useful for the performance tuning.  Vector operation can be implemented
           "piecewise", which means that the scalar operation is performed on every vector
           element; "in parallel", which means that the vector operation is implemented using
           scalars of wider type, which normally is more performance efficient; and "as a single
           scalar", which means that vector fits into a scalar type.

       -Wno-virtual-move-assign
           Suppress warnings about inheriting from a virtual base with a non-trivial C++11 move
           assignment operator.  This is dangerous because if the virtual base is reachable along
           more than one path, it is moved multiple times, which can mean both objects end up in
           the moved-from state.  If the move assignment operator is written to avoid moving from
           a moved-from object, this warning can be disabled.

       -Wvla
           Warn if variable length array is used in the code.  -Wno-vla prevents the -Wpedantic
           warning of the variable length array.

       -Wvolatile-register-var
           Warn if a register variable is declared volatile.  The volatile modifier does not
           inhibit all optimizations that may eliminate reads and/or writes to register
           variables.  This warning is enabled by -Wall.

       -Wdisabled-optimization
           Warn if a requested optimization pass is disabled.  This warning does not generally
           indicate that there is anything wrong with your code; it merely indicates that GCC's
           optimizers are unable to handle the code effectively.  Often, the problem is that your
           code is too big or too complex; GCC refuses to optimize programs when the optimization
           itself is likely to take inordinate amounts of time.

       -Wpointer-sign (C and Objective-C only)
           Warn for pointer argument passing or assignment with different signedness.  This
           option is only supported for C and Objective-C.  It is implied by -Wall and by
           -Wpedantic, which can be disabled with -Wno-pointer-sign.

       -Wstack-protector
           This option is only active when -fstack-protector is active.  It warns about functions
           that are not protected against stack smashing.

       -Woverlength-strings
           Warn about string constants that are longer than the "minimum maximum" length
           specified in the C standard.  Modern compilers generally allow string constants that
           are much longer than the standard's minimum limit, but very portable programs should
           avoid using longer strings.

           The limit applies after string constant concatenation, and does not count the trailing
           NUL.  In C90, the limit was 509 characters; in C99, it was raised to 4095.  C++98 does
           not specify a normative minimum maximum, so we do not diagnose overlength strings in
           C++.

           This option is implied by -Wpedantic, and can be disabled with
           -Wno-overlength-strings.

       -Wunsuffixed-float-constants (C and Objective-C only)
           Issue a warning for any floating constant that does not have a suffix.  When used
           together with -Wsystem-headers it warns about such constants in system header files.
           This can be useful when preparing code to use with the "FLOAT_CONST_DECIMAL64" pragma
           from the decimal floating-point extension to C99.

       -Wno-designated-init (C and Objective-C only)
           Suppress warnings when a positional initializer is used to initialize a structure that
           has been marked with the "designated_init" attribute.

   Options for Debugging Your Program or GCC
       GCC has various special options that are used for debugging either your program or GCC:

       -g  Produce debugging information in the operating system's native format (stabs, COFF,
           XCOFF, or DWARF 2).  GDB can work with this debugging information.

           On most systems that use stabs format, -g enables use of extra debugging information
           that only GDB can use; this extra information makes debugging work better in GDB but
           probably makes other debuggers crash or refuse to read the program.  If you want to
           control for certain whether to generate the extra information, use -gstabs+, -gstabs,
           -gxcoff+, -gxcoff, or -gvms (see below).

           GCC allows you to use -g with -O.  The shortcuts taken by optimized code may
           occasionally produce surprising results: some variables you declared may not exist at
           all; flow of control may briefly move where you did not expect it; some statements may
           not be executed because they compute constant results or their values are already at
           hand; some statements may execute in different places because they have been moved out
           of loops.

           Nevertheless it proves possible to debug optimized output.  This makes it reasonable
           to use the optimizer for programs that might have bugs.

           The following options are useful when GCC is generated with the capability for more
           than one debugging format.

       -gsplit-dwarf
           Separate as much dwarf debugging information as possible into a separate output file
           with the extension .dwo.  This option allows the build system to avoid linking files
           with debug information.  To be useful, this option requires a debugger capable of
           reading .dwo files.

       -ggdb
           Produce debugging information for use by GDB.  This means to use the most expressive
           format available (DWARF 2, stabs, or the native format if neither of those are
           supported), including GDB extensions if at all possible.

       -gpubnames
           Generate dwarf .debug_pubnames and .debug_pubtypes sections.

       -ggnu-pubnames
           Generate .debug_pubnames and .debug_pubtypes sections in a format suitable for
           conversion into a GDB index.  This option is only useful with a linker that can
           produce GDB index version 7.

       -gstabs
           Produce debugging information in stabs format (if that is supported), without GDB
           extensions.  This is the format used by DBX on most BSD systems.  On MIPS, Alpha and
           System V Release 4 systems this option produces stabs debugging output that is not
           understood by DBX or SDB.  On System V Release 4 systems this option requires the GNU
           assembler.

       -feliminate-unused-debug-symbols
           Produce debugging information in stabs format (if that is supported), for only symbols
           that are actually used.

       -femit-class-debug-always
           Instead of emitting debugging information for a C++ class in only one object file,
           emit it in all object files using the class.  This option should be used only with
           debuggers that are unable to handle the way GCC normally emits debugging information
           for classes because using this option increases the size of debugging information by
           as much as a factor of two.

       -fdebug-types-section
           When using DWARF Version 4 or higher, type DIEs can be put into their own
           ".debug_types" section instead of making them part of the ".debug_info" section.  It
           is more efficient to put them in a separate comdat sections since the linker can then
           remove duplicates.  But not all DWARF consumers support ".debug_types" sections yet
           and on some objects ".debug_types" produces larger instead of smaller debugging
           information.

       -gstabs+
           Produce debugging information in stabs format (if that is supported), using GNU
           extensions understood only by the GNU debugger (GDB).  The use of these extensions is
           likely to make other debuggers crash or refuse to read the program.

       -gcoff
           Produce debugging information in COFF format (if that is supported).  This is the
           format used by SDB on most System V systems prior to System V Release 4.

       -gxcoff
           Produce debugging information in XCOFF format (if that is supported).  This is the
           format used by the DBX debugger on IBM RS/6000 systems.

       -gxcoff+
           Produce debugging information in XCOFF format (if that is supported), using GNU
           extensions understood only by the GNU debugger (GDB).  The use of these extensions is
           likely to make other debuggers crash or refuse to read the program, and may cause
           assemblers other than the GNU assembler (GAS) to fail with an error.

       -gdwarf-version
           Produce debugging information in DWARF format (if that is supported).  The value of
           version may be either 2, 3, 4 or 5; the default version for most targets is 4.  DWARF
           Version 5 is only experimental.

           Note that with DWARF Version 2, some ports require and always use some non-conflicting
           DWARF 3 extensions in the unwind tables.

           Version 4 may require GDB 7.0 and -fvar-tracking-assignments for maximum benefit.

       -grecord-gcc-switches
           This switch causes the command-line options used to invoke the compiler that may
           affect code generation to be appended to the DW_AT_producer attribute in DWARF
           debugging information.  The options are concatenated with spaces separating them from
           each other and from the compiler version.  See also -frecord-gcc-switches for another
           way of storing compiler options into the object file.  This is the default.

       -gno-record-gcc-switches
           Disallow appending command-line options to the DW_AT_producer attribute in DWARF
           debugging information.

       -gstrict-dwarf
           Disallow using extensions of later DWARF standard version than selected with
           -gdwarf-version.  On most targets using non-conflicting DWARF extensions from later
           standard versions is allowed.

       -gno-strict-dwarf
           Allow using extensions of later DWARF standard version than selected with
           -gdwarf-version.

       -gz[=type]
           Produce compressed debug sections in DWARF format, if that is supported.  If type is
           not given, the default type depends on the capabilities of the assembler and linker
           used.  type may be one of none (don't compress debug sections), zlib (use zlib
           compression in ELF gABI format), or zlib-gnu (use zlib compression in traditional GNU
           format).  If the linker doesn't support writing compressed debug sections, the option
           is rejected.  Otherwise, if the assembler does not support them, -gz is silently
           ignored when producing object files.

       -gvms
           Produce debugging information in Alpha/VMS debug format (if that is supported).  This
           is the format used by DEBUG on Alpha/VMS systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gcofflevel
       -gxcofflevel
       -gvmslevel
           Request debugging information and also use level to specify how much information.  The
           default level is 2.

           Level 0 produces no debug information at all.  Thus, -g0 negates -g.

           Level 1 produces minimal information, enough for making backtraces in parts of the
           program that you don't plan to debug.  This includes descriptions of functions and
           external variables, and line number tables, but no information about local variables.

           Level 3 includes extra information, such as all the macro definitions present in the
           program.  Some debuggers support macro expansion when you use -g3.

           -gdwarf-2 does not accept a concatenated debug level, because GCC used to support an
           option -gdwarf that meant to generate debug information in version 1 of the DWARF
           format (which is very different from version 2), and it would have been too confusing.
           That debug format is long obsolete, but the option cannot be changed now.  Instead use
           an additional -glevel option to change the debug level for DWARF.

       -gtoggle
           Turn off generation of debug info, if leaving out this option generates it, or turn it
           on at level 2 otherwise.  The position of this argument in the command line does not
           matter; it takes effect after all other options are processed, and it does so only
           once, no matter how many times it is given.  This is mainly intended to be used with
           -fcompare-debug.

       -fsanitize=address
           Enable AddressSanitizer, a fast memory error detector.  Memory access instructions are
           instrumented to detect out-of-bounds and use-after-free bugs.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizer> for more details.  The
           run-time behavior can be influenced using the ASAN_OPTIONS environment variable.  When
           set to "help=1", the available options are shown at startup of the instrumended
           program.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags> for a
           list of supported options.

       -fsanitize=kernel-address
           Enable AddressSanitizer for Linux kernel.  See <https://github.com/google/kasan/wiki>
           for more details.

       -fsanitize=thread
           Enable ThreadSanitizer, a fast data race detector.  Memory access instructions are
           instrumented to detect data race bugs.  See
           <https://github.com/google/sanitizers/wiki#threadsanitizer> for more details. The run-
           time behavior can be influenced using the TSAN_OPTIONS environment variable; see
           <https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags> for a list of
           supported options.

       -fsanitize=leak
           Enable LeakSanitizer, a memory leak detector.  This option only matters for linking of
           executables and if neither -fsanitize=address nor -fsanitize=thread is used.  In that
           case the executable is linked against a library that overrides "malloc" and other
           allocator functions.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer> for more
           details.  The run-time behavior can be influenced using the LSAN_OPTIONS environment
           variable.

       -fsanitize=undefined
           Enable UndefinedBehaviorSanitizer, a fast undefined behavior detector.  Various
           computations are instrumented to detect undefined behavior at runtime.  Current
           suboptions are:

           -fsanitize=shift
               This option enables checking that the result of a shift operation is not
               undefined.  Note that what exactly is considered undefined differs slightly
               between C and C++, as well as between ISO C90 and C99, etc.

           -fsanitize=integer-divide-by-zero
               Detect integer division by zero as well as "INT_MIN / -1" division.

           -fsanitize=unreachable
               With this option, the compiler turns the "__builtin_unreachable" call into a
               diagnostics message call instead.  When reaching the "__builtin_unreachable" call,
               the behavior is undefined.

           -fsanitize=vla-bound
               This option instructs the compiler to check that the size of a variable length
               array is positive.

           -fsanitize=null
               This option enables pointer checking.  Particularly, the application built with
               this option turned on will issue an error message when it tries to dereference a
               NULL pointer, or if a reference (possibly an rvalue reference) is bound to a NULL
               pointer, or if a method is invoked on an object pointed by a NULL pointer.

           -fsanitize=return
               This option enables return statement checking.  Programs built with this option
               turned on will issue an error message when the end of a non-void function is
               reached without actually returning a value.  This option works in C++ only.

           -fsanitize=signed-integer-overflow
               This option enables signed integer overflow checking.  We check that the result of
               "+", "*", and both unary and binary "-" does not overflow in the signed
               arithmetics.  Note, integer promotion rules must be taken into account.  That is,
               the following is not an overflow:

                       signed char a = SCHAR_MAX;
                       a++;

           -fsanitize=bounds
               This option enables instrumentation of array bounds.  Various out of bounds
               accesses are detected.  Flexible array members, flexible array member-like arrays,
               and initializers of variables with static storage are not instrumented.

           -fsanitize=alignment
               This option enables checking of alignment of pointers when they are dereferenced,
               or when a reference is bound to insufficiently aligned target, or when a method or
               constructor is invoked on insufficiently aligned object.

           -fsanitize=object-size
               This option enables instrumentation of memory references using the
               "__builtin_object_size" function.  Various out of bounds pointer accesses are
               detected.

           -fsanitize=float-divide-by-zero
               Detect floating-point division by zero.  Unlike other similar options,
               -fsanitize=float-divide-by-zero is not enabled by -fsanitize=undefined, since
               floating-point division by zero can be a legitimate way of obtaining infinities
               and NaNs.

           -fsanitize=float-cast-overflow
               This option enables floating-point type to integer conversion checking.  We check
               that the result of the conversion does not overflow.  Unlike other similar
               options, -fsanitize=float-cast-overflow is not enabled by -fsanitize=undefined.
               This option does not work well with "FE_INVALID" exceptions enabled.

           -fsanitize=nonnull-attribute
               This option enables instrumentation of calls, checking whether null values are not
               passed to arguments marked as requiring a non-null value by the "nonnull" function
               attribute.

           -fsanitize=returns-nonnull-attribute
               This option enables instrumentation of return statements in functions marked with
               "returns_nonnull" function attribute, to detect returning of null values from such
               functions.

           -fsanitize=bool
               This option enables instrumentation of loads from bool.  If a value other than 0/1
               is loaded, a run-time error is issued.

           -fsanitize=enum
               This option enables instrumentation of loads from an enum type.  If a value
               outside the range of values for the enum type is loaded, a run-time error is
               issued.

           -fsanitize=vptr
               This option enables instrumentation of C++ member function calls, member accesses
               and some conversions between pointers to base and derived classes, to verify the
               referenced object has the correct dynamic type.

           While -ftrapv causes traps for signed overflows to be emitted, -fsanitize=undefined
           gives a diagnostic message.  This currently works only for the C family of languages.

       -fno-sanitize=all
           This option disables all previously enabled sanitizers.  -fsanitize=all is not
           allowed, as some sanitizers cannot be used together.

       -fasan-shadow-offset=number
           This option forces GCC to use custom shadow offset in AddressSanitizer checks.  It is
           useful for experimenting with different shadow memory layouts in Kernel
           AddressSanitizer.

       -fsanitize-recover[=opts]
           -fsanitize-recover= controls error recovery mode for sanitizers mentioned in comma-
           separated list of opts.  Enabling this option for a sanitizer component causes it to
           attempt to continue running the program as if no error happened.  This means multiple
           runtime errors can be reported in a single program run, and the exit code of the
           program may indicate success even when errors have been reported.  The
           -fno-sanitize-recover= option can be used to alter this behavior: only the first
           detected error is reported and program then exits with a non-zero exit code.

           Currently this feature only works for -fsanitize=undefined (and its suboptions except
           for -fsanitize=unreachable and -fsanitize=return), -fsanitize=float-cast-overflow,
           -fsanitize=float-divide-by-zero and -fsanitize=kernel-address.  For these sanitizers
           error recovery is turned on by default.  -fsanitize-recover=all and
           -fno-sanitize-recover=all is also accepted, the former enables recovery for all
           sanitizers that support it, the latter disables recovery for all sanitizers that
           support it.

           Syntax without explicit opts parameter is deprecated.  It is equivalent to

                   -fsanitize-recover=undefined,float-cast-overflow,float-divide-by-zero

           Similarly -fno-sanitize-recover is equivalent to

                   -fno-sanitize-recover=undefined,float-cast-overflow,float-divide-by-zero

       -fsanitize-undefined-trap-on-error
           The -fsanitize-undefined-trap-on-error option instructs the compiler to report
           undefined behavior using "__builtin_trap" rather than a "libubsan" library routine.
           The advantage of this is that the "libubsan" library is not needed and is not linked
           in, so this is usable even in freestanding environments.

       -fcheck-pointer-bounds
           Enable Pointer Bounds Checker instrumentation.  Each memory reference is instrumented
           with checks of the pointer used for memory access against bounds associated with that
           pointer.

           Currently there is only an implementation for Intel MPX available, thus x86 target and
           -mmpx are required to enable this feature.  MPX-based instrumentation requires a
           runtime library to enable MPX in hardware and handle bounds violation signals.  By
           default when -fcheck-pointer-bounds and -mmpx options are used to link a program, the
           GCC driver links against the libmpx runtime library and libmpxwrappers library.  It
           also passes '-z bndplt' to a linker in case it supports this option (which is checked
           on libmpx configuration).  Note that old versions of linker may ignore option.  Gold
           linker doesn't support '-z bndplt' option.  With no '-z bndplt' support in linker all
           calls to dynamic libraries lose passed bounds reducing overall protection level.  It's
           highly recommended to use linker with '-z bndplt' support.  In case such linker is not
           available it is adviced to always use -static-libmpxwrappers for better protection
           level or use -static to completely avoid external calls to dynamic libraries.  MPX-
           based instrumentation may be used for debugging and also may be included in production
           code to increase program security.  Depending on usage, you may have different
           requirements for the runtime library.  The current version of the MPX runtime library
           is more oriented for use as a debugging tool.  MPX runtime library usage implies
           -lpthread.  See also -static-libmpx.  The runtime library  behavior can be influenced
           using various CHKP_RT_* environment variables.  See
           <https://gcc.gnu.org/wiki/Intel%20MPX%20support%20in%20the%20GCC%20compiler> for more
           details.

           Generated instrumentation may be controlled by various -fchkp-* options and by the
           "bnd_variable_size" structure field attribute and "bnd_legacy", and "bnd_instrument"
           function attributes.  GCC also provides a number of built-in functions for controlling
           the Pointer Bounds Checker.

       -fchkp-check-incomplete-type
           Generate pointer bounds checks for variables with incomplete type.  Enabled by
           default.

       -fchkp-narrow-bounds
           Controls bounds used by Pointer Bounds Checker for pointers to object fields.  If
           narrowing is enabled then field bounds are used.  Otherwise object bounds are used.
           See also -fchkp-narrow-to-innermost-array and -fchkp-first-field-has-own-bounds.
           Enabled by default.

       -fchkp-first-field-has-own-bounds
           Forces Pointer Bounds Checker to use narrowed bounds for the address of the first
           field in the structure.  By default a pointer to the first field has the same bounds
           as a pointer to the whole structure.

       -fchkp-narrow-to-innermost-array
           Forces Pointer Bounds Checker to use bounds of the innermost arrays in case of nested
           static array access.  By default this option is disabled and bounds of the outermost
           array are used.

       -fchkp-optimize
           Enables Pointer Bounds Checker optimizations.  Enabled by default at optimization
           levels -O, -O2, -O3.

       -fchkp-use-fast-string-functions
           Enables use of *_nobnd versions of string functions (not copying bounds) by Pointer
           Bounds Checker.  Disabled by default.

       -fchkp-use-nochk-string-functions
           Enables use of *_nochk versions of string functions (not checking bounds) by Pointer
           Bounds Checker.  Disabled by default.

       -fchkp-use-static-bounds
           Allow Pointer Bounds Checker to generate static bounds holding bounds of static
           variables.  Enabled by default.

       -fchkp-use-static-const-bounds
           Use statically-initialized bounds for constant bounds instead of generating them each
           time they are required.  By default enabled when -fchkp-use-static-bounds is enabled.

       -fchkp-treat-zero-dynamic-size-as-infinite
           With this option, objects with incomplete type whose dynamically-obtained size is zero
           are treated as having infinite size instead by Pointer Bounds Checker.  This option
           may be helpful if a program is linked with a library missing size information for some
           symbols.  Disabled by default.

       -fchkp-check-read
           Instructs Pointer Bounds Checker to generate checks for all read accesses to memory.
           Enabled by default.

       -fchkp-check-write
           Instructs Pointer Bounds Checker to generate checks for all write accesses to memory.
           Enabled by default.

       -fchkp-store-bounds
           Instructs Pointer Bounds Checker to generate bounds stores for pointer writes.
           Enabled by default.

       -fchkp-instrument-calls
           Instructs Pointer Bounds Checker to pass pointer bounds to calls.  Enabled by default.

       -fchkp-instrument-marked-only
           Instructs Pointer Bounds Checker to instrument only functions marked with the
           "bnd_instrument" attribute.  Disabled by default.

       -fchkp-use-wrappers
           Allows Pointer Bounds Checker to replace calls to built-in functions with calls to
           wrapper functions.  When -fchkp-use-wrappers is used to link a program, the GCC driver
           automatically links against libmpxwrappers.  See also -static-libmpxwrappers.  Enabled
           by default.

       -fdump-final-insns[=file]
           Dump the final internal representation (RTL) to file.  If the optional argument is
           omitted (or if file is "."), the name of the dump file is determined by appending
           ".gkd" to the compilation output file name.

       -fcompare-debug[=opts]
           If no error occurs during compilation, run the compiler a second time, adding opts and
           -fcompare-debug-second to the arguments passed to the second compilation.  Dump the
           final internal representation in both compilations, and print an error if they differ.

           If the equal sign is omitted, the default -gtoggle is used.

           The environment variable GCC_COMPARE_DEBUG, if defined, non-empty and nonzero,
           implicitly enables -fcompare-debug.  If GCC_COMPARE_DEBUG is defined to a string
           starting with a dash, then it is used for opts, otherwise the default -gtoggle is
           used.

           -fcompare-debug=, with the equal sign but without opts, is equivalent to
           -fno-compare-debug, which disables the dumping of the final representation and the
           second compilation, preventing even GCC_COMPARE_DEBUG from taking effect.

           To verify full coverage during -fcompare-debug testing, set GCC_COMPARE_DEBUG to say
           -fcompare-debug-not-overridden, which GCC rejects as an invalid option in any actual
           compilation (rather than preprocessing, assembly or linking).  To get just a warning,
           setting GCC_COMPARE_DEBUG to -w%n-fcompare-debug not overridden will do.

       -fcompare-debug-second
           This option is implicitly passed to the compiler for the second compilation requested
           by -fcompare-debug, along with options to silence warnings, and omitting other options
           that would cause side-effect compiler outputs to files or to the standard output.
           Dump files and preserved temporary files are renamed so as to contain the ".gk"
           additional extension during the second compilation, to avoid overwriting those
           generated by the first.

           When this option is passed to the compiler driver, it causes the first compilation to
           be skipped, which makes it useful for little other than debugging the compiler proper.

       -feliminate-dwarf2-dups
           Compress DWARF 2 debugging information by eliminating duplicated information about
           each symbol.  This option only makes sense when generating DWARF 2 debugging
           information with -gdwarf-2.

       -femit-struct-debug-baseonly
           Emit debug information for struct-like types only when the base name of the
           compilation source file matches the base name of file in which the struct is defined.

           This option substantially reduces the size of debugging information, but at
           significant potential loss in type information to the debugger.  See
           -femit-struct-debug-reduced for a less aggressive option.  See
           -femit-struct-debug-detailed for more detailed control.

           This option works only with DWARF 2.

       -femit-struct-debug-reduced
           Emit debug information for struct-like types only when the base name of the
           compilation source file matches the base name of file in which the type is defined,
           unless the struct is a template or defined in a system header.

           This option significantly reduces the size of debugging information, with some
           potential loss in type information to the debugger.  See -femit-struct-debug-baseonly
           for a more aggressive option.  See -femit-struct-debug-detailed for more detailed
           control.

           This option works only with DWARF 2.

       -femit-struct-debug-detailed[=spec-list]
           Specify the struct-like types for which the compiler generates debug information.  The
           intent is to reduce duplicate struct debug information between different object files
           within the same program.

           This option is a detailed version of -femit-struct-debug-reduced and
           -femit-struct-debug-baseonly, which serves for most needs.

           A specification has the syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

           The optional first word limits the specification to structs that are used directly
           (dir:) or used indirectly (ind:).  A struct type is used directly when it is the type
           of a variable, member.  Indirect uses arise through pointers to structs.  That is,
           when use of an incomplete struct is valid, the use is indirect.  An example is struct
           one direct; struct two * indirect;.

           The optional second word limits the specification to ordinary structs (ord:) or
           generic structs (gen:).  Generic structs are a bit complicated to explain.  For C++,
           these are non-explicit specializations of template classes, or non-template classes
           within the above.  Other programming languages have generics, but
           -femit-struct-debug-detailed does not yet implement them.

           The third word specifies the source files for those structs for which the compiler
           should emit debug information.  The values none and any have the normal meaning.  The
           value base means that the base of name of the file in which the type declaration
           appears must match the base of the name of the main compilation file.  In practice,
           this means that when compiling foo.c, debug information is generated for types
           declared in that file and foo.h, but not other header files.  The value sys means
           those types satisfying base or declared in system or compiler headers.

           You may need to experiment to determine the best settings for your application.

           The default is -femit-struct-debug-detailed=all.

           This option works only with DWARF 2.

       -fno-merge-debug-strings
           Direct the linker to not merge together strings in the debugging information that are
           identical in different object files.  Merging is not supported by all assemblers or
           linkers.  Merging decreases the size of the debug information in the output file at
           the cost of increasing link processing time.  Merging is enabled by default.

       -fdebug-prefix-map=old=new
           When compiling files in directory old, record debugging information describing them as
           in new instead.

       -fno-dwarf2-cfi-asm
           Emit DWARF 2 unwind info as compiler generated ".eh_frame" section instead of using
           GAS ".cfi_*" directives.

       -p  Generate extra code to write profile information suitable for the analysis program
           prof.  You must use this option when compiling the source files you want data about,
           and you must also use it when linking.

       -pg Generate extra code to write profile information suitable for the analysis program
           gprof.  You must use this option when compiling the source files you want data about,
           and you must also use it when linking.

       -Q  Makes the compiler print out each function name as it is compiled, and print some
           statistics about each pass when it finishes.

       -ftime-report
           Makes the compiler print some statistics about the time consumed by each pass when it
           finishes.

       -fmem-report
           Makes the compiler print some statistics about permanent memory allocation when it
           finishes.

       -fmem-report-wpa
           Makes the compiler print some statistics about permanent memory allocation for the WPA
           phase only.

       -fpre-ipa-mem-report
       -fpost-ipa-mem-report
           Makes the compiler print some statistics about permanent memory allocation before or
           after interprocedural optimization.

       -fprofile-report
           Makes the compiler print some statistics about consistency of the (estimated) profile
           and effect of individual passes.

       -fstack-usage
           Makes the compiler output stack usage information for the program, on a per-function
           basis.  The filename for the dump is made by appending .su to the auxname.  auxname is
           generated from the name of the output file, if explicitly specified and it is not an
           executable, otherwise it is the basename of the source file.  An entry is made up of
           three fields:

           *   The name of the function.

           *   A number of bytes.

           *   One or more qualifiers: "static", "dynamic", "bounded".

           The qualifier "static" means that the function manipulates the stack statically: a
           fixed number of bytes are allocated for the frame on function entry and released on
           function exit; no stack adjustments are otherwise made in the function.  The second
           field is this fixed number of bytes.

           The qualifier "dynamic" means that the function manipulates the stack dynamically: in
           addition to the static allocation described above, stack adjustments are made in the
           body of the function, for example to push/pop arguments around function calls.  If the
           qualifier "bounded" is also present, the amount of these adjustments is bounded at
           compile time and the second field is an upper bound of the total amount of stack used
           by the function.  If it is not present, the amount of these adjustments is not bounded
           at compile time and the second field only represents the bounded part.

       -fprofile-arcs
           Add code so that program flow arcs are instrumented.  During execution the program
           records how many times each branch and call is executed and how many times it is taken
           or returns.  When the compiled program exits it saves this data to a file called
           auxname.gcda for each source file.  The data may be used for profile-directed
           optimizations (-fbranch-probabilities), or for test coverage analysis
           (-ftest-coverage).  Each object file's auxname is generated from the name of the
           output file, if explicitly specified and it is not the final executable, otherwise it
           is the basename of the source file.  In both cases any suffix is removed (e.g.
           foo.gcda for input file dir/foo.c, or dir/foo.gcda for output file specified as -o
           dir/foo.o).

       --coverage
           This option is used to compile and link code instrumented for coverage analysis.  The
           option is a synonym for -fprofile-arcs -ftest-coverage (when compiling) and -lgcov
           (when linking).  See the documentation for those options for more details.

           *   Compile the source files with -fprofile-arcs plus optimization and code generation
               options.  For test coverage analysis, use the additional -ftest-coverage option.
               You do not need to profile every source file in a program.

           *   Link your object files with -lgcov or -fprofile-arcs (the latter implies the
               former).

           *   Run the program on a representative workload to generate the arc profile
               information.  This may be repeated any number of times.  You can run concurrent
               instances of your program, and provided that the file system supports locking, the
               data files will be correctly updated.  Also "fork" calls are detected and
               correctly handled (double counting will not happen).

           *   For profile-directed optimizations, compile the source files again with the same
               optimization and code generation options plus -fbranch-probabilities.

           *   For test coverage analysis, use gcov to produce human readable information from
               the .gcno and .gcda files.  Refer to the gcov documentation for further
               information.

           With -fprofile-arcs, for each function of your program GCC creates a program flow
           graph, then finds a spanning tree for the graph.  Only arcs that are not on the
           spanning tree have to be instrumented: the compiler adds code to count the number of
           times that these arcs are executed.  When an arc is the only exit or only entrance to
           a block, the instrumentation code can be added to the block; otherwise, a new basic
           block must be created to hold the instrumentation code.

       -ftest-coverage
           Produce a notes file that the gcov code-coverage utility can use to show program
           coverage.  Each source file's note file is called auxname.gcno.  Refer to the
           -fprofile-arcs option above for a description of auxname and instructions on how to
           generate test coverage data.  Coverage data matches the source files more closely if
           you do not optimize.

       -fdbg-cnt-list
           Print the name and the counter upper bound for all debug counters.

       -fdbg-cnt=counter-value-list
           Set the internal debug counter upper bound.  counter-value-list is a comma-separated
           list of name:value pairs which sets the upper bound of each debug counter name to
           value.  All debug counters have the initial upper bound of "UINT_MAX"; thus "dbg_cnt"
           returns true always unless the upper bound is set by this option.  For example, with
           -fdbg-cnt=dce:10,tail_call:0, "dbg_cnt(dce)" returns true only for first 10
           invocations.

       -fenable-kind-pass
       -fdisable-kind-pass=range-list
           This is a set of options that are used to explicitly disable/enable optimization
           passes.  These options are intended for use for debugging GCC.  Compiler users should
           use regular options for enabling/disabling passes instead.

           -fdisable-ipa-pass
               Disable IPA pass pass. pass is the pass name.  If the same pass is statically
               invoked in the compiler multiple times, the pass name should be appended with a
               sequential number starting from 1.

           -fdisable-rtl-pass
           -fdisable-rtl-pass=range-list
               Disable RTL pass pass.  pass is the pass name.  If the same pass is statically
               invoked in the compiler multiple times, the pass name should be appended with a
               sequential number starting from 1.  range-list is a comma-separated list of
               function ranges or assembler names.  Each range is a number pair separated by a
               colon.  The range is inclusive in both ends.  If the range is trivial, the number
               pair can be simplified as a single number.  If the function's call graph node's
               uid falls within one of the specified ranges, the pass is disabled for that
               function.  The uid is shown in the function header of a dump file, and the pass
               names can be dumped by using option -fdump-passes.

           -fdisable-tree-pass
           -fdisable-tree-pass=range-list
               Disable tree pass pass.  See -fdisable-rtl for the description of option
               arguments.

           -fenable-ipa-pass
               Enable IPA pass pass.  pass is the pass name.  If the same pass is statically
               invoked in the compiler multiple times, the pass name should be appended with a
               sequential number starting from 1.

           -fenable-rtl-pass
           -fenable-rtl-pass=range-list
               Enable RTL pass pass.  See -fdisable-rtl for option argument description and
               examples.

           -fenable-tree-pass
           -fenable-tree-pass=range-list
               Enable tree pass pass.  See -fdisable-rtl for the description of option arguments.

           Here are some examples showing uses of these options.

                   # disable ccp1 for all functions
                      -fdisable-tree-ccp1
                   # disable complete unroll for function whose cgraph node uid is 1
                      -fenable-tree-cunroll=1
                   # disable gcse2 for functions at the following ranges [1,1],
                   # [300,400], and [400,1000]
                   # disable gcse2 for functions foo and foo2
                      -fdisable-rtl-gcse2=foo,foo2
                   # disable early inlining
                      -fdisable-tree-einline
                   # disable ipa inlining
                      -fdisable-ipa-inline
                   # enable tree full unroll
                      -fenable-tree-unroll

       -dletters
       -fdump-rtl-pass
       -fdump-rtl-pass=filename
           Says to make debugging dumps during compilation at times specified by letters.  This
           is used for debugging the RTL-based passes of the compiler.  The file names for most
           of the dumps are made by appending a pass number and a word to the dumpname, and the
           files are created in the directory of the output file. In case of =filename option,
           the dump is output on the given file instead of the pass numbered dump files. Note
           that the pass number is computed statically as passes get registered into the pass
           manager.  Thus the numbering is not related to the dynamic order of execution of
           passes.  In particular, a pass installed by a plugin could have a number over 200 even
           if it executed quite early.  dumpname is generated from the name of the output file,
           if explicitly specified and it is not an executable, otherwise it is the basename of
           the source file. These switches may have different effects when -E is used for
           preprocessing.

           Debug dumps can be enabled with a -fdump-rtl switch or some -d option letters.  Here
           are the possible letters for use in pass and letters, and their meanings:

           -fdump-rtl-alignments
               Dump after branch alignments have been computed.

           -fdump-rtl-asmcons
               Dump after fixing rtl statements that have unsatisfied in/out constraints.

           -fdump-rtl-auto_inc_dec
               Dump after auto-inc-dec discovery.  This pass is only run on architectures that
               have auto inc or auto dec instructions.

           -fdump-rtl-barriers
               Dump after cleaning up the barrier instructions.

           -fdump-rtl-bbpart
               Dump after partitioning hot and cold basic blocks.

           -fdump-rtl-bbro
               Dump after block reordering.

           -fdump-rtl-btl1
           -fdump-rtl-btl2
               -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping after the two branch target
               load optimization passes.

           -fdump-rtl-bypass
               Dump after jump bypassing and control flow optimizations.

           -fdump-rtl-combine
               Dump after the RTL instruction combination pass.

           -fdump-rtl-compgotos
               Dump after duplicating the computed gotos.

           -fdump-rtl-ce1
           -fdump-rtl-ce2
           -fdump-rtl-ce3
               -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable dumping after the three
               if conversion passes.

           -fdump-rtl-cprop_hardreg
               Dump after hard register copy propagation.

           -fdump-rtl-csa
               Dump after combining stack adjustments.

           -fdump-rtl-cse1
           -fdump-rtl-cse2
               -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the two common
               subexpression elimination passes.

           -fdump-rtl-dce
               Dump after the standalone dead code elimination passes.

           -fdump-rtl-dbr
               Dump after delayed branch scheduling.

           -fdump-rtl-dce1
           -fdump-rtl-dce2
               -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping after the two dead store
               elimination passes.

           -fdump-rtl-eh
               Dump after finalization of EH handling code.

           -fdump-rtl-eh_ranges
               Dump after conversion of EH handling range regions.

           -fdump-rtl-expand
               Dump after RTL generation.

           -fdump-rtl-fwprop1
           -fdump-rtl-fwprop2
               -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable dumping after the two forward
               propagation passes.

           -fdump-rtl-gcse1
           -fdump-rtl-gcse2
               -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping after global common
               subexpression elimination.

           -fdump-rtl-init-regs
               Dump after the initialization of the registers.

           -fdump-rtl-initvals
               Dump after the computation of the initial value sets.

           -fdump-rtl-into_cfglayout
               Dump after converting to cfglayout mode.

           -fdump-rtl-ira
               Dump after iterated register allocation.

           -fdump-rtl-jump
               Dump after the second jump optimization.

           -fdump-rtl-loop2
               -fdump-rtl-loop2 enables dumping after the rtl loop optimization passes.

           -fdump-rtl-mach
               Dump after performing the machine dependent reorganization pass, if that pass
               exists.

           -fdump-rtl-mode_sw
               Dump after removing redundant mode switches.

           -fdump-rtl-rnreg
               Dump after register renumbering.

           -fdump-rtl-outof_cfglayout
               Dump after converting from cfglayout mode.

           -fdump-rtl-peephole2
               Dump after the peephole pass.

           -fdump-rtl-postreload
               Dump after post-reload optimizations.

           -fdump-rtl-pro_and_epilogue
               Dump after generating the function prologues and epilogues.

           -fdump-rtl-sched1
           -fdump-rtl-sched2
               -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after the basic block
               scheduling passes.

           -fdump-rtl-ree
               Dump after sign/zero extension elimination.

           -fdump-rtl-seqabstr
               Dump after common sequence discovery.

           -fdump-rtl-shorten
               Dump after shortening branches.

           -fdump-rtl-sibling
               Dump after sibling call optimizations.

           -fdump-rtl-split1
           -fdump-rtl-split2
           -fdump-rtl-split3
           -fdump-rtl-split4
           -fdump-rtl-split5
               These options enable dumping after five rounds of instruction splitting.

           -fdump-rtl-sms
               Dump after modulo scheduling.  This pass is only run on some architectures.

           -fdump-rtl-stack
               Dump after conversion from GCC's "flat register file" registers to the x87's
               stack-like registers.  This pass is only run on x86 variants.

           -fdump-rtl-subreg1
           -fdump-rtl-subreg2
               -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable dumping after the two subreg
               expansion passes.

           -fdump-rtl-unshare
               Dump after all rtl has been unshared.

           -fdump-rtl-vartrack
               Dump after variable tracking.

           -fdump-rtl-vregs
               Dump after converting virtual registers to hard registers.

           -fdump-rtl-web
               Dump after live range splitting.

           -fdump-rtl-regclass
           -fdump-rtl-subregs_of_mode_init
           -fdump-rtl-subregs_of_mode_finish
           -fdump-rtl-dfinit
           -fdump-rtl-dfinish
               These dumps are defined but always produce empty files.

           -da
           -fdump-rtl-all
               Produce all the dumps listed above.

           -dA Annotate the assembler output with miscellaneous debugging information.

           -dD Dump all macro definitions, at the end of preprocessing, in addition to normal
               output.

           -dH Produce a core dump whenever an error occurs.

           -dp Annotate the assembler output with a comment indicating which pattern and
               alternative is used.  The length of each instruction is also printed.

           -dP Dump the RTL in the assembler output as a comment before each instruction.  Also
               turns on -dp annotation.

           -dx Just generate RTL for a function instead of compiling it.  Usually used with
               -fdump-rtl-expand.

       -fdump-noaddr
           When doing debugging dumps, suppress address output.  This makes it more feasible to
           use diff on debugging dumps for compiler invocations with different compiler binaries
           and/or different text / bss / data / heap / stack / dso start locations.

       -freport-bug
           Collect and dump debug information into temporary file if ICE in C/C++ compiler
           occured.

       -fdump-unnumbered
           When doing debugging dumps, suppress instruction numbers and address output.  This
           makes it more feasible to use diff on debugging dumps for compiler invocations with
           different options, in particular with and without -g.

       -fdump-unnumbered-links
           When doing debugging dumps (see -d option above), suppress instruction numbers for the
           links to the previous and next instructions in a sequence.

       -fdump-translation-unit (C++ only)
       -fdump-translation-unit-options (C++ only)
           Dump a representation of the tree structure for the entire translation unit to a file.
           The file name is made by appending .tu to the source file name, and the file is
           created in the same directory as the output file.  If the -options form is used,
           options controls the details of the dump as described for the -fdump-tree options.

       -fdump-class-hierarchy (C++ only)
       -fdump-class-hierarchy-options (C++ only)
           Dump a representation of each class's hierarchy and virtual function table layout to a
           file.  The file name is made by appending .class to the source file name, and the file
           is created in the same directory as the output file.  If the -options form is used,
           options controls the details of the dump as described for the -fdump-tree options.

       -fdump-ipa-switch
           Control the dumping at various stages of inter-procedural analysis language tree to a
           file.  The file name is generated by appending a switch specific suffix to the source
           file name, and the file is created in the same directory as the output file.  The
           following dumps are possible:

           all Enables all inter-procedural analysis dumps.

           cgraph
               Dumps information about call-graph optimization, unused function removal, and
               inlining decisions.

           inline
               Dump after function inlining.

       -fdump-passes
           Dump the list of optimization passes that are turned on and off by the current
           command-line options.

       -fdump-statistics-option
           Enable and control dumping of pass statistics in a separate file.  The file name is
           generated by appending a suffix ending in .statistics to the source file name, and the
           file is created in the same directory as the output file.  If the -option form is
           used, -stats causes counters to be summed over the whole compilation unit while
           -details dumps every event as the passes generate them.  The default with no option is
           to sum counters for each function compiled.

       -fdump-tree-switch
       -fdump-tree-switch-options
       -fdump-tree-switch-options=filename
           Control the dumping at various stages of processing the intermediate language tree to
           a file.  The file name is generated by appending a switch-specific suffix to the
           source file name, and the file is created in the same directory as the output file. In
           case of =filename option, the dump is output on the given file instead of the auto
           named dump files.  If the -options form is used, options is a list of - separated
           options which control the details of the dump.  Not all options are applicable to all
           dumps; those that are not meaningful are ignored.  The following options are available

           address
               Print the address of each node.  Usually this is not meaningful as it changes
               according to the environment and source file.  Its primary use is for tying up a
               dump file with a debug environment.

           asmname
               If "DECL_ASSEMBLER_NAME" has been set for a given decl, use that in the dump
               instead of "DECL_NAME".  Its primary use is ease of use working backward from
               mangled names in the assembly file.

           slim
               When dumping front-end intermediate representations, inhibit dumping of members of
               a scope or body of a function merely because that scope has been reached.  Only
               dump such items when they are directly reachable by some other path.

               When dumping pretty-printed trees, this option inhibits dumping the bodies of
               control structures.

               When dumping RTL, print the RTL in slim (condensed) form instead of the default
               LISP-like representation.

           raw Print a raw representation of the tree.  By default, trees are pretty-printed into
               a C-like representation.

           details
               Enable more detailed dumps (not honored by every dump option). Also include
               information from the optimization passes.

           stats
               Enable dumping various statistics about the pass (not honored by every dump
               option).

           blocks
               Enable showing basic block boundaries (disabled in raw dumps).

           graph
               For each of the other indicated dump files (-fdump-rtl-pass), dump a
               representation of the control flow graph suitable for viewing with GraphViz to
               file.passid.pass.dot.  Each function in the file is pretty-printed as a subgraph,
               so that GraphViz can render them all in a single plot.

               This option currently only works for RTL dumps, and the RTL is always dumped in
               slim form.

           vops
               Enable showing virtual operands for every statement.

           lineno
               Enable showing line numbers for statements.

           uid Enable showing the unique ID ("DECL_UID") for each variable.

           verbose
               Enable showing the tree dump for each statement.

           eh  Enable showing the EH region number holding each statement.

           scev
               Enable showing scalar evolution analysis details.

           optimized
               Enable showing optimization information (only available in certain passes).

           missed
               Enable showing missed optimization information (only available in certain passes).

           note
               Enable other detailed optimization information (only available in certain passes).

           =filename
               Instead of an auto named dump file, output into the given file name. The file
               names stdout and stderr are treated specially and are considered already open
               standard streams. For example,

                       gcc -O2 -ftree-vectorize -fdump-tree-vect-blocks=foo.dump
                            -fdump-tree-pre=stderr file.c

               outputs vectorizer dump into foo.dump, while the PRE dump is output on to stderr.
               If two conflicting dump filenames are given for the same pass, then the latter
               option overrides the earlier one.

           all Turn on all options, except raw, slim, verbose and lineno.

           optall
               Turn on all optimization options, i.e., optimized, missed, and note.

           The following tree dumps are possible:

           original
               Dump before any tree based optimization, to file.original.

           optimized
               Dump after all tree based optimization, to file.optimized.

           gimple
               Dump each function before and after the gimplification pass to a file.  The file
               name is made by appending .gimple to the source file name.

           cfg Dump the control flow graph of each function to a file.  The file name is made by
               appending .cfg to the source file name.

           ch  Dump each function after copying loop headers.  The file name is made by appending
               .ch to the source file name.

           ssa Dump SSA related information to a file.  The file name is made by appending .ssa
               to the source file name.

           alias
               Dump aliasing information for each function.  The file name is made by appending
               .alias to the source file name.

           ccp Dump each function after CCP.  The file name is made by appending .ccp to the
               source file name.

           storeccp
               Dump each function after STORE-CCP.  The file name is made by appending .storeccp
               to the source file name.

           pre Dump trees after partial redundancy elimination.  The file name is made by
               appending .pre to the source file name.

           fre Dump trees after full redundancy elimination.  The file name is made by appending
               .fre to the source file name.

           copyprop
               Dump trees after copy propagation.  The file name is made by appending .copyprop
               to the source file name.

           store_copyprop
               Dump trees after store copy-propagation.  The file name is made by appending
               .store_copyprop to the source file name.

           dce Dump each function after dead code elimination.  The file name is made by
               appending .dce to the source file name.

           sra Dump each function after performing scalar replacement of aggregates.  The file
               name is made by appending .sra to the source file name.

           sink
               Dump each function after performing code sinking.  The file name is made by
               appending .sink to the source file name.

           dom Dump each function after applying dominator tree optimizations.  The file name is
               made by appending .dom to the source file name.

           dse Dump each function after applying dead store elimination.  The file name is made
               by appending .dse to the source file name.

           phiopt
               Dump each function after optimizing PHI nodes into straightline code.  The file
               name is made by appending .phiopt to the source file name.

           forwprop
               Dump each function after forward propagating single use variables.  The file name
               is made by appending .forwprop to the source file name.

           copyrename
               Dump each function after applying the copy rename optimization.  The file name is
               made by appending .copyrename to the source file name.

           nrv Dump each function after applying the named return value optimization on generic
               trees.  The file name is made by appending .nrv to the source file name.

           vect
               Dump each function after applying vectorization of loops.  The file name is made
               by appending .vect to the source file name.

           slp Dump each function after applying vectorization of basic blocks.  The file name is
               made by appending .slp to the source file name.

           vrp Dump each function after Value Range Propagation (VRP).  The file name is made by
               appending .vrp to the source file name.

           all Enable all the available tree dumps with the flags provided in this option.

       -fopt-info
       -fopt-info-options
       -fopt-info-options=filename
           Controls optimization dumps from various optimization passes. If the -options form is
           used, options is a list of - separated option keywords to select the dump details and
           optimizations.

           The options can be divided into two groups: options describing the verbosity of the
           dump, and options describing which optimizations should be included. The options from
           both the groups can be freely mixed as they are non-overlapping. However, in case of
           any conflicts, the later options override the earlier options on the command line.

           The following options control the dump verbosity:

           optimized
               Print information when an optimization is successfully applied. It is up to a pass
               to decide which information is relevant. For example, the vectorizer passes print
               the source location of loops which are successfully vectorized.

           missed
               Print information about missed optimizations. Individual passes control which
               information to include in the output.

           note
               Print verbose information about optimizations, such as certain transformations,
               more detailed messages about decisions etc.

           all Print detailed optimization information. This includes optimized, missed, and
               note.

           One or more of the following option keywords can be used to describe a group of
           optimizations:

           ipa Enable dumps from all interprocedural optimizations.

           loop
               Enable dumps from all loop optimizations.

           inline
               Enable dumps from all inlining optimizations.

           vec Enable dumps from all vectorization optimizations.

           optall
               Enable dumps from all optimizations. This is a superset of the optimization groups
               listed above.

           If options is omitted, it defaults to optimized-optall, which means to dump all info
           about successful optimizations from all the passes.

           If the filename is provided, then the dumps from all the applicable optimizations are
           concatenated into the filename.  Otherwise the dump is output onto stderr. Though
           multiple -fopt-info options are accepted, only one of them can include a filename. If
           other filenames are provided then all but the first such option are ignored.

           Note that the output filename is overwritten in case of multiple translation units. If
           a combined output from multiple translation units is desired, stderr should be used
           instead.

           In the following example, the optimization info is output to stderr:

                   gcc -O3 -fopt-info

           This example:

                   gcc -O3 -fopt-info-missed=missed.all

           outputs missed optimization report from all the passes into missed.all, and this one:

                   gcc -O2 -ftree-vectorize -fopt-info-vec-missed

           prints information about missed optimization opportunities from vectorization passes
           on stderr.  Note that -fopt-info-vec-missed is equivalent to -fopt-info-missed-vec.

           As another example,

                   gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

           outputs information about missed optimizations as well as optimized locations from all
           the inlining passes into inline.txt.

           Finally, consider:

                   gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

           Here the two output filenames vec.miss and loop.opt are in conflict since only one
           output file is allowed. In this case, only the first option takes effect and the
           subsequent options are ignored. Thus only vec.miss is produced which contains dumps
           from the vectorizer about missed opportunities.

       -frandom-seed=number
           This option provides a seed that GCC uses in place of random numbers in generating
           certain symbol names that have to be different in every compiled file.  It is also
           used to place unique stamps in coverage data files and the object files that produce
           them.  You can use the -frandom-seed option to produce reproducibly identical object
           files.

           The number should be different for every file you compile.

       -fsched-verbose=n
           On targets that use instruction scheduling, this option controls the amount of
           debugging output the scheduler prints.  This information is written to standard error,
           unless -fdump-rtl-sched1 or -fdump-rtl-sched2 is specified, in which case it is output
           to the usual dump listing file, .sched1 or .sched2 respectively.  However for n
           greater than nine, the output is always printed to standard error.

           For n greater than zero, -fsched-verbose outputs the same information as
           -fdump-rtl-sched1 and -fdump-rtl-sched2.  For n greater than one, it also output basic
           block probabilities, detailed ready list information and unit/insn info.  For n
           greater than two, it includes RTL at abort point, control-flow and regions info.  And
           for n over four, -fsched-verbose also includes dependence info.

       -save-temps
       -save-temps=cwd
           Store the usual "temporary" intermediate files permanently; place them in the current
           directory and name them based on the source file.  Thus, compiling foo.c with -c
           -save-temps produces files foo.i and foo.s, as well as foo.o.  This creates a
           preprocessed foo.i output file even though the compiler now normally uses an
           integrated preprocessor.

           When used in combination with the -x command-line option, -save-temps is sensible
           enough to avoid over writing an input source file with the same extension as an
           intermediate file.  The corresponding intermediate file may be obtained by renaming
           the source file before using -save-temps.

           If you invoke GCC in parallel, compiling several different source files that share a
           common base name in different subdirectories or the same source file compiled for
           multiple output destinations, it is likely that the different parallel compilers will
           interfere with each other, and overwrite the temporary files.  For instance:

                   gcc -save-temps -o outdir1/foo.o indir1/foo.c&
                   gcc -save-temps -o outdir2/foo.o indir2/foo.c&

           may result in foo.i and foo.o being written to simultaneously by both compilers.

       -save-temps=obj
           Store the usual "temporary" intermediate files permanently.  If the -o option is used,
           the temporary files are based on the object file.  If the -o option is not used, the
           -save-temps=obj switch behaves like -save-temps.

           For example:

                   gcc -save-temps=obj -c foo.c
                   gcc -save-temps=obj -c bar.c -o dir/xbar.o
                   gcc -save-temps=obj foobar.c -o dir2/yfoobar

           creates foo.i, foo.s, dir/xbar.i, dir/xbar.s, dir2/yfoobar.i, dir2/yfoobar.s, and
           dir2/yfoobar.o.

       -time[=file]
           Report the CPU time taken by each subprocess in the compilation sequence.  For C
           source files, this is the compiler proper and assembler (plus the linker if linking is
           done).

           Without the specification of an output file, the output looks like this:

                   # cc1 0.12 0.01
                   # as 0.00 0.01

           The first number on each line is the "user time", that is time spent executing the
           program itself.  The second number is "system time", time spent executing operating
           system routines on behalf of the program.  Both numbers are in seconds.

           With the specification of an output file, the output is appended to the named file,
           and it looks like this:

                   0.12 0.01 cc1 <options>
                   0.00 0.01 as <options>

           The "user time" and the "system time" are moved before the program name, and the
           options passed to the program are displayed, so that one can later tell what file was
           being compiled, and with which options.

       -fvar-tracking
           Run variable tracking pass.  It computes where variables are stored at each position
           in code.  Better debugging information is then generated (if the debugging information
           format supports this information).

           It is enabled by default when compiling with optimization (-Os, -O, -O2, ...),
           debugging information (-g) and the debug info format supports it.

       -fvar-tracking-assignments
           Annotate assignments to user variables early in the compilation and attempt to carry
           the annotations over throughout the compilation all the way to the end, in an attempt
           to improve debug information while optimizing.  Use of -gdwarf-4 is recommended along
           with it.

           It can be enabled even if var-tracking is disabled, in which case annotations are
           created and maintained, but discarded at the end.  By default, this flag is enabled
           together with -fvar-tracking, except when selective scheduling is enabled.

       -fvar-tracking-assignments-toggle
           Toggle -fvar-tracking-assignments, in the same way that -gtoggle toggles -g.

       -print-file-name=library
           Print the full absolute name of the library file library that would be used when
           linking---and don't do anything else.  With this option, GCC does not compile or link
           anything; it just prints the file name.

       -print-multi-directory
           Print the directory name corresponding to the multilib selected by any other switches
           present in the command line.  This directory is supposed to exist in GCC_EXEC_PREFIX.

       -print-multi-lib
           Print the mapping from multilib directory names to compiler switches that enable them.
           The directory name is separated from the switches by ;, and each switch starts with an
           @ instead of the -, without spaces between multiple switches.  This is supposed to
           ease shell processing.

       -print-multi-os-directory
           Print the path to OS libraries for the selected multilib, relative to some lib
           subdirectory.  If OS libraries are present in the lib subdirectory and no multilibs
           are used, this is usually just ., if OS libraries are present in libsuffix sibling
           directories this prints e.g. ../lib64, ../lib or ../lib32, or if OS libraries are
           present in lib/subdir subdirectories it prints e.g. amd64, sparcv9 or ev6.

       -print-multiarch
           Print the path to OS libraries for the selected multiarch, relative to some lib
           subdirectory.

       -print-prog-name=program
           Like -print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
           Same as -print-file-name=libgcc.a.

           This is useful when you use -nostdlib or -nodefaultlibs but you do want to link with
           libgcc.a.  You can do:

                   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
           Print the name of the configured installation directory and a list of program and
           library directories gcc searches---and don't do anything else.

           This is useful when gcc prints the error message installation problem, cannot exec
           cpp0: No such file or directory.  To resolve this you either need to put cpp0 and the
           other compiler components where gcc expects to find them, or you can set the
           environment variable GCC_EXEC_PREFIX to the directory where you installed them.  Don't
           forget the trailing /.

       -print-sysroot
           Print the target sysroot directory that is used during compilation.  This is the
           target sysroot specified either at configure time or using the --sysroot option,
           possibly with an extra suffix that depends on compilation options.  If no target
           sysroot is specified, the option prints nothing.

       -print-sysroot-headers-suffix
           Print the suffix added to the target sysroot when searching for headers, or give an
           error if the compiler is not configured with such a suffix---and don't do anything
           else.

       -dumpmachine
           Print the compiler's target machine (for example, i686-pc-linux-gnu)---and don't do
           anything else.

       -dumpversion
           Print the compiler version (for example, 3.0)---and don't do anything else.

       -dumpspecs
           Print the compiler's built-in specs---and don't do anything else.  (This is used when
           GCC itself is being built.)

       -fno-eliminate-unused-debug-types
           Normally, when producing DWARF 2 output, GCC avoids producing debug symbol output for
           types that are nowhere used in the source file being compiled.  Sometimes it is useful
           to have GCC emit debugging information for all types declared in a compilation unit,
           regardless of whether or not they are actually used in that compilation unit, for
           example if, in the debugger, you want to cast a value to a type that is not actually
           used in your program (but is declared).  More often, however, this results in a
           significant amount of wasted space.

   Options That Control Optimization
       These options control various sorts of optimizations.

       Without any optimization option, the compiler's goal is to reduce the cost of compilation
       and to make debugging produce the expected results.  Statements are independent: if you
       stop the program with a breakpoint between statements, you can then assign a new value to
       any variable or change the program counter to any other statement in the function and get
       exactly the results you expect from the source code.

       Turning on optimization flags makes the compiler attempt to improve the performance and/or
       code size at the expense of compilation time and possibly the ability to debug the
       program.

       The compiler performs optimization based on the knowledge it has of the program.
       Compiling multiple files at once to a single output file mode allows the compiler to use
       information gained from all of the files when compiling each of them.

       Not all optimizations are controlled directly by a flag.  Only optimizations that have a
       flag are listed in this section.

       Most optimizations are only enabled if an -O level is set on the command line.  Otherwise
       they are disabled, even if individual optimization flags are specified.

       Depending on the target and how GCC was configured, a slightly different set of
       optimizations may be enabled at each -O level than those listed here.  You can invoke GCC
       with -Q --help=optimizers to find out the exact set of optimizations that are enabled at
       each level.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a lot more memory for
           a large function.

           With -O, the compiler tries to reduce code size and execution time, without performing
           any optimizations that take a great deal of compilation time.

           -O turns on the following optimization flags:

           -fauto-inc-dec -fbranch-count-reg -fcombine-stack-adjustments -fcompare-elim
           -fcprop-registers -fdce -fdefer-pop -fdelayed-branch -fdse -fforward-propagate
           -fguess-branch-probability -fif-conversion2 -fif-conversion
           -finline-functions-called-once -fipa-pure-const -fipa-profile -fipa-reference
           -fmerge-constants -fmove-loop-invariants -fshrink-wrap -fsplit-wide-types
           -ftree-bit-ccp -ftree-ccp -fssa-phiopt -ftree-ch -ftree-copy-prop -ftree-copyrename
           -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre -ftree-phiprop
           -ftree-sink -ftree-slsr -ftree-sra -ftree-pta -ftree-ter -funit-at-a-time

           -O also turns on -fomit-frame-pointer on machines where doing so does not interfere
           with debugging.

       -O2 Optimize even more.  GCC performs nearly all supported optimizations that do not
           involve a space-speed tradeoff.  As compared to -O, this option increases both
           compilation time and the performance of the generated code.

           -O2 turns on all optimization flags specified by -O.  It also turns on the following
           optimization flags: -fthread-jumps -falign-functions  -falign-jumps -falign-loops
           -falign-labels -fcaller-saves -fcrossjumping -fcse-follow-jumps  -fcse-skip-blocks
           -fdelete-null-pointer-checks -fdevirtualize -fdevirtualize-speculatively
           -fexpensive-optimizations -fgcse  -fgcse-lm -fhoist-adjacent-loads
           -finline-small-functions -findirect-inlining -fipa-cp -fipa-cp-alignment -fipa-sra
           -fipa-icf -fisolate-erroneous-paths-dereference -flra-remat -foptimize-sibling-calls
           -foptimize-strlen -fpartial-inlining -fpeephole2 -freorder-blocks
           -freorder-blocks-and-partition -freorder-functions -frerun-cse-after-loop
           -fsched-interblock  -fsched-spec -fschedule-insns  -fschedule-insns2 -fstrict-aliasing
           -fstrict-overflow -ftree-builtin-call-dce -ftree-switch-conversion -ftree-tail-merge
           -ftree-pre -ftree-vrp -fipa-ra

           Please note the warning under -fgcse about invoking -O2 on programs that use computed
           gotos.

           NOTE: In Ubuntu 8.10 and later versions, -D_FORTIFY_SOURCE=2 is set by default, and is
           activated when -O is set to 2 or higher.  This enables additional compile-time and
           run-time checks for several libc functions.  To disable, specify either
           -U_FORTIFY_SOURCE or -D_FORTIFY_SOURCE=0.

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2 and also turns on
           the -finline-functions, -funswitch-loops, -fpredictive-commoning, -fgcse-after-reload,
           -ftree-loop-vectorize, -ftree-loop-distribute-patterns, -ftree-slp-vectorize,
           -fvect-cost-model, -ftree-partial-pre and -fipa-cp-clone options.

       -O0 Reduce compilation time and make debugging produce the expected results.  This is the
           default.

       -Os Optimize for size.  -Os enables all -O2 optimizations that do not typically increase
           code size.  It also performs further optimizations designed to reduce code size.

           -Os disables the following optimization flags: -falign-functions  -falign-jumps
           -falign-loops -falign-labels  -freorder-blocks  -freorder-blocks-and-partition
           -fprefetch-loop-arrays

       -Ofast
           Disregard strict standards compliance.  -Ofast enables all -O3 optimizations.  It also
           enables optimizations that are not valid for all standard-compliant programs.  It
           turns on -ffast-math and the Fortran-specific -fno-protect-parens and -fstack-arrays.

       -Og Optimize debugging experience.  -Og enables optimizations that do not interfere with
           debugging. It should be the optimization level of choice for the standard edit-
           compile-debug cycle, offering a reasonable level of optimization while maintaining
           fast compilation and a good debugging experience.

           If you use multiple -O options, with or without level numbers, the last such option is
           the one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most flags have both
       positive and negative forms; the negative form of -ffoo is -fno-foo.  In the table below,
       only one of the forms is listed---the one you typically use.  You can figure out the other
       form by either removing no- or adding it.

       The following options control specific optimizations.  They are either activated by -O
       options or are related to ones that are.  You can use the following flags in the rare
       cases when "fine-tuning" of optimizations to be performed is desired.

       -fno-defer-pop
           Always pop the arguments to each function call as soon as that function returns.  For
           machines that must pop arguments after a function call, the compiler normally lets
           arguments accumulate on the stack for several function calls and pops them all at
           once.

           Disabled at levels -O, -O2, -O3, -Os.

       -fforward-propagate
           Perform a forward propagation pass on RTL.  The pass tries to combine two instructions
           and checks if the result can be simplified.  If loop unrolling is active, two passes
           are performed and the second is scheduled after loop unrolling.

           This option is enabled by default at optimization levels -O, -O2, -O3, -Os.

       -ffp-contract=style
           -ffp-contract=off disables floating-point expression contraction.  -ffp-contract=fast
           enables floating-point expression contraction such as forming of fused multiply-add
           operations if the target has native support for them.  -ffp-contract=on enables
           floating-point expression contraction if allowed by the language standard.  This is
           currently not implemented and treated equal to -ffp-contract=off.

           The default is -ffp-contract=fast.

       -fomit-frame-pointer
           Don't keep the frame pointer in a register for functions that don't need one.  This
           avoids the instructions to save, set up and restore frame pointers; it also makes an
           extra register available in many functions.  It also makes debugging impossible on
           some machines.

           On some machines, such as the VAX, this flag has no effect, because the standard
           calling sequence automatically handles the frame pointer and nothing is saved by
           pretending it doesn't exist.  The machine-description macro "FRAME_POINTER_REQUIRED"
           controls whether a target machine supports this flag.

           The default setting (when not optimizing for size) for 32-bit GNU/Linux x86 and 32-bit
           Darwin x86 targets is -fomit-frame-pointer.  You can configure GCC with the
           --enable-frame-pointer configure option to change the default.

           Enabled at levels -O, -O2, -O3, -Os.

       -foptimize-sibling-calls
           Optimize sibling and tail recursive calls.

           Enabled at levels -O2, -O3, -Os.

       -foptimize-strlen
           Optimize various standard C string functions (e.g. "strlen", "strchr" or "strcpy") and
           their "_FORTIFY_SOURCE" counterparts into faster alternatives.

           Enabled at levels -O2, -O3.

       -fno-inline
           Do not expand any functions inline apart from those marked with the "always_inline"
           attribute.  This is the default when not optimizing.

           Single functions can be exempted from inlining by marking them with the "noinline"
           attribute.

       -finline-small-functions
           Integrate functions into their callers when their body is smaller than expected
           function call code (so overall size of program gets smaller).  The compiler
           heuristically decides which functions are simple enough to be worth integrating in
           this way.  This inlining applies to all functions, even those not declared inline.

           Enabled at level -O2.

       -findirect-inlining
           Inline also indirect calls that are discovered to be known at compile time thanks to
           previous inlining.  This option has any effect only when inlining itself is turned on
           by the -finline-functions or -finline-small-functions options.

           Enabled at level -O2.

       -finline-functions
           Consider all functions for inlining, even if they are not declared inline.  The
           compiler heuristically decides which functions are worth integrating in this way.

           If all calls to a given function are integrated, and the function is declared
           "static", then the function is normally not output as assembler code in its own right.

           Enabled at level -O3.

       -finline-functions-called-once
           Consider all "static" functions called once for inlining into their caller even if
           they are not marked "inline".  If a call to a given function is integrated, then the
           function is not output as assembler code in its own right.

           Enabled at levels -O1, -O2, -O3 and -Os.

       -fearly-inlining
           Inline functions marked by "always_inline" and functions whose body seems smaller than
           the function call overhead early before doing -fprofile-generate instrumentation and
           real inlining pass.  Doing so makes profiling significantly cheaper and usually
           inlining faster on programs having large chains of nested wrapper functions.

           Enabled by default.

       -fipa-sra
           Perform interprocedural scalar replacement of aggregates, removal of unused parameters
           and replacement of parameters passed by reference by parameters passed by value.

           Enabled at levels -O2, -O3 and -Os.

       -finline-limit=n
           By default, GCC limits the size of functions that can be inlined.  This flag allows
           coarse control of this limit.  n is the size of functions that can be inlined in
           number of pseudo instructions.

           Inlining is actually controlled by a number of parameters, which may be specified
           individually by using --param name=value.  The -finline-limit=n option sets some of
           these parameters as follows:

           max-inline-insns-single
               is set to n/2.

           max-inline-insns-auto
               is set to n/2.

           See below for a documentation of the individual parameters controlling inlining and
           for the defaults of these parameters.

           Note: there may be no value to -finline-limit that results in default behavior.

           Note: pseudo instruction represents, in this particular context, an abstract
           measurement of function's size.  In no way does it represent a count of assembly
           instructions and as such its exact meaning might change from one release to an
           another.

       -fno-keep-inline-dllexport
           This is a more fine-grained version of -fkeep-inline-functions, which applies only to
           functions that are declared using the "dllexport" attribute or declspec

       -fkeep-inline-functions
           In C, emit "static" functions that are declared "inline" into the object file, even if
           the function has been inlined into all of its callers.  This switch does not affect
           functions using the "extern inline" extension in GNU C90.  In C++, emit any and all
           inline functions into the object file.

       -fkeep-static-consts
           Emit variables declared "static const" when optimization isn't turned on, even if the
           variables aren't referenced.

           GCC enables this option by default.  If you want to force the compiler to check if a
           variable is referenced, regardless of whether or not optimization is turned on, use
           the -fno-keep-static-consts option.

       -fmerge-constants
           Attempt to merge identical constants (string constants and floating-point constants)
           across compilation units.

           This option is the default for optimized compilation if the assembler and linker
           support it.  Use -fno-merge-constants to inhibit this behavior.

           Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
           Attempt to merge identical constants and identical variables.

           This option implies -fmerge-constants.  In addition to -fmerge-constants this
           considers e.g. even constant initialized arrays or initialized constant variables with
           integral or floating-point types.  Languages like C or C++ require each variable,
           including multiple instances of the same variable in recursive calls, to have distinct
           locations, so using this option results in non-conforming behavior.

       -fmodulo-sched
           Perform swing modulo scheduling immediately before the first scheduling pass.  This
           pass looks at innermost loops and reorders their instructions by overlapping different
           iterations.

       -fmodulo-sched-allow-regmoves
           Perform more aggressive SMS-based modulo scheduling with register moves allowed.  By
           setting this flag certain anti-dependences edges are deleted, which triggers the
           generation of reg-moves based on the life-range analysis.  This option is effective
           only with -fmodulo-sched enabled.

       -fno-branch-count-reg
           Do not use "decrement and branch" instructions on a count register, but instead
           generate a sequence of instructions that decrement a register, compare it against
           zero, then branch based upon the result.  This option is only meaningful on
           architectures that support such instructions, which include x86, PowerPC, IA-64 and
           S/390.

           Enabled by default at -O1 and higher.

           The default is -fbranch-count-reg.

       -fno-function-cse
           Do not put function addresses in registers; make each instruction that calls a
           constant function contain the function's address explicitly.

           This option results in less efficient code, but some strange hacks that alter the
           assembler output may be confused by the optimizations performed when this option is
           not used.

           The default is -ffunction-cse

       -fno-zero-initialized-in-bss
           If the target supports a BSS section, GCC by default puts variables that are
           initialized to zero into BSS.  This can save space in the resulting code.

           This option turns off this behavior because some programs explicitly rely on variables
           going to the data section---e.g., so that the resulting executable can find the
           beginning of that section and/or make assumptions based on that.

           The default is -fzero-initialized-in-bss.

       -fthread-jumps
           Perform optimizations that check to see if a jump branches to a location where another
           comparison subsumed by the first is found.  If so, the first branch is redirected to
           either the destination of the second branch or a point immediately following it,
           depending on whether the condition is known to be true or false.

           Enabled at levels -O2, -O3, -Os.

       -fsplit-wide-types
           When using a type that occupies multiple registers, such as "long long" on a 32-bit
           system, split the registers apart and allocate them independently.  This normally
           generates better code for those types, but may make debugging more difficult.

           Enabled at levels -O, -O2, -O3, -Os.

       -fcse-follow-jumps
           In common subexpression elimination (CSE), scan through jump instructions when the
           target of the jump is not reached by any other path.  For example, when CSE encounters
           an "if" statement with an "else" clause, CSE follows the jump when the condition
           tested is false.

           Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
           This is similar to -fcse-follow-jumps, but causes CSE to follow jumps that
           conditionally skip over blocks.  When CSE encounters a simple "if" statement with no
           else clause, -fcse-skip-blocks causes CSE to follow the jump around the body of the
           "if".

           Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
           Re-run common subexpression elimination after loop optimizations are performed.

           Enabled at levels -O2, -O3, -Os.

       -fgcse
           Perform a global common subexpression elimination pass.  This pass also performs
           global constant and copy propagation.

           Note: When compiling a program using computed gotos, a GCC extension, you may get
           better run-time performance if you disable the global common subexpression elimination
           pass by adding -fno-gcse to the command line.

           Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
           When -fgcse-lm is enabled, global common subexpression elimination attempts to move
           loads that are only killed by stores into themselves.  This allows a loop containing a
           load/store sequence to be changed to a load outside the loop, and a copy/store within
           the loop.

           Enabled by default when -fgcse is enabled.

       -fgcse-sm
           When -fgcse-sm is enabled, a store motion pass is run after global common
           subexpression elimination.  This pass attempts to move stores out of loops.  When used
           in conjunction with -fgcse-lm, loops containing a load/store sequence can be changed
           to a load before the loop and a store after the loop.

           Not enabled at any optimization level.

       -fgcse-las
           When -fgcse-las is enabled, the global common subexpression elimination pass
           eliminates redundant loads that come after stores to the same memory location (both
           partial and full redundancies).

           Not enabled at any optimization level.

       -fgcse-after-reload
           When -fgcse-after-reload is enabled, a redundant load elimination pass is performed
           after reload.  The purpose of this pass is to clean up redundant spilling.

       -faggressive-loop-optimizations
           This option tells the loop optimizer to use language constraints to derive bounds for
           the number of iterations of a loop.  This assumes that loop code does not invoke
           undefined behavior by for example causing signed integer overflows or out-of-bound
           array accesses.  The bounds for the number of iterations of a loop are used to guide
           loop unrolling and peeling and loop exit test optimizations.  This option is enabled
           by default.

       -funsafe-loop-optimizations
           This option tells the loop optimizer to assume that loop indices do not overflow, and
           that loops with nontrivial exit condition are not infinite.  This enables a wider
           range of loop optimizations even if the loop optimizer itself cannot prove that these
           assumptions are valid.  If you use -Wunsafe-loop-optimizations, the compiler warns you
           if it finds this kind of loop.

       -fcrossjumping
           Perform cross-jumping transformation.  This transformation unifies equivalent code and
           saves code size.  The resulting code may or may not perform better than without cross-
           jumping.

           Enabled at levels -O2, -O3, -Os.

       -fauto-inc-dec
           Combine increments or decrements of addresses with memory accesses.  This pass is
           always skipped on architectures that do not have instructions to support this.
           Enabled by default at -O and higher on architectures that support this.

       -fdce
           Perform dead code elimination (DCE) on RTL.  Enabled by default at -O and higher.

       -fdse
           Perform dead store elimination (DSE) on RTL.  Enabled by default at -O and higher.

       -fif-conversion
           Attempt to transform conditional jumps into branch-less equivalents.  This includes
           use of conditional moves, min, max, set flags and abs instructions, and some tricks
           doable by standard arithmetics.  The use of conditional execution on chips where it is
           available is controlled by -fif-conversion2.

           Enabled at levels -O, -O2, -O3, -Os.

       -fif-conversion2
           Use conditional execution (where available) to transform conditional jumps into
           branch-less equivalents.

           Enabled at levels -O, -O2, -O3, -Os.

       -fdeclone-ctor-dtor
           The C++ ABI requires multiple entry points for constructors and destructors: one for a
           base subobject, one for a complete object, and one for a virtual destructor that calls
           operator delete afterwards.  For a hierarchy with virtual bases, the base and complete
           variants are clones, which means two copies of the function.  With this option, the
           base and complete variants are changed to be thunks that call a common implementation.

           Enabled by -Os.

       -fdelete-null-pointer-checks
           Assume that programs cannot safely dereference null pointers, and that no code or data
           element resides there.  This enables simple constant folding optimizations at all
           optimization levels.  In addition, other optimization passes in GCC use this flag to
           control global dataflow analyses that eliminate useless checks for null pointers;
           these assume that if a pointer is checked after it has already been dereferenced, it
           cannot be null.

           Note however that in some environments this assumption is not true.  Use
           -fno-delete-null-pointer-checks to disable this optimization for programs that depend
           on that behavior.

           Some targets, especially embedded ones, disable this option at all levels.  Otherwise
           it is enabled at all levels: -O0, -O1, -O2, -O3, -Os.  Passes that use the information
           are enabled independently at different optimization levels.

       -fdevirtualize
           Attempt to convert calls to virtual functions to direct calls.  This is done both
           within a procedure and interprocedurally as part of indirect inlining
           (-findirect-inlining) and interprocedural constant propagation (-fipa-cp).  Enabled at
           levels -O2, -O3, -Os.

       -fdevirtualize-speculatively
           Attempt to convert calls to virtual functions to speculative direct calls.  Based on
           the analysis of the type inheritance graph, determine for a given call the set of
           likely targets. If the set is small, preferably of size 1, change the call into a
           conditional deciding between direct and indirect calls.  The speculative calls enable
           more optimizations, such as inlining.  When they seem useless after further
           optimization, they are converted back into original form.

       -fdevirtualize-at-ltrans
           Stream extra information needed for aggressive devirtualization when running the link-
           time optimizer in local transformation mode.  This option enables more
           devirtualization but significantly increases the size of streamed data. For this
           reason it is disabled by default.

       -fexpensive-optimizations
           Perform a number of minor optimizations that are relatively expensive.

           Enabled at levels -O2, -O3, -Os.

       -free
           Attempt to remove redundant extension instructions.  This is especially helpful for
           the x86-64 architecture, which implicitly zero-extends in 64-bit registers after
           writing to their lower 32-bit half.

           Enabled for Alpha, AArch64 and x86 at levels -O2, -O3, -Os.

       -fno-lifetime-dse
           In C++ the value of an object is only affected by changes within its lifetime: when
           the constructor begins, the object has an indeterminate value, and any changes during
           the lifetime of the object are dead when the object is destroyed.  Normally dead store
           elimination will take advantage of this; if your code relies on the value of the
           object storage persisting beyond the lifetime of the object, you can use this flag to
           disable this optimization.

       -flive-range-shrinkage
           Attempt to decrease register pressure through register live range shrinkage.  This is
           helpful for fast processors with small or moderate size register sets.

       -fira-algorithm=algorithm
           Use the specified coloring algorithm for the integrated register allocator.  The
           algorithm argument can be priority, which specifies Chow's priority coloring, or CB,
           which specifies Chaitin-Briggs coloring.  Chaitin-Briggs coloring is not implemented
           for all architectures, but for those targets that do support it, it is the default
           because it generates better code.

       -fira-region=region
           Use specified regions for the integrated register allocator.  The region argument
           should be one of the following:

           all Use all loops as register allocation regions.  This can give the best results for
               machines with a small and/or irregular register set.

           mixed
               Use all loops except for loops with small register pressure as the regions.  This
               value usually gives the best results in most cases and for most architectures, and
               is enabled by default when compiling with optimization for speed (-O, -O2, ...).

           one Use all functions as a single region.  This typically results in the smallest code
               size, and is enabled by default for -Os or -O0.

       -fira-hoist-pressure
           Use IRA to evaluate register pressure in the code hoisting pass for decisions to hoist
           expressions.  This option usually results in smaller code, but it can slow the
           compiler down.

           This option is enabled at level -Os for all targets.

       -fira-loop-pressure
           Use IRA to evaluate register pressure in loops for decisions to move loop invariants.
           This option usually results in generation of faster and smaller code on machines with
           large register files (>= 32 registers), but it can slow the compiler down.

           This option is enabled at level -O3 for some targets.

       -fno-ira-share-save-slots
           Disable sharing of stack slots used for saving call-used hard registers living through
           a call.  Each hard register gets a separate stack slot, and as a result function stack
           frames are larger.

       -fno-ira-share-spill-slots
           Disable sharing of stack slots allocated for pseudo-registers.  Each pseudo-register
           that does not get a hard register gets a separate stack slot, and as a result function
           stack frames are larger.

       -fira-verbose=n
           Control the verbosity of the dump file for the integrated register allocator.  The
           default value is 5.  If the value n is greater or equal to 10, the dump output is sent
           to stderr using the same format as n minus 10.

       -flra-remat
           Enable CFG-sensitive rematerialization in LRA.  Instead of loading values of spilled
           pseudos, LRA tries to rematerialize (recalculate) values if it is profitable.

           Enabled at levels -O2, -O3, -Os.

       -fdelayed-branch
           If supported for the target machine, attempt to reorder instructions to exploit
           instruction slots available after delayed branch instructions.

           Enabled at levels -O, -O2, -O3, -Os.

       -fschedule-insns
           If supported for the target machine, attempt to reorder instructions to eliminate
           execution stalls due to required data being unavailable.  This helps machines that
           have slow floating point or memory load instructions by allowing other instructions to
           be issued until the result of the load or floating-point instruction is required.

           Enabled at levels -O2, -O3.

       -fschedule-insns2
           Similar to -fschedule-insns, but requests an additional pass of instruction scheduling
           after register allocation has been done.  This is especially useful on machines with a
           relatively small number of registers and where memory load instructions take more than
           one cycle.

           Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
           Don't schedule instructions across basic blocks.  This is normally enabled by default
           when scheduling before register allocation, i.e.  with -fschedule-insns or at -O2 or
           higher.

       -fno-sched-spec
           Don't allow speculative motion of non-load instructions.  This is normally enabled by
           default when scheduling before register allocation, i.e.  with -fschedule-insns or at
           -O2 or higher.

       -fsched-pressure
           Enable register pressure sensitive insn scheduling before register allocation.  This
           only makes sense when scheduling before register allocation is enabled, i.e. with
           -fschedule-insns or at -O2 or higher.  Usage of this option can improve the generated
           code and decrease its size by preventing register pressure increase above the number
           of available hard registers and subsequent spills in register allocation.

       -fsched-spec-load
           Allow speculative motion of some load instructions.  This only makes sense when
           scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
           Allow speculative motion of more load instructions.  This only makes sense when
           scheduling before register allocation, i.e. with -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns
       -fsched-stalled-insns=n
           Define how many insns (if any) can be moved prematurely from the queue of stalled
           insns into the ready list during the second scheduling pass.  -fno-sched-stalled-insns
           means that no insns are moved prematurely, -fsched-stalled-insns=0 means there is no
           limit on how many queued insns can be moved prematurely.  -fsched-stalled-insns
           without a value is equivalent to -fsched-stalled-insns=1.

       -fsched-stalled-insns-dep
       -fsched-stalled-insns-dep=n
           Define how many insn groups (cycles) are examined for a dependency on a stalled insn
           that is a candidate for premature removal from the queue of stalled insns.  This has
           an effect only during the second scheduling pass, and only if -fsched-stalled-insns is
           used.  -fno-sched-stalled-insns-dep is equivalent to -fsched-stalled-insns-dep=0.
           -fsched-stalled-insns-dep without a value is equivalent to
           -fsched-stalled-insns-dep=1.

       -fsched2-use-superblocks
           When scheduling after register allocation, use superblock scheduling.  This allows
           motion across basic block boundaries, resulting in faster schedules.  This option is
           experimental, as not all machine descriptions used by GCC model the CPU closely enough
           to avoid unreliable results from the algorithm.

           This only makes sense when scheduling after register allocation, i.e. with
           -fschedule-insns2 or at -O2 or higher.

       -fsched-group-heuristic
           Enable the group heuristic in the scheduler.  This heuristic favors the instruction
           that belongs to a schedule group.  This is enabled by default when scheduling is
           enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-critical-path-heuristic
           Enable the critical-path heuristic in the scheduler.  This heuristic favors
           instructions on the critical path.  This is enabled by default when scheduling is
           enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-spec-insn-heuristic
           Enable the speculative instruction heuristic in the scheduler.  This heuristic favors
           speculative instructions with greater dependency weakness.  This is enabled by default
           when scheduling is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2
           or higher.

       -fsched-rank-heuristic
           Enable the rank heuristic in the scheduler.  This heuristic favors the instruction
           belonging to a basic block with greater size or frequency.  This is enabled by default
           when scheduling is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2
           or higher.

       -fsched-last-insn-heuristic
           Enable the last-instruction heuristic in the scheduler.  This heuristic favors the
           instruction that is less dependent on the last instruction scheduled.  This is enabled
           by default when scheduling is enabled, i.e. with -fschedule-insns or -fschedule-insns2
           or at -O2 or higher.

       -fsched-dep-count-heuristic
           Enable the dependent-count heuristic in the scheduler.  This heuristic favors the
           instruction that has more instructions depending on it.  This is enabled by default
           when scheduling is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2
           or higher.

       -freschedule-modulo-scheduled-loops
           Modulo scheduling is performed before traditional scheduling.  If a loop is modulo
           scheduled, later scheduling passes may change its schedule.  Use this option to
           control that behavior.

       -fselective-scheduling
           Schedule instructions using selective scheduling algorithm.  Selective scheduling runs
           instead of the first scheduler pass.

       -fselective-scheduling2
           Schedule instructions using selective scheduling algorithm.  Selective scheduling runs
           instead of the second scheduler pass.

       -fsel-sched-pipelining
           Enable software pipelining of innermost loops during selective scheduling.  This
           option has no effect unless one of -fselective-scheduling or -fselective-scheduling2
           is turned on.

       -fsel-sched-pipelining-outer-loops
           When pipelining loops during selective scheduling, also pipeline outer loops.  This
           option has no effect unless -fsel-sched-pipelining is turned on.

       -fsemantic-interposition
           Some object formats, like ELF, allow interposing of symbols by the dynamic linker.
           This means that for symbols exported from the DSO, the compiler cannot perform
           interprocedural propagation, inlining and other optimizations in anticipation that the
           function or variable in question may change. While this feature is useful, for
           example, to rewrite memory allocation functions by a debugging implementation, it is
           expensive in the terms of code quality.  With -fno-semantic-interposition the compiler
           assumes that if interposition happens for functions the overwriting function will have
           precisely the same semantics (and side effects).  Similarly if interposition happens
           for variables, the constructor of the variable will be the same. The flag has no
           effect for functions explicitly declared inline (where it is never allowed for
           interposition to change semantics) and for symbols explicitly declared weak.

       -fshrink-wrap
           Emit function prologues only before parts of the function that need it, rather than at
           the top of the function.  This flag is enabled by default at -O and higher.

       -fcaller-saves
           Enable allocation of values to registers that are clobbered by function calls, by
           emitting extra instructions to save and restore the registers around such calls.  Such
           allocation is done only when it seems to result in better code.

           This option is always enabled by default on certain machines, usually those which have
           no call-preserved registers to use instead.

           Enabled at levels -O2, -O3, -Os.

       -fcombine-stack-adjustments
           Tracks stack adjustments (pushes and pops) and stack memory references and then tries
           to find ways to combine them.

           Enabled by default at -O1 and higher.

       -fipa-ra
           Use caller save registers for allocation if those registers are not used by any called
           function.  In that case it is not necessary to save and restore them around calls.
           This is only possible if called functions are part of same compilation unit as current
           function and they are compiled before it.

           Enabled at levels -O2, -O3, -Os.

       -fconserve-stack
           Attempt to minimize stack usage.  The compiler attempts to use less stack space, even
           if that makes the program slower.  This option implies setting the large-stack-frame
           parameter to 100 and the large-stack-frame-growth parameter to 400.

       -ftree-reassoc
           Perform reassociation on trees.  This flag is enabled by default at -O and higher.

       -ftree-pre
           Perform partial redundancy elimination (PRE) on trees.  This flag is enabled by
           default at -O2 and -O3.

       -ftree-partial-pre
           Make partial redundancy elimination (PRE) more aggressive.  This flag is enabled by
           default at -O3.

       -ftree-forwprop
           Perform forward propagation on trees.  This flag is enabled by default at -O and
           higher.

       -ftree-fre
           Perform full redundancy elimination (FRE) on trees.  The difference between FRE and
           PRE is that FRE only considers expressions that are computed on all paths leading to
           the redundant computation.  This analysis is faster than PRE, though it exposes fewer
           redundancies.  This flag is enabled by default at -O and higher.

       -ftree-phiprop
           Perform hoisting of loads from conditional pointers on trees.  This pass is enabled by
           default at -O and higher.

       -fhoist-adjacent-loads
           Speculatively hoist loads from both branches of an if-then-else if the loads are from
           adjacent locations in the same structure and the target architecture has a conditional
           move instruction.  This flag is enabled by default at -O2 and higher.

       -ftree-copy-prop
           Perform copy propagation on trees.  This pass eliminates unnecessary copy operations.
           This flag is enabled by default at -O and higher.

       -fipa-pure-const
           Discover which functions are pure or constant.  Enabled by default at -O and higher.

       -fipa-reference
           Discover which static variables do not escape the compilation unit.  Enabled by
           default at -O and higher.

       -fipa-pta
           Perform interprocedural pointer analysis and interprocedural modification and
           reference analysis.  This option can cause excessive memory and compile-time usage on
           large compilation units.  It is not enabled by default at any optimization level.

       -fipa-profile
           Perform interprocedural profile propagation.  The functions called only from cold
           functions are marked as cold. Also functions executed once (such as "cold",
           "noreturn", static constructors or destructors) are identified. Cold functions and
           loop less parts of functions executed once are then optimized for size.  Enabled by
           default at -O and higher.

       -fipa-cp
           Perform interprocedural constant propagation.  This optimization analyzes the program
           to determine when values passed to functions are constants and then optimizes
           accordingly.  This optimization can substantially increase performance if the
           application has constants passed to functions.  This flag is enabled by default at
           -O2, -Os and -O3.

       -fipa-cp-clone
           Perform function cloning to make interprocedural constant propagation stronger.  When
           enabled, interprocedural constant propagation performs function cloning when
           externally visible function can be called with constant arguments.  Because this
           optimization can create multiple copies of functions, it may significantly increase
           code size (see --param ipcp-unit-growth=value).  This flag is enabled by default at
           -O3.

       -fipa-cp-alignment
           When enabled, this optimization propagates alignment of function parameters to support
           better vectorization and string operations.

           This flag is enabled by default at -O2 and -Os.  It requires that -fipa-cp is enabled.

       -fipa-icf
           Perform Identical Code Folding for functions and read-only variables.  The
           optimization reduces code size and may disturb unwind stacks by replacing a function
           by equivalent one with a different name. The optimization works more effectively with
           link time optimization enabled.

           Nevertheless the behavior is similar to Gold Linker ICF optimization, GCC ICF works on
           different levels and thus the optimizations are not same - there are equivalences that
           are found only by GCC and equivalences found only by Gold.

           This flag is enabled by default at -O2 and -Os.

       -fisolate-erroneous-paths-dereference
           Detect paths that trigger erroneous or undefined behavior due to dereferencing a null
           pointer.  Isolate those paths from the main control flow and turn the statement with
           erroneous or undefined behavior into a trap.  This flag is enabled by default at -O2
           and higher.

       -fisolate-erroneous-paths-attribute
           Detect paths that trigger erroneous or undefined behavior due a null value being used
           in a way forbidden by a "returns_nonnull" or "nonnull" attribute.  Isolate those paths
           from the main control flow and turn the statement with erroneous or undefined behavior
           into a trap.  This is not currently enabled, but may be enabled by -O2 in the future.

       -ftree-sink
           Perform forward store motion  on trees.  This flag is enabled by default at -O and
           higher.

       -ftree-bit-ccp
           Perform sparse conditional bit constant propagation on trees and propagate pointer
           alignment information.  This pass only operates on local scalar variables and is
           enabled by default at -O and higher.  It requires that -ftree-ccp is enabled.

       -ftree-ccp
           Perform sparse conditional constant propagation (CCP) on trees.  This pass only
           operates on local scalar variables and is enabled by default at -O and higher.

       -fssa-phiopt
           Perform pattern matching on SSA PHI nodes to optimize conditional code.  This pass is
           enabled by default at -O and higher.

       -ftree-switch-conversion
           Perform conversion of simple initializations in a switch to initializations from a
           scalar array.  This flag is enabled by default at -O2 and higher.

       -ftree-tail-merge
           Look for identical code sequences.  When found, replace one with a jump to the other.
           This optimization is known as tail merging or cross jumping.  This flag is enabled by
           default at -O2 and higher.  The compilation time in this pass can be limited using
           max-tail-merge-comparisons parameter and max-tail-merge-iterations parameter.

       -ftree-dce
           Perform dead code elimination (DCE) on trees.  This flag is enabled by default at -O
           and higher.

       -ftree-builtin-call-dce
           Perform conditional dead code elimination (DCE) for calls to built-in functions that
           may set "errno" but are otherwise side-effect free.  This flag is enabled by default
           at -O2 and higher if -Os is not also specified.

       -ftree-dominator-opts
           Perform a variety of simple scalar cleanups (constant/copy propagation, redundancy
           elimination, range propagation and expression simplification) based on a dominator
           tree traversal.  This also performs jump threading (to reduce jumps to jumps). This
           flag is enabled by default at -O and higher.

       -ftree-dse
           Perform dead store elimination (DSE) on trees.  A dead store is a store into a memory
           location that is later overwritten by another store without any intervening loads.  In
           this case the earlier store can be deleted.  This flag is enabled by default at -O and
           higher.

       -ftree-ch
           Perform loop header copying on trees.  This is beneficial since it increases
           effectiveness of code motion optimizations.  It also saves one jump.  This flag is
           enabled by default at -O and higher.  It is not enabled for -Os, since it usually
           increases code size.

       -ftree-loop-optimize
           Perform loop optimizations on trees.  This flag is enabled by default at -O and
           higher.

       -ftree-loop-linear
           Perform loop interchange transformations on tree.  Same as -floop-interchange.  To use
           this code transformation, GCC has to be configured with --with-isl to enable the
           Graphite loop transformation infrastructure.

       -floop-interchange
           Perform loop interchange transformations on loops.  Interchanging two nested loops
           switches the inner and outer loops.  For example, given a loop like:

                   DO J = 1, M
                     DO I = 1, N
                       A(J, I) = A(J, I) * C
                     ENDDO
                   ENDDO

           loop interchange transforms the loop as if it were written:

                   DO I = 1, N
                     DO J = 1, M
                       A(J, I) = A(J, I) * C
                     ENDDO
                   ENDDO

           which can be beneficial when "N" is larger than the caches, because in Fortran, the
           elements of an array are stored in memory contiguously by column, and the original
           loop iterates over rows, potentially creating at each access a cache miss.  This
           optimization applies to all the languages supported by GCC and is not limited to
           Fortran.  To use this code transformation, GCC has to be configured with --with-isl to
           enable the Graphite loop transformation infrastructure.

       -floop-strip-mine
           Perform loop strip mining transformations on loops.  Strip mining splits a loop into
           two nested loops.  The outer loop has strides equal to the strip size and the inner
           loop has strides of the original loop within a strip.  The strip length can be changed
           using the loop-block-tile-size parameter.  For example, given a loop like:

                   DO I = 1, N
                     A(I) = A(I) + C
                   ENDDO

           loop strip mining transforms the loop as if it were written:

                   DO II = 1, N, 51
                     DO I = II, min (II + 50, N)
                       A(I) = A(I) + C
                     ENDDO
                   ENDDO

           This optimization applies to all the languages supported by GCC and is not limited to
           Fortran.  To use this code transformation, GCC has to be configured with --with-isl to
           enable the Graphite loop transformation infrastructure.

       -floop-block
           Perform loop blocking transformations on loops.  Blocking strip mines each loop in the
           loop nest such that the memory accesses of the element loops fit inside caches.  The
           strip length can be changed using the loop-block-tile-size parameter.  For example,
           given a loop like:

                   DO I = 1, N
                     DO J = 1, M
                       A(J, I) = B(I) + C(J)
                     ENDDO
                   ENDDO

           loop blocking transforms the loop as if it were written:

                   DO II = 1, N, 51
                     DO JJ = 1, M, 51
                       DO I = II, min (II + 50, N)
                         DO J = JJ, min (JJ + 50, M)
                           A(J, I) = B(I) + C(J)
                         ENDDO
                       ENDDO
                     ENDDO
                   ENDDO

           which can be beneficial when "M" is larger than the caches, because the innermost loop
           iterates over a smaller amount of data which can be kept in the caches.  This
           optimization applies to all the languages supported by GCC and is not limited to
           Fortran.  To use this code transformation, GCC has to be configured with --with-isl to
           enable the Graphite loop transformation infrastructure.

       -fgraphite-identity
           Enable the identity transformation for graphite.  For every SCoP we generate the
           polyhedral representation and transform it back to gimple.  Using -fgraphite-identity
           we can check the costs or benefits of the GIMPLE -> GRAPHITE -> GIMPLE transformation.
           Some minimal optimizations are also performed by the code generator ISL, like index
           splitting and dead code elimination in loops.

       -floop-nest-optimize
           Enable the ISL based loop nest optimizer.  This is a generic loop nest optimizer based
           on the Pluto optimization algorithms.  It calculates a loop structure optimized for
           data-locality and parallelism.  This option is experimental.

       -floop-unroll-and-jam
           Enable unroll and jam for the ISL based loop nest optimizer.  The unroll factor can be
           changed using the loop-unroll-jam-size parameter.  The unrolled dimension (counting
           from the most inner one) can be changed using the loop-unroll-jam-depth parameter.
           .

       -floop-parallelize-all
           Use the Graphite data dependence analysis to identify loops that can be parallelized.
           Parallelize all the loops that can be analyzed to not contain loop carried dependences
           without checking that it is profitable to parallelize the loops.

       -fcheck-data-deps
           Compare the results of several data dependence analyzers.  This option is used for
           debugging the data dependence analyzers.

       -ftree-loop-if-convert
           Attempt to transform conditional jumps in the innermost loops to branch-less
           equivalents.  The intent is to remove control-flow from the innermost loops in order
           to improve the ability of the vectorization pass to handle these loops.  This is
           enabled by default if vectorization is enabled.

       -ftree-loop-if-convert-stores
           Attempt to also if-convert conditional jumps containing memory writes.  This
           transformation can be unsafe for multi-threaded programs as it transforms conditional
           memory writes into unconditional memory writes.  For example,

                   for (i = 0; i < N; i++)
                     if (cond)
                       A[i] = expr;

           is transformed to

                   for (i = 0; i < N; i++)
                     A[i] = cond ? expr : A[i];

           potentially producing data races.

       -ftree-loop-distribution
           Perform loop distribution.  This flag can improve cache performance on big loop bodies
           and allow further loop optimizations, like parallelization or vectorization, to take
           place.  For example, the loop

                   DO I = 1, N
                     A(I) = B(I) + C
                     D(I) = E(I) * F
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = B(I) + C
                   ENDDO
                   DO I = 1, N
                      D(I) = E(I) * F
                   ENDDO

       -ftree-loop-distribute-patterns
           Perform loop distribution of patterns that can be code generated with calls to a
           library.  This flag is enabled by default at -O3.

           This pass distributes the initialization loops and generates a call to memset zero.
           For example, the loop

                   DO I = 1, N
                     A(I) = 0
                     B(I) = A(I) + I
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = 0
                   ENDDO
                   DO I = 1, N
                      B(I) = A(I) + I
                   ENDDO

           and the initialization loop is transformed into a call to memset zero.

       -ftree-loop-im
           Perform loop invariant motion on trees.  This pass moves only invariants that are hard
           to handle at RTL level (function calls, operations that expand to nontrivial sequences
           of insns).  With -funswitch-loops it also moves operands of conditions that are
           invariant out of the loop, so that we can use just trivial invariantness analysis in
           loop unswitching.  The pass also includes store motion.

       -ftree-loop-ivcanon
           Create a canonical counter for number of iterations in loops for which determining
           number of iterations requires complicated analysis.  Later optimizations then may
           determine the number easily.  Useful especially in connection with unrolling.

       -fivopts
           Perform induction variable optimizations (strength reduction, induction variable
           merging and induction variable elimination) on trees.

       -ftree-parallelize-loops=n
           Parallelize loops, i.e., split their iteration space to run in n threads.  This is
           only possible for loops whose iterations are independent and can be arbitrarily
           reordered.  The optimization is only profitable on multiprocessor machines, for loops
           that are CPU-intensive, rather than constrained e.g. by memory bandwidth.  This option
           implies -pthread, and thus is only supported on targets that have support for
           -pthread.

       -ftree-pta
           Perform function-local points-to analysis on trees.  This flag is enabled by default
           at -O and higher.

       -ftree-sra
           Perform scalar replacement of aggregates.  This pass replaces structure references
           with scalars to prevent committing structures to memory too early.  This flag is
           enabled by default at -O and higher.

       -ftree-copyrename
           Perform copy renaming on trees.  This pass attempts to rename compiler temporaries to
           other variables at copy locations, usually resulting in variable names which more
           closely resemble the original variables.  This flag is enabled by default at -O and
           higher.

       -ftree-coalesce-inlined-vars
           Tell the copyrename pass (see -ftree-copyrename) to attempt to combine small user-
           defined variables too, but only if they are inlined from other functions.  It is a
           more limited form of -ftree-coalesce-vars.  This may harm debug information of such
           inlined variables, but it keeps variables of the inlined-into function apart from each
           other, such that they are more likely to contain the expected values in a debugging
           session.

       -ftree-coalesce-vars
           Tell the copyrename pass (see -ftree-copyrename) to attempt to combine small user-
           defined variables too, instead of just compiler temporaries.  This may severely limit
           the ability to debug an optimized program compiled with -fno-var-tracking-assignments.
           In the negated form, this flag prevents SSA coalescing of user variables, including
           inlined ones.  This option is enabled by default.

       -ftree-ter
           Perform temporary expression replacement during the SSA->normal phase.  Single
           use/single def temporaries are replaced at their use location with their defining
           expression.  This results in non-GIMPLE code, but gives the expanders much more
           complex trees to work on resulting in better RTL generation.  This is enabled by
           default at -O and higher.

       -ftree-slsr
           Perform straight-line strength reduction on trees.  This recognizes related
           expressions involving multiplications and replaces them by less expensive calculations
           when possible.  This is enabled by default at -O and higher.

       -ftree-vectorize
           Perform vectorization on trees. This flag enables -ftree-loop-vectorize and
           -ftree-slp-vectorize if not explicitly specified.

       -ftree-loop-vectorize
           Perform loop vectorization on trees. This flag is enabled by default at -O3 and when
           -ftree-vectorize is enabled.

       -ftree-slp-vectorize
           Perform basic block vectorization on trees. This flag is enabled by default at -O3 and
           when -ftree-vectorize is enabled.

       -fvect-cost-model=model
           Alter the cost model used for vectorization.  The model argument should be one of
           unlimited, dynamic or cheap.  With the unlimited model the vectorized code-path is
           assumed to be profitable while with the dynamic model a runtime check guards the
           vectorized code-path to enable it only for iteration counts that will likely execute
           faster than when executing the original scalar loop.  The cheap model disables
           vectorization of loops where doing so would be cost prohibitive for example due to
           required runtime checks for data dependence or alignment but otherwise is equal to the
           dynamic model.  The default cost model depends on other optimization flags and is
           either dynamic or cheap.

       -fsimd-cost-model=model
           Alter the cost model used for vectorization of loops marked with the OpenMP or Cilk
           Plus simd directive.  The model argument should be one of unlimited, dynamic, cheap.
           All values of model have the same meaning as described in -fvect-cost-model and by
           default a cost model defined with -fvect-cost-model is used.

       -ftree-vrp
           Perform Value Range Propagation on trees.  This is similar to the constant propagation
           pass, but instead of values, ranges of values are propagated.  This allows the
           optimizers to remove unnecessary range checks like array bound checks and null pointer
           checks.  This is enabled by default at -O2 and higher.  Null pointer check elimination
           is only done if -fdelete-null-pointer-checks is enabled.

       -fsplit-ivs-in-unroller
           Enables expression of values of induction variables in later iterations of the
           unrolled loop using the value in the first iteration.  This breaks long dependency
           chains, thus improving efficiency of the scheduling passes.

           A combination of -fweb and CSE is often sufficient to obtain the same effect.
           However, that is not reliable in cases where the loop body is more complicated than a
           single basic block.  It also does not work at all on some architectures due to
           restrictions in the CSE pass.

           This optimization is enabled by default.

       -fvariable-expansion-in-unroller
           With this option, the compiler creates multiple copies of some local variables when
           unrolling a loop, which can result in superior code.

       -fpartial-inlining
           Inline parts of functions.  This option has any effect only when inlining itself is
           turned on by the -finline-functions or -finline-small-functions options.

           Enabled at level -O2.

       -fpredictive-commoning
           Perform predictive commoning optimization, i.e., reusing computations (especially
           memory loads and stores) performed in previous iterations of loops.

           This option is enabled at level -O3.

       -fprefetch-loop-arrays
           If supported by the target machine, generate instructions to prefetch memory to
           improve the performance of loops that access large arrays.

           This option may generate better or worse code; results are highly dependent on the
           structure of loops within the source code.

           Disabled at level -Os.

       -fno-peephole
       -fno-peephole2
           Disable any machine-specific peephole optimizations.  The difference between
           -fno-peephole and -fno-peephole2 is in how they are implemented in the compiler; some
           targets use one, some use the other, a few use both.

           -fpeephole is enabled by default.  -fpeephole2 enabled at levels -O2, -O3, -Os.

       -fno-guess-branch-probability
           Do not guess branch probabilities using heuristics.

           GCC uses heuristics to guess branch probabilities if they are not provided by
           profiling feedback (-fprofile-arcs).  These heuristics are based on the control flow
           graph.  If some branch probabilities are specified by "__builtin_expect", then the
           heuristics are used to guess branch probabilities for the rest of the control flow
           graph, taking the "__builtin_expect" info into account.  The interactions between the
           heuristics and "__builtin_expect" can be complex, and in some cases, it may be useful
           to disable the heuristics so that the effects of "__builtin_expect" are easier to
           understand.

           The default is -fguess-branch-probability at levels -O, -O2, -O3, -Os.

       -freorder-blocks
           Reorder basic blocks in the compiled function in order to reduce number of taken
           branches and improve code locality.

           Enabled at levels -O2, -O3.

       -freorder-blocks-and-partition
           In addition to reordering basic blocks in the compiled function, in order to reduce
           number of taken branches, partitions hot and cold basic blocks into separate sections
           of the assembly and .o files, to improve paging and cache locality performance.

           This optimization is automatically turned off in the presence of exception handling,
           for linkonce sections, for functions with a user-defined section attribute and on any
           architecture that does not support named sections.

           Enabled for x86 at levels -O2, -O3.

       -freorder-functions
           Reorder functions in the object file in order to improve code locality.  This is
           implemented by using special subsections ".text.hot" for most frequently executed
           functions and ".text.unlikely" for unlikely executed functions.  Reordering is done by
           the linker so object file format must support named sections and linker must place
           them in a reasonable way.

           Also profile feedback must be available to make this option effective.  See
           -fprofile-arcs for details.

           Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
           Allow the compiler to assume the strictest aliasing rules applicable to the language
           being compiled.  For C (and C++), this activates optimizations based on the type of
           expressions.  In particular, an object of one type is assumed never to reside at the
           same address as an object of a different type, unless the types are almost the same.
           For example, an "unsigned int" can alias an "int", but not a "void*" or a "double".  A
           character type may alias any other type.

           Pay special attention to code like this:

                   union a_union {
                     int i;
                     double d;
                   };

                   int f() {
                     union a_union t;
                     t.d = 3.0;
                     return t.i;
                   }

           The practice of reading from a different union member than the one most recently
           written to (called "type-punning") is common.  Even with -fstrict-aliasing, type-
           punning is allowed, provided the memory is accessed through the union type.  So, the
           code above works as expected.    However, this code might not:

                   int f() {
                     union a_union t;
                     int* ip;
                     t.d = 3.0;
                     ip = &t.i;
                     return *ip;
                   }

           Similarly, access by taking the address, casting the resulting pointer and
           dereferencing the result has undefined behavior, even if the cast uses a union type,
           e.g.:

                   int f() {
                     double d = 3.0;
                     return ((union a_union *) &d)->i;
                   }

           The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os.

       -fstrict-overflow
           Allow the compiler to assume strict signed overflow rules, depending on the language
           being compiled.  For C (and C++) this means that overflow when doing arithmetic with
           signed numbers is undefined, which means that the compiler may assume that it does not
           happen.  This permits various optimizations.  For example, the compiler assumes that
           an expression like "i + 10 > i" is always true for signed "i".  This assumption is
           only valid if signed overflow is undefined, as the expression is false if "i + 10"
           overflows when using twos complement arithmetic.  When this option is in effect any
           attempt to determine whether an operation on signed numbers overflows must be written
           carefully to not actually involve overflow.

           This option also allows the compiler to assume strict pointer semantics: given a
           pointer to an object, if adding an offset to that pointer does not produce a pointer
           to the same object, the addition is undefined.  This permits the compiler to conclude
           that "p + u > p" is always true for a pointer "p" and unsigned integer "u".  This
           assumption is only valid because pointer wraparound is undefined, as the expression is
           false if "p + u" overflows using twos complement arithmetic.

           See also the -fwrapv option.  Using -fwrapv means that integer signed overflow is
           fully defined: it wraps.  When -fwrapv is used, there is no difference between
           -fstrict-overflow and -fno-strict-overflow for integers.  With -fwrapv certain types
           of overflow are permitted.  For example, if the compiler gets an overflow when doing
           arithmetic on constants, the overflowed value can still be used with -fwrapv, but not
           otherwise.

           The -fstrict-overflow option is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
           Align the start of functions to the next power-of-two greater than n, skipping up to n
           bytes.  For instance, -falign-functions=32 aligns functions to the next 32-byte
           boundary, but -falign-functions=24 aligns to the next 32-byte boundary only if this
           can be done by skipping 23 bytes or less.

           -fno-align-functions and -falign-functions=1 are equivalent and mean that functions
           are not aligned.

           Some assemblers only support this flag when n is a power of two; in that case, it is
           rounded up.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -falign-labels
       -falign-labels=n
           Align all branch targets to a power-of-two boundary, skipping up to n bytes like
           -falign-functions.  This option can easily make code slower, because it must insert
           dummy operations for when the branch target is reached in the usual flow of the code.

           -fno-align-labels and -falign-labels=1 are equivalent and mean that labels are not
           aligned.

           If -falign-loops or -falign-jumps are applicable and are greater than this value, then
           their values are used instead.

           If n is not specified or is zero, use a machine-dependent default which is very likely
           to be 1, meaning no alignment.

           Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
           Align loops to a power-of-two boundary, skipping up to n bytes like -falign-functions.
           If the loops are executed many times, this makes up for any execution of the dummy
           operations.

           -fno-align-loops and -falign-loops=1 are equivalent and mean that loops are not
           aligned.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
           Align branch targets to a power-of-two boundary, for branch targets where the targets
           can only be reached by jumping, skipping up to n bytes like -falign-functions.  In
           this case, no dummy operations need be executed.

           -fno-align-jumps and -falign-jumps=1 are equivalent and mean that loops are not
           aligned.

           If n is not specified or is zero, use a machine-dependent default.

           Enabled at levels -O2, -O3.

       -funit-at-a-time
           This option is left for compatibility reasons. -funit-at-a-time has no effect, while
           -fno-unit-at-a-time implies -fno-toplevel-reorder and -fno-section-anchors.

           Enabled by default.

       -fno-toplevel-reorder
           Do not reorder top-level functions, variables, and "asm" statements.  Output them in
           the same order that they appear in the input file.  When this option is used,
           unreferenced static variables are not removed.  This option is intended to support
           existing code that relies on a particular ordering.  For new code, it is better to use
           attributes when possible.

           Enabled at level -O0.  When disabled explicitly, it also implies -fno-section-anchors,
           which is otherwise enabled at -O0 on some targets.

       -fweb
           Constructs webs as commonly used for register allocation purposes and assign each web
           individual pseudo register.  This allows the register allocation pass to operate on
           pseudos directly, but also strengthens several other optimization passes, such as CSE,
           loop optimizer and trivial dead code remover.  It can, however, make debugging
           impossible, since variables no longer stay in a "home register".

           Enabled by default with -funroll-loops.

       -fwhole-program
           Assume that the current compilation unit represents the whole program being compiled.
           All public functions and variables with the exception of "main" and those merged by
           attribute "externally_visible" become static functions and in effect are optimized
           more aggressively by interprocedural optimizers.

           This option should not be used in combination with -flto.  Instead relying on a linker
           plugin should provide safer and more precise information.

       -flto[=n]
           This option runs the standard link-time optimizer.  When invoked with source code, it
           generates GIMPLE (one of GCC's internal representations) and writes it to special ELF
           sections in the object file.  When the object files are linked together, all the
           function bodies are read from these ELF sections and instantiated as if they had been
           part of the same translation unit.

           To use the link-time optimizer, -flto and optimization options should be specified at
           compile time and during the final link.  For example:

                   gcc -c -O2 -flto foo.c
                   gcc -c -O2 -flto bar.c
                   gcc -o myprog -flto -O2 foo.o bar.o

           The first two invocations to GCC save a bytecode representation of GIMPLE into special
           ELF sections inside foo.o and bar.o.  The final invocation reads the GIMPLE bytecode
           from foo.o and bar.o, merges the two files into a single internal image, and compiles
           the result as usual.  Since both foo.o and bar.o are merged into a single image, this
           causes all the interprocedural analyses and optimizations in GCC to work across the
           two files as if they were a single one.  This means, for example, that the inliner is
           able to inline functions in bar.o into functions in foo.o and vice-versa.

           Another (simpler) way to enable link-time optimization is:

                   gcc -o myprog -flto -O2 foo.c bar.c

           The above generates bytecode for foo.c and bar.c, merges them together into a single
           GIMPLE representation and optimizes them as usual to produce myprog.

           The only important thing to keep in mind is that to enable link-time optimizations you
           need to use the GCC driver to perform the link-step.  GCC then automatically performs
           link-time optimization if any of the objects involved were compiled with the -flto
           command-line option.  You generally should specify the optimization options to be used
           for link-time optimization though GCC tries to be clever at guessing an optimization
           level to use from the options used at compile-time if you fail to specify one at link-
           time.  You can always override the automatic decision to do link-time optimization at
           link-time by passing -fno-lto to the link command.

           To make whole program optimization effective, it is necessary to make certain whole
           program assumptions.  The compiler needs to know what functions and variables can be
           accessed by libraries and runtime outside of the link-time optimized unit.  When
           supported by the linker, the linker plugin (see -fuse-linker-plugin) passes
           information to the compiler about used and externally visible symbols.  When the
           linker plugin is not available, -fwhole-program should be used to allow the compiler
           to make these assumptions, which leads to more aggressive optimization decisions.

           When -fuse-linker-plugin is not enabled then, when a file is compiled with -flto, the
           generated object file is larger than a regular object file because it contains GIMPLE
           bytecodes and the usual final code (see -ffat-lto-objects.  This means that object
           files with LTO information can be linked as normal object files; if -fno-lto is passed
           to the linker, no interprocedural optimizations are applied.  Note that when
           -fno-fat-lto-objects is enabled the compile-stage is faster but you cannot perform a
           regular, non-LTO link on them.

           Additionally, the optimization flags used to compile individual files are not
           necessarily related to those used at link time.  For instance,

                   gcc -c -O0 -ffat-lto-objects -flto foo.c
                   gcc -c -O0 -ffat-lto-objects -flto bar.c
                   gcc -o myprog -O3 foo.o bar.o

           This produces individual object files with unoptimized assembler code, but the
           resulting binary myprog is optimized at -O3.  If, instead, the final binary is
           generated with -fno-lto, then myprog is not optimized.

           When producing the final binary, GCC only applies link-time optimizations to those
           files that contain bytecode.  Therefore, you can mix and match object files and
           libraries with GIMPLE bytecodes and final object code.  GCC automatically selects
           which files to optimize in LTO mode and which files to link without further
           processing.

           There are some code generation flags preserved by GCC when generating bytecodes, as
           they need to be used during the final link stage.  Generally options specified at
           link-time override those specified at compile-time.

           If you do not specify an optimization level option -O at link-time then GCC computes
           one based on the optimization levels used when compiling the object files.  The
           highest optimization level wins here.

           Currently, the following options and their setting are take from the first object file
           that explicitely specified it: -fPIC, -fpic, -fpie, -fcommon, -fexceptions,
           -fnon-call-exceptions, -fgnu-tm and all the -m target flags.

           Certain ABI changing flags are required to match in all compilation-units and trying
           to override this at link-time with a conflicting value is ignored.  This includes
           options such as -freg-struct-return and -fpcc-struct-return.

           Other options such as -ffp-contract, -fno-strict-overflow, -fwrapv, -fno-trapv or
           -fno-strict-aliasing are passed through to the link stage and merged conservatively
           for conflicting translation units.  Specifically -fno-strict-overflow, -fwrapv and
           -fno-trapv take precedence and for example -ffp-contract=off takes precedence over
           -ffp-contract=fast.  You can override them at linke-time.

           It is recommended that you compile all the files participating in the same link with
           the same options and also specify those options at link time.

           If LTO encounters objects with C linkage declared with incompatible types in separate
           translation units to be linked together (undefined behavior according to ISO C99
           6.2.7), a non-fatal diagnostic may be issued.  The behavior is still undefined at run
           time.  Similar diagnostics may be raised for other languages.

           Another feature of LTO is that it is possible to apply interprocedural optimizations
           on files written in different languages:

                   gcc -c -flto foo.c
                   g++ -c -flto bar.cc
                   gfortran -c -flto baz.f90
                   g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

           Notice that the final link is done with g++ to get the C++ runtime libraries and
           -lgfortran is added to get the Fortran runtime libraries.  In general, when mixing
           languages in LTO mode, you should use the same link command options as when mixing
           languages in a regular (non-LTO) compilation.

           If object files containing GIMPLE bytecode are stored in a library archive, say
           libfoo.a, it is possible to extract and use them in an LTO link if you are using a
           linker with plugin support.  To create static libraries suitable for LTO, use gcc-ar
           and gcc-ranlib instead of ar and ranlib; to show the symbols of object files with
           GIMPLE bytecode, use gcc-nm.  Those commands require that ar, ranlib and nm have been
           compiled with plugin support.  At link time, use the the flag -fuse-linker-plugin to
           ensure that the library participates in the LTO optimization process:

                   gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

           With the linker plugin enabled, the linker extracts the needed GIMPLE files from
           libfoo.a and passes them on to the running GCC to make them part of the aggregated
           GIMPLE image to be optimized.

           If you are not using a linker with plugin support and/or do not enable the linker
           plugin, then the objects inside libfoo.a are extracted and linked as usual, but they
           do not participate in the LTO optimization process.  In order to make a static library
           suitable for both LTO optimization and usual linkage, compile its object files with
           -flto -ffat-lto-objects.

           Link-time optimizations do not require the presence of the whole program to operate.
           If the program does not require any symbols to be exported, it is possible to combine
           -flto and -fwhole-program to allow the interprocedural optimizers to use more
           aggressive assumptions which may lead to improved optimization opportunities.  Use of
           -fwhole-program is not needed when linker plugin is active (see -fuse-linker-plugin).

           The current implementation of LTO makes no attempt to generate bytecode that is
           portable between different types of hosts.  The bytecode files are versioned and there
           is a strict version check, so bytecode files generated in one version of GCC do not
           work with an older or newer version of GCC.

           Link-time optimization does not work well with generation of debugging information.
           Combining -flto with -g is currently experimental and expected to produce unexpected
           results.

           If you specify the optional n, the optimization and code generation done at link time
           is executed in parallel using n parallel jobs by utilizing an installed make program.
           The environment variable MAKE may be used to override the program used.  The default
           value for n is 1.

           You can also specify -flto=jobserver to use GNU make's job server mode to determine
           the number of parallel jobs. This is useful when the Makefile calling GCC is already
           executing in parallel.  You must prepend a + to the command recipe in the parent
           Makefile for this to work.  This option likely only works if MAKE is GNU make.

       -flto-partition=alg
           Specify the partitioning algorithm used by the link-time optimizer.  The value is
           either 1to1 to specify a partitioning mirroring the original source files or balanced
           to specify partitioning into equally sized chunks (whenever possible) or max to create
           new partition for every symbol where possible.  Specifying none as an algorithm
           disables partitioning and streaming completely.  The default value is balanced. While
           1to1 can be used as an workaround for various code ordering issues, the max
           partitioning is intended for internal testing only.  The value one specifies that
           exactly one partition should be used while the value none bypasses partitioning and
           executes the link-time optimization step directly from the WPA phase.

       -flto-odr-type-merging
           Enable streaming of mangled types names of C++ types and their unification at
           linktime.  This increases size of LTO object files, but enable diagnostics about One
           Definition Rule violations.

       -flto-compression-level=n
           This option specifies the level of compression used for intermediate language written
           to LTO object files, and is only meaningful in conjunction with LTO mode (-flto).
           Valid values are 0 (no compression) to 9 (maximum compression).  Values outside this
           range are clamped to either 0 or 9.  If the option is not given, a default balanced
           compression setting is used.

       -flto-report
           Prints a report with internal details on the workings of the link-time optimizer.  The
           contents of this report vary from version to version.  It is meant to be useful to GCC
           developers when processing object files in LTO mode (via -flto).

           Disabled by default.

       -flto-report-wpa
           Like -flto-report, but only print for the WPA phase of Link Time Optimization.

       -fuse-linker-plugin
           Enables the use of a linker plugin during link-time optimization.  This option relies
           on plugin support in the linker, which is available in gold or in GNU ld 2.21 or
           newer.

           This option enables the extraction of object files with GIMPLE bytecode out of library
           archives. This improves the quality of optimization by exposing more code to the link-
           time optimizer.  This information specifies what symbols can be accessed externally
           (by non-LTO object or during dynamic linking).  Resulting code quality improvements on
           binaries (and shared libraries that use hidden visibility) are similar to
           -fwhole-program.  See -flto for a description of the effect of this flag and how to
           use it.

           This option is enabled by default when LTO support in GCC is enabled and GCC was
           configured for use with a linker supporting plugins (GNU ld 2.21 or newer or gold).

       -ffat-lto-objects
           Fat LTO objects are object files that contain both the intermediate language and the
           object code. This makes them usable for both LTO linking and normal linking. This
           option is effective only when compiling with -flto and is ignored at link time.

           -fno-fat-lto-objects improves compilation time over plain LTO, but requires the
           complete toolchain to be aware of LTO. It requires a linker with linker plugin support
           for basic functionality.  Additionally, nm, ar and ranlib need to support linker
           plugins to allow a full-featured build environment (capable of building static
           libraries etc).  GCC provides the gcc-ar, gcc-nm, gcc-ranlib wrappers to pass the
           right options to these tools. With non fat LTO makefiles need to be modified to use
           them.

           The default is -fno-fat-lto-objects on targets with linker plugin support.

       -fcompare-elim
           After register allocation and post-register allocation instruction splitting, identify
           arithmetic instructions that compute processor flags similar to a comparison operation
           based on that arithmetic.  If possible, eliminate the explicit comparison operation.

           This pass only applies to certain targets that cannot explicitly represent the
           comparison operation before register allocation is complete.

           Enabled at levels -O, -O2, -O3, -Os.

       -fcprop-registers
           After register allocation and post-register allocation instruction splitting, perform
           a copy-propagation pass to try to reduce scheduling dependencies and occasionally
           eliminate the copy.

           Enabled at levels -O, -O2, -O3, -Os.

       -fprofile-correction
           Profiles collected using an instrumented binary for multi-threaded programs may be
           inconsistent due to missed counter updates. When this option is specified, GCC uses
           heuristics to correct or smooth out such inconsistencies. By default, GCC emits an
           error message when an inconsistent profile is detected.

       -fprofile-dir=path
           Set the directory to search for the profile data files in to path.  This option
           affects only the profile data generated by -fprofile-generate, -ftest-coverage,
           -fprofile-arcs and used by -fprofile-use and -fbranch-probabilities and its related
           options.  Both absolute and relative paths can be used.  By default, GCC uses the
           current directory as path, thus the profile data file appears in the same directory as
           the object file.

       -fprofile-generate
       -fprofile-generate=path
           Enable options usually used for instrumenting application to produce profile useful
           for later recompilation with profile feedback based optimization.  You must use
           -fprofile-generate both when compiling and when linking your program.

           The following options are enabled: -fprofile-arcs, -fprofile-values, -fvpt.

           If path is specified, GCC looks at the path to find the profile feedback data files.
           See -fprofile-dir.

       -fprofile-use
       -fprofile-use=path
           Enable profile feedback-directed optimizations, and the following optimizations which
           are generally profitable only with profile feedback available: -fbranch-probabilities,
           -fvpt, -funroll-loops, -fpeel-loops, -ftracer, -ftree-vectorize, and ftree-loop-
           distribute-patterns.

           By default, GCC emits an error message if the feedback profiles do not match the
           source code.  This error can be turned into a warning by using -Wcoverage-mismatch.
           Note this may result in poorly optimized code.

           If path is specified, GCC looks at the path to find the profile feedback data files.
           See -fprofile-dir.

       -fauto-profile
       -fauto-profile=path
           Enable sampling-based feedback-directed optimizations, and the following optimizations
           which are generally profitable only with profile feedback available:
           -fbranch-probabilities, -fvpt, -funroll-loops, -fpeel-loops, -ftracer,
           -ftree-vectorize, -finline-functions, -fipa-cp, -fipa-cp-clone,
           -fpredictive-commoning, -funswitch-loops, -fgcse-after-reload, and
           -ftree-loop-distribute-patterns.

           path is the name of a file containing AutoFDO profile information.  If omitted, it
           defaults to fbdata.afdo in the current directory.

           Producing an AutoFDO profile data file requires running your program with the perf
           utility on a supported GNU/Linux target system.  For more information, see
           <https://perf.wiki.kernel.org/>.

           E.g.

                   perf record -e br_inst_retired:near_taken -b -o perf.data \
                       -- your_program

           Then use the create_gcov tool to convert the raw profile data to a format that can be
           used by GCC.  You must also supply the unstripped binary for your program to this
           tool.  See <https://github.com/google/autofdo>.

           E.g.

                   create_gcov --binary=your_program.unstripped --profile=perf.data \
                       --gcov=profile.afdo

       The following options control compiler behavior regarding floating-point arithmetic.
       These options trade off between speed and correctness.  All must be specifically enabled.

       -ffloat-store
           Do not store floating-point variables in registers, and inhibit other options that
           might change whether a floating-point value is taken from a register or memory.

           This option prevents undesirable excess precision on machines such as the 68000 where
           the floating registers (of the 68881) keep more precision than a "double" is supposed
           to have.  Similarly for the x86 architecture.  For most programs, the excess precision
           does only good, but a few programs rely on the precise definition of IEEE floating
           point.  Use -ffloat-store for such programs, after modifying them to store all
           pertinent intermediate computations into variables.

       -fexcess-precision=style
           This option allows further control over excess precision on machines where floating-
           point registers have more precision than the IEEE "float" and "double" types and the
           processor does not support operations rounding to those types.  By default,
           -fexcess-precision=fast is in effect; this means that operations are carried out in
           the precision of the registers and that it is unpredictable when rounding to the types
           specified in the source code takes place.  When compiling C, if
           -fexcess-precision=standard is specified then excess precision follows the rules
           specified in ISO C99; in particular, both casts and assignments cause values to be
           rounded to their semantic types (whereas -ffloat-store only affects assignments).
           This option is enabled by default for C if a strict conformance option such as
           -std=c99 is used.

           -fexcess-precision=standard is not implemented for languages other than C, and has no
           effect if -funsafe-math-optimizations or -ffast-math is specified.  On the x86, it
           also has no effect if -mfpmath=sse or -mfpmath=sse+387 is specified; in the former
           case, IEEE semantics apply without excess precision, and in the latter, rounding is
           unpredictable.

       -ffast-math
           Sets the options -fno-math-errno, -funsafe-math-optimizations, -ffinite-math-only,
           -fno-rounding-math, -fno-signaling-nans and -fcx-limited-range.

           This option causes the preprocessor macro "__FAST_MATH__" to be defined.

           This option is not turned on by any -O option besides -Ofast since it can result in
           incorrect output for programs that depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these specifications.

       -fno-math-errno
           Do not set "errno" after calling math functions that are executed with a single
           instruction, e.g., "sqrt".  A program that relies on IEEE exceptions for math error
           handling may want to use this flag for speed while maintaining IEEE arithmetic
           compatibility.

           This option is not turned on by any -O option since it can result in incorrect output
           for programs that depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these specifications.

           The default is -fmath-errno.

           On Darwin systems, the math library never sets "errno".  There is therefore no reason
           for the compiler to consider the possibility that it might, and -fno-math-errno is the
           default.

       -funsafe-math-optimizations
           Allow optimizations for floating-point arithmetic that (a) assume that arguments and
           results are valid and (b) may violate IEEE or ANSI standards.  When used at link-time,
           it may include libraries or startup files that change the default FPU control word or
           other similar optimizations.

           This option is not turned on by any -O option since it can result in incorrect output
           for programs that depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these specifications.  Enables
           -fno-signed-zeros, -fno-trapping-math, -fassociative-math and -freciprocal-math.

           The default is -fno-unsafe-math-optimizations.

       -fassociative-math
           Allow re-association of operands in series of floating-point operations.  This
           violates the ISO C and C++ language standard by possibly changing computation result.
           NOTE: re-ordering may change the sign of zero as well as ignore NaNs and inhibit or
           create underflow or overflow (and thus cannot be used on code that relies on rounding
           behavior like "(x + 2**52) - 2**52".  May also reorder floating-point comparisons and
           thus may not be used when ordered comparisons are required.  This option requires that
           both -fno-signed-zeros and -fno-trapping-math be in effect.  Moreover, it doesn't make
           much sense with -frounding-math. For Fortran the option is automatically enabled when
           both -fno-signed-zeros and -fno-trapping-math are in effect.

           The default is -fno-associative-math.

       -freciprocal-math
           Allow the reciprocal of a value to be used instead of dividing by the value if this
           enables optimizations.  For example "x / y" can be replaced with "x * (1/y)", which is
           useful if "(1/y)" is subject to common subexpression elimination.  Note that this
           loses precision and increases the number of flops operating on the value.

           The default is -fno-reciprocal-math.

       -ffinite-math-only
           Allow optimizations for floating-point arithmetic that assume that arguments and
           results are not NaNs or +-Infs.

           This option is not turned on by any -O option since it can result in incorrect output
           for programs that depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these specifications.

           The default is -fno-finite-math-only.

       -fno-signed-zeros
           Allow optimizations for floating-point arithmetic that ignore the signedness of zero.
           IEEE arithmetic specifies the behavior of distinct +0.0 and -0.0 values, which then
           prohibits simplification of expressions such as x+0.0 or 0.0*x (even with
           -ffinite-math-only).  This option implies that the sign of a zero result isn't
           significant.

           The default is -fsigned-zeros.

       -fno-trapping-math
           Compile code assuming that floating-point operations cannot generate user-visible
           traps.  These traps include division by zero, overflow, underflow, inexact result and
           invalid operation.  This option requires that -fno-signaling-nans be in effect.
           Setting this option may allow faster code if one relies on "non-stop" IEEE arithmetic,
           for example.

           This option should never be turned on by any -O option since it can result in
           incorrect output for programs that depend on an exact implementation of IEEE or ISO
           rules/specifications for math functions.

           The default is -ftrapping-math.

       -frounding-math
           Disable transformations and optimizations that assume default floating-point rounding
           behavior.  This is round-to-zero for all floating point to integer conversions, and
           round-to-nearest for all other arithmetic truncations.  This option should be
           specified for programs that change the FP rounding mode dynamically, or that may be
           executed with a non-default rounding mode.  This option disables constant folding of
           floating-point expressions at compile time (which may be affected by rounding mode)
           and arithmetic transformations that are unsafe in the presence of sign-dependent
           rounding modes.

           The default is -fno-rounding-math.

           This option is experimental and does not currently guarantee to disable all GCC
           optimizations that are affected by rounding mode.  Future versions of GCC may provide
           finer control of this setting using C99's "FENV_ACCESS" pragma.  This command-line
           option will be used to specify the default state for "FENV_ACCESS".

       -fsignaling-nans
           Compile code assuming that IEEE signaling NaNs may generate user-visible traps during
           floating-point operations.  Setting this option disables optimizations that may change
           the number of exceptions visible with signaling NaNs.  This option implies
           -ftrapping-math.

           This option causes the preprocessor macro "__SUPPORT_SNAN__" to be defined.

           The default is -fno-signaling-nans.

           This option is experimental and does not currently guarantee to disable all GCC
           optimizations that affect signaling NaN behavior.

       -fsingle-precision-constant
           Treat floating-point constants as single precision instead of implicitly converting
           them to double-precision constants.

       -fcx-limited-range
           When enabled, this option states that a range reduction step is not needed when
           performing complex division.  Also, there is no checking whether the result of a
           complex multiplication or division is "NaN + I*NaN", with an attempt to rescue the
           situation in that case.  The default is -fno-cx-limited-range, but is enabled by
           -ffast-math.

           This option controls the default setting of the ISO C99 "CX_LIMITED_RANGE" pragma.
           Nevertheless, the option applies to all languages.

       -fcx-fortran-rules
           Complex multiplication and division follow Fortran rules.  Range reduction is done as
           part of complex division, but there is no checking whether the result of a complex
           multiplication or division is "NaN + I*NaN", with an attempt to rescue the situation
           in that case.

           The default is -fno-cx-fortran-rules.

       The following options control optimizations that may improve performance, but are not
       enabled by any -O options.  This section includes experimental options that may produce
       broken code.

       -fbranch-probabilities
           After running a program compiled with -fprofile-arcs, you can compile it a second time
           using -fbranch-probabilities, to improve optimizations based on the number of times
           each branch was taken.  When a program compiled with -fprofile-arcs exits, it saves
           arc execution counts to a file called sourcename.gcda for each source file.  The
           information in this data file is very dependent on the structure of the generated
           code, so you must use the same source code and the same optimization options for both
           compilations.

           With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each JUMP_INSN and
           CALL_INSN.  These can be used to improve optimization.  Currently, they are only used
           in one place: in reorg.c, instead of guessing which path a branch is most likely to
           take, the REG_BR_PROB values are used to exactly determine which path is taken more
           often.

       -fprofile-values
           If combined with -fprofile-arcs, it adds code so that some data about values of
           expressions in the program is gathered.

           With -fbranch-probabilities, it reads back the data gathered from profiling values of
           expressions for usage in optimizations.

           Enabled with -fprofile-generate and -fprofile-use.

       -fprofile-reorder-functions
           Function reordering based on profile instrumentation collects first time of execution
           of a function and orders these functions in ascending order.

           Enabled with -fprofile-use.

       -fvpt
           If combined with -fprofile-arcs, this option instructs the compiler to add code to
           gather information about values of expressions.

           With -fbranch-probabilities, it reads back the data gathered and actually performs the
           optimizations based on them.  Currently the optimizations include specialization of
           division operations using the knowledge about the value of the denominator.

       -frename-registers
           Attempt to avoid false dependencies in scheduled code by making use of registers left
           over after register allocation.  This optimization most benefits processors with lots
           of registers.  Depending on the debug information format adopted by the target,
           however, it can make debugging impossible, since variables no longer stay in a "home
           register".

           Enabled by default with -funroll-loops and -fpeel-loops.

       -fschedule-fusion
           Performs a target dependent pass over the instruction stream to schedule instructions
           of same type together because target machine can execute them more efficiently if they
           are adjacent to each other in the instruction flow.

           Enabled at levels -O2, -O3, -Os.

       -ftracer
           Perform tail duplication to enlarge superblock size.  This transformation simplifies
           the control flow of the function allowing other optimizations to do a better job.

           Enabled with -fprofile-use.

       -funroll-loops
           Unroll loops whose number of iterations can be determined at compile time or upon
           entry to the loop.  -funroll-loops implies -frerun-cse-after-loop, -fweb and
           -frename-registers.  It also turns on complete loop peeling (i.e. complete removal of
           loops with a small constant number of iterations).  This option makes code larger, and
           may or may not make it run faster.

           Enabled with -fprofile-use.

       -funroll-all-loops
           Unroll all loops, even if their number of iterations is uncertain when the loop is
           entered.  This usually makes programs run more slowly.  -funroll-all-loops implies the
           same options as -funroll-loops.

       -fpeel-loops
           Peels loops for which there is enough information that they do not roll much (from
           profile feedback).  It also turns on complete loop peeling (i.e. complete removal of
           loops with small constant number of iterations).

           Enabled with -fprofile-use.

       -fmove-loop-invariants
           Enables the loop invariant motion pass in the RTL loop optimizer.  Enabled at level
           -O1

       -funswitch-loops
           Move branches with loop invariant conditions out of the loop, with duplicates of the
           loop on both branches (modified according to result of the condition).

       -ffunction-sections
       -fdata-sections
           Place each function or data item into its own section in the output file if the target
           supports arbitrary sections.  The name of the function or the name of the data item
           determines the section's name in the output file.

           Use these options on systems where the linker can perform optimizations to improve
           locality of reference in the instruction space.  Most systems using the ELF object
           format and SPARC processors running Solaris 2 have linkers with such optimizations.
           AIX may have these optimizations in the future.

           Only use these options when there are significant benefits from doing so.  When you
           specify these options, the assembler and linker create larger object and executable
           files and are also slower.  You cannot use gprof on all systems if you specify this
           option, and you may have problems with debugging if you specify both this option and
           -g.

       -fbranch-target-load-optimize
           Perform branch target register load optimization before prologue / epilogue threading.
           The use of target registers can typically be exposed only during reload, thus hoisting
           loads out of loops and doing inter-block scheduling needs a separate optimization
           pass.

       -fbranch-target-load-optimize2
           Perform branch target register load optimization after prologue / epilogue threading.

       -fbtr-bb-exclusive
           When performing branch target register load optimization, don't reuse branch target
           registers within any basic block.

       -fstack-protector
           Emit extra code to check for buffer overflows, such as stack smashing attacks.  This
           is done by adding a guard variable to functions with vulnerable objects.  This
           includes functions that call "alloca", and functions with buffers larger than 8 bytes.
           The guards are initialized when a function is entered and then checked when the
           function exits.  If a guard check fails, an error message is printed and the program
           exits.

       -fstack-protector-all
           Like -fstack-protector except that all functions are protected.

       -fstack-protector-strong
           Like -fstack-protector but includes additional functions to be protected --- those
           that have local array definitions, or have references to local frame addresses.

       -fstack-protector-explicit
           Like -fstack-protector but only protects those functions which have the
           "stack_protect" attribute

       -fstdarg-opt
           Optimize the prologue of variadic argument functions with respect to usage of those
           arguments.

       -fsection-anchors
           Try to reduce the number of symbolic address calculations by using shared "anchor"
           symbols to address nearby objects.  This transformation can help to reduce the number
           of GOT entries and GOT accesses on some targets.

           For example, the implementation of the following function "foo":

                   static int a, b, c;
                   int foo (void) { return a + b + c; }

           usually calculates the addresses of all three variables, but if you compile it with
           -fsection-anchors, it accesses the variables from a common anchor point instead.  The
           effect is similar to the following pseudocode (which isn't valid C):

                   int foo (void)
                   {
                     register int *xr = &x;
                     return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                   }

           Not all targets support this option.

       --param name=value
           In some places, GCC uses various constants to control the amount of optimization that
           is done.  For example, GCC does not inline functions that contain more than a certain
           number of instructions.  You can control some of these constants on the command line
           using the --param option.

           The names of specific parameters, and the meaning of the values, are tied to the
           internals of the compiler, and are subject to change without notice in future
           releases.

           In each case, the value is an integer.  The allowable choices for name are:

           predictable-branch-outcome
               When branch is predicted to be taken with probability lower than this threshold
               (in percent), then it is considered well predictable. The default is 10.

           max-crossjump-edges
               The maximum number of incoming edges to consider for cross-jumping.  The algorithm
               used by -fcrossjumping is O(N^2) in the number of edges incoming to each block.
               Increasing values mean more aggressive optimization, making the compilation time
               increase with probably small improvement in executable size.

           min-crossjump-insns
               The minimum number of instructions that must be matched at the end of two blocks
               before cross-jumping is performed on them.  This value is ignored in the case
               where all instructions in the block being cross-jumped from are matched.  The
               default value is 5.

           max-grow-copy-bb-insns
               The maximum code size expansion factor when copying basic blocks instead of
               jumping.  The expansion is relative to a jump instruction.  The default value is
               8.

           max-goto-duplication-insns
               The maximum number of instructions to duplicate to a block that jumps to a
               computed goto.  To avoid O(N^2) behavior in a number of passes, GCC factors
               computed gotos early in the compilation process, and unfactors them as late as
               possible.  Only computed jumps at the end of a basic blocks with no more than max-
               goto-duplication-insns are unfactored.  The default value is 8.

           max-delay-slot-insn-search
               The maximum number of instructions to consider when looking for an instruction to
               fill a delay slot.  If more than this arbitrary number of instructions are
               searched, the time savings from filling the delay slot are minimal, so stop
               searching.  Increasing values mean more aggressive optimization, making the
               compilation time increase with probably small improvement in execution time.

           max-delay-slot-live-search
               When trying to fill delay slots, the maximum number of instructions to consider
               when searching for a block with valid live register information.  Increasing this
               arbitrarily chosen value means more aggressive optimization, increasing the
               compilation time.  This parameter should be removed when the delay slot code is
               rewritten to maintain the control-flow graph.

           max-gcse-memory
               The approximate maximum amount of memory that can be allocated in order to perform
               the global common subexpression elimination optimization.  If more memory than
               specified is required, the optimization is not done.

           max-gcse-insertion-ratio
               If the ratio of expression insertions to deletions is larger than this value for
               any expression, then RTL PRE inserts or removes the expression and thus leaves
               partially redundant computations in the instruction stream.  The default value is
               20.

           max-pending-list-length
               The maximum number of pending dependencies scheduling allows before flushing the
               current state and starting over.  Large functions with few branches or calls can
               create excessively large lists which needlessly consume memory and resources.

           max-modulo-backtrack-attempts
               The maximum number of backtrack attempts the scheduler should make when modulo
               scheduling a loop.  Larger values can exponentially increase compilation time.

           max-inline-insns-single
               Several parameters control the tree inliner used in GCC.  This number sets the
               maximum number of instructions (counted in GCC's internal representation) in a
               single function that the tree inliner considers for inlining.  This only affects
               functions declared inline and methods implemented in a class declaration (C++).
               The default value is 400.

           max-inline-insns-auto
               When you use -finline-functions (included in -O3), a lot of functions that would
               otherwise not be considered for inlining by the compiler are investigated.  To
               those functions, a different (more restrictive) limit compared to functions
               declared inline can be applied.  The default value is 40.

           inline-min-speedup
               When estimated performance improvement of caller + callee runtime exceeds this
               threshold (in precent), the function can be inlined regardless the limit on
               --param max-inline-insns-single and --param max-inline-insns-auto.

           large-function-insns
               The limit specifying really large functions.  For functions larger than this limit
               after inlining, inlining is constrained by --param large-function-growth.  This
               parameter is useful primarily to avoid extreme compilation time caused by non-
               linear algorithms used by the back end.  The default value is 2700.

           large-function-growth
               Specifies maximal growth of large function caused by inlining in percents.  The
               default value is 100 which limits large function growth to 2.0 times the original
               size.

           large-unit-insns
               The limit specifying large translation unit.  Growth caused by inlining of units
               larger than this limit is limited by --param inline-unit-growth.  For small units
               this might be too tight.  For example, consider a unit consisting of function A
               that is inline and B that just calls A three times.  If B is small relative to A,
               the growth of unit is 300\% and yet such inlining is very sane.  For very large
               units consisting of small inlineable functions, however, the overall unit growth
               limit is needed to avoid exponential explosion of code size.  Thus for smaller
               units, the size is increased to --param large-unit-insns before applying --param
               inline-unit-growth.  The default is 10000.

           inline-unit-growth
               Specifies maximal overall growth of the compilation unit caused by inlining.  The
               default value is 20 which limits unit growth to 1.2 times the original size. Cold
               functions (either marked cold via an attribute or by profile feedback) are not
               accounted into the unit size.

           ipcp-unit-growth
               Specifies maximal overall growth of the compilation unit caused by interprocedural
               constant propagation.  The default value is 10 which limits unit growth to 1.1
               times the original size.

           large-stack-frame
               The limit specifying large stack frames.  While inlining the algorithm is trying
               to not grow past this limit too much.  The default value is 256 bytes.

           large-stack-frame-growth
               Specifies maximal growth of large stack frames caused by inlining in percents.
               The default value is 1000 which limits large stack frame growth to 11 times the
               original size.

           max-inline-insns-recursive
           max-inline-insns-recursive-auto
               Specifies the maximum number of instructions an out-of-line copy of a self-
               recursive inline function can grow into by performing recursive inlining.

               --param max-inline-insns-recursive applies to functions declared inline.  For
               functions not declared inline, recursive inlining happens only when
               -finline-functions (included in -O3) is enabled; --param max-inline-insns-
               recursive-auto applies instead.  The default value is 450.

           max-inline-recursive-depth
           max-inline-recursive-depth-auto
               Specifies the maximum recursion depth used for recursive inlining.

               --param max-inline-recursive-depth applies to functions declared inline.  For
               functions not declared inline, recursive inlining happens only when
               -finline-functions (included in -O3) is enabled; --param max-inline-recursive-
               depth-auto applies instead.  The default value is 8.

           min-inline-recursive-probability
               Recursive inlining is profitable only for function having deep recursion in
               average and can hurt for function having little recursion depth by increasing the
               prologue size or complexity of function body to other optimizers.

               When profile feedback is available (see -fprofile-generate) the actual recursion
               depth can be guessed from probability that function recurses via a given call
               expression.  This parameter limits inlining only to call expressions whose
               probability exceeds the given threshold (in percents).  The default value is 10.

           early-inlining-insns
               Specify growth that the early inliner can make.  In effect it increases the amount
               of inlining for code having a large abstraction penalty.  The default value is 14.

           max-early-inliner-iterations
               Limit of iterations of the early inliner.  This basically bounds the number of
               nested indirect calls the early inliner can resolve.  Deeper chains are still
               handled by late inlining.

           comdat-sharing-probability
               Probability (in percent) that C++ inline function with comdat visibility are
               shared across multiple compilation units.  The default value is 20.

           profile-func-internal-id
               A parameter to control whether to use function internal id in profile database
               lookup. If the value is 0, the compiler uses an id that is based on function
               assembler name and filename, which makes old profile data more tolerant to source
               changes such as function reordering etc.  The default value is 0.

           min-vect-loop-bound
               The minimum number of iterations under which loops are not vectorized when
               -ftree-vectorize is used.  The number of iterations after vectorization needs to
               be greater than the value specified by this option to allow vectorization.  The
               default value is 0.

           gcse-cost-distance-ratio
               Scaling factor in calculation of maximum distance an expression can be moved by
               GCSE optimizations.  This is currently supported only in the code hoisting pass.
               The bigger the ratio, the more aggressive code hoisting is with simple
               expressions, i.e., the expressions that have cost less than gcse-unrestricted-
               cost.  Specifying 0 disables hoisting of simple expressions.  The default value is
               10.

           gcse-unrestricted-cost
               Cost, roughly measured as the cost of a single typical machine instruction, at
               which GCSE optimizations do not constrain the distance an expression can travel.
               This is currently supported only in the code hoisting pass.  The lesser the cost,
               the more aggressive code hoisting is.  Specifying 0 allows all expressions to
               travel unrestricted distances.  The default value is 3.

           max-hoist-depth
               The depth of search in the dominator tree for expressions to hoist.  This is used
               to avoid quadratic behavior in hoisting algorithm.  The value of 0 does not limit
               on the search, but may slow down compilation of huge functions.  The default value
               is 30.

           max-tail-merge-comparisons
               The maximum amount of similar bbs to compare a bb with.  This is used to avoid
               quadratic behavior in tree tail merging.  The default value is 10.

           max-tail-merge-iterations
               The maximum amount of iterations of the pass over the function.  This is used to
               limit compilation time in tree tail merging.  The default value is 2.

           max-unrolled-insns
               The maximum number of instructions that a loop may have to be unrolled.  If a loop
               is unrolled, this parameter also determines how many times the loop code is
               unrolled.

           max-average-unrolled-insns
               The maximum number of instructions biased by probabilities of their execution that
               a loop may have to be unrolled.  If a loop is unrolled, this parameter also
               determines how many times the loop code is unrolled.

           max-unroll-times
               The maximum number of unrollings of a single loop.

           max-peeled-insns
               The maximum number of instructions that a loop may have to be peeled.  If a loop
               is peeled, this parameter also determines how many times the loop code is peeled.

           max-peel-times
               The maximum number of peelings of a single loop.

           max-peel-branches
               The maximum number of branches on the hot path through the peeled sequence.

           max-completely-peeled-insns
               The maximum number of insns of a completely peeled loop.

           max-completely-peel-times
               The maximum number of iterations of a loop to be suitable for complete peeling.

           max-completely-peel-loop-nest-depth
               The maximum depth of a loop nest suitable for complete peeling.

           max-unswitch-insns
               The maximum number of insns of an unswitched loop.

           max-unswitch-level
               The maximum number of branches unswitched in a single loop.

           lim-expensive
               The minimum cost of an expensive expression in the loop invariant motion.

           iv-consider-all-candidates-bound
               Bound on number of candidates for induction variables, below which all candidates
               are considered for each use in induction variable optimizations.  If there are
               more candidates than this, only the most relevant ones are considered to avoid
               quadratic time complexity.

           iv-max-considered-uses
               The induction variable optimizations give up on loops that contain more induction
               variable uses.

           iv-always-prune-cand-set-bound
               If the number of candidates in the set is smaller than this value, always try to
               remove unnecessary ivs from the set when adding a new one.

           scev-max-expr-size
               Bound on size of expressions used in the scalar evolutions analyzer.  Large
               expressions slow the analyzer.

           scev-max-expr-complexity
               Bound on the complexity of the expressions in the scalar evolutions analyzer.
               Complex expressions slow the analyzer.

           omega-max-vars
               The maximum number of variables in an Omega constraint system.  The default value
               is 128.

           omega-max-geqs
               The maximum number of inequalities in an Omega constraint system.  The default
               value is 256.

           omega-max-eqs
               The maximum number of equalities in an Omega constraint system.  The default value
               is 128.

           omega-max-wild-cards
               The maximum number of wildcard variables that the Omega solver is able to insert.
               The default value is 18.

           omega-hash-table-size
               The size of the hash table in the Omega solver.  The default value is 550.

           omega-max-keys
               The maximal number of keys used by the Omega solver.  The default value is 500.

           omega-eliminate-redundant-constraints
               When set to 1, use expensive methods to eliminate all redundant constraints.  The
               default value is 0.

           vect-max-version-for-alignment-checks
               The maximum number of run-time checks that can be performed when doing loop
               versioning for alignment in the vectorizer.

           vect-max-version-for-alias-checks
               The maximum number of run-time checks that can be performed when doing loop
               versioning for alias in the vectorizer.

           vect-max-peeling-for-alignment
               The maximum number of loop peels to enhance access alignment for vectorizer. Value
               -1 means 'no limit'.

           max-iterations-to-track
               The maximum number of iterations of a loop the brute-force algorithm for analysis
               of the number of iterations of the loop tries to evaluate.

           hot-bb-count-ws-permille
               A basic block profile count is considered hot if it contributes to the given
               permillage (i.e. 0...1000) of the entire profiled execution.

           hot-bb-frequency-fraction
               Select fraction of the entry block frequency of executions of basic block in
               function given basic block needs to have to be considered hot.

           max-predicted-iterations
               The maximum number of loop iterations we predict statically.  This is useful in
               cases where a function contains a single loop with known bound and another loop
               with unknown bound.  The known number of iterations is predicted correctly, while
               the unknown number of iterations average to roughly 10.  This means that the loop
               without bounds appears artificially cold relative to the other one.

           builtin-expect-probability
               Control the probability of the expression having the specified value. This
               parameter takes a percentage (i.e. 0 ... 100) as input.  The default probability
               of 90 is obtained empirically.

           align-threshold
               Select fraction of the maximal frequency of executions of a basic block in a
               function to align the basic block.

           align-loop-iterations
               A loop expected to iterate at least the selected number of iterations is aligned.

           tracer-dynamic-coverage
           tracer-dynamic-coverage-feedback
               This value is used to limit superblock formation once the given percentage of
               executed instructions is covered.  This limits unnecessary code size expansion.

               The tracer-dynamic-coverage-feedback parameter is used only when profile feedback
               is available.  The real profiles (as opposed to statically estimated ones) are
               much less balanced allowing the threshold to be larger value.

           tracer-max-code-growth
               Stop tail duplication once code growth has reached given percentage.  This is a
               rather artificial limit, as most of the duplicates are eliminated later in cross
               jumping, so it may be set to much higher values than is the desired code growth.

           tracer-min-branch-ratio
               Stop reverse growth when the reverse probability of best edge is less than this
               threshold (in percent).

           tracer-min-branch-ratio
           tracer-min-branch-ratio-feedback
               Stop forward growth if the best edge has probability lower than this threshold.

               Similarly to tracer-dynamic-coverage two values are present, one for compilation
               for profile feedback and one for compilation without.  The value for compilation
               with profile feedback needs to be more conservative (higher) in order to make
               tracer effective.

           max-cse-path-length
               The maximum number of basic blocks on path that CSE considers.  The default is 10.

           max-cse-insns
               The maximum number of instructions CSE processes before flushing.  The default is
               1000.

           ggc-min-expand
               GCC uses a garbage collector to manage its own memory allocation.  This parameter
               specifies the minimum percentage by which the garbage collector's heap should be
               allowed to expand between collections.  Tuning this may improve compilation speed;
               it has no effect on code generation.

               The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when RAM >= 1GB.
               If "getrlimit" is available, the notion of "RAM" is the smallest of actual RAM and
               "RLIMIT_DATA" or "RLIMIT_AS".  If GCC is not able to calculate RAM on a particular
               platform, the lower bound of 30% is used.  Setting this parameter and ggc-min-
               heapsize to zero causes a full collection to occur at every opportunity.  This is
               extremely slow, but can be useful for debugging.

           ggc-min-heapsize
               Minimum size of the garbage collector's heap before it begins bothering to collect
               garbage.  The first collection occurs after the heap expands by ggc-min-expand%
               beyond ggc-min-heapsize.  Again, tuning this may improve compilation speed, and
               has no effect on code generation.

               The default is the smaller of RAM/8, RLIMIT_RSS, or a limit that tries to ensure
               that RLIMIT_DATA or RLIMIT_AS are not exceeded, but with a lower bound of 4096
               (four megabytes) and an upper bound of 131072 (128 megabytes).  If GCC is not able
               to calculate RAM on a particular platform, the lower bound is used.  Setting this
               parameter very large effectively disables garbage collection.  Setting this
               parameter and ggc-min-expand to zero causes a full collection to occur at every
               opportunity.

           max-reload-search-insns
               The maximum number of instruction reload should look backward for equivalent
               register.  Increasing values mean more aggressive optimization, making the
               compilation time increase with probably slightly better performance.  The default
               value is 100.

           max-cselib-memory-locations
               The maximum number of memory locations cselib should take into account.
               Increasing values mean more aggressive optimization, making the compilation time
               increase with probably slightly better performance.  The default value is 500.

           reorder-blocks-duplicate
           reorder-blocks-duplicate-feedback
               Used by the basic block reordering pass to decide whether to use unconditional
               branch or duplicate the code on its destination.  Code is duplicated when its
               estimated size is smaller than this value multiplied by the estimated size of
               unconditional jump in the hot spots of the program.

               The reorder-block-duplicate-feedback parameter is used only when profile feedback
               is available.  It may be set to higher values than reorder-block-duplicate since
               information about the hot spots is more accurate.

           max-sched-ready-insns
               The maximum number of instructions ready to be issued the scheduler should
               consider at any given time during the first scheduling pass.  Increasing values
               mean more thorough searches, making the compilation time increase with probably
               little benefit.  The default value is 100.

           max-sched-region-blocks
               The maximum number of blocks in a region to be considered for interblock
               scheduling.  The default value is 10.

           max-pipeline-region-blocks
               The maximum number of blocks in a region to be considered for pipelining in the
               selective scheduler.  The default value is 15.

           max-sched-region-insns
               The maximum number of insns in a region to be considered for interblock
               scheduling.  The default value is 100.

           max-pipeline-region-insns
               The maximum number of insns in a region to be considered for pipelining in the
               selective scheduler.  The default value is 200.

           min-spec-prob
               The minimum probability (in percents) of reaching a source block for interblock
               speculative scheduling.  The default value is 40.

           max-sched-extend-regions-iters
               The maximum number of iterations through CFG to extend regions.  A value of 0 (the
               default) disables region extensions.

           max-sched-insn-conflict-delay
               The maximum conflict delay for an insn to be considered for speculative motion.
               The default value is 3.

           sched-spec-prob-cutoff
               The minimal probability of speculation success (in percents), so that speculative
               insns are scheduled.  The default value is 40.

           sched-spec-state-edge-prob-cutoff
               The minimum probability an edge must have for the scheduler to save its state
               across it.  The default value is 10.

           sched-mem-true-dep-cost
               Minimal distance (in CPU cycles) between store and load targeting same memory
               locations.  The default value is 1.

           selsched-max-lookahead
               The maximum size of the lookahead window of selective scheduling.  It is a depth
               of search for available instructions.  The default value is 50.

           selsched-max-sched-times
               The maximum number of times that an instruction is scheduled during selective
               scheduling.  This is the limit on the number of iterations through which the
               instruction may be pipelined.  The default value is 2.

           selsched-max-insns-to-rename
               The maximum number of best instructions in the ready list that are considered for
               renaming in the selective scheduler.  The default value is 2.

           sms-min-sc
               The minimum value of stage count that swing modulo scheduler generates.  The
               default value is 2.

           max-last-value-rtl
               The maximum size measured as number of RTLs that can be recorded in an expression
               in combiner for a pseudo register as last known value of that register.  The
               default is 10000.

           max-combine-insns
               The maximum number of instructions the RTL combiner tries to combine.  The default
               value is 2 at -Og and 4 otherwise.

           integer-share-limit
               Small integer constants can use a shared data structure, reducing the compiler's
               memory usage and increasing its speed.  This sets the maximum value of a shared
               integer constant.  The default value is 256.

           ssp-buffer-size
               The minimum size of buffers (i.e. arrays) that receive stack smashing protection
               when -fstack-protection is used.

           min-size-for-stack-sharing
               The minimum size of variables taking part in stack slot sharing when not
               optimizing. The default value is 32.

           max-jump-thread-duplication-stmts
               Maximum number of statements allowed in a block that needs to be duplicated when
               threading jumps.

           max-fields-for-field-sensitive
               Maximum number of fields in a structure treated in a field sensitive manner during
               pointer analysis.  The default is zero for -O0 and -O1, and 100 for -Os, -O2, and
               -O3.

           prefetch-latency
               Estimate on average number of instructions that are executed before prefetch
               finishes.  The distance prefetched ahead is proportional to this constant.
               Increasing this number may also lead to less streams being prefetched (see
               simultaneous-prefetches).

           simultaneous-prefetches
               Maximum number of prefetches that can run at the same time.

           l1-cache-line-size
               The size of cache line in L1 cache, in bytes.

           l1-cache-size
               The size of L1 cache, in kilobytes.

           l2-cache-size
               The size of L2 cache, in kilobytes.

           min-insn-to-prefetch-ratio
               The minimum ratio between the number of instructions and the number of prefetches
               to enable prefetching in a loop.

           prefetch-min-insn-to-mem-ratio
               The minimum ratio between the number of instructions and the number of memory
               references to enable prefetching in a loop.

           use-canonical-types
               Whether the compiler should use the "canonical" type system.  By default, this
               should always be 1, which uses a more efficient internal mechanism for comparing
               types in C++ and Objective-C++.  However, if bugs in the canonical type system are
               causing compilation failures, set this value to 0 to disable canonical types.

           switch-conversion-max-branch-ratio
               Switch initialization conversion refuses to create arrays that are bigger than
               switch-conversion-max-branch-ratio times the number of branches in the switch.

           max-partial-antic-length
               Maximum length of the partial antic set computed during the tree partial
               redundancy elimination optimization (-ftree-pre) when optimizing at -O3 and above.
               For some sorts of source code the enhanced partial redundancy elimination
               optimization can run away, consuming all of the memory available on the host
               machine.  This parameter sets a limit on the length of the sets that are computed,
               which prevents the runaway behavior.  Setting a value of 0 for this parameter
               allows an unlimited set length.

           sccvn-max-scc-size
               Maximum size of a strongly connected component (SCC) during SCCVN processing.  If
               this limit is hit, SCCVN processing for the whole function is not done and
               optimizations depending on it are disabled.  The default maximum SCC size is
               10000.

           sccvn-max-alias-queries-per-access
               Maximum number of alias-oracle queries we perform when looking for redundancies
               for loads and stores.  If this limit is hit the search is aborted and the load or
               store is not considered redundant.  The number of queries is algorithmically
               limited to the number of stores on all paths from the load to the function entry.
               The default maxmimum number of queries is 1000.

           ira-max-loops-num
               IRA uses regional register allocation by default.  If a function contains more
               loops than the number given by this parameter, only at most the given number of
               the most frequently-executed loops form regions for regional register allocation.
               The default value of the parameter is 100.

           ira-max-conflict-table-size
               Although IRA uses a sophisticated algorithm to compress the conflict table, the
               table can still require excessive amounts of memory for huge functions.  If the
               conflict table for a function could be more than the size in MB given by this
               parameter, the register allocator instead uses a faster, simpler, and lower-
               quality algorithm that does not require building a pseudo-register conflict table.
               The default value of the parameter is 2000.

           ira-loop-reserved-regs
               IRA can be used to evaluate more accurate register pressure in loops for decisions
               to move loop invariants (see -O3).  The number of available registers reserved for
               some other purposes is given by this parameter.  The default value of the
               parameter is 2, which is the minimal number of registers needed by typical
               instructions.  This value is the best found from numerous experiments.

           lra-inheritance-ebb-probability-cutoff
               LRA tries to reuse values reloaded in registers in subsequent insns.  This
               optimization is called inheritance.  EBB is used as a region to do this
               optimization.  The parameter defines a minimal fall-through edge probability in
               percentage used to add BB to inheritance EBB in LRA.  The default value of the
               parameter is 40.  The value was chosen from numerous runs of SPEC2000 on x86-64.

           loop-invariant-max-bbs-in-loop
               Loop invariant motion can be very expensive, both in compilation time and in
               amount of needed compile-time memory, with very large loops.  Loops with more
               basic blocks than this parameter won't have loop invariant motion optimization
               performed on them.  The default value of the parameter is 1000 for -O1 and 10000
               for -O2 and above.

           loop-max-datarefs-for-datadeps
               Building data dapendencies is expensive for very large loops.  This parameter
               limits the number of data references in loops that are considered for data
               dependence analysis.  These large loops are no handled by the optimizations using
               loop data dependencies.  The default value is 1000.

           max-vartrack-size
               Sets a maximum number of hash table slots to use during variable tracking dataflow
               analysis of any function.  If this limit is exceeded with variable tracking at
               assignments enabled, analysis for that function is retried without it, after
               removing all debug insns from the function.  If the limit is exceeded even without
               debug insns, var tracking analysis is completely disabled for the function.
               Setting the parameter to zero makes it unlimited.

           max-vartrack-expr-depth
               Sets a maximum number of recursion levels when attempting to map variable names or
               debug temporaries to value expressions.  This trades compilation time for more
               complete debug information.  If this is set too low, value expressions that are
               available and could be represented in debug information may end up not being used;
               setting this higher may enable the compiler to find more complex debug
               expressions, but compile time and memory use may grow.  The default is 12.

           min-nondebug-insn-uid
               Use uids starting at this parameter for nondebug insns.  The range below the
               parameter is reserved exclusively for debug insns created by
               -fvar-tracking-assignments, but debug insns may get (non-overlapping) uids above
               it if the reserved range is exhausted.

           ipa-sra-ptr-growth-factor
               IPA-SRA replaces a pointer to an aggregate with one or more new parameters only
               when their cumulative size is less or equal to ipa-sra-ptr-growth-factor times the
               size of the original pointer parameter.

           sra-max-scalarization-size-Ospeed
           sra-max-scalarization-size-Osize
               The two Scalar Reduction of Aggregates passes (SRA and IPA-SRA) aim to replace
               scalar parts of aggregates with uses of independent scalar variables.  These
               parameters control the maximum size, in storage units, of aggregate which is
               considered for replacement when compiling for speed (sra-max-scalarization-size-
               Ospeed) or size (sra-max-scalarization-size-Osize) respectively.

           tm-max-aggregate-size
               When making copies of thread-local variables in a transaction, this parameter
               specifies the size in bytes after which variables are saved with the logging
               functions as opposed to save/restore code sequence pairs.  This option only
               applies when using -fgnu-tm.

           graphite-max-nb-scop-params
               To avoid exponential effects in the Graphite loop transforms, the number of
               parameters in a Static Control Part (SCoP) is bounded.  The default value is 10
               parameters.  A variable whose value is unknown at compilation time and defined
               outside a SCoP is a parameter of the SCoP.

           graphite-max-bbs-per-function
               To avoid exponential effects in the detection of SCoPs, the size of the functions
               analyzed by Graphite is bounded.  The default value is 100 basic blocks.

           loop-block-tile-size
               Loop blocking or strip mining transforms, enabled with -floop-block or
               -floop-strip-mine, strip mine each loop in the loop nest by a given number of
               iterations.  The strip length can be changed using the loop-block-tile-size
               parameter.  The default value is 51 iterations.

           loop-unroll-jam-size
               Specify the unroll factor for the -floop-unroll-and-jam option.  The default value
               is 4.

           loop-unroll-jam-depth
               Specify the dimension to be unrolled (counting from the most inner loop) for the
               -floop-unroll-and-jam.  The default value is 2.

           ipa-cp-value-list-size
               IPA-CP attempts to track all possible values and types passed to a function's
               parameter in order to propagate them and perform devirtualization.  ipa-cp-value-
               list-size is the maximum number of values and types it stores per one formal
               parameter of a function.

           ipa-cp-eval-threshold
               IPA-CP calculates its own score of cloning profitability heuristics and performs
               those cloning opportunities with scores that exceed ipa-cp-eval-threshold.

           ipa-cp-recursion-penalty
               Percentage penalty the recursive functions will receive when they are evaluated
               for cloning.

           ipa-cp-single-call-penalty
               Percentage penalty functions containg a single call to another function will
               receive when they are evaluated for cloning.

           ipa-max-agg-items
               IPA-CP is also capable to propagate a number of scalar values passed in an
               aggregate. ipa-max-agg-items controls the maximum number of such values per one
               parameter.

           ipa-cp-loop-hint-bonus
               When IPA-CP determines that a cloning candidate would make the number of
               iterations of a loop known, it adds a bonus of ipa-cp-loop-hint-bonus to the
               profitability score of the candidate.

           ipa-cp-array-index-hint-bonus
               When IPA-CP determines that a cloning candidate would make the index of an array
               access known, it adds a bonus of ipa-cp-array-index-hint-bonus to the
               profitability score of the candidate.

           ipa-max-aa-steps
               During its analysis of function bodies, IPA-CP employs alias analysis in order to
               track values pointed to by function parameters.  In order not spend too much time
               analyzing huge functions, it gives up and consider all memory clobbered after
               examining ipa-max-aa-steps statements modifying memory.

           lto-partitions
               Specify desired number of partitions produced during WHOPR compilation.  The
               number of partitions should exceed the number of CPUs used for compilation.  The
               default value is 32.

           lto-minpartition
               Size of minimal partition for WHOPR (in estimated instructions).  This prevents
               expenses of splitting very small programs into too many partitions.

           cxx-max-namespaces-for-diagnostic-help
               The maximum number of namespaces to consult for suggestions when C++ name lookup
               fails for an identifier.  The default is 1000.

           sink-frequency-threshold
               The maximum relative execution frequency (in percents) of the target block
               relative to a statement's original block to allow statement sinking of a
               statement.  Larger numbers result in more aggressive statement sinking.  The
               default value is 75.  A small positive adjustment is applied for statements with
               memory operands as those are even more profitable so sink.

           max-stores-to-sink
               The maximum number of conditional stores paires that can be sunk.  Set to 0 if
               either vectorization (-ftree-vectorize) or if-conversion (-ftree-loop-if-convert)
               is disabled.  The default is 2.

           allow-store-data-races
               Allow optimizers to introduce new data races on stores.  Set to 1 to allow,
               otherwise to 0.  This option is enabled by default at optimization level -Ofast.

           case-values-threshold
               The smallest number of different values for which it is best to use a jump-table
               instead of a tree of conditional branches.  If the value is 0, use the default for
               the machine.  The default is 0.

           tree-reassoc-width
               Set the maximum number of instructions executed in parallel in reassociated tree.
               This parameter overrides target dependent heuristics used by default if has non
               zero value.

           sched-pressure-algorithm
               Choose between the two available implementations of -fsched-pressure.  Algorithm 1
               is the original implementation and is the more likely to prevent instructions from
               being reordered.  Algorithm 2 was designed to be a compromise between the
               relatively conservative approach taken by algorithm 1 and the rather aggressive
               approach taken by the default scheduler.  It relies more heavily on having a
               regular register file and accurate register pressure classes.  See haifa-sched.c
               in the GCC sources for more details.

               The default choice depends on the target.

           max-slsr-cand-scan
               Set the maximum number of existing candidates that are considered when seeking a
               basis for a new straight-line strength reduction candidate.

           asan-globals
               Enable buffer overflow detection for global objects.  This kind of protection is
               enabled by default if you are using -fsanitize=address option.  To disable global
               objects protection use --param asan-globals=0.

           asan-stack
               Enable buffer overflow detection for stack objects.  This kind of protection is
               enabled by default when using-fsanitize=address.  To disable stack protection use
               --param asan-stack=0 option.

           asan-instrument-reads
               Enable buffer overflow detection for memory reads.  This kind of protection is
               enabled by default when using -fsanitize=address.  To disable memory reads
               protection use --param asan-instrument-reads=0.

           asan-instrument-writes
               Enable buffer overflow detection for memory writes.  This kind of protection is
               enabled by default when using -fsanitize=address.  To disable memory writes
               protection use --param asan-instrument-writes=0 option.

           asan-memintrin
               Enable detection for built-in functions.  This kind of protection is enabled by
               default when using -fsanitize=address.  To disable built-in functions protection
               use --param asan-memintrin=0.

           asan-use-after-return
               Enable detection of use-after-return.  This kind of protection is enabled by
               default when using -fsanitize=address option.  To disable use-after-return
               detection use --param asan-use-after-return=0.

           asan-instrumentation-with-call-threshold
               If number of memory accesses in function being instrumented is greater or equal to
               this number, use callbacks instead of inline checks.  E.g. to disable inline code
               use --param asan-instrumentation-with-call-threshold=0.

           chkp-max-ctor-size
               Static constructors generated by Pointer Bounds Checker may become very large and
               significantly increase compile time at optimization level -O1 and higher.  This
               parameter is a maximum nubmer of statements in a single generated constructor.
               Default value is 5000.

           max-fsm-thread-path-insns
               Maximum number of instructions to copy when duplicating blocks on a finite state
               automaton jump thread path.  The default is 100.

           max-fsm-thread-length
               Maximum number of basic blocks on a finite state automaton jump thread path.  The
               default is 10.

           max-fsm-thread-paths
               Maximum number of new jump thread paths to create for a finite state automaton.
               The default is 50.

   Options Controlling the Preprocessor
       These options control the C preprocessor, which is run on each C source file before actual
       compilation.

       If you use the -E option, nothing is done except preprocessing.  Some of these options
       make sense only together with -E because they cause the preprocessor output to be
       unsuitable for actual compilation.

       -Wp,option
           You can use -Wp,option to bypass the compiler driver and pass option directly through
           to the preprocessor.  If option contains commas, it is split into multiple options at
           the commas.  However, many options are modified, translated or interpreted by the
           compiler driver before being passed to the preprocessor, and -Wp forcibly bypasses
           this phase.  The preprocessor's direct interface is undocumented and subject to
           change, so whenever possible you should avoid using -Wp and let the driver handle the
           options instead.

       -Xpreprocessor option
           Pass option as an option to the preprocessor.  You can use this to supply system-
           specific preprocessor options that GCC does not recognize.

           If you want to pass an option that takes an argument, you must use -Xpreprocessor
           twice, once for the option and once for the argument.

       -no-integrated-cpp
           Perform preprocessing as a separate pass before compilation.  By default, GCC performs
           preprocessing as an integrated part of input tokenization and parsing.  If this option
           is provided, the appropriate language front end (cc1, cc1plus, or cc1obj for C, C++,
           and Objective-C, respectively) is instead invoked twice, once for preprocessing only
           and once for actual compilation of the preprocessed input.  This option may be useful
           in conjunction with the -B or -wrapper options to specify an alternate preprocessor or
           perform additional processing of the program source between normal preprocessing and
           compilation.

       -D name
           Predefine name as a macro, with definition 1.

       -D name=definition
           The contents of definition are tokenized and processed as if they appeared during
           translation phase three in a #define directive.  In particular, the definition will be
           truncated by embedded newline characters.

           If you are invoking the preprocessor from a shell or shell-like program you may need
           to use the shell's quoting syntax to protect characters such as spaces that have a
           meaning in the shell syntax.

           If you wish to define a function-like macro on the command line, write its argument
           list with surrounding parentheses before the equals sign (if any).  Parentheses are
           meaningful to most shells, so you will need to quote the option.  With sh and csh,
           -D'name(args...)=definition' works.

           -D and -U options are processed in the order they are given on the command line.  All
           -imacros file and -include file options are processed after all -D and -U options.

       -U name
           Cancel any previous definition of name, either built in or provided with a -D option.

       -undef
           Do not predefine any system-specific or GCC-specific macros.  The standard predefined
           macros remain defined.

       -I dir
           Add the directory dir to the list of directories to be searched for header files.
           Directories named by -I are searched before the standard system include directories.
           If the directory dir is a standard system include directory, the option is ignored to
           ensure that the default search order for system directories and the special treatment
           of system headers are not defeated .  If dir begins with "=", then the "=" will be
           replaced by the sysroot prefix; see --sysroot and -isysroot.

       -o file
           Write output to file.  This is the same as specifying file as the second non-option
           argument to cpp.  gcc has a different interpretation of a second non-option argument,
           so you must use -o to specify the output file.

       -Wall
           Turns on all optional warnings which are desirable for normal code.  At present this
           is -Wcomment, -Wtrigraphs, -Wmultichar and a warning about integer promotion causing a
           change of sign in "#if" expressions.  Note that many of the preprocessor's warnings
           are on by default and have no options to control them.

       -Wcomment
       -Wcomments
           Warn whenever a comment-start sequence /* appears in a /* comment, or whenever a
           backslash-newline appears in a // comment.  (Both forms have the same effect.)

       -Wtrigraphs
           Most trigraphs in comments cannot affect the meaning of the program.  However, a
           trigraph that would form an escaped newline (??/ at the end of a line) can, by
           changing where the comment begins or ends.  Therefore, only trigraphs that would form
           escaped newlines produce warnings inside a comment.

           This option is implied by -Wall.  If -Wall is not given, this option is still enabled
           unless trigraphs are enabled.  To get trigraph conversion without warnings, but get
           the other -Wall warnings, use -trigraphs -Wall -Wno-trigraphs.

       -Wtraditional
           Warn about certain constructs that behave differently in traditional and ISO C.  Also
           warn about ISO C constructs that have no traditional C equivalent, and problematic
           constructs which should be avoided.

       -Wundef
           Warn whenever an identifier which is not a macro is encountered in an #if directive,
           outside of defined.  Such identifiers are replaced with zero.

       -Wunused-macros
           Warn about macros defined in the main file that are unused.  A macro is used if it is
           expanded or tested for existence at least once.  The preprocessor will also warn if
           the macro has not been used at the time it is redefined or undefined.

           Built-in macros, macros defined on the command line, and macros defined in include
           files are not warned about.

           Note: If a macro is actually used, but only used in skipped conditional blocks, then
           CPP will report it as unused.  To avoid the warning in such a case, you might improve
           the scope of the macro's definition by, for example, moving it into the first skipped
           block.  Alternatively, you could provide a dummy use with something like:

                   #if defined the_macro_causing_the_warning
                   #endif

       -Wendif-labels
           Warn whenever an #else or an #endif are followed by text.  This usually happens in
           code of the form

                   #if FOO
                   ...
                   #else FOO
                   ...
                   #endif FOO

           The second and third "FOO" should be in comments, but often are not in older programs.
           This warning is on by default.

       -Werror
           Make all warnings into hard errors.  Source code which triggers warnings will be
           rejected.

       -Wsystem-headers
           Issue warnings for code in system headers.  These are normally unhelpful in finding
           bugs in your own code, therefore suppressed.  If you are responsible for the system
           library, you may want to see them.

       -w  Suppress all warnings, including those which GNU CPP issues by default.

       -pedantic
           Issue all the mandatory diagnostics listed in the C standard.  Some of them are left
           out by default, since they trigger frequently on harmless code.

       -pedantic-errors
           Issue all the mandatory diagnostics, and make all mandatory diagnostics into errors.
           This includes mandatory diagnostics that GCC issues without -pedantic but treats as
           warnings.

       -M  Instead of outputting the result of preprocessing, output a rule suitable for make
           describing the dependencies of the main source file.  The preprocessor outputs one
           make rule containing the object file name for that source file, a colon, and the names
           of all the included files, including those coming from -include or -imacros command-
           line options.

           Unless specified explicitly (with -MT or -MQ), the object file name consists of the
           name of the source file with any suffix replaced with object file suffix and with any
           leading directory parts removed.  If there are many included files then the rule is
           split into several lines using \-newline.  The rule has no commands.

           This option does not suppress the preprocessor's debug output, such as -dM.  To avoid
           mixing such debug output with the dependency rules you should explicitly specify the
           dependency output file with -MF, or use an environment variable like
           DEPENDENCIES_OUTPUT.  Debug output will still be sent to the regular output stream as
           normal.

           Passing -M to the driver implies -E, and suppresses warnings with an implicit -w.

       -MM Like -M but do not mention header files that are found in system header directories,
           nor header files that are included, directly or indirectly, from such a header.

           This implies that the choice of angle brackets or double quotes in an #include
           directive does not in itself determine whether that header will appear in -MM
           dependency output.  This is a slight change in semantics from GCC versions 3.0 and
           earlier.

       -MF file
           When used with -M or -MM, specifies a file to write the dependencies to.  If no -MF
           switch is given the preprocessor sends the rules to the same place it would have sent
           preprocessed output.

           When used with the driver options -MD or -MMD, -MF overrides the default dependency
           output file.

       -MG In conjunction with an option such as -M requesting dependency generation, -MG assumes
           missing header files are generated files and adds them to the dependency list without
           raising an error.  The dependency filename is taken directly from the "#include"
           directive without prepending any path.  -MG also suppresses preprocessed output, as a
           missing header file renders this useless.

           This feature is used in automatic updating of makefiles.

       -MP This option instructs CPP to add a phony target for each dependency other than the
           main file, causing each to depend on nothing.  These dummy rules work around errors
           make gives if you remove header files without updating the Makefile to match.

           This is typical output:

                   test.o: test.c test.h

                   test.h:

       -MT target
           Change the target of the rule emitted by dependency generation.  By default CPP takes
           the name of the main input file, deletes any directory components and any file suffix
           such as .c, and appends the platform's usual object suffix.  The result is the target.

           An -MT option will set the target to be exactly the string you specify.  If you want
           multiple targets, you can specify them as a single argument to -MT, or use multiple
           -MT options.

           For example, -MT '$(objpfx)foo.o' might give

                   $(objpfx)foo.o: foo.c

       -MQ target
           Same as -MT, but it quotes any characters which are special to Make.
           -MQ '$(objpfx)foo.o' gives

                   $$(objpfx)foo.o: foo.c

           The default target is automatically quoted, as if it were given with -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.  The driver
           determines file based on whether an -o option is given.  If it is, the driver uses its
           argument but with a suffix of .d, otherwise it takes the name of the input file,
           removes any directory components and suffix, and applies a .d suffix.

           If -MD is used in conjunction with -E, any -o switch is understood to specify the
           dependency output file, but if used without -E, each -o is understood to specify a
           target object file.

           Since -E is not implied, -MD can be used to generate a dependency output file as a
           side-effect of the compilation process.

       -MMD
           Like -MD except mention only user header files, not system header files.

       -fpch-deps
           When using precompiled headers, this flag will cause the dependency-output flags to
           also list the files from the precompiled header's dependencies.  If not specified only
           the precompiled header would be listed and not the files that were used to create it
           because those files are not consulted when a precompiled header is used.

       -fpch-preprocess
           This option allows use of a precompiled header together with -E.  It inserts a special
           "#pragma", "#pragma GCC pch_preprocess "filename"" in the output to mark the place
           where the precompiled header was found, and its filename.  When -fpreprocessed is in
           use, GCC recognizes this "#pragma" and loads the PCH.

           This option is off by default, because the resulting preprocessed output is only
           really suitable as input to GCC.  It is switched on by -save-temps.

           You should not write this "#pragma" in your own code, but it is safe to edit the
           filename if the PCH file is available in a different location.  The filename may be
           absolute or it may be relative to GCC's current directory.

       -x c
       -x c++
       -x objective-c
       -x assembler-with-cpp
           Specify the source language: C, C++, Objective-C, or assembly.  This has nothing to do
           with standards conformance or extensions; it merely selects which base syntax to
           expect.  If you give none of these options, cpp will deduce the language from the
           extension of the source file: .c, .cc, .m, or .S.  Some other common extensions for
           C++ and assembly are also recognized.  If cpp does not recognize the extension, it
           will treat the file as C; this is the most generic mode.

           Note: Previous versions of cpp accepted a -lang option which selected both the
           language and the standards conformance level.  This option has been removed, because
           it conflicts with the -l option.

       -std=standard
       -ansi
           Specify the standard to which the code should conform.  Currently CPP knows about C
           and C++ standards; others may be added in the future.

           standard may be one of:

           "c90"
           "c89"
           "iso9899:1990"
               The ISO C standard from 1990.  c90 is the customary shorthand for this version of
               the standard.

               The -ansi option is equivalent to -std=c90.

           "iso9899:199409"
               The 1990 C standard, as amended in 1994.

           "iso9899:1999"
           "c99"
           "iso9899:199x"
           "c9x"
               The revised ISO C standard, published in December 1999.  Before publication, this
               was known as C9X.

           "iso9899:2011"
           "c11"
           "c1x"
               The revised ISO C standard, published in December 2011.  Before publication, this
               was known as C1X.

           "gnu90"
           "gnu89"
               The 1990 C standard plus GNU extensions.  This is the default.

           "gnu99"
           "gnu9x"
               The 1999 C standard plus GNU extensions.

           "gnu11"
           "gnu1x"
               The 2011 C standard plus GNU extensions.

           "c++98"
               The 1998 ISO C++ standard plus amendments.

           "gnu++98"
               The same as -std=c++98 plus GNU extensions.  This is the default for C++ code.

       -I- Split the include path.  Any directories specified with -I options before -I- are
           searched only for headers requested with "#include "file""; they are not searched for
           "#include <file>".  If additional directories are specified with -I options after the
           -I-, those directories are searched for all #include directives.

           In addition, -I- inhibits the use of the directory of the current file directory as
           the first search directory for "#include "file"".  This option has been deprecated.

       -nostdinc
           Do not search the standard system directories for header files.  Only the directories
           you have specified with -I options (and the directory of the current file, if
           appropriate) are searched.

       -nostdinc++
           Do not search for header files in the C++-specific standard directories, but do still
           search the other standard directories.  (This option is used when building the C++
           library.)

       -include file
           Process file as if "#include "file"" appeared as the first line of the primary source
           file.  However, the first directory searched for file is the preprocessor's working
           directory instead of the directory containing the main source file.  If not found
           there, it is searched for in the remainder of the "#include "..."" search chain as
           normal.

           If multiple -include options are given, the files are included in the order they
           appear on the command line.

       -imacros file
           Exactly like -include, except that any output produced by scanning file is thrown
           away.  Macros it defines remain defined.  This allows you to acquire all the macros
           from a header without also processing its declarations.

           All files specified by -imacros are processed before all files specified by -include.

       -idirafter dir
           Search dir for header files, but do it after all directories specified with -I and the
           standard system directories have been exhausted.  dir is treated as a system include
           directory.  If dir begins with "=", then the "=" will be replaced by the sysroot
           prefix; see --sysroot and -isysroot.

       -iprefix prefix
           Specify prefix as the prefix for subsequent -iwithprefix options.  If the prefix
           represents a directory, you should include the final /.

       -iwithprefix dir
       -iwithprefixbefore dir
           Append dir to the prefix specified previously with -iprefix, and add the resulting
           directory to the include search path.  -iwithprefixbefore puts it in the same place -I
           would; -iwithprefix puts it where -idirafter would.

       -isysroot dir
           This option is like the --sysroot option, but applies only to header files (except for
           Darwin targets, where it applies to both header files and libraries).  See the
           --sysroot option for more information.

       -imultilib dir
           Use dir as a subdirectory of the directory containing target-specific C++ headers.

       -isystem dir
           Search dir for header files, after all directories specified by -I but before the
           standard system directories.  Mark it as a system directory, so that it gets the same
           special treatment as is applied to the standard system directories.  If dir begins
           with "=", then the "=" will be replaced by the sysroot prefix; see --sysroot and
           -isysroot.

       -iquote dir
           Search dir only for header files requested with "#include "file""; they are not
           searched for "#include <file>", before all directories specified by -I and before the
           standard system directories.  If dir begins with "=", then the "=" will be replaced by
           the sysroot prefix; see --sysroot and -isysroot.

       -fdirectives-only
           When preprocessing, handle directives, but do not expand macros.

           The option's behavior depends on the -E and -fpreprocessed options.

           With -E, preprocessing is limited to the handling of directives such as "#define",
           "#ifdef", and "#error".  Other preprocessor operations, such as macro expansion and
           trigraph conversion are not performed.  In addition, the -dD option is implicitly
           enabled.

           With -fpreprocessed, predefinition of command line and most builtin macros is
           disabled.  Macros such as "__LINE__", which are contextually dependent, are handled
           normally.  This enables compilation of files previously preprocessed with "-E
           -fdirectives-only".

           With both -E and -fpreprocessed, the rules for -fpreprocessed take precedence.  This
           enables full preprocessing of files previously preprocessed with "-E
           -fdirectives-only".

       -fdollars-in-identifiers
           Accept $ in identifiers.

       -fextended-identifiers
           Accept universal character names in identifiers.  This option is enabled by default
           for C99 (and later C standard versions) and C++.

       -fno-canonical-system-headers
           When preprocessing, do not shorten system header paths with canonicalization.

       -fpreprocessed
           Indicate to the preprocessor that the input file has already been preprocessed.  This
           suppresses things like macro expansion, trigraph conversion, escaped newline splicing,
           and processing of most directives.  The preprocessor still recognizes and removes
           comments, so that you can pass a file preprocessed with -C to the compiler without
           problems.  In this mode the integrated preprocessor is little more than a tokenizer
           for the front ends.

           -fpreprocessed is implicit if the input file has one of the extensions .i, .ii or .mi.
           These are the extensions that GCC uses for preprocessed files created by -save-temps.

       -ftabstop=width
           Set the distance between tab stops.  This helps the preprocessor report correct column
           numbers in warnings or errors, even if tabs appear on the line.  If the value is less
           than 1 or greater than 100, the option is ignored.  The default is 8.

       -fdebug-cpp
           This option is only useful for debugging GCC.  When used with -E, dumps debugging
           information about location maps.  Every token in the output is preceded by the dump of
           the map its location belongs to.  The dump of the map holding the location of a token
           would be:

                   {"P":F</file/path>;"F":F</includer/path>;"L":<line_num>;"C":<col_num>;"S":<system_header_p>;"M":<map_address>;"E":<macro_expansion_p>,"loc":<location>}

           When used without -E, this option has no effect.

       -ftrack-macro-expansion[=level]
           Track locations of tokens across macro expansions. This allows the compiler to emit
           diagnostic about the current macro expansion stack when a compilation error occurs in
           a macro expansion. Using this option makes the preprocessor and the compiler consume
           more memory. The level parameter can be used to choose the level of precision of token
           location tracking thus decreasing the memory consumption if necessary. Value 0 of
           level de-activates this option just as if no -ftrack-macro-expansion was present on
           the command line. Value 1 tracks tokens locations in a degraded mode for the sake of
           minimal memory overhead. In this mode all tokens resulting from the expansion of an
           argument of a function-like macro have the same location. Value 2 tracks tokens
           locations completely. This value is the most memory hungry.  When this option is given
           no argument, the default parameter value is 2.

           Note that "-ftrack-macro-expansion=2" is activated by default.

       -fexec-charset=charset
           Set the execution character set, used for string and character constants.  The default
           is UTF-8.  charset can be any encoding supported by the system's "iconv" library
           routine.

       -fwide-exec-charset=charset
           Set the wide execution character set, used for wide string and character constants.
           The default is UTF-32 or UTF-16, whichever corresponds to the width of "wchar_t".  As
           with -fexec-charset, charset can be any encoding supported by the system's "iconv"
           library routine; however, you will have problems with encodings that do not fit
           exactly in "wchar_t".

       -finput-charset=charset
           Set the input character set, used for translation from the character set of the input
           file to the source character set used by GCC.  If the locale does not specify, or GCC
           cannot get this information from the locale, the default is UTF-8.  This can be
           overridden by either the locale or this command-line option.  Currently the command-
           line option takes precedence if there's a conflict.  charset can be any encoding
           supported by the system's "iconv" library routine.

       -fworking-directory
           Enable generation of linemarkers in the preprocessor output that will let the compiler
           know the current working directory at the time of preprocessing.  When this option is
           enabled, the preprocessor will emit, after the initial linemarker, a second linemarker
           with the current working directory followed by two slashes.  GCC will use this
           directory, when it's present in the preprocessed input, as the directory emitted as
           the current working directory in some debugging information formats.  This option is
           implicitly enabled if debugging information is enabled, but this can be inhibited with
           the negated form -fno-working-directory.  If the -P flag is present in the command
           line, this option has no effect, since no "#line" directives are emitted whatsoever.

       -fno-show-column
           Do not print column numbers in diagnostics.  This may be necessary if diagnostics are
           being scanned by a program that does not understand the column numbers, such as
           dejagnu.

       -A predicate=answer
           Make an assertion with the predicate predicate and answer answer.  This form is
           preferred to the older form -A predicate(answer), which is still supported, because it
           does not use shell special characters.

       -A -predicate=answer
           Cancel an assertion with the predicate predicate and answer answer.

       -dCHARS
           CHARS is a sequence of one or more of the following characters, and must not be
           preceded by a space.  Other characters are interpreted by the compiler proper, or
           reserved for future versions of GCC, and so are silently ignored.  If you specify
           characters whose behavior conflicts, the result is undefined.

           M   Instead of the normal output, generate a list of #define directives for all the
               macros defined during the execution of the preprocessor, including predefined
               macros.  This gives you a way of finding out what is predefined in your version of
               the preprocessor.  Assuming you have no file foo.h, the command

                       touch foo.h; cpp -dM foo.h

               will show all the predefined macros.

               If you use -dM without the -E option, -dM is interpreted as a synonym for
               -fdump-rtl-mach.

           D   Like M except in two respects: it does not include the predefined macros, and it
               outputs both the #define directives and the result of preprocessing.  Both kinds
               of output go to the standard output file.

           N   Like D, but emit only the macro names, not their expansions.

           I   Output #include directives in addition to the result of preprocessing.

           U   Like D except that only macros that are expanded, or whose definedness is tested
               in preprocessor directives, are output; the output is delayed until the use or
               test of the macro; and #undef directives are also output for macros tested but
               undefined at the time.

       -P  Inhibit generation of linemarkers in the output from the preprocessor.  This might be
           useful when running the preprocessor on something that is not C code, and will be sent
           to a program which might be confused by the linemarkers.

       -C  Do not discard comments.  All comments are passed through to the output file, except
           for comments in processed directives, which are deleted along with the directive.

           You should be prepared for side effects when using -C; it causes the preprocessor to
           treat comments as tokens in their own right.  For example, comments appearing at the
           start of what would be a directive line have the effect of turning that line into an
           ordinary source line, since the first token on the line is no longer a #.

       -CC Do not discard comments, including during macro expansion.  This is like -C, except
           that comments contained within macros are also passed through to the output file where
           the macro is expanded.

           In addition to the side-effects of the -C option, the -CC option causes all C++-style
           comments inside a macro to be converted to C-style comments.  This is to prevent later
           use of that macro from inadvertently commenting out the remainder of the source line.

           The -CC option is generally used to support lint comments.

       -traditional-cpp
           Try to imitate the behavior of old-fashioned C preprocessors, as opposed to ISO C
           preprocessors.

       -trigraphs
           Process trigraph sequences.  These are three-character sequences, all starting with
           ??, that are defined by ISO C to stand for single characters.  For example, ??/ stands
           for \, so '??/n' is a character constant for a newline.  By default, GCC ignores
           trigraphs, but in standard-conforming modes it converts them.  See the -std and -ansi
           options.

           The nine trigraphs and their replacements are

                   Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                   Replacement:      [    ]    {    }    #    \    ^    |    ~

       -remap
           Enable special code to work around file systems which only permit very short file
           names, such as MS-DOS.

       --help
       --target-help
           Print text describing all the command-line options instead of preprocessing anything.

       -v  Verbose mode.  Print out GNU CPP's version number at the beginning of execution, and
           report the final form of the include path.

       -H  Print the name of each header file used, in addition to other normal activities.  Each
           name is indented to show how deep in the #include stack it is.  Precompiled header
           files are also printed, even if they are found to be invalid; an invalid precompiled
           header file is printed with ...x and a valid one with ...! .

       -version
       --version
           Print out GNU CPP's version number.  With one dash, proceed to preprocess as normal.
           With two dashes, exit immediately.

   Passing Options to the Assembler
       You can pass options to the assembler.

       -Wa,option
           Pass option as an option to the assembler.  If option contains commas, it is split
           into multiple options at the commas.

       -Xassembler option
           Pass option as an option to the assembler.  You can use this to supply system-specific
           assembler options that GCC does not recognize.

           If you want to pass an option that takes an argument, you must use -Xassembler twice,
           once for the option and once for the argument.

   Options for Linking
       These options come into play when the compiler links object files into an executable
       output file.  They are meaningless if the compiler is not doing a link step.

       object-file-name
           A file name that does not end in a special recognized suffix is considered to name an
           object file or library.  (Object files are distinguished from libraries by the linker
           according to the file contents.)  If linking is done, these object files are used as
           input to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and object file names
           should not be used as arguments.

       -fuse-ld=bfd
           Use the bfd linker instead of the default linker.

       -fuse-ld=gold
           Use the gold linker instead of the default linker.

       -llibrary
       -l library
           Search the library named library when linking.  (The second alternative with the
           library as a separate argument is only for POSIX compliance and is not recommended.)

           It makes a difference where in the command you write this option; the linker searches
           and processes libraries and object files in the order they are specified.  Thus, foo.o
           -lz bar.o searches library z after file foo.o but before bar.o.  If bar.o refers to
           functions in z, those functions may not be loaded.

           The linker searches a standard list of directories for the library, which is actually
           a file named liblibrary.a.  The linker then uses this file as if it had been specified
           precisely by name.

           The directories searched include several standard system directories plus any that you
           specify with -L.

           Normally the files found this way are library files---archive files whose members are
           object files.  The linker handles an archive file by scanning through it for members
           which define symbols that have so far been referenced but not defined.  But if the
           file that is found is an ordinary object file, it is linked in the usual fashion.  The
           only difference between using an -l option and specifying a file name is that -l
           surrounds library with lib and .a and searches several directories.

       -lobjc
           You need this special case of the -l option in order to link an Objective-C or
           Objective-C++ program.

       -nostartfiles
           Do not use the standard system startup files when linking.  The standard system
           libraries are used normally, unless -nostdlib or -nodefaultlibs is used.

       -nodefaultlibs
           Do not use the standard system libraries when linking.  Only the libraries you specify
           are passed to the linker, and options specifying linkage of the system libraries, such
           as -static-libgcc or -shared-libgcc, are ignored.  The standard startup files are used
           normally, unless -nostartfiles is used.

           The compiler may generate calls to "memcmp", "memset", "memcpy" and "memmove".  These
           entries are usually resolved by entries in libc.  These entry points should be
           supplied through some other mechanism when this option is specified.

       -nostdlib
           Do not use the standard system startup files or libraries when linking.  No startup
           files and only the libraries you specify are passed to the linker, and options
           specifying linkage of the system libraries, such as -static-libgcc or -shared-libgcc,
           are ignored.

           The compiler may generate calls to "memcmp", "memset", "memcpy" and "memmove".  These
           entries are usually resolved by entries in libc.  These entry points should be
           supplied through some other mechanism when this option is specified.

           One of the standard libraries bypassed by -nostdlib and -nodefaultlibs is libgcc.a, a
           library of internal subroutines which GCC uses to overcome shortcomings of particular
           machines, or special needs for some languages.

           In most cases, you need libgcc.a even when you want to avoid other standard libraries.
           In other words, when you specify -nostdlib or -nodefaultlibs you should usually
           specify -lgcc as well.  This ensures that you have no unresolved references to
           internal GCC library subroutines.  (An example of such an internal subroutine is
           "__main", used to ensure C++ constructors are called.)

       -pie
           Produce a position independent executable on targets that support it.  For predictable
           results, you must also specify the same set of options used for compilation (-fpie,
           -fPIE, or model suboptions) when you specify this linker option.

       -no-pie
           Don't produce a position independent executable.

       -rdynamic
           Pass the flag -export-dynamic to the ELF linker, on targets that support it. This
           instructs the linker to add all symbols, not only used ones, to the dynamic symbol
           table. This option is needed for some uses of "dlopen" or to allow obtaining
           backtraces from within a program.

       -s  Remove all symbol table and relocation information from the executable.

       -static
           On systems that support dynamic linking, this prevents linking with the shared
           libraries.  On other systems, this option has no effect.

       -shared
           Produce a shared object which can then be linked with other objects to form an
           executable.  Not all systems support this option.  For predictable results, you must
           also specify the same set of options used for compilation (-fpic, -fPIC, or model
           suboptions) when you specify this linker option.[1]

       -shared-libgcc
       -static-libgcc
           On systems that provide libgcc as a shared library, these options force the use of
           either the shared or static version, respectively.  If no shared version of libgcc was
           built when the compiler was configured, these options have no effect.

           There are several situations in which an application should use the shared libgcc
           instead of the static version.  The most common of these is when the application
           wishes to throw and catch exceptions across different shared libraries.  In that case,
           each of the libraries as well as the application itself should use the shared libgcc.

           Therefore, the G++ and GCJ drivers automatically add -shared-libgcc whenever you build
           a shared library or a main executable, because C++ and Java programs typically use
           exceptions, so this is the right thing to do.

           If, instead, you use the GCC driver to create shared libraries, you may find that they
           are not always linked with the shared libgcc.  If GCC finds, at its configuration
           time, that you have a non-GNU linker or a GNU linker that does not support option
           --eh-frame-hdr, it links the shared version of libgcc into shared libraries by
           default.  Otherwise, it takes advantage of the linker and optimizes away the linking
           with the shared version of libgcc, linking with the static version of libgcc by
           default.  This allows exceptions to propagate through such shared libraries, without
           incurring relocation costs at library load time.

           However, if a library or main executable is supposed to throw or catch exceptions, you
           must link it using the G++ or GCJ driver, as appropriate for the languages used in the
           program, or using the option -shared-libgcc, such that it is linked with the shared
           libgcc.

       -static-libasan
           When the -fsanitize=address option is used to link a program, the GCC driver
           automatically links against libasan.  If libasan is available as a shared library, and
           the -static option is not used, then this links against the shared version of libasan.
           The -static-libasan option directs the GCC driver to link libasan statically, without
           necessarily linking other libraries statically.

       -static-libtsan
           When the -fsanitize=thread option is used to link a program, the GCC driver
           automatically links against libtsan.  If libtsan is available as a shared library, and
           the -static option is not used, then this links against the shared version of libtsan.
           The -static-libtsan option directs the GCC driver to link libtsan statically, without
           necessarily linking other libraries statically.

       -static-liblsan
           When the -fsanitize=leak option is used to link a program, the GCC driver
           automatically links against liblsan.  If liblsan is available as a shared library, and
           the -static option is not used, then this links against the shared version of liblsan.
           The -static-liblsan option directs the GCC driver to link liblsan statically, without
           necessarily linking other libraries statically.

       -static-libubsan
           When the -fsanitize=undefined option is used to link a program, the GCC driver
           automatically links against libubsan.  If libubsan is available as a shared library,
           and the -static option is not used, then this links against the shared version of
           libubsan.  The -static-libubsan option directs the GCC driver to link libubsan
           statically, without necessarily linking other libraries statically.

       -static-libmpx
           When the -fcheck-pointer bounds and -mmpx options are used to link a program, the GCC
           driver automatically links against libmpx.  If libmpx is available as a shared
           library, and the -static option is not used, then this links against the shared
           version of libmpx.  The -static-libmpx option directs the GCC driver to link libmpx
           statically, without necessarily linking other libraries statically.

       -static-libmpxwrappers
           When the -fcheck-pointer bounds and -mmpx options are used to link a program without
           also using -fno-chkp-use-wrappers, the GCC driver automatically links against
           libmpxwrappers.  If libmpxwrappers is available as a shared library, and the -static
           option is not used, then this links against the shared version of libmpxwrappers.  The
           -static-libmpxwrappers option directs the GCC driver to link libmpxwrappers
           statically, without necessarily linking other libraries statically.

       -static-libstdc++
           When the g++ program is used to link a C++ program, it normally automatically links
           against libstdc++.  If libstdc++ is available as a shared library, and the -static
           option is not used, then this links against the shared version of libstdc++.  That is
           normally fine.  However, it is sometimes useful to freeze the version of libstdc++
           used by the program without going all the way to a fully static link.  The
           -static-libstdc++ option directs the g++ driver to link libstdc++ statically, without
           necessarily linking other libraries statically.

       -symbolic
           Bind references to global symbols when building a shared object.  Warn about any
           unresolved references (unless overridden by the link editor option -Xlinker -z
           -Xlinker defs).  Only a few systems support this option.

       -T script
           Use script as the linker script.  This option is supported by most systems using the
           GNU linker.  On some targets, such as bare-board targets without an operating system,
           the -T option may be required when linking to avoid references to undefined symbols.

       -Xlinker option
           Pass option as an option to the linker.  You can use this to supply system-specific
           linker options that GCC does not recognize.

           If you want to pass an option that takes a separate argument, you must use -Xlinker
           twice, once for the option and once for the argument.  For example, to pass -assert
           definitions, you must write -Xlinker -assert -Xlinker definitions.  It does not work
           to write -Xlinker "-assert definitions", because this passes the entire string as a
           single argument, which is not what the linker expects.

           When using the GNU linker, it is usually more convenient to pass arguments to linker
           options using the option=value syntax than as separate arguments.  For example, you
           can specify -Xlinker -Map=output.map rather than -Xlinker -Map -Xlinker output.map.
           Other linkers may not support this syntax for command-line options.

       -Wl,option
           Pass option as an option to the linker.  If option contains commas, it is split into
           multiple options at the commas.  You can use this syntax to pass an argument to the
           option.  For example, -Wl,-Map,output.map passes -Map output.map to the linker.  When
           using the GNU linker, you can also get the same effect with -Wl,-Map=output.map.

           NOTE: In Ubuntu 8.10 and later versions, for LDFLAGS, the option -Wl,-z,relro is used.
           To disable, use -Wl,-z,norelro.

       -u symbol
           Pretend the symbol symbol is undefined, to force linking of library modules to define
           it.  You can use -u multiple times with different symbols to force loading of
           additional library modules.

       -z keyword
           -z is passed directly on to the linker along with the keyword keyword. See the section
           in the documentation of your linker for permitted values and their meanings.

   Options for Directory Search
       These options specify directories to search for header files, for libraries and for parts
       of the compiler:

       -Idir
           Add the directory dir to the head of the list of directories to be searched for header
           files.  This can be used to override a system header file, substituting your own
           version, since these directories are searched before the system header file
           directories.  However, you should not use this option to add directories that contain
           vendor-supplied system header files (use -isystem for that).  If you use more than one
           -I option, the directories are scanned in left-to-right order; the standard system
           directories come after.

           If a standard system include directory, or a directory specified with -isystem, is
           also specified with -I, the -I option is ignored.  The directory is still searched but
           as a system directory at its normal position in the system include chain.  This is to
           ensure that GCC's procedure to fix buggy system headers and the ordering for the
           "include_next" directive are not inadvertently changed.  If you really need to change
           the search order for system directories, use the -nostdinc and/or -isystem options.

       -iplugindir=dir
           Set the directory to search for plugins that are passed by -fplugin=name instead of
           -fplugin=path/name.so.  This option is not meant to be used by the user, but only
           passed by the driver.

       -iquotedir
           Add the directory dir to the head of the list of directories to be searched for header
           files only for the case of "#include "file""; they are not searched for "#include
           <file>", otherwise just like -I.

       -Ldir
           Add directory dir to the list of directories to be searched for -l.

       -Bprefix
           This option specifies where to find the executables, libraries, include files, and
           data files of the compiler itself.

           The compiler driver program runs one or more of the subprograms cpp, cc1, as and ld.
           It tries prefix as a prefix for each program it tries to run, both with and without
           machine/version/.

           For each subprogram to be run, the compiler driver first tries the -B prefix, if any.
           If that name is not found, or if -B is not specified, the driver tries two standard
           prefixes, /usr/lib/gcc/ and /usr/local/lib/gcc/.  If neither of those results in a
           file name that is found, the unmodified program name is searched for using the
           directories specified in your PATH environment variable.

           The compiler checks to see if the path provided by -B refers to a directory, and if
           necessary it adds a directory separator character at the end of the path.

           -B prefixes that effectively specify directory names also apply to libraries in the
           linker, because the compiler translates these options into -L options for the linker.
           They also apply to include files in the preprocessor, because the compiler translates
           these options into -isystem options for the preprocessor.  In this case, the compiler
           appends include to the prefix.

           The runtime support file libgcc.a can also be searched for using the -B prefix, if
           needed.  If it is not found there, the two standard prefixes above are tried, and that
           is all.  The file is left out of the link if it is not found by those means.

           Another way to specify a prefix much like the -B prefix is to use the environment
           variable GCC_EXEC_PREFIX.

           As a special kludge, if the path provided by -B is [dir/]stageN/, where N is a number
           in the range 0 to 9, then it is replaced by [dir/]include.  This is to help with boot-
           strapping the compiler.

       -specs=file
           Process file after the compiler reads in the standard specs file, in order to override
           the defaults which the gcc driver program uses when determining what switches to pass
           to cc1, cc1plus, as, ld, etc.  More than one -specs=file can be specified on the
           command line, and they are processed in order, from left to right.

       --sysroot=dir
           Use dir as the logical root directory for headers and libraries.  For example, if the
           compiler normally searches for headers in /usr/include and libraries in /usr/lib, it
           instead searches dir/usr/include and dir/usr/lib.

           If you use both this option and the -isysroot option, then the --sysroot option
           applies to libraries, but the -isysroot option applies to header files.

           The GNU linker (beginning with version 2.16) has the necessary support for this
           option.  If your linker does not support this option, the header file aspect of
           --sysroot still works, but the library aspect does not.

       --no-sysroot-suffix
           For some targets, a suffix is added to the root directory specified with --sysroot,
           depending on the other options used, so that headers may for example be found in
           dir/suffix/usr/include instead of dir/usr/include.  This option disables the addition
           of such a suffix.

       -I- This option has been deprecated.  Please use -iquote instead for -I directories before
           the -I- and remove the -I- option.  Any directories you specify with -I options before
           the -I- option are searched only for the case of "#include "file""; they are not
           searched for "#include <file>".

           If additional directories are specified with -I options after the -I- option, these
           directories are searched for all "#include" directives.  (Ordinarily all -I
           directories are used this way.)

           In addition, the -I- option inhibits the use of the current directory (where the
           current input file came from) as the first search directory for "#include "file"".
           There is no way to override this effect of -I-.  With -I. you can specify searching
           the directory that is current when the compiler is invoked.  That is not exactly the
           same as what the preprocessor does by default, but it is often satisfactory.

           -I- does not inhibit the use of the standard system directories for header files.
           Thus, -I- and -nostdinc are independent.

   Specifying Target Machine and Compiler Version
       The usual way to run GCC is to run the executable called gcc, or machine-gcc when cross-
       compiling, or machine-gcc-version to run a version other than the one that was installed
       last.

   Hardware Models and Configurations
       Each target machine types can have its own special options, starting with -m, to choose
       among various hardware models or configurations---for example, 68010 vs 68020, floating
       coprocessor or none.  A single installed version of the compiler can compile for any model
       or configuration, according to the options specified.

       Some configurations of the compiler also support additional special options, usually for
       compatibility with other compilers on the same platform.

       AArch64 Options

       These options are defined for AArch64 implementations:

       -mabi=name
           Generate code for the specified data model.  Permissible values are ilp32 for SysV-
           like data model where int, long int and pointer are 32-bit, and lp64 for SysV-like
           data model where int is 32-bit, but long int and pointer are 64-bit.

           The default depends on the specific target configuration.  Note that the LP64 and
           ILP32 ABIs are not link-compatible; you must compile your entire program with the same
           ABI, and link with a compatible set of libraries.

       -mbig-endian
           Generate big-endian code.  This is the default when GCC is configured for an
           aarch64_be-*-* target.

       -mgeneral-regs-only
           Generate code which uses only the general registers.

       -mlittle-endian
           Generate little-endian code.  This is the default when GCC is configured for an
           aarch64-*-* but not an aarch64_be-*-* target.

       -mcmodel=tiny
           Generate code for the tiny code model.  The program and its statically defined symbols
           must be within 1GB of each other.  Pointers are 64 bits.  Programs can be statically
           or dynamically linked.  This model is not fully implemented and mostly treated as
           small.

       -mcmodel=small
           Generate code for the small code model.  The program and its statically defined
           symbols must be within 4GB of each other.  Pointers are 64 bits.  Programs can be
           statically or dynamically linked.  This is the default code model.

       -mcmodel=large
           Generate code for the large code model.  This makes no assumptions about addresses and
           sizes of sections.  Pointers are 64 bits.  Programs can be statically linked only.

       -mstrict-align
           Do not assume that unaligned memory references are handled by the system.

       -momit-leaf-frame-pointer
       -mno-omit-leaf-frame-pointer
           Omit or keep the frame pointer in leaf functions.  The former behaviour is the
           default.

       -mtls-dialect=desc
           Use TLS descriptors as the thread-local storage mechanism for dynamic accesses of TLS
           variables.  This is the default.

       -mtls-dialect=traditional
           Use traditional TLS as the thread-local storage mechanism for dynamic accesses of TLS
           variables.

       -mfix-cortex-a53-835769
       -mno-fix-cortex-a53-835769
           Enable or disable the workaround for the ARM Cortex-A53 erratum number 835769.  This
           involves inserting a NOP instruction between memory instructions and 64-bit integer
           multiply-accumulate instructions.

       -mfix-cortex-a53-843419
       -mno-fix-cortex-a53-843419
           Enable or disable the workaround for the ARM Cortex-A53 erratum number 843419.  This
           erratum workaround is made at link time and this will only pass the corresponding flag
           to the linker.

       -march=name
           Specify the name of the target architecture, optionally suffixed by one or more
           feature modifiers.  This option has the form -march=arch{+[no]feature}*, where the
           only permissible value for arch is armv8-a.  The permissible values for feature are
           documented in the sub-section below.

           Where conflicting feature modifiers are specified, the right-most feature is used.

           GCC uses this name to determine what kind of instructions it can emit when generating
           assembly code.

           Where -march is specified without either of -mtune or -mcpu also being specified, the
           code is tuned to perform well across a range of target processors implementing the
           target architecture.

       -mtune=name
           Specify the name of the target processor for which GCC should tune the performance of
           the code.  Permissible values for this option are: generic, cortex-a53, cortex-a57,
           cortex-a72, exynos-m1, thunderx, xgene1.

           Additionally, this option can specify that GCC should tune the performance of the code
           for a big.LITTLE system.  Permissible values for this option are:
           cortex-a57.cortex-a53, cortex-a72.cortex-a53.

           Where none of -mtune=, -mcpu= or -march= are specified, the code is tuned to perform
           well across a range of target processors.

           This option cannot be suffixed by feature modifiers.

       -mcpu=name
           Specify the name of the target processor, optionally suffixed by one or more feature
           modifiers.  This option has the form -mcpu=cpu{+[no]feature}*, where the permissible
           values for cpu are the same as those available for -mtune.

           The permissible values for feature are documented in the sub-section below.

           Where conflicting feature modifiers are specified, the right-most feature is used.

           GCC uses this name to determine what kind of instructions it can emit when generating
           assembly code (as if by -march) and to determine the target processor for which to
           tune for performance (as if by -mtune).  Where this option is used in conjunction with
           -march or -mtune, those options take precedence over the appropriate part of this
           option.

       -march and -mcpu Feature Modifiers

       Feature modifiers used with -march and -mcpu can be one the following:

       crc Enable CRC extension.

       crypto
           Enable Crypto extension.  This implies Advanced SIMD is enabled.

       fp  Enable floating-point instructions.

       simd
           Enable Advanced SIMD instructions.  This implies floating-point instructions are
           enabled.  This is the default for all current possible values for options -march and
           -mcpu=.

       Adapteva Epiphany Options

       These -m options are defined for Adapteva Epiphany:

       -mhalf-reg-file
           Don't allocate any register in the range "r32"..."r63".  That allows code to run on
           hardware variants that lack these registers.

       -mprefer-short-insn-regs
           Preferrentially allocate registers that allow short instruction generation.  This can
           result in increased instruction count, so this may either reduce or increase overall
           code size.

       -mbranch-cost=num
           Set the cost of branches to roughly num "simple" instructions.  This cost is only a
           heuristic and is not guaranteed to produce consistent results across releases.

       -mcmove
           Enable the generation of conditional moves.

       -mnops=num
           Emit num NOPs before every other generated instruction.

       -mno-soft-cmpsf
           For single-precision floating-point comparisons, emit an "fsub" instruction and test
           the flags.  This is faster than a software comparison, but can get incorrect results
           in the presence of NaNs, or when two different small numbers are compared such that
           their difference is calculated as zero.  The default is -msoft-cmpsf, which uses
           slower, but IEEE-compliant, software comparisons.

       -mstack-offset=num
           Set the offset between the top of the stack and the stack pointer.  E.g., a value of 8
           means that the eight bytes in the range "sp+0...sp+7" can be used by leaf functions
           without stack allocation.  Values other than 8 or 16 are untested and unlikely to
           work.  Note also that this option changes the ABI; compiling a program with a
           different stack offset than the libraries have been compiled with generally does not
           work.  This option can be useful if you want to evaluate if a different stack offset
           would give you better code, but to actually use a different stack offset to build
           working programs, it is recommended to configure the toolchain with the appropriate
           --with-stack-offset=num option.

       -mno-round-nearest
           Make the scheduler assume that the rounding mode has been set to truncating.  The
           default is -mround-nearest.

       -mlong-calls
           If not otherwise specified by an attribute, assume all calls might be beyond the
           offset range of the "b" / "bl" instructions, and therefore load the function address
           into a register before performing a (otherwise direct) call.  This is the default.

       -mshort-calls
           If not otherwise specified by an attribute, assume all direct calls are in the range
           of the "b" / "bl" instructions, so use these instructions for direct calls.  The
           default is -mlong-calls.

       -msmall16
           Assume addresses can be loaded as 16-bit unsigned values.  This does not apply to
           function addresses for which -mlong-calls semantics are in effect.

       -mfp-mode=mode
           Set the prevailing mode of the floating-point unit.  This determines the floating-
           point mode that is provided and expected at function call and return time.  Making
           this mode match the mode you predominantly need at function start can make your
           programs smaller and faster by avoiding unnecessary mode switches.

           mode can be set to one the following values:

           caller
               Any mode at function entry is valid, and retained or restored when the function
               returns, and when it calls other functions.  This mode is useful for compiling
               libraries or other compilation units you might want to incorporate into different
               programs with different prevailing FPU modes, and the convenience of being able to
               use a single object file outweighs the size and speed overhead for any extra mode
               switching that might be needed, compared with what would be needed with a more
               specific choice of prevailing FPU mode.

           truncate
               This is the mode used for floating-point calculations with truncating (i.e. round
               towards zero) rounding mode.  That includes conversion from floating point to
               integer.

           round-nearest
               This is the mode used for floating-point calculations with round-to-nearest-or-
               even rounding mode.

           int This is the mode used to perform integer calculations in the FPU, e.g.  integer
               multiply, or integer multiply-and-accumulate.

           The default is -mfp-mode=caller

       -mnosplit-lohi
       -mno-postinc
       -mno-postmodify
           Code generation tweaks that disable, respectively, splitting of 32-bit loads,
           generation of post-increment addresses, and generation of post-modify addresses.  The
           defaults are msplit-lohi, -mpost-inc, and -mpost-modify.

       -mnovect-double
           Change the preferred SIMD mode to SImode.  The default is -mvect-double, which uses
           DImode as preferred SIMD mode.

       -max-vect-align=num
           The maximum alignment for SIMD vector mode types.  num may be 4 or 8.  The default is
           8.  Note that this is an ABI change, even though many library function interfaces are
           unaffected if they don't use SIMD vector modes in places that affect size and/or
           alignment of relevant types.

       -msplit-vecmove-early
           Split vector moves into single word moves before reload.  In theory this can give
           better register allocation, but so far the reverse seems to be generally the case.

       -m1reg-reg
           Specify a register to hold the constant -1, which makes loading small negative
           constants and certain bitmasks faster.  Allowable values for reg are r43 and r63,
           which specify use of that register as a fixed register, and none, which means that no
           register is used for this purpose.  The default is -m1reg-none.

       ARC Options

       The following options control the architecture variant for which code is being compiled:

       -mbarrel-shifter
           Generate instructions supported by barrel shifter.  This is the default unless
           -mcpu=ARC601 is in effect.

       -mcpu=cpu
           Set architecture type, register usage, and instruction scheduling parameters for cpu.
           There are also shortcut alias options available for backward compatibility and
           convenience.  Supported values for cpu are

           ARC600
               Compile for ARC600.  Aliases: -mA6, -mARC600.

           ARC601
               Compile for ARC601.  Alias: -mARC601.

           ARC700
               Compile for ARC700.  Aliases: -mA7, -mARC700.  This is the default when configured
               with --with-cpu=arc700.

       -mdpfp
       -mdpfp-compact
           FPX: Generate Double Precision FPX instructions, tuned for the compact implementation.

       -mdpfp-fast
           FPX: Generate Double Precision FPX instructions, tuned for the fast implementation.

       -mno-dpfp-lrsr
           Disable LR and SR instructions from using FPX extension aux registers.

       -mea
           Generate Extended arithmetic instructions.  Currently only "divaw", "adds", "subs",
           and "sat16" are supported.  This is always enabled for -mcpu=ARC700.

       -mno-mpy
           Do not generate mpy instructions for ARC700.

       -mmul32x16
           Generate 32x16 bit multiply and mac instructions.

       -mmul64
           Generate mul64 and mulu64 instructions.  Only valid for -mcpu=ARC600.

       -mnorm
           Generate norm instruction.  This is the default if -mcpu=ARC700 is in effect.

       -mspfp
       -mspfp-compact
           FPX: Generate Single Precision FPX instructions, tuned for the compact implementation.

       -mspfp-fast
           FPX: Generate Single Precision FPX instructions, tuned for the fast implementation.

       -msimd
           Enable generation of ARC SIMD instructions via target-specific builtins.  Only valid
           for -mcpu=ARC700.

       -msoft-float
           This option ignored; it is provided for compatibility purposes only.  Software
           floating point code is emitted by default, and this default can overridden by FPX
           options; mspfp, mspfp-compact, or mspfp-fast for single precision, and mdpfp, mdpfp-
           compact, or mdpfp-fast for double precision.

       -mswap
           Generate swap instructions.

       The following options are passed through to the assembler, and also define preprocessor
       macro symbols.

       -mdsp-packa
           Passed down to the assembler to enable the DSP Pack A extensions.  Also sets the
           preprocessor symbol "__Xdsp_packa".

       -mdvbf
           Passed down to the assembler to enable the dual viterbi butterfly extension.  Also
           sets the preprocessor symbol "__Xdvbf".

       -mlock
           Passed down to the assembler to enable the Locked Load/Store Conditional extension.
           Also sets the preprocessor symbol "__Xlock".

       -mmac-d16
           Passed down to the assembler.  Also sets the preprocessor symbol "__Xxmac_d16".

       -mmac-24
           Passed down to the assembler.  Also sets the preprocessor symbol "__Xxmac_24".

       -mrtsc
           Passed down to the assembler to enable the 64-bit Time-Stamp Counter extension
           instruction.  Also sets the preprocessor symbol "__Xrtsc".

       -mswape
           Passed down to the assembler to enable the swap byte ordering extension instruction.
           Also sets the preprocessor symbol "__Xswape".

       -mtelephony
           Passed down to the assembler to enable dual and single operand instructions for
           telephony.  Also sets the preprocessor symbol "__Xtelephony".

       -mxy
           Passed down to the assembler to enable the XY Memory extension.  Also sets the
           preprocessor symbol "__Xxy".

       The following options control how the assembly code is annotated:

       -misize
           Annotate assembler instructions with estimated addresses.

       -mannotate-align
           Explain what alignment considerations lead to the decision to make an instruction
           short or long.

       The following options are passed through to the linker:

       -marclinux
           Passed through to the linker, to specify use of the "arclinux" emulation.  This option
           is enabled by default in tool chains built for "arc-linux-uclibc" and
           "arceb-linux-uclibc" targets when profiling is not requested.

       -marclinux_prof
           Passed through to the linker, to specify use of the "arclinux_prof" emulation.  This
           option is enabled by default in tool chains built for "arc-linux-uclibc" and
           "arceb-linux-uclibc" targets when profiling is requested.

       The following options control the semantics of generated code:

       -mepilogue-cfi
           Enable generation of call frame information for epilogues.

       -mno-epilogue-cfi
           Disable generation of call frame information for epilogues.

       -mlong-calls
           Generate call insns as register indirect calls, thus providing access to the full
           32-bit address range.

       -mmedium-calls
           Don't use less than 25 bit addressing range for calls, which is the offset available
           for an unconditional branch-and-link instruction.  Conditional execution of function
           calls is suppressed, to allow use of the 25-bit range, rather than the 21-bit range
           with conditional branch-and-link.  This is the default for tool chains built for
           "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -mno-sdata
           Do not generate sdata references.  This is the default for tool chains built for
           "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

       -mucb-mcount
           Instrument with mcount calls as used in UCB code.  I.e. do the counting in the callee,
           not the caller.  By default ARC instrumentation counts in the caller.

       -mvolatile-cache
           Use ordinarily cached memory accesses for volatile references.  This is the default.

       -mno-volatile-cache
           Enable cache bypass for volatile references.

       The following options fine tune code generation:

       -malign-call
           Do alignment optimizations for call instructions.

       -mauto-modify-reg
           Enable the use of pre/post modify with register displacement.

       -mbbit-peephole
           Enable bbit peephole2.

       -mno-brcc
           This option disables a target-specific pass in arc_reorg to generate "BRcc"
           instructions.  It has no effect on "BRcc" generation driven by the combiner pass.

       -mcase-vector-pcrel
           Use pc-relative switch case tables - this enables case table shortening.  This is the
           default for -Os.

       -mcompact-casesi
           Enable compact casesi pattern.  This is the default for -Os.

       -mno-cond-exec
           Disable ARCompact specific pass to generate conditional execution instructions.  Due
           to delay slot scheduling and interactions between operand numbers, literal sizes,
           instruction lengths, and the support for conditional execution, the target-independent
           pass to generate conditional execution is often lacking, so the ARC port has kept a
           special pass around that tries to find more conditional execution generating
           opportunities after register allocation, branch shortening, and delay slot scheduling
           have been done.  This pass generally, but not always, improves performance and code
           size, at the cost of extra compilation time, which is why there is an option to switch
           it off.  If you have a problem with call instructions exceeding their allowable offset
           range because they are conditionalized, you should consider using -mmedium-calls
           instead.

       -mearly-cbranchsi
           Enable pre-reload use of the cbranchsi pattern.

       -mexpand-adddi
           Expand "adddi3" and "subdi3" at rtl generation time into "add.f", "adc" etc.

       -mindexed-loads
           Enable the use of indexed loads.  This can be problematic because some optimizers then
           assume that indexed stores exist, which is not the case.

       -mlra
           Enable Local Register Allocation.  This is still experimental for ARC, so by default
           the compiler uses standard reload (i.e. -mno-lra).

       -mlra-priority-none
           Don't indicate any priority for target registers.

       -mlra-priority-compact
           Indicate target register priority for r0..r3 / r12..r15.

       -mlra-priority-noncompact
           Reduce target regsiter priority for r0..r3 / r12..r15.

       -mno-millicode
           When optimizing for size (using -Os), prologues and epilogues that have to save or
           restore a large number of registers are often shortened by using call to a special
           function in libgcc; this is referred to as a millicode call.  As these calls can pose
           performance issues, and/or cause linking issues when linking in a nonstandard way,
           this option is provided to turn off millicode call generation.

       -mmixed-code
           Tweak register allocation to help 16-bit instruction generation.  This generally has
           the effect of decreasing the average instruction size while increasing the instruction
           count.

       -mq-class
           Enable 'q' instruction alternatives.  This is the default for -Os.

       -mRcq
           Enable Rcq constraint handling - most short code generation depends on this.  This is
           the default.

       -mRcw
           Enable Rcw constraint handling - ccfsm condexec mostly depends on this.  This is the
           default.

       -msize-level=level
           Fine-tune size optimization with regards to instruction lengths and alignment.  The
           recognized values for level are:

           0   No size optimization.  This level is deprecated and treated like 1.

           1   Short instructions are used opportunistically.

           2   In addition, alignment of loops and of code after barriers are dropped.

           3   In addition, optional data alignment is dropped, and the option Os is enabled.

           This defaults to 3 when -Os is in effect.  Otherwise, the behavior when this is not
           set is equivalent to level 1.

       -mtune=cpu
           Set instruction scheduling parameters for cpu, overriding any implied by -mcpu=.

           Supported values for cpu are

           ARC600
               Tune for ARC600 cpu.

           ARC601
               Tune for ARC601 cpu.

           ARC700
               Tune for ARC700 cpu with standard multiplier block.

           ARC700-xmac
               Tune for ARC700 cpu with XMAC block.

           ARC725D
               Tune for ARC725D cpu.

           ARC750D
               Tune for ARC750D cpu.

       -mmultcost=num
           Cost to assume for a multiply instruction, with 4 being equal to a normal instruction.

       -munalign-prob-threshold=probability
           Set probability threshold for unaligning branches.  When tuning for ARC700 and
           optimizing for speed, branches without filled delay slot are preferably emitted
           unaligned and long, unless profiling indicates that the probability for the branch to
           be taken is below probability.  The default is (REG_BR_PROB_BASE/2), i.e. 5000.

       The following options are maintained for backward compatibility, but are now deprecated
       and will be removed in a future release:

       -margonaut
           Obsolete FPX.

       -mbig-endian
       -EB Compile code for big endian targets.  Use of these options is now deprecated.  Users
           wanting big-endian code, should use the "arceb-elf32" and "arceb-linux-uclibc" targets
           when building the tool chain, for which big-endian is the default.

       -mlittle-endian
       -EL Compile code for little endian targets.  Use of these options is now deprecated.
           Users wanting little-endian code should use the "arc-elf32" and "arc-linux-uclibc"
           targets when building the tool chain, for which little-endian is the default.

       -mbarrel_shifter
           Replaced by -mbarrel-shifter.

       -mdpfp_compact
           Replaced by -mdpfp-compact.

       -mdpfp_fast
           Replaced by -mdpfp-fast.

       -mdsp_packa
           Replaced by -mdsp-packa.

       -mEA
           Replaced by -mea.

       -mmac_24
           Replaced by -mmac-24.

       -mmac_d16
           Replaced by -mmac-d16.

       -mspfp_compact
           Replaced by -mspfp-compact.

       -mspfp_fast
           Replaced by -mspfp-fast.

       -mtune=cpu
           Values arc600, arc601, arc700 and arc700-xmac for cpu are replaced by ARC600, ARC601,
           ARC700 and ARC700-xmac respectively

       -multcost=num
           Replaced by -mmultcost.

       ARM Options

       These -m options are defined for the ARM port:

       -mabi=name
           Generate code for the specified ABI.  Permissible values are: apcs-gnu, atpcs, aapcs,
           aapcs-linux and iwmmxt.

       -mapcs-frame
           Generate a stack frame that is compliant with the ARM Procedure Call Standard for all
           functions, even if this is not strictly necessary for correct execution of the code.
           Specifying -fomit-frame-pointer with this option causes the stack frames not to be
           generated for leaf functions.  The default is -mno-apcs-frame.  This option is
           deprecated.

       -mapcs
           This is a synonym for -mapcs-frame and is deprecated.

       -mthumb-interwork
           Generate code that supports calling between the ARM and Thumb instruction sets.
           Without this option, on pre-v5 architectures, the two instruction sets cannot be
           reliably used inside one program.  The default is -mno-thumb-interwork, since slightly
           larger code is generated when -mthumb-interwork is specified.  In AAPCS configurations
           this option is meaningless.

       -mno-sched-prolog
           Prevent the reordering of instructions in the function prologue, or the merging of
           those instruction with the instructions in the function's body.  This means that all
           functions start with a recognizable set of instructions (or in fact one of a choice
           from a small set of different function prologues), and this information can be used to
           locate the start of functions inside an executable piece of code.  The default is
           -msched-prolog.

       -mfloat-abi=name
           Specifies which floating-point ABI to use.  Permissible values are: soft, softfp and
           hard.

           Specifying soft causes GCC to generate output containing library calls for floating-
           point operations.  softfp allows the generation of code using hardware floating-point
           instructions, but still uses the soft-float calling conventions.  hard allows
           generation of floating-point instructions and uses FPU-specific calling conventions.

           The default depends on the specific target configuration.  Note that the hard-float
           and soft-float ABIs are not link-compatible; you must compile your entire program with
           the same ABI, and link with a compatible set of libraries.

       -mlittle-endian
           Generate code for a processor running in little-endian mode.  This is the default for
           all standard configurations.

       -mbig-endian
           Generate code for a processor running in big-endian mode; the default is to compile
           code for a little-endian processor.

       -march=name
           This specifies the name of the target ARM architecture.  GCC uses this name to
           determine what kind of instructions it can emit when generating assembly code.  This
           option can be used in conjunction with or instead of the -mcpu= option.  Permissible
           names are: armv2, armv2a, armv3, armv3m, armv4, armv4t, armv5, armv5t, armv5e,
           armv5te, armv6, armv6j, armv6t2, armv6z, armv6zk, armv6-m, armv7, armv7-a, armv7-r,
           armv7-m, armv7e-m, armv7ve, armv8-a, armv8-a+crc, iwmmxt, iwmmxt2, ep9312.

           -march=armv7ve is the armv7-a architecture with virtualization extensions.

           -march=armv8-a+crc enables code generation for the ARMv8-A architecture together with
           the optional CRC32 extensions.

           -march=native causes the compiler to auto-detect the architecture of the build
           computer.  At present, this feature is only supported on GNU/Linux, and not all
           architectures are recognized.  If the auto-detect is unsuccessful the option has no
           effect.

       -mtune=name
           This option specifies the name of the target ARM processor for which GCC should tune
           the performance of the code.  For some ARM implementations better performance can be
           obtained by using this option.  Permissible names are: arm2, arm250, arm3, arm6,
           arm60, arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di, arm7dmi, arm70,
           arm700, arm700i, arm710, arm710c, arm7100, arm720, arm7500, arm7500fe, arm7tdmi,
           arm7tdmi-s, arm710t, arm720t, arm740t, strongarm, strongarm110, strongarm1100,
           strongarm1110, arm8, arm810, arm9, arm9e, arm920, arm920t, arm922t, arm946e-s,
           arm966e-s, arm968e-s, arm926ej-s, arm940t, arm9tdmi, arm10tdmi, arm1020t, arm1026ej-s,
           arm10e, arm1020e, arm1022e, arm1136j-s, arm1136jf-s, mpcore, mpcorenovfp, arm1156t2-s,
           arm1156t2f-s, arm1176jz-s, arm1176jzf-s, cortex-a5, cortex-a7, cortex-a8, cortex-a9,
           cortex-a12, cortex-a15, cortex-a53, cortex-a57, cortex-a72, cortex-r4, cortex-r4f,
           cortex-r5, cortex-r7, cortex-m7, cortex-m4, cortex-m3, cortex-m1, cortex-m0,
           cortex-m0plus, cortex-m1.small-multiply, cortex-m0.small-multiply,
           cortex-m0plus.small-multiply, exynos-m1, marvell-pj4, xscale, iwmmxt, iwmmxt2, ep9312,
           fa526, fa626, fa606te, fa626te, fmp626, fa726te, xgene1.

           Additionally, this option can specify that GCC should tune the performance of the code
           for a big.LITTLE system.  Permissible names are: cortex-a15.cortex-a7,
           cortex-a57.cortex-a53, cortex-a72.cortex-a53.

           -mtune=generic-arch specifies that GCC should tune the performance for a blend of
           processors within architecture arch.  The aim is to generate code that run well on the
           current most popular processors, balancing between optimizations that benefit some
           CPUs in the range, and avoiding performance pitfalls of other CPUs.  The effects of
           this option may change in future GCC versions as CPU models come and go.

           -mtune=native causes the compiler to auto-detect the CPU of the build computer.  At
           present, this feature is only supported on GNU/Linux, and not all architectures are
           recognized.  If the auto-detect is unsuccessful the option has no effect.

       -mcpu=name
           This specifies the name of the target ARM processor.  GCC uses this name to derive the
           name of the target ARM architecture (as if specified by -march) and the ARM processor
           type for which to tune for performance (as if specified by -mtune).  Where this option
           is used in conjunction with -march or -mtune, those options take precedence over the
           appropriate part of this option.

           Permissible names for this option are the same as those for -mtune.

           -mcpu=generic-arch is also permissible, and is equivalent to -march=arch
           -mtune=generic-arch.  See -mtune for more information.

           -mcpu=native causes the compiler to auto-detect the CPU of the build computer.  At
           present, this feature is only supported on GNU/Linux, and not all architectures are
           recognized.  If the auto-detect is unsuccessful the option has no effect.

       -mfpu=name
           This specifies what floating-point hardware (or hardware emulation) is available on
           the target.  Permissible names are: vfp, vfpv3, vfpv3-fp16, vfpv3-d16, vfpv3-d16-fp16,
           vfpv3xd, vfpv3xd-fp16, neon, neon-fp16, vfpv4, vfpv4-d16, fpv4-sp-d16, neon-vfpv4,
           fpv5-d16, fpv5-sp-d16, fp-armv8, neon-fp-armv8, and crypto-neon-fp-armv8.

           If -msoft-float is specified this specifies the format of floating-point values.

           If the selected floating-point hardware includes the NEON extension (e.g. -mfpu=neon),
           note that floating-point operations are not generated by GCC's auto-vectorization pass
           unless -funsafe-math-optimizations is also specified.  This is because NEON hardware
           does not fully implement the IEEE 754 standard for floating-point arithmetic (in
           particular denormal values are treated as zero), so the use of NEON instructions may
           lead to a loss of precision.

       -mfp16-format=name
           Specify the format of the "__fp16" half-precision floating-point type.  Permissible
           names are none, ieee, and alternative; the default is none, in which case the "__fp16"
           type is not defined.

       -mstructure-size-boundary=n
           The sizes of all structures and unions are rounded up to a multiple of the number of
           bits set by this option.  Permissible values are 8, 32 and 64.  The default value
           varies for different toolchains.  For the COFF targeted toolchain the default value is
           8.  A value of 64 is only allowed if the underlying ABI supports it.

           Specifying a larger number can produce faster, more efficient code, but can also
           increase the size of the program.  Different values are potentially incompatible.
           Code compiled with one value cannot necessarily expect to work with code or libraries
           compiled with another value, if they exchange information using structures or unions.

       -mabort-on-noreturn
           Generate a call to the function "abort" at the end of a "noreturn" function.  It is
           executed if the function tries to return.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the address of the
           function into a register and then performing a subroutine call on this register.  This
           switch is needed if the target function lies outside of the 64-megabyte addressing
           range of the offset-based version of subroutine call instruction.

           Even if this switch is enabled, not all function calls are turned into long calls.
           The heuristic is that static functions, functions that have the "short_call"
           attribute, functions that are inside the scope of a "#pragma no_long_calls" directive,
           and functions whose definitions have already been compiled within the current
           compilation unit are not turned into long calls.  The exceptions to this rule are that
           weak function definitions, functions with the "long_call" attribute or the "section"
           attribute, and functions that are within the scope of a "#pragma long_calls" directive
           are always turned into long calls.

           This feature is not enabled by default.  Specifying -mno-long-calls restores the
           default behavior, as does placing the function calls within the scope of a "#pragma
           long_calls_off" directive.  Note these switches have no effect on how the compiler
           generates code to handle function calls via function pointers.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather than loading it in the
           prologue for each function.  The runtime system is responsible for initializing this
           register with an appropriate value before execution begins.

       -mpic-register=reg
           Specify the register to be used for PIC addressing.  For standard PIC base case, the
           default is any suitable register determined by compiler.  For single PIC base case,
           the default is R9 if target is EABI based or stack-checking is enabled, otherwise the
           default is R10.

       -mpic-data-is-text-relative
           Assume that each data segments are relative to text segment at load time.  Therefore,
           it permits addressing data using PC-relative operations.  This option is on by default
           for targets other than VxWorks RTP.

       -mpoke-function-name
           Write the name of each function into the text section, directly preceding the function
           prologue.  The generated code is similar to this:

                        t0
                            .ascii "arm_poke_function_name", 0
                            .align
                        t1
                            .word 0xff000000 + (t1 - t0)
                        arm_poke_function_name
                            mov     ip, sp
                            stmfd   sp!, {fp, ip, lr, pc}
                            sub     fp, ip, #4

           When performing a stack backtrace, code can inspect the value of "pc" stored at "fp +
           0".  If the trace function then looks at location "pc - 12" and the top 8 bits are
           set, then we know that there is a function name embedded immediately preceding this
           location and has length "((pc[-3]) & 0xff000000)".

       -mthumb
       -marm
           Select between generating code that executes in ARM and Thumb states.  The default for
           most configurations is to generate code that executes in ARM state, but the default
           can be changed by configuring GCC with the --with-mode=state configure option.

       -mtpcs-frame
           Generate a stack frame that is compliant with the Thumb Procedure Call Standard for
           all non-leaf functions.  (A leaf function is one that does not call any other
           functions.)  The default is -mno-tpcs-frame.

       -mtpcs-leaf-frame
           Generate a stack frame that is compliant with the Thumb Procedure Call Standard for
           all leaf functions.  (A leaf function is one that does not call any other functions.)
           The default is -mno-apcs-leaf-frame.

       -mcallee-super-interworking
           Gives all externally visible functions in the file being compiled an ARM instruction
           set header which switches to Thumb mode before executing the rest of the function.
           This allows these functions to be called from non-interworking code.  This option is
           not valid in AAPCS configurations because interworking is enabled by default.

       -mcaller-super-interworking
           Allows calls via function pointers (including virtual functions) to execute correctly
           regardless of whether the target code has been compiled for interworking or not.
           There is a small overhead in the cost of executing a function pointer if this option
           is enabled.  This option is not valid in AAPCS configurations because interworking is
           enabled by default.

       -mtp=name
           Specify the access model for the thread local storage pointer.  The valid models are
           soft, which generates calls to "__aeabi_read_tp", cp15, which fetches the thread
           pointer from "cp15" directly (supported in the arm6k architecture), and auto, which
           uses the best available method for the selected processor.  The default setting is
           auto.

       -mtls-dialect=dialect
           Specify the dialect to use for accessing thread local storage.  Two dialects are
           supported---gnu and gnu2.  The gnu dialect selects the original GNU scheme for
           supporting local and global dynamic TLS models.  The gnu2 dialect selects the GNU
           descriptor scheme, which provides better performance for shared libraries.  The GNU
           descriptor scheme is compatible with the original scheme, but does require new
           assembler, linker and library support.  Initial and local exec TLS models are
           unaffected by this option and always use the original scheme.

       -mword-relocations
           Only generate absolute relocations on word-sized values (i.e. R_ARM_ABS32).  This is
           enabled by default on targets (uClinux, SymbianOS) where the runtime loader imposes
           this restriction, and when -fpic or -fPIC is specified.

       -mfix-cortex-m3-ldrd
           Some Cortex-M3 cores can cause data corruption when "ldrd" instructions with
           overlapping destination and base registers are used.  This option avoids generating
           these instructions.  This option is enabled by default when -mcpu=cortex-m3 is
           specified.

       -munaligned-access
       -mno-unaligned-access
           Enables (or disables) reading and writing of 16- and 32- bit values from addresses
           that are not 16- or 32- bit aligned.  By default unaligned access is disabled for all
           pre-ARMv6 and all ARMv6-M architectures, and enabled for all other architectures.  If
           unaligned access is not enabled then words in packed data structures are accessed a
           byte at a time.

           The ARM attribute "Tag_CPU_unaligned_access" is set in the generated object file to
           either true or false, depending upon the setting of this option.  If unaligned access
           is enabled then the preprocessor symbol "__ARM_FEATURE_UNALIGNED" is also defined.

       -mneon-for-64bits
           Enables using Neon to handle scalar 64-bits operations. This is disabled by default
           since the cost of moving data from core registers to Neon is high.

       -mslow-flash-data
           Assume loading data from flash is slower than fetching instruction.  Therefore literal
           load is minimized for better performance.  This option is only supported when
           compiling for ARMv7 M-profile and off by default.

       -masm-syntax-unified
           Assume inline assembler is using unified asm syntax.  The default is currently off
           which implies divided syntax.  Currently this option is available only for Thumb1 and
           has no effect on ARM state and Thumb2.  However, this may change in future releases of
           GCC.  Divided syntax should be considered deprecated.

       -mrestrict-it
           Restricts generation of IT blocks to conform to the rules of ARMv8.  IT blocks can
           only contain a single 16-bit instruction from a select set of instructions. This
           option is on by default for ARMv8 Thumb mode.

       -mprint-tune-info
           Print CPU tuning information as comment in assembler file.  This is an option used
           only for regression testing of the compiler and not intended for ordinary use in
           compiling code.  This option is disabled by default.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
           Specify Atmel AVR instruction set architectures (ISA) or MCU type.

           The default for this option is@tie{}avr2.

           GCC supports the following AVR devices and ISAs:

           "avr2"
               "Classic" devices with up to 8@tie{}KiB of program memory.  mcu@tie{}= "attiny22",
               "attiny26", "at90c8534", "at90s2313", "at90s2323", "at90s2333", "at90s2343",
               "at90s4414", "at90s4433", "at90s4434", "at90s8515", "at90s8535".

           "avr25"
               "Classic" devices with up to 8@tie{}KiB of program memory and with the "MOVW"
               instruction.  mcu@tie{}= "ata5272", "ata6616c", "attiny13", "attiny13a",
               "attiny2313", "attiny2313a", "attiny24", "attiny24a", "attiny25", "attiny261",
               "attiny261a", "attiny43u", "attiny4313", "attiny44", "attiny44a", "attiny441",
               "attiny45", "attiny461", "attiny461a", "attiny48", "attiny828", "attiny84",
               "attiny84a", "attiny841", "attiny85", "attiny861", "attiny861a", "attiny87",
               "attiny88", "at86rf401".

           "avr3"
               "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB of  program memory.
               mcu@tie{}= "at43usb355", "at76c711".

           "avr31"
               "Classic" devices with 128@tie{}KiB of program memory.  mcu@tie{}= "atmega103",
               "at43usb320".

           "avr35"
               "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB of program memory and with
               the "MOVW" instruction.  mcu@tie{}= "ata5505", "ata6617c", "ata664251",
               "atmega16u2", "atmega32u2", "atmega8u2", "attiny1634", "attiny167", "at90usb162",
               "at90usb82".

           "avr4"
               "Enhanced" devices with up to 8@tie{}KiB of program memory.  mcu@tie{}= "ata6285",
               "ata6286", "ata6289", "ata6612c", "atmega48", "atmega48a", "atmega48p",
               "atmega48pa", "atmega8", "atmega8a", "atmega8hva", "atmega8515", "atmega8535",
               "atmega88", "atmega88a", "atmega88p", "atmega88pa", "at90pwm1", "at90pwm2",
               "at90pwm2b", "at90pwm3", "at90pwm3b", "at90pwm81".

           "avr5"
               "Enhanced" devices with 16@tie{}KiB up to 64@tie{}KiB of program memory.
               mcu@tie{}= "ata5702m322", "ata5782", "ata5790", "ata5790n", "ata5795", "ata5831",
               "ata6613c", "ata6614q", "atmega16", "atmega16a", "atmega16hva", "atmega16hva2",
               "atmega16hvb", "atmega16hvbrevb", "atmega16m1", "atmega16u4", "atmega161",
               "atmega162", "atmega163", "atmega164a", "atmega164p", "atmega164pa", "atmega165",
               "atmega165a", "atmega165p", "atmega165pa", "atmega168", "atmega168a",
               "atmega168p", "atmega168pa", "atmega169", "atmega169a", "atmega169p",
               "atmega169pa", "atmega32", "atmega32a", "atmega32c1", "atmega32hvb",
               "atmega32hvbrevb", "atmega32m1", "atmega32u4", "atmega32u6", "atmega323",
               "atmega324a", "atmega324p", "atmega324pa", "atmega325", "atmega325a",
               "atmega325p", "atmega325pa", "atmega3250", "atmega3250a", "atmega3250p",
               "atmega3250pa", "atmega328", "atmega328p", "atmega329", "atmega329a",
               "atmega329p", "atmega329pa", "atmega3290", "atmega3290a", "atmega3290p",
               "atmega3290pa", "atmega406", "atmega64", "atmega64a", "atmega64c1", "atmega64hve",
               "atmega64hve2", "atmega64m1", "atmega64rfr2", "atmega640", "atmega644",
               "atmega644a", "atmega644p", "atmega644pa", "atmega644rfr2", "atmega645",
               "atmega645a", "atmega645p", "atmega6450", "atmega6450a", "atmega6450p",
               "atmega649", "atmega649a", "atmega649p", "atmega6490", "atmega6490a",
               "atmega6490p", "at90can32", "at90can64", "at90pwm161", "at90pwm216", "at90pwm316",
               "at90scr100", "at90usb646", "at90usb647", "at94k", "m3000".

           "avr51"
               "Enhanced" devices with 128@tie{}KiB of program memory.  mcu@tie{}= "atmega128",
               "atmega128a", "atmega128rfa1", "atmega128rfr2", "atmega1280", "atmega1281",
               "atmega1284", "atmega1284p", "atmega1284rfr2", "at90can128", "at90usb1286",
               "at90usb1287".

           "avr6"
               "Enhanced" devices with 3-byte PC, i.e. with more than 128@tie{}KiB of program
               memory.  mcu@tie{}= "atmega256rfr2", "atmega2560", "atmega2561", "atmega2564rfr2".

           "avrxmega2"
               "XMEGA" devices with more than 8@tie{}KiB and up to 64@tie{}KiB of program memory.
               mcu@tie{}= "atxmega16a4", "atxmega16a4u", "atxmega16c4", "atxmega16d4",
               "atxmega16e5", "atxmega32a4", "atxmega32a4u", "atxmega32c3", "atxmega32c4",
               "atxmega32d3", "atxmega32d4", "atxmega32e5", "atxmega8e5".

           "avrxmega4"
               "XMEGA" devices with more than 64@tie{}KiB and up to 128@tie{}KiB of program
               memory.  mcu@tie{}= "atxmega64a3", "atxmega64a3u", "atxmega64a4u", "atxmega64b1",
               "atxmega64b3", "atxmega64c3", "atxmega64d3", "atxmega64d4".

           "avrxmega5"
               "XMEGA" devices with more than 64@tie{}KiB and up to 128@tie{}KiB of program
               memory and more than 64@tie{}KiB of RAM.  mcu@tie{}= "atxmega64a1",
               "atxmega64a1u".

           "avrxmega6"
               "XMEGA" devices with more than 128@tie{}KiB of program memory.  mcu@tie{}=
               "atxmega128a3", "atxmega128a3u", "atxmega128b1", "atxmega128b3", "atxmega128c3",
               "atxmega128d3", "atxmega128d4", "atxmega192a3", "atxmega192a3u", "atxmega192c3",
               "atxmega192d3", "atxmega256a3", "atxmega256a3b", "atxmega256a3bu",
               "atxmega256a3u", "atxmega256c3", "atxmega256d3", "atxmega384c3", "atxmega384d3".

           "avrxmega7"
               "XMEGA" devices with more than 128@tie{}KiB of program memory and more than
               64@tie{}KiB of RAM.  mcu@tie{}= "atxmega128a1", "atxmega128a1u", "atxmega128a4u".

           "avrtiny"
               "TINY" Tiny core devices with 512@tie{}B up to 4@tie{}KiB of program memory.
               mcu@tie{}= "attiny10", "attiny20", "attiny4", "attiny40", "attiny5", "attiny9".

           "avr1"
               This ISA is implemented by the minimal AVR core and supported for assembler only.
               mcu@tie{}= "attiny11", "attiny12", "attiny15", "attiny28", "at90s1200".

       -maccumulate-args
           Accumulate outgoing function arguments and acquire/release the needed stack space for
           outgoing function arguments once in function prologue/epilogue.  Without this option,
           outgoing arguments are pushed before calling a function and popped afterwards.

           Popping the arguments after the function call can be expensive on AVR so that
           accumulating the stack space might lead to smaller executables because arguments need
           not to be removed from the stack after such a function call.

           This option can lead to reduced code size for functions that perform several calls to
           functions that get their arguments on the stack like calls to printf-like functions.

       -mbranch-cost=cost
           Set the branch costs for conditional branch instructions to cost.  Reasonable values
           for cost are small, non-negative integers. The default branch cost is 0.

       -mcall-prologues
           Functions prologues/epilogues are expanded as calls to appropriate subroutines.  Code
           size is smaller.

       -mint8
           Assume "int" to be 8-bit integer.  This affects the sizes of all types: a "char" is 1
           byte, an "int" is 1 byte, a "long" is 2 bytes, and "long long" is 4 bytes.  Please
           note that this option does not conform to the C standards, but it results in smaller
           code size.

       -mn-flash=num
           Assume that the flash memory has a size of num times 64@tie{}KiB.

       -mno-interrupts
           Generated code is not compatible with hardware interrupts.  Code size is smaller.

       -mrelax
           Try to replace "CALL" resp. "JMP" instruction by the shorter "RCALL" resp. "RJMP"
           instruction if applicable.  Setting -mrelax just adds the --mlink-relax option to the
           assembler's command line and the --relax option to the linker's command line.

           Jump relaxing is performed by the linker because jump offsets are not known before
           code is located. Therefore, the assembler code generated by the compiler is the same,
           but the instructions in the executable may differ from instructions in the assembler
           code.

           Relaxing must be turned on if linker stubs are needed, see the section on "EIND" and
           linker stubs below.

       -mrmw
           Assume that the device supports the Read-Modify-Write instructions "XCH", "LAC", "LAS"
           and "LAT".

       -msp8
           Treat the stack pointer register as an 8-bit register, i.e. assume the high byte of
           the stack pointer is zero.  In general, you don't need to set this option by hand.

           This option is used internally by the compiler to select and build multilibs for
           architectures "avr2" and "avr25".  These architectures mix devices with and without
           "SPH".  For any setting other than -mmcu=avr2 or -mmcu=avr25 the compiler driver adds
           or removes this option from the compiler proper's command line, because the compiler
           then knows if the device or architecture has an 8-bit stack pointer and thus no "SPH"
           register or not.

       -mstrict-X
           Use address register "X" in a way proposed by the hardware.  This means that "X" is
           only used in indirect, post-increment or pre-decrement addressing.

           Without this option, the "X" register may be used in the same way as "Y" or "Z" which
           then is emulated by additional instructions.  For example, loading a value with
           "X+const" addressing with a small non-negative "const < 64" to a register Rn is
           performed as

                   adiw r26, const   ; X += const
                   ld   <Rn>, X        ; <Rn> = *X
                   sbiw r26, const   ; X -= const

       -mtiny-stack
           Only change the lower 8@tie{}bits of the stack pointer.

       -nodevicelib
           Don't link against AVR-LibC's device specific library "libdev.a".

       -Waddr-space-convert
           Warn about conversions between address spaces in the case where the resulting address
           space is not contained in the incoming address space.

       "EIND" and Devices with More Than 128 Ki Bytes of Flash

       Pointers in the implementation are 16@tie{}bits wide.  The address of a function or label
       is represented as word address so that indirect jumps and calls can target any code
       address in the range of 64@tie{}Ki words.

       In order to facilitate indirect jump on devices with more than 128@tie{}Ki bytes of
       program memory space, there is a special function register called "EIND" that serves as
       most significant part of the target address when "EICALL" or "EIJMP" instructions are
       used.

       Indirect jumps and calls on these devices are handled as follows by the compiler and are
       subject to some limitations:

       *   The compiler never sets "EIND".

       *   The compiler uses "EIND" implicitely in "EICALL"/"EIJMP" instructions or might read
           "EIND" directly in order to emulate an indirect call/jump by means of a "RET"
           instruction.

       *   The compiler assumes that "EIND" never changes during the startup code or during the
           application. In particular, "EIND" is not saved/restored in function or interrupt
           service routine prologue/epilogue.

       *   For indirect calls to functions and computed goto, the linker generates stubs. Stubs
           are jump pads sometimes also called trampolines. Thus, the indirect call/jump jumps to
           such a stub.  The stub contains a direct jump to the desired address.

       *   Linker relaxation must be turned on so that the linker generates the stubs correctly
           in all situations. See the compiler option -mrelax and the linker option --relax.
           There are corner cases where the linker is supposed to generate stubs but aborts
           without relaxation and without a helpful error message.

       *   The default linker script is arranged for code with "EIND = 0".  If code is supposed
           to work for a setup with "EIND != 0", a custom linker script has to be used in order
           to place the sections whose name start with ".trampolines" into the segment where
           "EIND" points to.

       *   The startup code from libgcc never sets "EIND".  Notice that startup code is a blend
           of code from libgcc and AVR-LibC.  For the impact of AVR-LibC on "EIND", see the AVR-
           LibC user manual ("http://nongnu.org/avr-libc/user-manual/").

       *   It is legitimate for user-specific startup code to set up "EIND" early, for example by
           means of initialization code located in section ".init3". Such code runs prior to
           general startup code that initializes RAM and calls constructors, but after the bit of
           startup code from AVR-LibC that sets "EIND" to the segment where the vector table is
           located.

                   #include <avr/io.h>

                   static void
                   __attribute__((section(".init3"),naked,used,no_instrument_function))
                   init3_set_eind (void)
                   {
                     __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
                                     "out %i0,r24" :: "n" (&EIND) : "r24","memory");
                   }

           The "__trampolines_start" symbol is defined in the linker script.

       *   Stubs are generated automatically by the linker if the following two conditions are
           met:

           -<The address of a label is taken by means of the "gs" modifier>
               (short for generate stubs) like so:

                       LDI r24, lo8(gs(<func>))
                       LDI r25, hi8(gs(<func>))

           -<The final location of that label is in a code segment>
               outside the segment where the stubs are located.

       *   The compiler emits such "gs" modifiers for code labels in the following situations:

           -<Taking address of a function or code label.>
           -<Computed goto.>
           -<If prologue-save function is used, see -mcall-prologues>
               command-line option.

           -<Switch/case dispatch tables. If you do not want such dispatch>
               tables you can specify the -fno-jump-tables command-line option.

           -<C and C++ constructors/destructors called during startup/shutdown.>
           -<If the tools hit a "gs()" modifier explained above.>
       *   Jumping to non-symbolic addresses like so is not supported:

                   int main (void)
                   {
                       /* Call function at word address 0x2 */
                       return ((int(*)(void)) 0x2)();
                   }

           Instead, a stub has to be set up, i.e. the function has to be called through a symbol
           ("func_4" in the example):

                   int main (void)
                   {
                       extern int func_4 (void);

                       /* Call function at byte address 0x4 */
                       return func_4();
                   }

           and the application be linked with -Wl,--defsym,func_4=0x4.  Alternatively, "func_4"
           can be defined in the linker script.

       Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special Function Registers

       Some AVR devices support memories larger than the 64@tie{}KiB range that can be accessed
       with 16-bit pointers.  To access memory locations outside this 64@tie{}KiB range, the
       contentent of a "RAMP" register is used as high part of the address: The "X", "Y", "Z"
       address register is concatenated with the "RAMPX", "RAMPY", "RAMPZ" special function
       register, respectively, to get a wide address. Similarly, "RAMPD" is used together with
       direct addressing.

       *   The startup code initializes the "RAMP" special function registers with zero.

       *   If a AVR Named Address Spaces,named address space other than generic or "__flash" is
           used, then "RAMPZ" is set as needed before the operation.

       *   If the device supports RAM larger than 64@tie{}KiB and the compiler needs to change
           "RAMPZ" to accomplish an operation, "RAMPZ" is reset to zero after the operation.

       *   If the device comes with a specific "RAMP" register, the ISR prologue/epilogue
           saves/restores that SFR and initializes it with zero in case the ISR code might
           (implicitly) use it.

       *   RAM larger than 64@tie{}KiB is not supported by GCC for AVR targets.  If you use
           inline assembler to read from locations outside the 16-bit address range and change
           one of the "RAMP" registers, you must reset it to zero after the access.

       AVR Built-in Macros

       GCC defines several built-in macros so that the user code can test for the presence or
       absence of features.  Almost any of the following built-in macros are deduced from device
       capabilities and thus triggered by the -mmcu= command-line option.

       For even more AVR-specific built-in macros see AVR Named Address Spaces and AVR Built-in
       Functions.

       "__AVR_ARCH__"
           Build-in macro that resolves to a decimal number that identifies the architecture and
           depends on the -mmcu=mcu option.  Possible values are:

           2, 25, 3, 31, 35, 4, 5, 51, 6

           for mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4", "avr5", "avr51", "avr6",

           respectively and

           100, 102, 104, 105, 106, 107

           for mcu="avrtiny", "avrxmega2", "avrxmega4", "avrxmega5", "avrxmega6", "avrxmega7",
           respectively.  If mcu specifies a device, this built-in macro is set accordingly. For
           example, with -mmcu=atmega8 the macro is defined to 4.

       "__AVR_Device__"
           Setting -mmcu=device defines this built-in macro which reflects the device's name. For
           example, -mmcu=atmega8 defines the built-in macro "__AVR_ATmega8__", -mmcu=attiny261a
           defines "__AVR_ATtiny261A__", etc.

           The built-in macros' names follow the scheme "__AVR_Device__" where Device is the
           device name as from the AVR user manual. The difference between Device in the built-in
           macro and device in -mmcu=device is that the latter is always lowercase.

           If device is not a device but only a core architecture like avr51, this macro is not
           defined.

       "__AVR_DEVICE_NAME__"
           Setting -mmcu=device defines this built-in macro to the device's name. For example,
           with -mmcu=atmega8 the macro is defined to "atmega8".

           If device is not a device but only a core architecture like avr51, this macro is not
           defined.

       "__AVR_XMEGA__"
           The device / architecture belongs to the XMEGA family of devices.

       "__AVR_HAVE_ELPM__"
           The device has the the "ELPM" instruction.

       "__AVR_HAVE_ELPMX__"
           The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions.

       "__AVR_HAVE_MOVW__"
           The device has the "MOVW" instruction to perform 16-bit register-register moves.

       "__AVR_HAVE_LPMX__"
           The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions.

       "__AVR_HAVE_MUL__"
           The device has a hardware multiplier.

       "__AVR_HAVE_JMP_CALL__"
           The device has the "JMP" and "CALL" instructions.  This is the case for devices with
           at least 16@tie{}KiB of program memory.

       "__AVR_HAVE_EIJMP_EICALL__"
       "__AVR_3_BYTE_PC__"
           The device has the "EIJMP" and "EICALL" instructions.  This is the case for devices
           with more than 128@tie{}KiB of program memory.  This also means that the program
           counter (PC) is 3@tie{}bytes wide.

       "__AVR_2_BYTE_PC__"
           The program counter (PC) is 2@tie{}bytes wide. This is the case for devices with up to
           128@tie{}KiB of program memory.

       "__AVR_HAVE_8BIT_SP__"
       "__AVR_HAVE_16BIT_SP__"
           The stack pointer (SP) register is treated as 8-bit respectively 16-bit register by
           the compiler.  The definition of these macros is affected by -mtiny-stack.

       "__AVR_HAVE_SPH__"
       "__AVR_SP8__"
           The device has the SPH (high part of stack pointer) special function register or has
           an 8-bit stack pointer, respectively.  The definition of these macros is affected by
           -mmcu= and in the cases of -mmcu=avr2 and -mmcu=avr25 also by -msp8.

       "__AVR_HAVE_RAMPD__"
       "__AVR_HAVE_RAMPX__"
       "__AVR_HAVE_RAMPY__"
       "__AVR_HAVE_RAMPZ__"
           The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ" special function register,
           respectively.

       "__NO_INTERRUPTS__"
           This macro reflects the -mno-interrupts command-line option.

       "__AVR_ERRATA_SKIP__"
       "__AVR_ERRATA_SKIP_JMP_CALL__"
           Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit instructions because of a
           hardware erratum.  Skip instructions are "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE".
           The second macro is only defined if "__AVR_HAVE_JMP_CALL__" is also set.

       "__AVR_ISA_RMW__"
           The device has Read-Modify-Write instructions (XCH, LAC, LAS and LAT).

       "__AVR_SFR_OFFSET__=offset"
           Instructions that can address I/O special function registers directly like "IN",
           "OUT", "SBI", etc. may use a different address as if addressed by an instruction to
           access RAM like "LD" or "STS". This offset depends on the device architecture and has
           to be subtracted from the RAM address in order to get the respective I/O@tie{}address.

       "__WITH_AVRLIBC__"
           The compiler is configured to be used together with AVR-Libc.  See the --with-avrlibc
           configure option.

       Blackfin Options

       -mcpu=cpu[-sirevision]
           Specifies the name of the target Blackfin processor.  Currently, cpu can be one of
           bf512, bf514, bf516, bf518, bf522, bf523, bf524, bf525, bf526, bf527, bf531, bf532,
           bf533, bf534, bf536, bf537, bf538, bf539, bf542, bf544, bf547, bf548, bf549, bf542m,
           bf544m, bf547m, bf548m, bf549m, bf561, bf592.

           The optional sirevision specifies the silicon revision of the target Blackfin
           processor.  Any workarounds available for the targeted silicon revision are enabled.
           If sirevision is none, no workarounds are enabled.  If sirevision is any, all
           workarounds for the targeted processor are enabled.  The "__SILICON_REVISION__" macro
           is defined to two hexadecimal digits representing the major and minor numbers in the
           silicon revision.  If sirevision is none, the "__SILICON_REVISION__" is not defined.
           If sirevision is any, the "__SILICON_REVISION__" is defined to be 0xffff.  If this
           optional sirevision is not used, GCC assumes the latest known silicon revision of the
           targeted Blackfin processor.

           GCC defines a preprocessor macro for the specified cpu.  For the bfin-elf toolchain,
           this option causes the hardware BSP provided by libgloss to be linked in if -msim is
           not given.

           Without this option, bf532 is used as the processor by default.

           Note that support for bf561 is incomplete.  For bf561, only the preprocessor macro is
           defined.

       -msim
           Specifies that the program will be run on the simulator.  This causes the simulator
           BSP provided by libgloss to be linked in.  This option has effect only for bfin-elf
           toolchain.  Certain other options, such as -mid-shared-library and -mfdpic, imply
           -msim.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf functions.  This avoids the
           instructions to save, set up and restore frame pointers and makes an extra register
           available in leaf functions.  The option -fomit-frame-pointer removes the frame
           pointer for all functions, which might make debugging harder.

       -mspecld-anomaly
           When enabled, the compiler ensures that the generated code does not contain
           speculative loads after jump instructions. If this option is used,
           "__WORKAROUND_SPECULATIVE_LOADS" is defined.

       -mno-specld-anomaly
           Don't generate extra code to prevent speculative loads from occurring.

       -mcsync-anomaly
           When enabled, the compiler ensures that the generated code does not contain CSYNC or
           SSYNC instructions too soon after conditional branches.  If this option is used,
           "__WORKAROUND_SPECULATIVE_SYNCS" is defined.

       -mno-csync-anomaly
           Don't generate extra code to prevent CSYNC or SSYNC instructions from occurring too
           soon after a conditional branch.

       -mlow-64k
           When enabled, the compiler is free to take advantage of the knowledge that the entire
           program fits into the low 64k of memory.

       -mno-low-64k
           Assume that the program is arbitrarily large.  This is the default.

       -mstack-check-l1
           Do stack checking using information placed into L1 scratchpad memory by the uClinux
           kernel.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID method.  This allows
           for execute in place and shared libraries in an environment without virtual memory
           management.  This option implies -fPIC.  With a bfin-elf target, this option implies
           -msim.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are being used.  This is
           the default.

       -mleaf-id-shared-library
           Generate code that supports shared libraries via the library ID method, but assumes
           that this library or executable won't link against any other ID shared libraries.
           That allows the compiler to use faster code for jumps and calls.

       -mno-leaf-id-shared-library
           Do not assume that the code being compiled won't link against any ID shared libraries.
           Slower code is generated for jump and call insns.

       -mshared-library-id=n
           Specifies the identification number of the ID-based shared library being compiled.
           Specifying a value of 0 generates more compact code; specifying other values forces
           the allocation of that number to the current library but is no more space- or time-
           efficient than omitting this option.

       -msep-data
           Generate code that allows the data segment to be located in a different area of memory
           from the text segment.  This allows for execute in place in an environment without
           virtual memory management by eliminating relocations against the text section.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text segment.  This is
           the default.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the address of the
           function into a register and then performing a subroutine call on this register.  This
           switch is needed if the target function lies outside of the 24-bit addressing range of
           the offset-based version of subroutine call instruction.

           This feature is not enabled by default.  Specifying -mno-long-calls restores the
           default behavior.  Note these switches have no effect on how the compiler generates
           code to handle function calls via function pointers.

       -mfast-fp
           Link with the fast floating-point library. This library relaxes some of the IEEE
           floating-point standard's rules for checking inputs against Not-a-Number (NAN), in the
           interest of performance.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions that are not known to
           bind locally.  It has no effect without -mfdpic.

       -mmulticore
           Build a standalone application for multicore Blackfin processors.  This option causes
           proper start files and link scripts supporting multicore to be used, and defines the
           macro "__BFIN_MULTICORE".  It can only be used with -mcpu=bf561[-sirevision].

           This option can be used with -mcorea or -mcoreb, which selects the one-application-
           per-core programming model.  Without -mcorea or -mcoreb, the
           single-application/dual-core programming model is used. In this model, the main
           function of Core B should be named as "coreb_main".

           If this option is not used, the single-core application programming model is used.

       -mcorea
           Build a standalone application for Core A of BF561 when using the one-application-per-
           core programming model. Proper start files and link scripts are used to support Core
           A, and the macro "__BFIN_COREA" is defined.  This option can only be used in
           conjunction with -mmulticore.

       -mcoreb
           Build a standalone application for Core B of BF561 when using the one-application-per-
           core programming model. Proper start files and link scripts are used to support Core
           B, and the macro "__BFIN_COREB" is defined. When this option is used, "coreb_main"
           should be used instead of "main".  This option can only be used in conjunction with
           -mmulticore.

       -msdram
           Build a standalone application for SDRAM. Proper start files and link scripts are used
           to put the application into SDRAM, and the macro "__BFIN_SDRAM" is defined.  The
           loader should initialize SDRAM before loading the application.

       -micplb
           Assume that ICPLBs are enabled at run time.  This has an effect on certain anomaly
           workarounds.  For Linux targets, the default is to assume ICPLBs are enabled; for
           standalone applications the default is off.

       C6X Options

       -march=name
           This specifies the name of the target architecture.  GCC uses this name to determine
           what kind of instructions it can emit when generating assembly code.  Permissible
           names are: c62x, c64x, c64x+, c67x, c67x+, c674x.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default.

       -msim
           Choose startup files and linker script suitable for the simulator.

       -msdata=default
           Put small global and static data in the ".neardata" section, which is pointed to by
           register "B14".  Put small uninitialized global and static data in the ".bss" section,
           which is adjacent to the ".neardata" section.  Put small read-only data into the
           ".rodata" section.  The corresponding sections used for large pieces of data are
           ".fardata", ".far" and ".const".

       -msdata=all
           Put all data, not just small objects, into the sections reserved for small data, and
           use addressing relative to the "B14" register to access them.

       -msdata=none
           Make no use of the sections reserved for small data, and use absolute addresses to
           access all data.  Put all initialized global and static data in the ".fardata"
           section, and all uninitialized data in the ".far" section.  Put all constant data into
           the ".const" section.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
           Generate code for the specified architecture.  The choices for architecture-type are
           v3, v8 and v10 for respectively ETRAX 4, ETRAX 100, and ETRAX 100 LX.  Default is v0
           except for cris-axis-linux-gnu, where the default is v10.

       -mtune=architecture-type
           Tune to architecture-type everything applicable about the generated code, except for
           the ABI and the set of available instructions.  The choices for architecture-type are
           the same as for -march=architecture-type.

       -mmax-stack-frame=n
           Warn when the stack frame of a function exceeds n bytes.

       -metrax4
       -metrax100
           The options -metrax4 and -metrax100 are synonyms for -march=v3 and -march=v8
           respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
           Work around a bug in the "muls" and "mulu" instructions for CPU models where it
           applies.  This option is active by default.

       -mpdebug
           Enable CRIS-specific verbose debug-related information in the assembly code.  This
           option also has the effect of turning off the #NO_APP formatted-code indicator to the
           assembler at the beginning of the assembly file.

       -mcc-init
           Do not use condition-code results from previous instruction; always emit compare and
           test instructions before use of condition codes.

       -mno-side-effects
           Do not emit instructions with side effects in addressing modes other than post-
           increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
           These options (no- options) arrange (eliminate arrangements) for the stack frame,
           individual data and constants to be aligned for the maximum single data access size
           for the chosen CPU model.  The default is to arrange for 32-bit alignment.  ABI
           details such as structure layout are not affected by these options.

       -m32-bit
       -m16-bit
       -m8-bit
           Similar to the stack- data- and const-align options above, these options arrange for
           stack frame, writable data and constants to all be 32-bit, 16-bit or 8-bit aligned.
           The default is 32-bit alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
           With -mno-prologue-epilogue, the normal function prologue and epilogue which set up
           the stack frame are omitted and no return instructions or return sequences are
           generated in the code.  Use this option only together with visual inspection of the
           compiled code: no warnings or errors are generated when call-saved registers must be
           saved, or storage for local variables needs to be allocated.

       -mno-gotplt
       -mgotplt
           With -fpic and -fPIC, don't generate (do generate) instruction sequences that load
           addresses for functions from the PLT part of the GOT rather than (traditional on other
           architectures) calls to the PLT.  The default is -mgotplt.

       -melf
           Legacy no-op option only recognized with the cris-axis-elf and cris-axis-linux-gnu
           targets.

       -mlinux
           Legacy no-op option only recognized with the cris-axis-linux-gnu target.

       -sim
           This option, recognized for the cris-axis-elf, arranges to link with input-output
           functions from a simulator library.  Code, initialized data and zero-initialized data
           are allocated consecutively.

       -sim2
           Like -sim, but pass linker options to locate initialized data at 0x40000000 and zero-
           initialized data at 0x80000000.

       CR16 Options

       These options are defined specifically for the CR16 ports.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mcr16cplus
       -mcr16c
           Generate code for CR16C or CR16C+ architecture. CR16C+ architecture is default.

       -msim
           Links the library libsim.a which is in compatible with simulator. Applicable to ELF
           compiler only.

       -mint32
           Choose integer type as 32-bit wide.

       -mbit-ops
           Generates "sbit"/"cbit" instructions for bit manipulations.

       -mdata-model=model
           Choose a data model. The choices for model are near, far or medium. medium is default.
           However, far is not valid with -mcr16c, as the CR16C architecture does not support the
           far data model.

       Darwin Options

       These options are defined for all architectures running the Darwin operating system.

       FSF GCC on Darwin does not create "fat" object files; it creates an object file for the
       single architecture that GCC was built to target.  Apple's GCC on Darwin does create "fat"
       files if multiple -arch options are used; it does so by running the compiler or linker
       multiple times and joining the results together with lipo.

       The subtype of the file created (like ppc7400 or ppc970 or i686) is determined by the
       flags that specify the ISA that GCC is targeting, like -mcpu or -march.  The
       -force_cpusubtype_ALL option can be used to override this.

       The Darwin tools vary in their behavior when presented with an ISA mismatch.  The
       assembler, as, only permits instructions to be used that are valid for the subtype of the
       file it is generating, so you cannot put 64-bit instructions in a ppc750 object file.  The
       linker for shared libraries, /usr/bin/libtool, fails and prints an error if asked to
       create a shared library with a less restrictive subtype than its input files (for
       instance, trying to put a ppc970 object file in a ppc7400 library).  The linker for
       executables, ld, quietly gives the executable the most restrictive subtype of any of its
       input files.

       -Fdir
           Add the framework directory dir to the head of the list of directories to be searched
           for header files.  These directories are interleaved with those specified by -I
           options and are scanned in a left-to-right order.

           A framework directory is a directory with frameworks in it.  A framework is a
           directory with a Headers and/or PrivateHeaders directory contained directly in it that
           ends in .framework.  The name of a framework is the name of this directory excluding
           the .framework.  Headers associated with the framework are found in one of those two
           directories, with Headers being searched first.  A subframework is a framework
           directory that is in a framework's Frameworks directory.  Includes of subframework
           headers can only appear in a header of a framework that contains the subframework, or
           in a sibling subframework header.  Two subframeworks are siblings if they occur in the
           same framework.  A subframework should not have the same name as a framework; a
           warning is issued if this is violated.  Currently a subframework cannot have
           subframeworks; in the future, the mechanism may be extended to support this.  The
           standard frameworks can be found in /System/Library/Frameworks and
           /Library/Frameworks.  An example include looks like "#include <Framework/header.h>",
           where Framework denotes the name of the framework and header.h is found in the
           PrivateHeaders or Headers directory.

       -iframeworkdir
           Like -F except the directory is a treated as a system directory.  The main difference
           between this -iframework and -F is that with -iframework the compiler does not warn
           about constructs contained within header files found via dir.  This option is valid
           only for the C family of languages.

       -gused
           Emit debugging information for symbols that are used.  For stabs debugging format,
           this enables -feliminate-unused-debug-symbols.  This is by default ON.

       -gfull
           Emit debugging information for all symbols and types.

       -mmacosx-version-min=version
           The earliest version of MacOS X that this executable will run on is version.  Typical
           values of version include 10.1, 10.2, and 10.3.9.

           If the compiler was built to use the system's headers by default, then the default for
           this option is the system version on which the compiler is running, otherwise the
           default is to make choices that are compatible with as many systems and code bases as
           possible.

       -mkernel
           Enable kernel development mode.  The -mkernel option sets -static, -fno-common,
           -fno-use-cxa-atexit, -fno-exceptions, -fno-non-call-exceptions, -fapple-kext,
           -fno-weak and -fno-rtti where applicable.  This mode also sets -mno-altivec,
           -msoft-float, -fno-builtin and -mlong-branch for PowerPC targets.

       -mone-byte-bool
           Override the defaults for "bool" so that "sizeof(bool)==1".  By default "sizeof(bool)"
           is 4 when compiling for Darwin/PowerPC and 1 when compiling for Darwin/x86, so this
           option has no effect on x86.

           Warning: The -mone-byte-bool switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Using this switch may require
           recompiling all other modules in a program, including system libraries.  Use this
           switch to conform to a non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
           Generate code suitable for fast turnaround development, such as to allow GDB to
           dynamically load .o files into already-running programs.  -findirect-data and
           -ffix-and-continue are provided for backwards compatibility.

       -all_load
           Loads all members of static archive libraries.  See man ld(1) for more information.

       -arch_errors_fatal
           Cause the errors having to do with files that have the wrong architecture to be fatal.

       -bind_at_load
           Causes the output file to be marked such that the dynamic linker will bind all
           undefined references when the file is loaded or launched.

       -bundle
           Produce a Mach-o bundle format file.  See man ld(1) for more information.

       -bundle_loader executable
           This option specifies the executable that will load the build output file being
           linked.  See man ld(1) for more information.

       -dynamiclib
           When passed this option, GCC produces a dynamic library instead of an executable when
           linking, using the Darwin libtool command.

       -force_cpusubtype_ALL
           This causes GCC's output file to have the ALL subtype, instead of one controlled by
           the -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
           These options are passed to the Darwin linker.  The Darwin linker man page describes
           them in detail.

       DEC Alpha Options

       These -m options are defined for the DEC Alpha implementations:

       -mno-soft-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions for floating-point
           operations.  When -msoft-float is specified, functions in libgcc.a are used to perform
           floating-point operations.  Unless they are replaced by routines that emulate the
           floating-point operations, or compiled in such a way as to call such emulations
           routines, these routines issue floating-point operations.   If you are compiling for
           an Alpha without floating-point operations, you must ensure that the library is built
           so as not to call them.

           Note that Alpha implementations without floating-point operations are required to have
           floating-point registers.

       -mfp-reg
       -mno-fp-regs
           Generate code that uses (does not use) the floating-point register set.  -mno-fp-regs
           implies -msoft-float.  If the floating-point register set is not used, floating-point
           operands are passed in integer registers as if they were integers and floating-point
           results are passed in $0 instead of $f0.  This is a non-standard calling sequence, so
           any function with a floating-point argument or return value called by code compiled
           with -mno-fp-regs must also be compiled with that option.

           A typical use of this option is building a kernel that does not use, and hence need
           not save and restore, any floating-point registers.

       -mieee
           The Alpha architecture implements floating-point hardware optimized for maximum
           performance.  It is mostly compliant with the IEEE floating-point standard.  However,
           for full compliance, software assistance is required.  This option generates code
           fully IEEE-compliant code except that the inexact-flag is not maintained (see below).
           If this option is turned on, the preprocessor macro "_IEEE_FP" is defined during
           compilation.  The resulting code is less efficient but is able to correctly support
           denormalized numbers and exceptional IEEE values such as not-a-number and plus/minus
           infinity.  Other Alpha compilers call this option -ieee_with_no_inexact.

           DEBIAN SPECIFIC: This option is on by default for alpha-linux-gnu, unless
           -ffinite-math-only (which is part of the -ffast-math set) is specified, because the
           software functions in the GNU libc math libraries generate denormalized numbers, NaNs,
           and infs (all of which will cause a programs to SIGFPE when it attempts to use the
           results without -mieee).

       -mieee-with-inexact
           This is like -mieee except the generated code also maintains the IEEE inexact-flag.
           Turning on this option causes the generated code to implement fully-compliant IEEE
           math.  In addition to "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro.
           On some Alpha implementations the resulting code may execute significantly slower than
           the code generated by default.  Since there is very little code that depends on the
           inexact-flag, you should normally not specify this option.  Other Alpha compilers call
           this option -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
           This option controls what floating-point related traps are enabled.  Other Alpha
           compilers call this option -fptm trap-mode.  The trap mode can be set to one of four
           values:

           n   This is the default (normal) setting.  The only traps that are enabled are the
               ones that cannot be disabled in software (e.g., division by zero trap).

           u   In addition to the traps enabled by n, underflow traps are enabled as well.

           su  Like u, but the instructions are marked to be safe for software completion (see
               Alpha architecture manual for details).

           sui Like su, but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
           Selects the IEEE rounding mode.  Other Alpha compilers call this option -fprm
           rounding-mode.  The rounding-mode can be one of:

           n   Normal IEEE rounding mode.  Floating-point numbers are rounded towards the nearest
               machine number or towards the even machine number in case of a tie.

           m   Round towards minus infinity.

           c   Chopped rounding mode.  Floating-point numbers are rounded towards zero.

           d   Dynamic rounding mode.  A field in the floating-point control register (fpcr, see
               Alpha architecture reference manual) controls the rounding mode in effect.  The C
               library initializes this register for rounding towards plus infinity.  Thus,
               unless your program modifies the fpcr, d corresponds to round towards plus
               infinity.

       -mtrap-precision=trap-precision
           In the Alpha architecture, floating-point traps are imprecise.  This means without
           software assistance it is impossible to recover from a floating trap and program
           execution normally needs to be terminated.  GCC can generate code that can assist
           operating system trap handlers in determining the exact location that caused a
           floating-point trap.  Depending on the requirements of an application, different
           levels of precisions can be selected:

           p   Program precision.  This option is the default and means a trap handler can only
               identify which program caused a floating-point exception.

           f   Function precision.  The trap handler can determine the function that caused a
               floating-point exception.

           i   Instruction precision.  The trap handler can determine the exact instruction that
               caused a floating-point exception.

           Other Alpha compilers provide the equivalent options called -scope_safe and
           -resumption_safe.

       -mieee-conformant
           This option marks the generated code as IEEE conformant.  You must not use this option
           unless you also specify -mtrap-precision=i and either -mfp-trap-mode=su or
           -mfp-trap-mode=sui.  Its only effect is to emit the line .eflag 48 in the function
           prologue of the generated assembly file.

       -mbuild-constants
           Normally GCC examines a 32- or 64-bit integer constant to see if it can construct it
           from smaller constants in two or three instructions.  If it cannot, it outputs the
           constant as a literal and generates code to load it from the data segment at run time.

           Use this option to require GCC to construct all integer constants using code, even if
           it takes more instructions (the maximum is six).

           You typically use this option to build a shared library dynamic loader.  Itself a
           shared library, it must relocate itself in memory before it can find the variables and
           constants in its own data segment.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
           Indicate whether GCC should generate code to use the optional BWX, CIX, FIX and MAX
           instruction sets.  The default is to use the instruction sets supported by the CPU
           type specified via -mcpu= option or that of the CPU on which GCC was built if none is
           specified.

       -mfloat-vax
       -mfloat-ieee
           Generate code that uses (does not use) VAX F and G floating-point arithmetic instead
           of IEEE single and double precision.

       -mexplicit-relocs
       -mno-explicit-relocs
           Older Alpha assemblers provided no way to generate symbol relocations except via
           assembler macros.  Use of these macros does not allow optimal instruction scheduling.
           GNU binutils as of version 2.12 supports a new syntax that allows the compiler to
           explicitly mark which relocations should apply to which instructions.  This option is
           mostly useful for debugging, as GCC detects the capabilities of the assembler when it
           is built and sets the default accordingly.

       -msmall-data
       -mlarge-data
           When -mexplicit-relocs is in effect, static data is accessed via gp-relative
           relocations.  When -msmall-data is used, objects 8 bytes long or smaller are placed in
           a small data area (the ".sdata" and ".sbss" sections) and are accessed via 16-bit
           relocations off of the $gp register.  This limits the size of the small data area to
           64KB, but allows the variables to be directly accessed via a single instruction.

           The default is -mlarge-data.  With this option the data area is limited to just below
           2GB.  Programs that require more than 2GB of data must use "malloc" or "mmap" to
           allocate the data in the heap instead of in the program's data segment.

           When generating code for shared libraries, -fpic implies -msmall-data and -fPIC
           implies -mlarge-data.

       -msmall-text
       -mlarge-text
           When -msmall-text is used, the compiler assumes that the code of the entire program
           (or shared library) fits in 4MB, and is thus reachable with a branch instruction.
           When -msmall-data is used, the compiler can assume that all local symbols share the
           same $gp value, and thus reduce the number of instructions required for a function
           call from 4 to 1.

           The default is -mlarge-text.

       -mcpu=cpu_type
           Set the instruction set and instruction scheduling parameters for machine type
           cpu_type.  You can specify either the EV style name or the corresponding chip number.
           GCC supports scheduling parameters for the EV4, EV5 and EV6 family of processors and
           chooses the default values for the instruction set from the processor you specify.  If
           you do not specify a processor type, GCC defaults to the processor on which the
           compiler was built.

           Supported values for cpu_type are

           ev4
           ev45
           21064
               Schedules as an EV4 and has no instruction set extensions.

           ev5
           21164
               Schedules as an EV5 and has no instruction set extensions.

           ev56
           21164a
               Schedules as an EV5 and supports the BWX extension.

           pca56
           21164pc
           21164PC
               Schedules as an EV5 and supports the BWX and MAX extensions.

           ev6
           21264
               Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.

           ev67
           21264a
               Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.

           Native toolchains also support the value native, which selects the best architecture
           option for the host processor.  -mcpu=native has no effect if GCC does not recognize
           the processor.

       -mtune=cpu_type
           Set only the instruction scheduling parameters for machine type cpu_type.  The
           instruction set is not changed.

           Native toolchains also support the value native, which selects the best architecture
           option for the host processor.  -mtune=native has no effect if GCC does not recognize
           the processor.

       -mmemory-latency=time
           Sets the latency the scheduler should assume for typical memory references as seen by
           the application.  This number is highly dependent on the memory access patterns used
           by the application and the size of the external cache on the machine.

           Valid options for time are

           number
               A decimal number representing clock cycles.

           L1
           L2
           L3
           main
               The compiler contains estimates of the number of clock cycles for "typical" EV4 &
               EV5 hardware for the Level 1, 2 & 3 caches (also called Dcache, Scache, and
               Bcache), as well as to main memory.  Note that L3 is only valid for EV5.

       FR30 Options

       These options are defined specifically for the FR30 port.

       -msmall-model
           Use the small address space model.  This can produce smaller code, but it does assume
           that all symbolic values and addresses fit into a 20-bit range.

       -mno-lsim
           Assume that runtime support has been provided and so there is no need to include the
           simulator library (libsim.a) on the linker command line.

       FRV Options

       -mgpr-32
           Only use the first 32 general-purpose registers.

       -mgpr-64
           Use all 64 general-purpose registers.

       -mfpr-32
           Use only the first 32 floating-point registers.

       -mfpr-64
           Use all 64 floating-point registers.

       -mhard-float
           Use hardware instructions for floating-point operations.

       -msoft-float
           Use library routines for floating-point operations.

       -malloc-cc
           Dynamically allocate condition code registers.

       -mfixed-cc
           Do not try to dynamically allocate condition code registers, only use "icc0" and
           "fcc0".

       -mdword
           Change ABI to use double word insns.

       -mno-dword
           Do not use double word instructions.

       -mdouble
           Use floating-point double instructions.

       -mno-double
           Do not use floating-point double instructions.

       -mmedia
           Use media instructions.

       -mno-media
           Do not use media instructions.

       -mmuladd
           Use multiply and add/subtract instructions.

       -mno-muladd
           Do not use multiply and add/subtract instructions.

       -mfdpic
           Select the FDPIC ABI, which uses function descriptors to represent pointers to
           functions.  Without any PIC/PIE-related options, it implies -fPIE.  With -fpic or
           -fpie, it assumes GOT entries and small data are within a 12-bit range from the GOT
           base address; with -fPIC or -fPIE, GOT offsets are computed with 32 bits.  With a
           bfin-elf target, this option implies -msim.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions that are not known to
           bind locally.  It has no effect without -mfdpic.  It's enabled by default if
           optimizing for speed and compiling for shared libraries (i.e., -fPIC or -fpic), or
           when an optimization option such as -O3 or above is present in the command line.

       -mTLS
           Assume a large TLS segment when generating thread-local code.

       -mtls
           Do not assume a large TLS segment when generating thread-local code.

       -mgprel-ro
           Enable the use of "GPREL" relocations in the FDPIC ABI for data that is known to be in
           read-only sections.  It's enabled by default, except for -fpic or -fpie: even though
           it may help make the global offset table smaller, it trades 1 instruction for 4.  With
           -fPIC or -fPIE, it trades 3 instructions for 4, one of which may be shared by multiple
           symbols, and it avoids the need for a GOT entry for the referenced symbol, so it's
           more likely to be a win.  If it is not, -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
           Link with the (library, not FD) pic libraries.  It's implied by -mlibrary-pic, as well
           as by -fPIC and -fpic without -mfdpic.  You should never have to use it explicitly.

       -mlinked-fp
           Follow the EABI requirement of always creating a frame pointer whenever a stack frame
           is allocated.  This option is enabled by default and can be disabled with
           -mno-linked-fp.

       -mlong-calls
           Use indirect addressing to call functions outside the current compilation unit.  This
           allows the functions to be placed anywhere within the 32-bit address space.

       -malign-labels
           Try to align labels to an 8-byte boundary by inserting NOPs into the previous packet.
           This option only has an effect when VLIW packing is enabled.  It doesn't create new
           packets; it merely adds NOPs to existing ones.

       -mlibrary-pic
           Generate position-independent EABI code.

       -macc-4
           Use only the first four media accumulator registers.

       -macc-8
           Use all eight media accumulator registers.

       -mpack
           Pack VLIW instructions.

       -mno-pack
           Do not pack VLIW instructions.

       -mno-eflags
           Do not mark ABI switches in e_flags.

       -mcond-move
           Enable the use of conditional-move instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mno-cond-move
           Disable the use of conditional-move instructions.

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mscc
           Enable the use of conditional set instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mno-scc
           Disable the use of conditional set instructions.

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mcond-exec
           Enable the use of conditional execution (default).

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mno-cond-exec
           Disable the use of conditional execution.

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mvliw-branch
           Run a pass to pack branches into VLIW instructions (default).

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mno-vliw-branch
           Do not run a pass to pack branches into VLIW instructions.

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mmulti-cond-exec
           Enable optimization of "&&" and "||" in conditional execution (default).

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mno-multi-cond-exec
           Disable optimization of "&&" and "||" in conditional execution.

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mnested-cond-exec
           Enable nested conditional execution optimizations (default).

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -mno-nested-cond-exec
           Disable nested conditional execution optimizations.

           This switch is mainly for debugging the compiler and will likely be removed in a
           future version.

       -moptimize-membar
           This switch removes redundant "membar" instructions from the compiler-generated code.
           It is enabled by default.

       -mno-optimize-membar
           This switch disables the automatic removal of redundant "membar" instructions from the
           generated code.

       -mtomcat-stats
           Cause gas to print out tomcat statistics.

       -mcpu=cpu
           Select the processor type for which to generate code.  Possible values are frv, fr550,
           tomcat, fr500, fr450, fr405, fr400, fr300 and simple.

       GNU/Linux Options

       These -m options are defined for GNU/Linux targets:

       -mglibc
           Use the GNU C library.  This is the default except on *-*-linux-*uclibc* and
           *-*-linux-*android* targets.

       -muclibc
           Use uClibc C library.  This is the default on *-*-linux-*uclibc* targets.

       -mbionic
           Use Bionic C library.  This is the default on *-*-linux-*android* targets.

       -mandroid
           Compile code compatible with Android platform.  This is the default on
           *-*-linux-*android* targets.

           When compiling, this option enables -mbionic, -fPIC, -fno-exceptions and -fno-rtti by
           default.  When linking, this option makes the GCC driver pass Android-specific options
           to the linker.  Finally, this option causes the preprocessor macro "__ANDROID__" to be
           defined.

       -tno-android-cc
           Disable compilation effects of -mandroid, i.e., do not enable -mbionic, -fPIC,
           -fno-exceptions and -fno-rtti by default.

       -tno-android-ld
           Disable linking effects of -mandroid, i.e., pass standard Linux linking options to the
           linker.

       H8/300 Options

       These -m options are defined for the H8/300 implementations:

       -mrelax
           Shorten some address references at link time, when possible; uses the linker option
           -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in the normal mode.  This switch must be used
           either with -mh or -ms.

       -ms2600
           Generate code for the H8S/2600.  This switch must be used with -ms.

       -mexr
           Extended registers are stored on stack before execution of function with monitor
           attribute. Default option is -mexr.  This option is valid only for H8S targets.

       -mno-exr
           Extended registers are not stored on stack before execution of function with monitor
           attribute. Default option is -mno-exr.  This option is valid only for H8S targets.

       -mint32
           Make "int" data 32 bits by default.

       -malign-300
           On the H8/300H and H8S, use the same alignment rules as for the H8/300.  The default
           for the H8/300H and H8S is to align longs and floats on 4-byte boundaries.
           -malign-300 causes them to be aligned on 2-byte boundaries.  This option has no effect
           on the H8/300.

       HPPA Options

       These -m options are defined for the HPPA family of computers:

       -march=architecture-type
           Generate code for the specified architecture.  The choices for architecture-type are
           1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for PA 2.0 processors.  Refer to
           /usr/lib/sched.models on an HP-UX system to determine the proper architecture option
           for your machine.  Code compiled for lower numbered architectures runs on higher
           numbered architectures, but not the other way around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
           Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

       -mjump-in-delay
           This option is ignored and provided for compatibility purposes only.

       -mdisable-fpregs
           Prevent floating-point registers from being used in any manner.  This is necessary for
           compiling kernels that perform lazy context switching of floating-point registers.  If
           you use this option and attempt to perform floating-point operations, the compiler
           aborts.

       -mdisable-indexing
           Prevent the compiler from using indexing address modes.  This avoids some rather
           obscure problems when compiling MIG generated code under MACH.

       -mno-space-regs
           Generate code that assumes the target has no space registers.  This allows GCC to
           generate faster indirect calls and use unscaled index address modes.

           Such code is suitable for level 0 PA systems and kernels.

       -mfast-indirect-calls
           Generate code that assumes calls never cross space boundaries.  This allows GCC to
           emit code that performs faster indirect calls.

           This option does not work in the presence of shared libraries or nested functions.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed register
           is one that the register allocator cannot use.  This is useful when compiling kernel
           code.  A register range is specified as two registers separated by a dash.  Multiple
           register ranges can be specified separated by a comma.

       -mlong-load-store
           Generate 3-instruction load and store sequences as sometimes required by the HP-UX 10
           linker.  This is equivalent to the +k option to the HP compilers.

       -mportable-runtime
           Use the portable calling conventions proposed by HP for ELF systems.

       -mgas
           Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
           Schedule code according to the constraints for the machine type cpu-type.  The choices
           for cpu-type are 700 7100, 7100LC, 7200, 7300 and 8000.  Refer to
           /usr/lib/sched.models on an HP-UX system to determine the proper scheduling option for
           your machine.  The default scheduling is 8000.

       -mlinker-opt
           Enable the optimization pass in the HP-UX linker.  Note this makes symbolic debugging
           impossible.  It also triggers a bug in the HP-UX 8 and HP-UX 9 linkers in which they
           give bogus error messages when linking some programs.

       -msoft-float
           Generate output containing library calls for floating point.  Warning: the requisite
           libraries are not available for all HPPA targets.  Normally the facilities of the
           machine's usual C compiler are used, but this cannot be done directly in cross-
           compilation.  You must make your own arrangements to provide suitable library
           functions for cross-compilation.

           -msoft-float changes the calling convention in the output file; therefore, it is only
           useful if you compile all of a program with this option.  In particular, you need to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this
           to work.

       -msio
           Generate the predefine, "_SIO", for server IO.  The default is -mwsio.  This generates
           the predefines, "__hp9000s700", "__hp9000s700__" and "_WSIO", for workstation IO.
           These options are available under HP-UX and HI-UX.

       -mgnu-ld
           Use options specific to GNU ld.  This passes -shared to ld when building a shared
           library.  It is the default when GCC is configured, explicitly or implicitly, with the
           GNU linker.  This option does not affect which ld is called; it only changes what
           parameters are passed to that ld.  The ld that is called is determined by the
           --with-ld configure option, GCC's program search path, and finally by the user's PATH.
           The linker used by GCC can be printed using which `gcc -print-prog-name=ld`.  This
           option is only available on the 64-bit HP-UX GCC, i.e. configured with
           hppa*64*-*-hpux*.

       -mhp-ld
           Use options specific to HP ld.  This passes -b to ld when building a shared library
           and passes +Accept TypeMismatch to ld on all links.  It is the default when GCC is
           configured, explicitly or implicitly, with the HP linker.  This option does not affect
           which ld is called; it only changes what parameters are passed to that ld.  The ld
           that is called is determined by the --with-ld configure option, GCC's program search
           path, and finally by the user's PATH.  The linker used by GCC can be printed using
           which `gcc -print-prog-name=ld`.  This option is only available on the 64-bit HP-UX
           GCC, i.e. configured with hppa*64*-*-hpux*.

       -mlong-calls
           Generate code that uses long call sequences.  This ensures that a call is always able
           to reach linker generated stubs.  The default is to generate long calls only when the
           distance from the call site to the beginning of the function or translation unit, as
           the case may be, exceeds a predefined limit set by the branch type being used.  The
           limits for normal calls are 7,600,000 and 240,000 bytes, respectively for the PA 2.0
           and PA 1.X architectures.  Sibcalls are always limited at 240,000 bytes.

           Distances are measured from the beginning of functions when using the
           -ffunction-sections option, or when using the -mgas and -mno-portable-runtime options
           together under HP-UX with the SOM linker.

           It is normally not desirable to use this option as it degrades performance.  However,
           it may be useful in large applications, particularly when partial linking is used to
           build the application.

           The types of long calls used depends on the capabilities of the assembler and linker,
           and the type of code being generated.  The impact on systems that support long
           absolute calls, and long pic symbol-difference or pc-relative calls should be
           relatively small.  However, an indirect call is used on 32-bit ELF systems in pic code
           and it is quite long.

       -munix=unix-std
           Generate compiler predefines and select a startfile for the specified UNIX standard.
           The choices for unix-std are 93, 95 and 98.  93 is supported on all HP-UX versions.
           95 is available on HP-UX 10.10 and later.  98 is available on HP-UX 11.11 and later.
           The default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to 11.00, and 98
           for HP-UX 11.11 and later.

           -munix=93 provides the same predefines as GCC 3.3 and 3.4.  -munix=95 provides
           additional predefines for "XOPEN_UNIX" and "_XOPEN_SOURCE_EXTENDED", and the startfile
           unix95.o.  -munix=98 provides additional predefines for "_XOPEN_UNIX",
           "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and "_INCLUDE_XOPEN_SOURCE_500",
           and the startfile unix98.o.

           It is important to note that this option changes the interfaces for various library
           routines.  It also affects the operational behavior of the C library.  Thus, extreme
           care is needed in using this option.

           Library code that is intended to operate with more than one UNIX standard must test,
           set and restore the variable "__xpg4_extended_mask" as appropriate.  Most GNU software
           doesn't provide this capability.

       -nolibdld
           Suppress the generation of link options to search libdld.sl when the -static option is
           specified on HP-UX 10 and later.

       -static
           The HP-UX implementation of setlocale in libc has a dependency on libdld.sl.  There
           isn't an archive version of libdld.sl.  Thus, when the -static option is specified,
           special link options are needed to resolve this dependency.

           On HP-UX 10 and later, the GCC driver adds the necessary options to link with
           libdld.sl when the -static option is specified.  This causes the resulting binary to
           be dynamic.  On the 64-bit port, the linkers generate dynamic binaries by default in
           any case.  The -nolibdld option can be used to prevent the GCC driver from adding
           these link options.

       -threads
           Add support for multithreading with the dce thread library under HP-UX.  This option
           sets flags for both the preprocessor and linker.

       IA-64 Options

       These are the -m options defined for the Intel IA-64 architecture.

       -mbig-endian
           Generate code for a big-endian target.  This is the default for HP-UX.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default for AIX5 and GNU/Linux.

       -mgnu-as
       -mno-gnu-as
           Generate (or don't) code for the GNU assembler.  This is the default.

       -mgnu-ld
       -mno-gnu-ld
           Generate (or don't) code for the GNU linker.  This is the default.

       -mno-pic
           Generate code that does not use a global pointer register.  The result is not position
           independent code, and violates the IA-64 ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
           Generate (or don't) a stop bit immediately before and after volatile asm statements.

       -mregister-names
       -mno-register-names
           Generate (or don't) in, loc, and out register names for the stacked registers.  This
           may make assembler output more readable.

       -mno-sdata
       -msdata
           Disable (or enable) optimizations that use the small data section.  This may be useful
           for working around optimizer bugs.

       -mconstant-gp
           Generate code that uses a single constant global pointer value.  This is useful when
           compiling kernel code.

       -mauto-pic
           Generate code that is self-relocatable.  This implies -mconstant-gp.  This is useful
           when compiling firmware code.

       -minline-float-divide-min-latency
           Generate code for inline divides of floating-point values using the minimum latency
           algorithm.

       -minline-float-divide-max-throughput
           Generate code for inline divides of floating-point values using the maximum throughput
           algorithm.

       -mno-inline-float-divide
           Do not generate inline code for divides of floating-point values.

       -minline-int-divide-min-latency
           Generate code for inline divides of integer values using the minimum latency
           algorithm.

       -minline-int-divide-max-throughput
           Generate code for inline divides of integer values using the maximum throughput
           algorithm.

       -mno-inline-int-divide
           Do not generate inline code for divides of integer values.

       -minline-sqrt-min-latency
           Generate code for inline square roots using the minimum latency algorithm.

       -minline-sqrt-max-throughput
           Generate code for inline square roots using the maximum throughput algorithm.

       -mno-inline-sqrt
           Do not generate inline code for "sqrt".

       -mfused-madd
       -mno-fused-madd
           Do (don't) generate code that uses the fused multiply/add or multiply/subtract
           instructions.  The default is to use these instructions.

       -mno-dwarf2-asm
       -mdwarf2-asm
           Don't (or do) generate assembler code for the DWARF 2 line number debugging info.
           This may be useful when not using the GNU assembler.

       -mearly-stop-bits
       -mno-early-stop-bits
           Allow stop bits to be placed earlier than immediately preceding the instruction that
           triggered the stop bit.  This can improve instruction scheduling, but does not always
           do so.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed register
           is one that the register allocator cannot use.  This is useful when compiling kernel
           code.  A register range is specified as two registers separated by a dash.  Multiple
           register ranges can be specified separated by a comma.

       -mtls-size=tls-size
           Specify bit size of immediate TLS offsets.  Valid values are 14, 22, and 64.

       -mtune=cpu-type
           Tune the instruction scheduling for a particular CPU, Valid values are itanium,
           itanium1, merced, itanium2, and mckinley.

       -milp32
       -mlp64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int,
           long and pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and
           pointer to 64 bits.  These are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
           (Dis/En)able data speculative scheduling before reload.  This results in generation of
           "ld.a" instructions and the corresponding check instructions ("ld.c" / "chk.a").  The
           default is 'disable'.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
           (En/Dis)able data speculative scheduling after reload.  This results in generation of
           "ld.a" instructions and the corresponding check instructions ("ld.c" / "chk.a").  The
           default is 'enable'.

       -mno-sched-control-spec
       -msched-control-spec
           (Dis/En)able control speculative scheduling.  This feature is available only during
           region scheduling (i.e. before reload).  This results in generation of the "ld.s"
           instructions and the corresponding check instructions "chk.s".  The default is
           'disable'.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on the data
           speculative loads before reload.  This is effective only with -msched-br-data-spec
           enabled.  The default is 'enable'.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on the data
           speculative loads after reload.  This is effective only with -msched-ar-data-spec
           enabled.  The default is 'enable'.

       -msched-in-control-spec
       -mno-sched-in-control-spec
           (En/Dis)able speculative scheduling of the instructions that are dependent on the
           control speculative loads.  This is effective only with -msched-control-spec enabled.
           The default is 'enable'.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
           If enabled, data-speculative instructions are chosen for schedule only if there are no
           other choices at the moment.  This makes the use of the data speculation much more
           conservative.  The default is 'disable'.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
           If enabled, control-speculative instructions are chosen for schedule only if there are
           no other choices at the moment.  This makes the use of the control speculation much
           more conservative.  The default is 'disable'.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
           If enabled, speculative dependencies are considered during computation of the
           instructions priorities.  This makes the use of the speculation a bit more
           conservative.  The default is 'disable'.

       -msched-spec-ldc
           Use a simple data speculation check.  This option is on by default.

       -msched-control-spec-ldc
           Use a simple check for control speculation.  This option is on by default.

       -msched-stop-bits-after-every-cycle
           Place a stop bit after every cycle when scheduling.  This option is on by default.

       -msched-fp-mem-deps-zero-cost
           Assume that floating-point stores and loads are not likely to cause a conflict when
           placed into the same instruction group.  This option is disabled by default.

       -msel-sched-dont-check-control-spec
           Generate checks for control speculation in selective scheduling.  This flag is
           disabled by default.

       -msched-max-memory-insns=max-insns
           Limit on the number of memory insns per instruction group, giving lower priority to
           subsequent memory insns attempting to schedule in the same instruction group.
           Frequently useful to prevent cache bank conflicts.  The default value is 1.

       -msched-max-memory-insns-hard-limit
           Makes the limit specified by msched-max-memory-insns a hard limit, disallowing more
           than that number in an instruction group.  Otherwise, the limit is "soft", meaning
           that non-memory operations are preferred when the limit is reached, but memory
           operations may still be scheduled.

       LM32 Options

       These -m options are defined for the LatticeMico32 architecture:

       -mbarrel-shift-enabled
           Enable barrel-shift instructions.

       -mdivide-enabled
           Enable divide and modulus instructions.

       -mmultiply-enabled
           Enable multiply instructions.

       -msign-extend-enabled
           Enable sign extend instructions.

       -muser-enabled
           Enable user-defined instructions.

       M32C Options

       -mcpu=name
           Select the CPU for which code is generated.  name may be one of r8c for the R8C/Tiny
           series, m16c for the M16C (up to /60) series, m32cm for the M16C/80 series, or m32c
           for the M32C/80 series.

       -msim
           Specifies that the program will be run on the simulator.  This causes an alternate
           runtime library to be linked in which supports, for example, file I/O.  You must not
           use this option when generating programs that will run on real hardware; you must
           provide your own runtime library for whatever I/O functions are needed.

       -memregs=number
           Specifies the number of memory-based pseudo-registers GCC uses during code generation.
           These pseudo-registers are used like real registers, so there is a tradeoff between
           GCC's ability to fit the code into available registers, and the performance penalty of
           using memory instead of registers.  Note that all modules in a program must be
           compiled with the same value for this option.  Because of that, you must not use this
           option with GCC's default runtime libraries.

       M32R/D Options

       These -m options are defined for Renesas M32R/D architectures:

       -m32r2
           Generate code for the M32R/2.

       -m32rx
           Generate code for the M32R/X.

       -m32r
           Generate code for the M32R.  This is the default.

       -mmodel=small
           Assume all objects live in the lower 16MB of memory (so that their addresses can be
           loaded with the "ld24" instruction), and assume all subroutines are reachable with the
           "bl" instruction.  This is the default.

           The addressability of a particular object can be set with the "model" attribute.

       -mmodel=medium
           Assume objects may be anywhere in the 32-bit address space (the compiler generates
           "seth/add3" instructions to load their addresses), and assume all subroutines are
           reachable with the "bl" instruction.

       -mmodel=large
           Assume objects may be anywhere in the 32-bit address space (the compiler generates
           "seth/add3" instructions to load their addresses), and assume subroutines may not be
           reachable with the "bl" instruction (the compiler generates the much slower
           "seth/add3/jl" instruction sequence).

       -msdata=none
           Disable use of the small data area.  Variables are put into one of ".data", ".bss", or
           ".rodata" (unless the "section" attribute has been specified).  This is the default.

           The small data area consists of sections ".sdata" and ".sbss".  Objects may be
           explicitly put in the small data area with the "section" attribute using one of these
           sections.

       -msdata=sdata
           Put small global and static data in the small data area, but do not generate special
           code to reference them.

       -msdata=use
           Put small global and static data in the small data area, and generate special
           instructions to reference them.

       -G num
           Put global and static objects less than or equal to num bytes into the small data or
           BSS sections instead of the normal data or BSS sections.  The default value of num is
           8.  The -msdata option must be set to one of sdata or use for this option to have any
           effect.

           All modules should be compiled with the same -G num value.  Compiling with different
           values of num may or may not work; if it doesn't the linker gives an error
           message---incorrect code is not generated.

       -mdebug
           Makes the M32R-specific code in the compiler display some statistics that might help
           in debugging programs.

       -malign-loops
           Align all loops to a 32-byte boundary.

       -mno-align-loops
           Do not enforce a 32-byte alignment for loops.  This is the default.

       -missue-rate=number
           Issue number instructions per cycle.  number can only be 1 or 2.

       -mbranch-cost=number
           number can only be 1 or 2.  If it is 1 then branches are preferred over conditional
           code, if it is 2, then the opposite applies.

       -mflush-trap=number
           Specifies the trap number to use to flush the cache.  The default is 12.  Valid
           numbers are between 0 and 15 inclusive.

       -mno-flush-trap
           Specifies that the cache cannot be flushed by using a trap.

       -mflush-func=name
           Specifies the name of the operating system function to call to flush the cache.  The
           default is _flush_cache, but a function call is only used if a trap is not available.

       -mno-flush-func
           Indicates that there is no OS function for flushing the cache.

       M680x0 Options

       These are the -m options defined for M680x0 and ColdFire processors.  The default settings
       depend on which architecture was selected when the compiler was configured; the defaults
       for the most common choices are given below.

       -march=arch
           Generate code for a specific M680x0 or ColdFire instruction set architecture.
           Permissible values of arch for M680x0 architectures are: 68000, 68010, 68020, 68030,
           68040, 68060 and cpu32.  ColdFire architectures are selected according to Freescale's
           ISA classification and the permissible values are: isaa, isaaplus, isab and isac.

           GCC defines a macro "__mcfarch__" whenever it is generating code for a ColdFire
           target.  The arch in this macro is one of the -march arguments given above.

           When used together, -march and -mtune select code that runs on a family of similar
           processors but that is optimized for a particular microarchitecture.

       -mcpu=cpu
           Generate code for a specific M680x0 or ColdFire processor.  The M680x0 cpus are:
           68000, 68010, 68020, 68030, 68040, 68060, 68302, 68332 and cpu32.  The ColdFire cpus
           are given by the table below, which also classifies the CPUs into families:

           Family : -mcpu arguments
           51 : 51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe 51qm
           5206 : 5202 5204 5206
           5206e : 5206e
           5208 : 5207 5208
           5211a : 5210a 5211a
           5213 : 5211 5212 5213
           5216 : 5214 5216
           52235 : 52230 52231 52232 52233 52234 52235
           5225 : 5224 5225
           52259 : 52252 52254 52255 52256 52258 52259
           5235 : 5232 5233 5234 5235 523x
           5249 : 5249
           5250 : 5250
           5271 : 5270 5271
           5272 : 5272
           5275 : 5274 5275
           5282 : 5280 5281 5282 528x
           53017 : 53011 53012 53013 53014 53015 53016 53017
           5307 : 5307
           5329 : 5327 5328 5329 532x
           5373 : 5372 5373 537x
           5407 : 5407
           5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483 5484 5485

           -mcpu=cpu overrides -march=arch if arch is compatible with cpu.  Other combinations of
           -mcpu and -march are rejected.

           GCC defines the macro "__mcf_cpu_cpu" when ColdFire target cpu is selected.  It also
           defines "__mcf_family_family", where the value of family is given by the table above.

       -mtune=tune
           Tune the code for a particular microarchitecture within the constraints set by -march
           and -mcpu.  The M680x0 microarchitectures are: 68000, 68010, 68020, 68030, 68040,
           68060 and cpu32.  The ColdFire microarchitectures are: cfv1, cfv2, cfv3, cfv4 and
           cfv4e.

           You can also use -mtune=68020-40 for code that needs to run relatively well on 68020,
           68030 and 68040 targets.  -mtune=68020-60 is similar but includes 68060 targets as
           well.  These two options select the same tuning decisions as -m68020-40 and -m68020-60
           respectively.

           GCC defines the macros "__mcarch" and "__mcarch__" when tuning for 680x0 architecture
           arch.  It also defines "mcarch" unless either -ansi or a non-GNU -std option is used.
           If GCC is tuning for a range of architectures, as selected by -mtune=68020-40 or
           -mtune=68020-60, it defines the macros for every architecture in the range.

           GCC also defines the macro "__muarch__" when tuning for ColdFire microarchitecture
           uarch, where uarch is one of the arguments given above.

       -m68000
       -mc68000
           Generate output for a 68000.  This is the default when the compiler is configured for
           68000-based systems.  It is equivalent to -march=68000.

           Use this option for microcontrollers with a 68000 or EC000 core, including the 68008,
           68302, 68306, 68307, 68322, 68328 and 68356.

       -m68010
           Generate output for a 68010.  This is the default when the compiler is configured for
           68010-based systems.  It is equivalent to -march=68010.

       -m68020
       -mc68020
           Generate output for a 68020.  This is the default when the compiler is configured for
           68020-based systems.  It is equivalent to -march=68020.

       -m68030
           Generate output for a 68030.  This is the default when the compiler is configured for
           68030-based systems.  It is equivalent to -march=68030.

       -m68040
           Generate output for a 68040.  This is the default when the compiler is configured for
           68040-based systems.  It is equivalent to -march=68040.

           This option inhibits the use of 68881/68882 instructions that have to be emulated by
           software on the 68040.  Use this option if your 68040 does not have code to emulate
           those instructions.

       -m68060
           Generate output for a 68060.  This is the default when the compiler is configured for
           68060-based systems.  It is equivalent to -march=68060.

           This option inhibits the use of 68020 and 68881/68882 instructions that have to be
           emulated by software on the 68060.  Use this option if your 68060 does not have code
           to emulate those instructions.

       -mcpu32
           Generate output for a CPU32.  This is the default when the compiler is configured for
           CPU32-based systems.  It is equivalent to -march=cpu32.

           Use this option for microcontrollers with a CPU32 or CPU32+ core, including the 68330,
           68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349 and 68360.

       -m5200
           Generate output for a 520X ColdFire CPU.  This is the default when the compiler is
           configured for 520X-based systems.  It is equivalent to -mcpu=5206, and is now
           deprecated in favor of that option.

           Use this option for microcontroller with a 5200 core, including the MCF5202, MCF5203,
           MCF5204 and MCF5206.

       -m5206e
           Generate output for a 5206e ColdFire CPU.  The option is now deprecated in favor of
           the equivalent -mcpu=5206e.

       -m528x
           Generate output for a member of the ColdFire 528X family.  The option is now
           deprecated in favor of the equivalent -mcpu=528x.

       -m5307
           Generate output for a ColdFire 5307 CPU.  The option is now deprecated in favor of the
           equivalent -mcpu=5307.

       -m5407
           Generate output for a ColdFire 5407 CPU.  The option is now deprecated in favor of the
           equivalent -mcpu=5407.

       -mcfv4e
           Generate output for a ColdFire V4e family CPU (e.g. 547x/548x).  This includes use of
           hardware floating-point instructions.  The option is equivalent to -mcpu=547x, and is
           now deprecated in favor of that option.

       -m68020-40
           Generate output for a 68040, without using any of the new instructions.  This results
           in code that can run relatively efficiently on either a 68020/68881 or a 68030 or a
           68040.  The generated code does use the 68881 instructions that are emulated on the
           68040.

           The option is equivalent to -march=68020 -mtune=68020-40.

       -m68020-60
           Generate output for a 68060, without using any of the new instructions.  This results
           in code that can run relatively efficiently on either a 68020/68881 or a 68030 or a
           68040.  The generated code does use the 68881 instructions that are emulated on the
           68060.

           The option is equivalent to -march=68020 -mtune=68020-60.

       -mhard-float
       -m68881
           Generate floating-point instructions.  This is the default for 68020 and above, and
           for ColdFire devices that have an FPU.  It defines the macro "__HAVE_68881__" on
           M680x0 targets and "__mcffpu__" on ColdFire targets.

       -msoft-float
           Do not generate floating-point instructions; use library calls instead.  This is the
           default for 68000, 68010, and 68832 targets.  It is also the default for ColdFire
           devices that have no FPU.

       -mdiv
       -mno-div
           Generate (do not generate) ColdFire hardware divide and remainder instructions.  If
           -march is used without -mcpu, the default is "on" for ColdFire architectures and "off"
           for M680x0 architectures.  Otherwise, the default is taken from the target CPU (either
           the default CPU, or the one specified by -mcpu).  For example, the default is "off"
           for -mcpu=5206 and "on" for -mcpu=5206e.

           GCC defines the macro "__mcfhwdiv__" when this option is enabled.

       -mshort
           Consider type "int" to be 16 bits wide, like "short int".  Additionally, parameters
           passed on the stack are also aligned to a 16-bit boundary even on targets whose API
           mandates promotion to 32-bit.

       -mno-short
           Do not consider type "int" to be 16 bits wide.  This is the default.

       -mnobitfield
       -mno-bitfield
           Do not use the bit-field instructions.  The -m68000, -mcpu32 and -m5200 options imply
           -mnobitfield.

       -mbitfield
           Do use the bit-field instructions.  The -m68020 option implies -mbitfield.  This is
           the default if you use a configuration designed for a 68020.

       -mrtd
           Use a different function-calling convention, in which functions that take a fixed
           number of arguments return with the "rtd" instruction, which pops their arguments
           while returning.  This saves one instruction in the caller since there is no need to
           pop the arguments there.

           This calling convention is incompatible with the one normally used on Unix, so you
           cannot use it if you need to call libraries compiled with the Unix compiler.

           Also, you must provide function prototypes for all functions that take variable
           numbers of arguments (including "printf"); otherwise incorrect code is generated for
           calls to those functions.

           In addition, seriously incorrect code results if you call a function with too many
           arguments.  (Normally, extra arguments are harmlessly ignored.)

           The "rtd" instruction is supported by the 68010, 68020, 68030, 68040, 68060 and CPU32
           processors, but not by the 68000 or 5200.

       -mno-rtd
           Do not use the calling conventions selected by -mrtd.  This is the default.

       -malign-int
       -mno-align-int
           Control whether GCC aligns "int", "long", "long long", "float", "double", and "long
           double" variables on a 32-bit boundary (-malign-int) or a 16-bit boundary
           (-mno-align-int).  Aligning variables on 32-bit boundaries produces code that runs
           somewhat faster on processors with 32-bit busses at the expense of more memory.

           Warning: if you use the -malign-int switch, GCC aligns structures containing the above
           types differently than most published application binary interface specifications for
           the m68k.

       -mpcrel
           Use the pc-relative addressing mode of the 68000 directly, instead of using a global
           offset table.  At present, this option implies -fpic, allowing at most a 16-bit offset
           for pc-relative addressing.  -fPIC is not presently supported with -mpcrel, though
           this could be supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
           Do not (do) assume that unaligned memory references are handled by the system.

       -msep-data
           Generate code that allows the data segment to be located in a different area of memory
           from the text segment.  This allows for execute-in-place in an environment without
           virtual memory management.  This option implies -fPIC.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text segment.  This is
           the default.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID method.  This allows
           for execute-in-place and shared libraries in an environment without virtual memory
           management.  This option implies -fPIC.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are being used.  This is
           the default.

       -mshared-library-id=n
           Specifies the identification number of the ID-based shared library being compiled.
           Specifying a value of 0 generates more compact code; specifying other values forces
           the allocation of that number to the current library, but is no more space- or time-
           efficient than omitting this option.

       -mxgot
       -mno-xgot
           When generating position-independent code for ColdFire, generate code that works if
           the GOT has more than 8192 entries.  This code is larger and slower than code
           generated without this option.  On M680x0 processors, this option is not needed; -fPIC
           suffices.

           GCC normally uses a single instruction to load values from the GOT.  While this is
           relatively efficient, it only works if the GOT is smaller than about 64k.  Anything
           larger causes the linker to report an error such as:

                   relocation truncated to fit: R_68K_GOT16O foobar

           If this happens, you should recompile your code with -mxgot.  It should then work with
           very large GOTs.  However, code generated with -mxgot is less efficient, since it
           takes 4 instructions to fetch the value of a global symbol.

           Note that some linkers, including newer versions of the GNU linker, can create
           multiple GOTs and sort GOT entries.  If you have such a linker, you should only need
           to use -mxgot when compiling a single object file that accesses more than 8192 GOT
           entries.  Very few do.

           These options have no effect unless GCC is generating position-independent code.

       MCore Options

       These are the -m options defined for the Motorola M*Core processors.

       -mhardlit
       -mno-hardlit
           Inline constants into the code stream if it can be done in two instructions or less.

       -mdiv
       -mno-div
           Use the divide instruction.  (Enabled by default).

       -mrelax-immediate
       -mno-relax-immediate
           Allow arbitrary-sized immediates in bit operations.

       -mwide-bitfields
       -mno-wide-bitfields
           Always treat bit-fields as "int"-sized.

       -m4byte-functions
       -mno-4byte-functions
           Force all functions to be aligned to a 4-byte boundary.

       -mcallgraph-data
       -mno-callgraph-data
           Emit callgraph information.

       -mslow-bytes
       -mno-slow-bytes
           Prefer word access when reading byte quantities.

       -mlittle-endian
       -mbig-endian
           Generate code for a little-endian target.

       -m210
       -m340
           Generate code for the 210 processor.

       -mno-lsim
           Assume that runtime support has been provided and so omit the simulator library
           (libsim.a) from the linker command line.

       -mstack-increment=size
           Set the maximum amount for a single stack increment operation.  Large values can
           increase the speed of programs that contain functions that need a large amount of
           stack space, but they can also trigger a segmentation fault if the stack is extended
           too much.  The default value is 0x1000.

       MeP Options

       -mabsdiff
           Enables the "abs" instruction, which is the absolute difference between two registers.

       -mall-opts
           Enables all the optional instructions---average, multiply, divide, bit operations,
           leading zero, absolute difference, min/max, clip, and saturation.

       -maverage
           Enables the "ave" instruction, which computes the average of two registers.

       -mbased=n
           Variables of size n bytes or smaller are placed in the ".based" section by default.
           Based variables use the $tp register as a base register, and there is a 128-byte limit
           to the ".based" section.

       -mbitops
           Enables the bit operation instructions---bit test ("btstm"), set ("bsetm"), clear
           ("bclrm"), invert ("bnotm"), and test-and-set ("tas").

       -mc=name
           Selects which section constant data is placed in.  name may be tiny, near, or far.

       -mclip
           Enables the "clip" instruction.  Note that -mclip is not useful unless you also
           provide -mminmax.

       -mconfig=name
           Selects one of the built-in core configurations.  Each MeP chip has one or more
           modules in it; each module has a core CPU and a variety of coprocessors, optional
           instructions, and peripherals.  The "MeP-Integrator" tool, not part of GCC, provides
           these configurations through this option; using this option is the same as using all
           the corresponding command-line options.  The default configuration is default.

       -mcop
           Enables the coprocessor instructions.  By default, this is a 32-bit coprocessor.  Note
           that the coprocessor is normally enabled via the -mconfig= option.

       -mcop32
           Enables the 32-bit coprocessor's instructions.

       -mcop64
           Enables the 64-bit coprocessor's instructions.

       -mivc2
           Enables IVC2 scheduling.  IVC2 is a 64-bit VLIW coprocessor.

       -mdc
           Causes constant variables to be placed in the ".near" section.

       -mdiv
           Enables the "div" and "divu" instructions.

       -meb
           Generate big-endian code.

       -mel
           Generate little-endian code.

       -mio-volatile
           Tells the compiler that any variable marked with the "io" attribute is to be
           considered volatile.

       -ml Causes variables to be assigned to the ".far" section by default.

       -mleadz
           Enables the "leadz" (leading zero) instruction.

       -mm Causes variables to be assigned to the ".near" section by default.

       -mminmax
           Enables the "min" and "max" instructions.

       -mmult
           Enables the multiplication and multiply-accumulate instructions.

       -mno-opts
           Disables all the optional instructions enabled by -mall-opts.

       -mrepeat
           Enables the "repeat" and "erepeat" instructions, used for low-overhead looping.

       -ms Causes all variables to default to the ".tiny" section.  Note that there is a
           65536-byte limit to this section.  Accesses to these variables use the %gp base
           register.

       -msatur
           Enables the saturation instructions.  Note that the compiler does not currently
           generate these itself, but this option is included for compatibility with other tools,
           like "as".

       -msdram
           Link the SDRAM-based runtime instead of the default ROM-based runtime.

       -msim
           Link the simulator run-time libraries.

       -msimnovec
           Link the simulator runtime libraries, excluding built-in support for reset and
           exception vectors and tables.

       -mtf
           Causes all functions to default to the ".far" section.  Without this option, functions
           default to the ".near" section.

       -mtiny=n
           Variables that are n bytes or smaller are allocated to the ".tiny" section.  These
           variables use the $gp base register.  The default for this option is 4, but note that
           there's a 65536-byte limit to the ".tiny" section.

       MicroBlaze Options

       -msoft-float
           Use software emulation for floating point (default).

       -mhard-float
           Use hardware floating-point instructions.

       -mmemcpy
           Do not optimize block moves, use "memcpy".

       -mno-clearbss
           This option is deprecated.  Use -fno-zero-initialized-in-bss instead.

       -mcpu=cpu-type
           Use features of, and schedule code for, the given CPU.  Supported values are in the
           format vX.YY.Z, where X is a major version, YY is the minor version, and Z is
           compatibility code.  Example values are v3.00.a, v4.00.b, v5.00.a, v5.00.b, v5.00.b,
           v6.00.a.

       -mxl-soft-mul
           Use software multiply emulation (default).

       -mxl-soft-div
           Use software emulation for divides (default).

       -mxl-barrel-shift
           Use the hardware barrel shifter.

       -mxl-pattern-compare
           Use pattern compare instructions.

       -msmall-divides
           Use table lookup optimization for small signed integer divisions.

       -mxl-stack-check
           This option is deprecated.  Use -fstack-check instead.

       -mxl-gp-opt
           Use GP-relative ".sdata"/".sbss" sections.

       -mxl-multiply-high
           Use multiply high instructions for high part of 32x32 multiply.

       -mxl-float-convert
           Use hardware floating-point conversion instructions.

       -mxl-float-sqrt
           Use hardware floating-point square root instruction.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.

       -mxl-reorder
           Use reorder instructions (swap and byte reversed load/store).

       -mxl-mode-app-model
           Select application model app-model.  Valid models are

           executable
               normal executable (default), uses startup code crt0.o.

           xmdstub
               for use with Xilinx Microprocessor Debugger (XMD) based software intrusive debug
               agent called xmdstub. This uses startup file crt1.o and sets the start address of
               the program to 0x800.

           bootstrap
               for applications that are loaded using a bootloader.  This model uses startup file
               crt2.o which does not contain a processor reset vector handler. This is suitable
               for transferring control on a processor reset to the bootloader rather than the
               application.

           novectors
               for applications that do not require any of the MicroBlaze vectors. This option
               may be useful for applications running within a monitoring application. This model
               uses crt3.o as a startup file.

           Option -xl-mode-app-model is a deprecated alias for -mxl-mode-app-model.

       MIPS Options

       -EB Generate big-endian code.

       -EL Generate little-endian code.  This is the default for mips*el-*-* configurations.

       -march=arch
           Generate code that runs on arch, which can be the name of a generic MIPS ISA, or the
           name of a particular processor.  The ISA names are: mips1, mips2, mips3, mips4,
           mips32, mips32r2, mips32r3, mips32r5, mips32r6, mips64, mips64r2, mips64r3, mips64r5
           and mips64r6.  The processor names are: 4kc, 4km, 4kp, 4ksc, 4kec, 4kem, 4kep, 4ksd,
           5kc, 5kf, 20kc, 24kc, 24kf2_1, 24kf1_1, 24kec, 24kef2_1, 24kef1_1, 34kc, 34kf2_1,
           34kf1_1, 34kn, 74kc, 74kf2_1, 74kf1_1, 74kf3_2, 1004kc, 1004kf2_1, 1004kf1_1,
           loongson2e, loongson2f, loongson3a, m4k, m14k, m14kc, m14ke, m14kec, octeon, octeon+,
           octeon2, octeon3, orion, p5600, r2000, r3000, r3900, r4000, r4400, r4600, r4650,
           r4700, r6000, r8000, rm7000, rm9000, r10000, r12000, r14000, r16000, sb1, sr71000,
           vr4100, vr4111, vr4120, vr4130, vr4300, vr5000, vr5400, vr5500, xlr and xlp.  The
           special value from-abi selects the most compatible architecture for the selected ABI
           (that is, mips1 for 32-bit ABIs and mips3 for 64-bit ABIs).

           The native Linux/GNU toolchain also supports the value native, which selects the best
           architecture option for the host processor.  -march=native has no effect if GCC does
           not recognize the processor.

           In processor names, a final 000 can be abbreviated as k (for example, -march=r2k).
           Prefixes are optional, and vr may be written r.

           Names of the form nf2_1 refer to processors with FPUs clocked at half the rate of the
           core, names of the form nf1_1 refer to processors with FPUs clocked at the same rate
           as the core, and names of the form nf3_2 refer to processors with FPUs clocked a ratio
           of 3:2 with respect to the core.  For compatibility reasons, nf is accepted as a
           synonym for nf2_1 while nx and bfx are accepted as synonyms for nf1_1.

           GCC defines two macros based on the value of this option.  The first is "_MIPS_ARCH",
           which gives the name of target architecture, as a string.  The second has the form
           "_MIPS_ARCH_foo", where foo is the capitalized value of "_MIPS_ARCH".  For example,
           -march=r2000 sets "_MIPS_ARCH" to "r2000" and defines the macro "_MIPS_ARCH_R2000".

           Note that the "_MIPS_ARCH" macro uses the processor names given above.  In other
           words, it has the full prefix and does not abbreviate 000 as k.  In the case of from-
           abi, the macro names the resolved architecture (either "mips1" or "mips3").  It names
           the default architecture when no -march option is given.

       -mtune=arch
           Optimize for arch.  Among other things, this option controls the way instructions are
           scheduled, and the perceived cost of arithmetic operations.  The list of arch values
           is the same as for -march.

           When this option is not used, GCC optimizes for the processor specified by -march.  By
           using -march and -mtune together, it is possible to generate code that runs on a
           family of processors, but optimize the code for one particular member of that family.

           -mtune defines the macros "_MIPS_TUNE" and "_MIPS_TUNE_foo", which work in the same
           way as the -march ones described above.

       -mips1
           Equivalent to -march=mips1.

       -mips2
           Equivalent to -march=mips2.

       -mips3
           Equivalent to -march=mips3.

       -mips4
           Equivalent to -march=mips4.

       -mips32
           Equivalent to -march=mips32.

       -mips32r3
           Equivalent to -march=mips32r3.

       -mips32r5
           Equivalent to -march=mips32r5.

       -mips32r6
           Equivalent to -march=mips32r6.

       -mips64
           Equivalent to -march=mips64.

       -mips64r2
           Equivalent to -march=mips64r2.

       -mips64r3
           Equivalent to -march=mips64r3.

       -mips64r5
           Equivalent to -march=mips64r5.

       -mips64r6
           Equivalent to -march=mips64r6.

       -mips16
       -mno-mips16
           Generate (do not generate) MIPS16 code.  If GCC is targeting a MIPS32 or MIPS64
           architecture, it makes use of the MIPS16e ASE.

           MIPS16 code generation can also be controlled on a per-function basis by means of
           "mips16" and "nomips16" attributes.

       -mflip-mips16
           Generate MIPS16 code on alternating functions.  This option is provided for regression
           testing of mixed MIPS16/non-MIPS16 code generation, and is not intended for ordinary
           use in compiling user code.

       -minterlink-compressed
       -mno-interlink-compressed
           Require (do not require) that code using the standard (uncompressed) MIPS ISA be link-
           compatible with MIPS16 and microMIPS code, and vice versa.

           For example, code using the standard ISA encoding cannot jump directly to MIPS16 or
           microMIPS code; it must either use a call or an indirect jump.  -minterlink-compressed
           therefore disables direct jumps unless GCC knows that the target of the jump is not
           compressed.

       -minterlink-mips16
       -mno-interlink-mips16
           Aliases of -minterlink-compressed and -mno-interlink-compressed.  These options
           predate the microMIPS ASE and are retained for backwards compatibility.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
           Generate code for the given ABI.

           Note that the EABI has a 32-bit and a 64-bit variant.  GCC normally generates 64-bit
           code when you select a 64-bit architecture, but you can use -mgp32 to get 32-bit code
           instead.

           For information about the O64 ABI, see <http://gcc.gnu.org/projects/mipso64-abi.html>.

           GCC supports a variant of the o32 ABI in which floating-point registers are 64 rather
           than 32 bits wide.  You can select this combination with -mabi=32 -mfp64.  This ABI
           relies on the "mthc1" and "mfhc1" instructions and is therefore only supported for
           MIPS32R2, MIPS32R3 and MIPS32R5 processors.

           The register assignments for arguments and return values remain the same, but each
           scalar value is passed in a single 64-bit register rather than a pair of 32-bit
           registers.  For example, scalar floating-point values are returned in $f0 only, not a
           $f0/$f1 pair.  The set of call-saved registers also remains the same in that the even-
           numbered double-precision registers are saved.

           Two additional variants of the o32 ABI are supported to enable a transition from
           32-bit to 64-bit registers.  These are FPXX (-mfpxx) and FP64A (-mfp64
           -mno-odd-spreg).  The FPXX extension mandates that all code must execute correctly
           when run using 32-bit or 64-bit registers.  The code can be interlinked with either
           FP32 or FP64, but not both.  The FP64A extension is similar to the FP64 extension but
           forbids the use of odd-numbered single-precision registers.  This can be used in
           conjunction with the "FRE" mode of FPUs in MIPS32R5 processors and allows both FP32
           and FP64A code to interlink and run in the same process without changing FPU modes.

       -mabicalls
       -mno-abicalls
           Generate (do not generate) code that is suitable for SVR4-style dynamic objects.
           -mabicalls is the default for SVR4-based systems.

       -mshared
       -mno-shared
           Generate (do not generate) code that is fully position-independent, and that can
           therefore be linked into shared libraries.  This option only affects -mabicalls.

           All -mabicalls code has traditionally been position-independent, regardless of options
           like -fPIC and -fpic.  However, as an extension, the GNU toolchain allows executables
           to use absolute accesses for locally-binding symbols.  It can also use shorter GP
           initialization sequences and generate direct calls to locally-defined functions.  This
           mode is selected by -mno-shared.

           -mno-shared depends on binutils 2.16 or higher and generates objects that can only be
           linked by the GNU linker.  However, the option does not affect the ABI of the final
           executable; it only affects the ABI of relocatable objects.  Using -mno-shared
           generally makes executables both smaller and quicker.

           -mshared is the default.

       -mplt
       -mno-plt
           Assume (do not assume) that the static and dynamic linkers support PLTs and copy
           relocations.  This option only affects -mno-shared -mabicalls.  For the n64 ABI, this
           option has no effect without -msym32.

           You can make -mplt the default by configuring GCC with --with-mips-plt.  The default
           is -mno-plt otherwise.

       -mxgot
       -mno-xgot
           Lift (do not lift) the usual restrictions on the size of the global offset table.

           GCC normally uses a single instruction to load values from the GOT.  While this is
           relatively efficient, it only works if the GOT is smaller than about 64k.  Anything
           larger causes the linker to report an error such as:

                   relocation truncated to fit: R_MIPS_GOT16 foobar

           If this happens, you should recompile your code with -mxgot.  This works with very
           large GOTs, although the code is also less efficient, since it takes three
           instructions to fetch the value of a global symbol.

           Note that some linkers can create multiple GOTs.  If you have such a linker, you
           should only need to use -mxgot when a single object file accesses more than 64k's
           worth of GOT entries.  Very few do.

           These options have no effect unless GCC is generating position independent code.

       -mgp32
           Assume that general-purpose registers are 32 bits wide.

       -mgp64
           Assume that general-purpose registers are 64 bits wide.

       -mfp32
           Assume that floating-point registers are 32 bits wide.

       -mfp64
           Assume that floating-point registers are 64 bits wide.

       -mfpxx
           Do not assume the width of floating-point registers.

       -mhard-float
           Use floating-point coprocessor instructions.

       -msoft-float
           Do not use floating-point coprocessor instructions.  Implement floating-point
           calculations using library calls instead.

       -mno-float
           Equivalent to -msoft-float, but additionally asserts that the program being compiled
           does not perform any floating-point operations.  This option is presently supported
           only by some bare-metal MIPS configurations, where it may select a special set of
           libraries that lack all floating-point support (including, for example, the floating-
           point "printf" formats).  If code compiled with -mno-float accidentally contains
           floating-point operations, it is likely to suffer a link-time or run-time failure.

       -msingle-float
           Assume that the floating-point coprocessor only supports single-precision operations.

       -mdouble-float
           Assume that the floating-point coprocessor supports double-precision operations.  This
           is the default.

       -modd-spreg
       -mno-odd-spreg
           Enable the use of odd-numbered single-precision floating-point registers for the o32
           ABI.  This is the default for processors that are known to support these registers.
           When using the o32 FPXX ABI, -mno-odd-spreg is set by default.

       -mabs=2008
       -mabs=legacy
           These options control the treatment of the special not-a-number (NaN) IEEE 754
           floating-point data with the "abs.fmt" and "neg.fmt" machine instructions.

           By default or when -mabs=legacy is used the legacy treatment is selected.  In this
           case these instructions are considered arithmetic and avoided where correct operation
           is required and the input operand might be a NaN.  A longer sequence of instructions
           that manipulate the sign bit of floating-point datum manually is used instead unless
           the -ffinite-math-only option has also been specified.

           The -mabs=2008 option selects the IEEE 754-2008 treatment.  In this case these
           instructions are considered non-arithmetic and therefore operating correctly in all
           cases, including in particular where the input operand is a NaN.  These instructions
           are therefore always used for the respective operations.

       -mnan=2008
       -mnan=legacy
           These options control the encoding of the special not-a-number (NaN) IEEE 754
           floating-point data.

           The -mnan=legacy option selects the legacy encoding.  In this case quiet NaNs (qNaNs)
           are denoted by the first bit of their trailing significand field being 0, whereas
           signalling NaNs (sNaNs) are denoted by the first bit of their trailing significand
           field being 1.

           The -mnan=2008 option selects the IEEE 754-2008 encoding.  In this case qNaNs are
           denoted by the first bit of their trailing significand field being 1, whereas sNaNs
           are denoted by the first bit of their trailing significand field being 0.

           The default is -mnan=legacy unless GCC has been configured with --with-nan=2008.

       -mllsc
       -mno-llsc
           Use (do not use) ll, sc, and sync instructions to implement atomic memory built-in
           functions.  When neither option is specified, GCC uses the instructions if the target
           architecture supports them.

           -mllsc is useful if the runtime environment can emulate the instructions and -mno-llsc
           can be useful when compiling for nonstandard ISAs.  You can make either option the
           default by configuring GCC with --with-llsc and --without-llsc respectively.
           --with-llsc is the default for some configurations; see the installation documentation
           for details.

       -mdsp
       -mno-dsp
           Use (do not use) revision 1 of the MIPS DSP ASE.
             This option defines the preprocessor macro "__mips_dsp".  It also defines
           "__mips_dsp_rev" to 1.

       -mdspr2
       -mno-dspr2
           Use (do not use) revision 2 of the MIPS DSP ASE.
             This option defines the preprocessor macros "__mips_dsp" and "__mips_dspr2".  It
           also defines "__mips_dsp_rev" to 2.

       -msmartmips
       -mno-smartmips
           Use (do not use) the MIPS SmartMIPS ASE.

       -mpaired-single
       -mno-paired-single
           Use (do not use) paired-single floating-point instructions.
             This option requires hardware floating-point support to be enabled.

       -mdmx
       -mno-mdmx
           Use (do not use) MIPS Digital Media Extension instructions.  This option can only be
           used when generating 64-bit code and requires hardware floating-point support to be
           enabled.

       -mips3d
       -mno-mips3d
           Use (do not use) the MIPS-3D ASE.  The option -mips3d implies -mpaired-single.

       -mmicromips
       -mno-micromips
           Generate (do not generate) microMIPS code.

           MicroMIPS code generation can also be controlled on a per-function basis by means of
           "micromips" and "nomicromips" attributes.

       -mmt
       -mno-mt
           Use (do not use) MT Multithreading instructions.

       -mmcu
       -mno-mcu
           Use (do not use) the MIPS MCU ASE instructions.

       -meva
       -mno-eva
           Use (do not use) the MIPS Enhanced Virtual Addressing instructions.

       -mvirt
       -mno-virt
           Use (do not use) the MIPS Virtualization Application Specific instructions.

       -mxpa
       -mno-xpa
           Use (do not use) the MIPS eXtended Physical Address (XPA) instructions.

       -mlong64
           Force "long" types to be 64 bits wide.  See -mlong32 for an explanation of the default
           and the way that the pointer size is determined.

       -mlong32
           Force "long", "int", and pointer types to be 32 bits wide.

           The default size of "int"s, "long"s and pointers depends on the ABI.  All the
           supported ABIs use 32-bit "int"s.  The n64 ABI uses 64-bit "long"s, as does the 64-bit
           EABI; the others use 32-bit "long"s.  Pointers are the same size as "long"s, or the
           same size as integer registers, whichever is smaller.

       -msym32
       -mno-sym32
           Assume (do not assume) that all symbols have 32-bit values, regardless of the selected
           ABI.  This option is useful in combination with -mabi=64 and -mno-abicalls because it
           allows GCC to generate shorter and faster references to symbolic addresses.

       -G num
           Put definitions of externally-visible data in a small data section if that data is no
           bigger than num bytes.  GCC can then generate more efficient accesses to the data; see
           -mgpopt for details.

           The default -G option depends on the configuration.

       -mlocal-sdata
       -mno-local-sdata
           Extend (do not extend) the -G behavior to local data too, such as to static variables
           in C.  -mlocal-sdata is the default for all configurations.

           If the linker complains that an application is using too much small data, you might
           want to try rebuilding the less performance-critical parts with -mno-local-sdata.  You
           might also want to build large libraries with -mno-local-sdata, so that the libraries
           leave more room for the main program.

       -mextern-sdata
       -mno-extern-sdata
           Assume (do not assume) that externally-defined data is in a small data section if the
           size of that data is within the -G limit.  -mextern-sdata is the default for all
           configurations.

           If you compile a module Mod with -mextern-sdata -G num -mgpopt, and Mod references a
           variable Var that is no bigger than num bytes, you must make sure that Var is placed
           in a small data section.  If Var is defined by another module, you must either compile
           that module with a high-enough -G setting or attach a "section" attribute to Var's
           definition.  If Var is common, you must link the application with a high-enough -G
           setting.

           The easiest way of satisfying these restrictions is to compile and link every module
           with the same -G option.  However, you may wish to build a library that supports
           several different small data limits.  You can do this by compiling the library with
           the highest supported -G setting and additionally using -mno-extern-sdata to stop the
           library from making assumptions about externally-defined data.

       -mgpopt
       -mno-gpopt
           Use (do not use) GP-relative accesses for symbols that are known to be in a small data
           section; see -G, -mlocal-sdata and -mextern-sdata.  -mgpopt is the default for all
           configurations.

           -mno-gpopt is useful for cases where the $gp register might not hold the value of
           "_gp".  For example, if the code is part of a library that might be used in a boot
           monitor, programs that call boot monitor routines pass an unknown value in $gp.  (In
           such situations, the boot monitor itself is usually compiled with -G0.)

           -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata.

       -membedded-data
       -mno-embedded-data
           Allocate variables to the read-only data section first if possible, then next in the
           small data section if possible, otherwise in data.  This gives slightly slower code
           than the default, but reduces the amount of RAM required when executing, and thus may
           be preferred for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
           Put uninitialized "const" variables in the read-only data section.  This option is
           only meaningful in conjunction with -membedded-data.

       -mcode-readable=setting
           Specify whether GCC may generate code that reads from executable sections.  There are
           three possible settings:

           -mcode-readable=yes
               Instructions may freely access executable sections.  This is the default setting.

           -mcode-readable=pcrel
               MIPS16 PC-relative load instructions can access executable sections, but other
               instructions must not do so.  This option is useful on 4KSc and 4KSd processors
               when the code TLBs have the Read Inhibit bit set.  It is also useful on processors
               that can be configured to have a dual instruction/data SRAM interface and that,
               like the M4K, automatically redirect PC-relative loads to the instruction RAM.

           -mcode-readable=no
               Instructions must not access executable sections.  This option can be useful on
               targets that are configured to have a dual instruction/data SRAM interface but
               that (unlike the M4K) do not automatically redirect PC-relative loads to the
               instruction RAM.

       -msplit-addresses
       -mno-split-addresses
           Enable (disable) use of the "%hi()" and "%lo()" assembler relocation operators.  This
           option has been superseded by -mexplicit-relocs but is retained for backwards
           compatibility.

       -mexplicit-relocs
       -mno-explicit-relocs
           Use (do not use) assembler relocation operators when dealing with symbolic addresses.
           The alternative, selected by -mno-explicit-relocs, is to use assembler macros instead.

           -mexplicit-relocs is the default if GCC was configured to use an assembler that
           supports relocation operators.

       -mcheck-zero-division
       -mno-check-zero-division
           Trap (do not trap) on integer division by zero.

           The default is -mcheck-zero-division.

       -mdivide-traps
       -mdivide-breaks
           MIPS systems check for division by zero by generating either a conditional trap or a
           break instruction.  Using traps results in smaller code, but is only supported on MIPS
           II and later.  Also, some versions of the Linux kernel have a bug that prevents trap
           from generating the proper signal ("SIGFPE").  Use -mdivide-traps to allow conditional
           traps on architectures that support them and -mdivide-breaks to force the use of
           breaks.

           The default is usually -mdivide-traps, but this can be overridden at configure time
           using --with-divide=breaks.  Divide-by-zero checks can be completely disabled using
           -mno-check-zero-division.

       -mmemcpy
       -mno-memcpy
           Force (do not force) the use of "memcpy" for non-trivial block moves.  The default is
           -mno-memcpy, which allows GCC to inline most constant-sized copies.

       -mlong-calls
       -mno-long-calls
           Disable (do not disable) use of the "jal" instruction.  Calling functions using "jal"
           is more efficient but requires the caller and callee to be in the same 256 megabyte
           segment.

           This option has no effect on abicalls code.  The default is -mno-long-calls.

       -mmad
       -mno-mad
           Enable (disable) use of the "mad", "madu" and "mul" instructions, as provided by the
           R4650 ISA.

       -mimadd
       -mno-imadd
           Enable (disable) use of the "madd" and "msub" integer instructions.  The default is
           -mimadd on architectures that support "madd" and "msub" except for the 74k
           architecture where it was found to generate slower code.

       -mfused-madd
       -mno-fused-madd
           Enable (disable) use of the floating-point multiply-accumulate instructions, when they
           are available.  The default is -mfused-madd.

           On the R8000 CPU when multiply-accumulate instructions are used, the intermediate
           product is calculated to infinite precision and is not subject to the FCSR Flush to
           Zero bit.  This may be undesirable in some circumstances.  On other processors the
           result is numerically identical to the equivalent computation using separate multiply,
           add, subtract and negate instructions.

       -nocpp
           Tell the MIPS assembler to not run its preprocessor over user assembler files (with a
           .s suffix) when assembling them.

       -mfix-24k
       -mno-fix-24k
           Work around the 24K E48 (lost data on stores during refill) errata.  The workarounds
           are implemented by the assembler rather than by GCC.

       -mfix-r4000
       -mno-fix-r4000
           Work around certain R4000 CPU errata:

           -   A double-word or a variable shift may give an incorrect result if executed
               immediately after starting an integer division.

           -   A double-word or a variable shift may give an incorrect result if executed while
               an integer multiplication is in progress.

           -   An integer division may give an incorrect result if started in a delay slot of a
               taken branch or a jump.

       -mfix-r4400
       -mno-fix-r4400
           Work around certain R4400 CPU errata:

           -   A double-word or a variable shift may give an incorrect result if executed
               immediately after starting an integer division.

       -mfix-r10000
       -mno-fix-r10000
           Work around certain R10000 errata:

           -   "ll"/"sc" sequences may not behave atomically on revisions prior to 3.0.  They may
               deadlock on revisions 2.6 and earlier.

           This option can only be used if the target architecture supports branch-likely
           instructions.  -mfix-r10000 is the default when -march=r10000 is used; -mno-fix-r10000
           is the default otherwise.

       -mfix-rm7000
       -mno-fix-rm7000
           Work around the RM7000 "dmult"/"dmultu" errata.  The workarounds are implemented by
           the assembler rather than by GCC.

       -mfix-vr4120
       -mno-fix-vr4120
           Work around certain VR4120 errata:

           -   "dmultu" does not always produce the correct result.

           -   "div" and "ddiv" do not always produce the correct result if one of the operands
               is negative.

           The workarounds for the division errata rely on special functions in libgcc.a.  At
           present, these functions are only provided by the "mips64vr*-elf" configurations.

           Other VR4120 errata require a NOP to be inserted between certain pairs of
           instructions.  These errata are handled by the assembler, not by GCC itself.

       -mfix-vr4130
           Work around the VR4130 "mflo"/"mfhi" errata.  The workarounds are implemented by the
           assembler rather than by GCC, although GCC avoids using "mflo" and "mfhi" if the
           VR4130 "macc", "macchi", "dmacc" and "dmacchi" instructions are available instead.

       -mfix-sb1
       -mno-fix-sb1
           Work around certain SB-1 CPU core errata.  (This flag currently works around the SB-1
           revision 2 "F1" and "F2" floating-point errata.)

       -mr10k-cache-barrier=setting
           Specify whether GCC should insert cache barriers to avoid the side-effects of
           speculation on R10K processors.

           In common with many processors, the R10K tries to predict the outcome of a conditional
           branch and speculatively executes instructions from the "taken" branch.  It later
           aborts these instructions if the predicted outcome is wrong.  However, on the R10K,
           even aborted instructions can have side effects.

           This problem only affects kernel stores and, depending on the system, kernel loads.
           As an example, a speculatively-executed store may load the target memory into cache
           and mark the cache line as dirty, even if the store itself is later aborted.  If a DMA
           operation writes to the same area of memory before the "dirty" line is flushed, the
           cached data overwrites the DMA-ed data.  See the R10K processor manual for a full
           description, including other potential problems.

           One workaround is to insert cache barrier instructions before every memory access that
           might be speculatively executed and that might have side effects even if aborted.
           -mr10k-cache-barrier=setting controls GCC's implementation of this workaround.  It
           assumes that aborted accesses to any byte in the following regions does not have side
           effects:

           1.  the memory occupied by the current function's stack frame;

           2.  the memory occupied by an incoming stack argument;

           3.  the memory occupied by an object with a link-time-constant address.

           It is the kernel's responsibility to ensure that speculative accesses to these regions
           are indeed safe.

           If the input program contains a function declaration such as:

                   void foo (void);

           then the implementation of "foo" must allow "j foo" and "jal foo" to be executed
           speculatively.  GCC honors this restriction for functions it compiles itself.  It
           expects non-GCC functions (such as hand-written assembly code) to do the same.

           The option has three forms:

           -mr10k-cache-barrier=load-store
               Insert a cache barrier before a load or store that might be speculatively executed
               and that might have side effects even if aborted.

           -mr10k-cache-barrier=store
               Insert a cache barrier before a store that might be speculatively executed and
               that might have side effects even if aborted.

           -mr10k-cache-barrier=none
               Disable the insertion of cache barriers.  This is the default setting.

       -mflush-func=func
       -mno-flush-func
           Specifies the function to call to flush the I and D caches, or to not call any such
           function.  If called, the function must take the same arguments as the common
           "_flush_func", that is, the address of the memory range for which the cache is being
           flushed, the size of the memory range, and the number 3 (to flush both caches).  The
           default depends on the target GCC was configured for, but commonly is either
           "_flush_func" or "__cpu_flush".

       mbranch-cost=num
           Set the cost of branches to roughly num "simple" instructions.  This cost is only a
           heuristic and is not guaranteed to produce consistent results across releases.  A zero
           cost redundantly selects the default, which is based on the -mtune setting.

       -mbranch-likely
       -mno-branch-likely
           Enable or disable use of Branch Likely instructions, regardless of the default for the
           selected architecture.  By default, Branch Likely instructions may be generated if
           they are supported by the selected architecture.  An exception is for the MIPS32 and
           MIPS64 architectures and processors that implement those architectures; for those,
           Branch Likely instructions are not be generated by default because the MIPS32 and
           MIPS64 architectures specifically deprecate their use.

       -mfp-exceptions
       -mno-fp-exceptions
           Specifies whether FP exceptions are enabled.  This affects how FP instructions are
           scheduled for some processors.  The default is that FP exceptions are enabled.

           For instance, on the SB-1, if FP exceptions are disabled, and we are emitting 64-bit
           code, then we can use both FP pipes.  Otherwise, we can only use one FP pipe.

       -mvr4130-align
       -mno-vr4130-align
           The VR4130 pipeline is two-way superscalar, but can only issue two instructions
           together if the first one is 8-byte aligned.  When this option is enabled, GCC aligns
           pairs of instructions that it thinks should execute in parallel.

           This option only has an effect when optimizing for the VR4130.  It normally makes code
           faster, but at the expense of making it bigger.  It is enabled by default at
           optimization level -O3.

       -msynci
       -mno-synci
           Enable (disable) generation of "synci" instructions on architectures that support it.
           The "synci" instructions (if enabled) are generated when "__builtin___clear_cache" is
           compiled.

           This option defaults to -mno-synci, but the default can be overridden by configuring
           GCC with --with-synci.

           When compiling code for single processor systems, it is generally safe to use "synci".
           However, on many multi-core (SMP) systems, it does not invalidate the instruction
           caches on all cores and may lead to undefined behavior.

       -mrelax-pic-calls
       -mno-relax-pic-calls
           Try to turn PIC calls that are normally dispatched via register $25 into direct calls.
           This is only possible if the linker can resolve the destination at link-time and if
           the destination is within range for a direct call.

           -mrelax-pic-calls is the default if GCC was configured to use an assembler and a
           linker that support the ".reloc" assembly directive and -mexplicit-relocs is in
           effect.  With -mno-explicit-relocs, this optimization can be performed by the
           assembler and the linker alone without help from the compiler.

       -mmcount-ra-address
       -mno-mcount-ra-address
           Emit (do not emit) code that allows "_mcount" to modify the calling function's return
           address.  When enabled, this option extends the usual "_mcount" interface with a new
           ra-address parameter, which has type "intptr_t *" and is passed in register $12.
           "_mcount" can then modify the return address by doing both of the following:

           *   Returning the new address in register $31.

           *   Storing the new address in "*ra-address", if ra-address is nonnull.

           The default is -mno-mcount-ra-address.

       MMIX Options

       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
           Specify that intrinsic library functions are being compiled, passing all values in
           registers, no matter the size.

       -mepsilon
       -mno-epsilon
           Generate floating-point comparison instructions that compare with respect to the "rE"
           epsilon register.

       -mabi=mmixware
       -mabi=gnu
           Generate code that passes function parameters and return values that (in the called
           function) are seen as registers $0 and up, as opposed to the GNU ABI which uses global
           registers $231 and up.

       -mzero-extend
       -mno-zero-extend
           When reading data from memory in sizes shorter than 64 bits, use (do not use) zero-
           extending load instructions by default, rather than sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
           Make the result of a division yielding a remainder have the same sign as the divisor.
           With the default, -mno-knuthdiv, the sign of the remainder follows the sign of the
           dividend.  Both methods are arithmetically valid, the latter being almost exclusively
           used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
           Prepend (do not prepend) a : to all global symbols, so the assembly code can be used
           with the "PREFIX" assembly directive.

       -melf
           Generate an executable in the ELF format, rather than the default mmo format used by
           the mmix simulator.

       -mbranch-predict
       -mno-branch-predict
           Use (do not use) the probable-branch instructions, when static branch prediction
           indicates a probable branch.

       -mbase-addresses
       -mno-base-addresses
           Generate (do not generate) code that uses base addresses.  Using a base address
           automatically generates a request (handled by the assembler and the linker) for a
           constant to be set up in a global register.  The register is used for one or more base
           address requests within the range 0 to 255 from the value held in the register.  The
           generally leads to short and fast code, but the number of different data items that
           can be addressed is limited.  This means that a program that uses lots of static data
           may require -mno-base-addresses.

       -msingle-exit
       -mno-single-exit
           Force (do not force) generated code to have a single exit point in each function.

       MN10300 Options

       These -m options are defined for Matsushita MN10300 architectures:

       -mmult-bug
           Generate code to avoid bugs in the multiply instructions for the MN10300 processors.
           This is the default.

       -mno-mult-bug
           Do not generate code to avoid bugs in the multiply instructions for the MN10300
           processors.

       -mam33
           Generate code using features specific to the AM33 processor.

       -mno-am33
           Do not generate code using features specific to the AM33 processor.  This is the
           default.

       -mam33-2
           Generate code using features specific to the AM33/2.0 processor.

       -mam34
           Generate code using features specific to the AM34 processor.

       -mtune=cpu-type
           Use the timing characteristics of the indicated CPU type when scheduling instructions.
           This does not change the targeted processor type.  The CPU type must be one of
           mn10300, am33, am33-2 or am34.

       -mreturn-pointer-on-d0
           When generating a function that returns a pointer, return the pointer in both "a0" and
           "d0".  Otherwise, the pointer is returned only in "a0", and attempts to call such
           functions without a prototype result in errors.  Note that this option is on by
           default; use -mno-return-pointer-on-d0 to disable it.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       -mrelax
           Indicate to the linker that it should perform a relaxation optimization pass to
           shorten branches, calls and absolute memory addresses.  This option only has an effect
           when used on the command line for the final link step.

           This option makes symbolic debugging impossible.

       -mliw
           Allow the compiler to generate Long Instruction Word instructions if the target is the
           AM33 or later.  This is the default.  This option defines the preprocessor macro
           "__LIW__".

       -mnoliw
           Do not allow the compiler to generate Long Instruction Word instructions.  This option
           defines the preprocessor macro "__NO_LIW__".

       -msetlb
           Allow the compiler to generate the SETLB and Lcc instructions if the target is the
           AM33 or later.  This is the default.  This option defines the preprocessor macro
           "__SETLB__".

       -mnosetlb
           Do not allow the compiler to generate SETLB or Lcc instructions.  This option defines
           the preprocessor macro "__NO_SETLB__".

       Moxie Options

       -meb
           Generate big-endian code.  This is the default for moxie-*-* configurations.

       -mel
           Generate little-endian code.

       -mmul.x
           Generate mul.x and umul.x instructions.  This is the default for moxiebox-*-*
           configurations.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       MSP430 Options

       These options are defined for the MSP430:

       -masm-hex
           Force assembly output to always use hex constants.  Normally such constants are signed
           decimals, but this option is available for testsuite and/or aesthetic purposes.

       -mmcu=
           Select the MCU to target.  This is used to create a C preprocessor symbol based upon
           the MCU name, converted to upper case and pre- and post-fixed with __.  This in turn
           is used by the msp430.h header file to select an MCU-specific supplementary header
           file.

           The option also sets the ISA to use.  If the MCU name is one that is known to only
           support the 430 ISA then that is selected, otherwise the 430X ISA is selected.  A
           generic MCU name of msp430 can also be used to select the 430 ISA.  Similarly the
           generic msp430x MCU name selects the 430X ISA.

           In addition an MCU-specific linker script is added to the linker command line.  The
           script's name is the name of the MCU with .ld appended.  Thus specifying -mmcu=xxx on
           the gcc command line defines the C preprocessor symbol "__XXX__" and cause the linker
           to search for a script called xxx.ld.

           This option is also passed on to the assembler.

       -mcpu=
           Specifies the ISA to use.  Accepted values are msp430, msp430x and msp430xv2.  This
           option is deprecated.  The -mmcu= option should be used to select the ISA.

       -msim
           Link to the simulator runtime libraries and linker script.  Overrides any scripts that
           would be selected by the -mmcu= option.

       -mlarge
           Use large-model addressing (20-bit pointers, 32-bit "size_t").

       -msmall
           Use small-model addressing (16-bit pointers, 16-bit "size_t").

       -mrelax
           This option is passed to the assembler and linker, and allows the linker to perform
           certain optimizations that cannot be done until the final link.

       mhwmult=
           Describes the type of hardware multiply supported by the target.  Accepted values are
           none for no hardware multiply, 16bit for the original 16-bit-only multiply supported
           by early MCUs.  32bit for the 16/32-bit multiply supported by later MCUs and f5series
           for the 16/32-bit multiply supported by F5-series MCUs.  A value of auto can also be
           given.  This tells GCC to deduce the hardware multiply support based upon the MCU name
           provided by the -mmcu option.  If no -mmcu option is specified then 32bit hardware
           multiply support is assumed.  auto is the default setting.

           Hardware multiplies are normally performed by calling a library routine.  This saves
           space in the generated code.  When compiling at -O3 or higher however the hardware
           multiplier is invoked inline.  This makes for bigger, but faster code.

           The hardware multiply routines disable interrupts whilst running and restore the
           previous interrupt state when they finish.  This makes them safe to use inside
           interrupt handlers as well as in normal code.

       -minrt
           Enable the use of a minimum runtime environment - no static initializers or
           constructors.  This is intended for memory-constrained devices.  The compiler includes
           special symbols in some objects that tell the linker and runtime which code fragments
           are required.

       NDS32 Options

       These options are defined for NDS32 implementations:

       -mbig-endian
           Generate code in big-endian mode.

       -mlittle-endian
           Generate code in little-endian mode.

       -mreduced-regs
           Use reduced-set registers for register allocation.

       -mfull-regs
           Use full-set registers for register allocation.

       -mcmov
           Generate conditional move instructions.

       -mno-cmov
           Do not generate conditional move instructions.

       -mperf-ext
           Generate performance extension instructions.

       -mno-perf-ext
           Do not generate performance extension instructions.

       -mv3push
           Generate v3 push25/pop25 instructions.

       -mno-v3push
           Do not generate v3 push25/pop25 instructions.

       -m16-bit
           Generate 16-bit instructions.

       -mno-16-bit
           Do not generate 16-bit instructions.

       -misr-vector-size=num
           Specify the size of each interrupt vector, which must be 4 or 16.

       -mcache-block-size=num
           Specify the size of each cache block, which must be a power of 2 between 4 and 512.

       -march=arch
           Specify the name of the target architecture.

       -mcmodel=code-model
           Set the code model to one of

           small
               All the data and read-only data segments must be within 512KB addressing space.
               The text segment must be within 16MB addressing space.

           medium
               The data segment must be within 512KB while the read-only data segment can be
               within 4GB addressing space.  The text segment should be still within 16MB
               addressing space.

           large
               All the text and data segments can be within 4GB addressing space.

       -mctor-dtor
           Enable constructor/destructor feature.

       -mrelax
           Guide linker to relax instructions.

       Nios II Options

       These are the options defined for the Altera Nios II processor.

       -G num
           Put global and static objects less than or equal to num bytes into the small data or
           BSS sections instead of the normal data or BSS sections.  The default value of num is
           8.

       -mgpopt=option
       -mgpopt
       -mno-gpopt
           Generate (do not generate) GP-relative accesses.  The following option names are
           recognized:

           none
               Do not generate GP-relative accesses.

           local
               Generate GP-relative accesses for small data objects that are not external or
               weak.  Also use GP-relative addressing for objects that have been explicitly
               placed in a small data section via a "section" attribute.

           global
               As for local, but also generate GP-relative accesses for small data objects that
               are external or weak.  If you use this option, you must ensure that all parts of
               your program (including libraries) are compiled with the same -G setting.

           data
               Generate GP-relative accesses for all data objects in the program.  If you use
               this option, the entire data and BSS segments of your program must fit in 64K of
               memory and you must use an appropriate linker script to allocate them within the
               addressible range of the global pointer.

           all Generate GP-relative addresses for function pointers as well as data pointers.  If
               you use this option, the entire text, data, and BSS segments of your program must
               fit in 64K of memory and you must use an appropriate linker script to allocate
               them within the addressible range of the global pointer.

           -mgpopt is equivalent to -mgpopt=local, and -mno-gpopt is equivalent to -mgpopt=none.

           The default is -mgpopt except when -fpic or -fPIC is specified to generate position-
           independent code.  Note that the Nios II ABI does not permit GP-relative accesses from
           shared libraries.

           You may need to specify -mno-gpopt explicitly when building programs that include
           large amounts of small data, including large GOT data sections.  In this case, the
           16-bit offset for GP-relative addressing may not be large enough to allow access to
           the entire small data section.

       -mel
       -meb
           Generate little-endian (default) or big-endian (experimental) code, respectively.

       -mbypass-cache
       -mno-bypass-cache
           Force all load and store instructions to always bypass cache by using I/O variants of
           the instructions. The default is not to bypass the cache.

       -mno-cache-volatile
       -mcache-volatile
           Volatile memory access bypass the cache using the I/O variants of the load and store
           instructions. The default is not to bypass the cache.

       -mno-fast-sw-div
       -mfast-sw-div
           Do not use table-based fast divide for small numbers. The default is to use the fast
           divide at -O3 and above.

       -mno-hw-mul
       -mhw-mul
       -mno-hw-mulx
       -mhw-mulx
       -mno-hw-div
       -mhw-div
           Enable or disable emitting "mul", "mulx" and "div" family of instructions by the
           compiler. The default is to emit "mul" and not emit "div" and "mulx".

       -mcustom-insn=N
       -mno-custom-insn
           Each -mcustom-insn=N option enables use of a custom instruction with encoding N when
           generating code that uses insn.  For example, -mcustom-fadds=253 generates custom
           instruction 253 for single-precision floating-point add operations instead of the
           default behavior of using a library call.

           The following values of insn are supported.  Except as otherwise noted, floating-point
           operations are expected to be implemented with normal IEEE 754 semantics and
           correspond directly to the C operators or the equivalent GCC built-in functions.

           Single-precision floating point:

           fadds, fsubs, fdivs, fmuls
               Binary arithmetic operations.

           fnegs
               Unary negation.

           fabss
               Unary absolute value.

           fcmpeqs, fcmpges, fcmpgts, fcmples, fcmplts, fcmpnes
               Comparison operations.

           fmins, fmaxs
               Floating-point minimum and maximum.  These instructions are only generated if
               -ffinite-math-only is specified.

           fsqrts
               Unary square root operation.

           fcoss, fsins, ftans, fatans, fexps, flogs
               Floating-point trigonometric and exponential functions.  These instructions are
               only generated if -funsafe-math-optimizations is also specified.

           Double-precision floating point:

           faddd, fsubd, fdivd, fmuld
               Binary arithmetic operations.

           fnegd
               Unary negation.

           fabsd
               Unary absolute value.

           fcmpeqd, fcmpged, fcmpgtd, fcmpled, fcmpltd, fcmpned
               Comparison operations.

           fmind, fmaxd
               Double-precision minimum and maximum.  These instructions are only generated if
               -ffinite-math-only is specified.

           fsqrtd
               Unary square root operation.

           fcosd, fsind, ftand, fatand, fexpd, flogd
               Double-precision trigonometric and exponential functions.  These instructions are
               only generated if -funsafe-math-optimizations is also specified.

           Conversions:

           fextsd
               Conversion from single precision to double precision.

           ftruncds
               Conversion from double precision to single precision.

           fixsi, fixsu, fixdi, fixdu
               Conversion from floating point to signed or unsigned integer types, with
               truncation towards zero.

           round
               Conversion from single-precision floating point to signed integer, rounding to the
               nearest integer and ties away from zero.  This corresponds to the
               "__builtin_lroundf" function when -fno-math-errno is used.

           floatis, floatus, floatid, floatud
               Conversion from signed or unsigned integer types to floating-point types.

           In addition, all of the following transfer instructions for internal registers X and Y
           must be provided to use any of the double-precision floating-point instructions.
           Custom instructions taking two double-precision source operands expect the first
           operand in the 64-bit register X.  The other operand (or only operand of a unary
           operation) is given to the custom arithmetic instruction with the least significant
           half in source register src1 and the most significant half in src2.  A custom
           instruction that returns a double-precision result returns the most significant 32
           bits in the destination register and the other half in 32-bit register Y.  GCC
           automatically generates the necessary code sequences to write register X and/or read
           register Y when double-precision floating-point instructions are used.

           fwrx
               Write src1 into the least significant half of X and src2 into the most significant
               half of X.

           fwry
               Write src1 into Y.

           frdxhi, frdxlo
               Read the most or least (respectively) significant half of X and store it in dest.

           frdy
               Read the value of Y and store it into dest.

           Note that you can gain more local control over generation of Nios II custom
           instructions by using the "target("custom-insn=N")" and "target("no-custom-insn")"
           function attributes or pragmas.

       -mcustom-fpu-cfg=name
           This option enables a predefined, named set of custom instruction encodings (see
           -mcustom-insn above).  Currently, the following sets are defined:

           -mcustom-fpu-cfg=60-1 is equivalent to: -mcustom-fmuls=252 -mcustom-fadds=253
           -mcustom-fsubs=254 -fsingle-precision-constant

           -mcustom-fpu-cfg=60-2 is equivalent to: -mcustom-fmuls=252 -mcustom-fadds=253
           -mcustom-fsubs=254 -mcustom-fdivs=255 -fsingle-precision-constant

           -mcustom-fpu-cfg=72-3 is equivalent to: -mcustom-floatus=243 -mcustom-fixsi=244
           -mcustom-floatis=245 -mcustom-fcmpgts=246 -mcustom-fcmples=249 -mcustom-fcmpeqs=250
           -mcustom-fcmpnes=251 -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254
           -mcustom-fdivs=255 -fsingle-precision-constant

           Custom instruction assignments given by individual -mcustom-insn= options override
           those given by -mcustom-fpu-cfg=, regardless of the order of the options on the
           command line.

           Note that you can gain more local control over selection of a FPU configuration by
           using the "target("custom-fpu-cfg=name")" function attribute or pragma.

       These additional -m options are available for the Altera Nios II ELF (bare-metal) target:

       -mhal
           Link with HAL BSP.  This suppresses linking with the GCC-provided C runtime startup
           and termination code, and is typically used in conjunction with -msys-crt0= to specify
           the location of the alternate startup code provided by the HAL BSP.

       -msmallc
           Link with a limited version of the C library, -lsmallc, rather than Newlib.

       -msys-crt0=startfile
           startfile is the file name of the startfile (crt0) to use when linking.  This option
           is only useful in conjunction with -mhal.

       -msys-lib=systemlib
           systemlib is the library name of the library that provides low-level system calls
           required by the C library, e.g. "read" and "write".  This option is typically used to
           link with a library provided by a HAL BSP.

       Nvidia PTX Options

       These options are defined for Nvidia PTX:

       -m32
       -m64
           Generate code for 32-bit or 64-bit ABI.

       -mmainkernel
           Link in code for a __main kernel.  This is for stand-alone instead of offloading
           execution.

       PDP-11 Options

       These options are defined for the PDP-11:

       -mfpu
           Use hardware FPP floating point.  This is the default.  (FIS floating point on the
           PDP-11/40 is not supported.)

       -msoft-float
           Do not use hardware floating point.

       -mac0
           Return floating-point results in ac0 (fr0 in Unix assembler syntax).

       -mno-ac0
           Return floating-point results in memory.  This is the default.

       -m40
           Generate code for a PDP-11/40.

       -m45
           Generate code for a PDP-11/45.  This is the default.

       -m10
           Generate code for a PDP-11/10.

       -mbcopy-builtin
           Use inline "movmemhi" patterns for copying memory.  This is the default.

       -mbcopy
           Do not use inline "movmemhi" patterns for copying memory.

       -mint16
       -mno-int32
           Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
           Use 32-bit "int".

       -mfloat64
       -mno-float32
           Use 64-bit "float".  This is the default.

       -mfloat32
       -mno-float64
           Use 32-bit "float".

       -mabshi
           Use "abshi2" pattern.  This is the default.

       -mno-abshi
           Do not use "abshi2" pattern.

       -mbranch-expensive
           Pretend that branches are expensive.  This is for experimenting with code generation
           only.

       -mbranch-cheap
           Do not pretend that branches are expensive.  This is the default.

       -munix-asm
           Use Unix assembler syntax.  This is the default when configured for pdp11-*-bsd.

       -mdec-asm
           Use DEC assembler syntax.  This is the default when configured for any PDP-11 target
           other than pdp11-*-bsd.

       picoChip Options

       These -m options are defined for picoChip implementations:

       -mae=ae_type
           Set the instruction set, register set, and instruction scheduling parameters for array
           element type ae_type.  Supported values for ae_type are ANY, MUL, and MAC.

           -mae=ANY selects a completely generic AE type.  Code generated with this option runs
           on any of the other AE types.  The code is not as efficient as it would be if compiled
           for a specific AE type, and some types of operation (e.g., multiplication) do not work
           properly on all types of AE.

           -mae=MUL selects a MUL AE type.  This is the most useful AE type for compiled code,
           and is the default.

           -mae=MAC selects a DSP-style MAC AE.  Code compiled with this option may suffer from
           poor performance of byte (char) manipulation, since the DSP AE does not provide
           hardware support for byte load/stores.

       -msymbol-as-address
           Enable the compiler to directly use a symbol name as an address in a load/store
           instruction, without first loading it into a register.  Typically, the use of this
           option generates larger programs, which run faster than when the option isn't used.
           However, the results vary from program to program, so it is left as a user option,
           rather than being permanently enabled.

       -mno-inefficient-warnings
           Disables warnings about the generation of inefficient code.  These warnings can be
           generated, for example, when compiling code that performs byte-level memory operations
           on the MAC AE type.  The MAC AE has no hardware support for byte-level memory
           operations, so all byte load/stores must be synthesized from word load/store
           operations.  This is inefficient and a warning is generated to indicate that you
           should rewrite the code to avoid byte operations, or to target an AE type that has the
           necessary hardware support.  This option disables these warnings.

       PowerPC Options

       These are listed under

       RL78 Options

       -msim
           Links in additional target libraries to support operation within a simulator.

       -mmul=none
       -mmul=g13
       -mmul=rl78
           Specifies the type of hardware multiplication support to be used.  The default is
           none, which uses software multiplication functions.  The g13 option is for the
           hardware multiply/divide peripheral only on the RL78/G13 targets.  The rl78 option is
           for the standard hardware multiplication defined in the RL78 software manual.

       -m64bit-doubles
       -m32bit-doubles
           Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits (-m32bit-doubles)
           in size.  The default is -m32bit-doubles.

       IBM RS/6000 and PowerPC Options

       These -m options are defined for the IBM RS/6000 and PowerPC:

       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mpopcntd
       -mno-popcntd
       -mfprnd
       -mno-fprnd
       -mcmpb
       -mno-cmpb
       -mmfpgpr
       -mno-mfpgpr
       -mhard-dfp
       -mno-hard-dfp
           You use these options to specify which instructions are available on the processor you
           are using.  The default value of these options is determined when configuring GCC.
           Specifying the -mcpu=cpu_type overrides the specification of these options.  We
           recommend you use the -mcpu=cpu_type option rather than the options listed above.

           Specifying -mpowerpc-gpopt allows GCC to use the optional PowerPC architecture
           instructions in the General Purpose group, including floating-point square root.
           Specifying -mpowerpc-gfxopt allows GCC to use the optional PowerPC architecture
           instructions in the Graphics group, including floating-point select.

           The -mmfcrf option allows GCC to generate the move from condition register field
           instruction implemented on the POWER4 processor and other processors that support the
           PowerPC V2.01 architecture.  The -mpopcntb option allows GCC to generate the popcount
           and double-precision FP reciprocal estimate instruction implemented on the POWER5
           processor and other processors that support the PowerPC V2.02 architecture.  The
           -mpopcntd option allows GCC to generate the popcount instruction implemented on the
           POWER7 processor and other processors that support the PowerPC V2.06 architecture.
           The -mfprnd option allows GCC to generate the FP round to integer instructions
           implemented on the POWER5+ processor and other processors that support the PowerPC
           V2.03 architecture.  The -mcmpb option allows GCC to generate the compare bytes
           instruction implemented on the POWER6 processor and other processors that support the
           PowerPC V2.05 architecture.  The -mmfpgpr option allows GCC to generate the FP move
           to/from general-purpose register instructions implemented on the POWER6X processor and
           other processors that support the extended PowerPC V2.05 architecture.  The -mhard-dfp
           option allows GCC to generate the decimal floating-point instructions implemented on
           some POWER processors.

           The -mpowerpc64 option allows GCC to generate the additional 64-bit instructions that
           are found in the full PowerPC64 architecture and to treat GPRs as 64-bit, doubleword
           quantities.  GCC defaults to -mno-powerpc64.

       -mcpu=cpu_type
           Set architecture type, register usage, and instruction scheduling parameters for
           machine type cpu_type.  Supported values for cpu_type are 401, 403, 405, 405fp, 440,
           440fp, 464, 464fp, 476, 476fp, 505, 601, 602, 603, 603e, 604, 604e, 620, 630, 740,
           7400, 7450, 750, 801, 821, 823, 860, 970, 8540, a2, e300c2, e300c3, e500mc, e500mc64,
           e5500, e6500, ec603e, G3, G4, G5, titan, power3, power4, power5, power5+, power6,
           power6x, power7, power8, powerpc, powerpc64, powerpc64le, and rs64.

           -mcpu=powerpc, -mcpu=powerpc64, and -mcpu=powerpc64le specify pure 32-bit PowerPC
           (either endian), 64-bit big endian PowerPC and 64-bit little endian PowerPC
           architecture machine types, with an appropriate, generic processor model assumed for
           scheduling purposes.

           The other options specify a specific processor.  Code generated under those options
           runs best on that processor, and may not run at all on others.

           The -mcpu options automatically enable or disable the following options:

           -maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple -mpopcntb -mpopcntd  -mpowerpc64
           -mpowerpc-gpopt  -mpowerpc-gfxopt  -msingle-float -mdouble-float -msimple-fpu -mstring
           -mmulhw  -mdlmzb  -mmfpgpr -mvsx -mcrypto -mdirect-move -mpower8-fusion
           -mpower8-vector -mquad-memory -mquad-memory-atomic

           The particular options set for any particular CPU varies between compiler versions,
           depending on what setting seems to produce optimal code for that CPU; it doesn't
           necessarily reflect the actual hardware's capabilities.  If you wish to set an
           individual option to a particular value, you may specify it after the -mcpu option,
           like -mcpu=970 -mno-altivec.

           On AIX, the -maltivec and -mpowerpc64 options are not enabled or disabled by the -mcpu
           option at present because AIX does not have full support for these options.  You may
           still enable or disable them individually if you're sure it'll work in your
           environment.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not set
           the architecture type or register usage, as -mcpu=cpu_type does.  The same values for
           cpu_type are used for -mtune as for -mcpu.  If both are specified, the code generated
           uses the architecture and registers set by -mcpu, but the scheduling parameters set by
           -mtune.

       -mcmodel=small
           Generate PowerPC64 code for the small model: The TOC is limited to 64k.

       -mcmodel=medium
           Generate PowerPC64 code for the medium model: The TOC and other static data may be up
           to a total of 4G in size.

       -mcmodel=large
           Generate PowerPC64 code for the large model: The TOC may be up to 4G in size.  Other
           data and code is only limited by the 64-bit address space.

       -maltivec
       -mno-altivec
           Generate code that uses (does not use) AltiVec instructions, and also enable the use
           of built-in functions that allow more direct access to the AltiVec instruction set.
           You may also need to set -mabi=altivec to adjust the current ABI with AltiVec ABI
           enhancements.

           When -maltivec is used, rather than -maltivec=le or -maltivec=be, the element order
           for Altivec intrinsics such as "vec_splat", "vec_extract", and "vec_insert" match
           array element order corresponding to the endianness of the target.  That is, element
           zero identifies the leftmost element in a vector register when targeting a big-endian
           platform, and identifies the rightmost element in a vector register when targeting a
           little-endian platform.

       -maltivec=be
           Generate Altivec instructions using big-endian element order, regardless of whether
           the target is big- or little-endian.  This is the default when targeting a big-endian
           platform.

           The element order is used to interpret element numbers in Altivec intrinsics such as
           "vec_splat", "vec_extract", and "vec_insert".  By default, these match array element
           order corresponding to the endianness for the target.

       -maltivec=le
           Generate Altivec instructions using little-endian element order, regardless of whether
           the target is big- or little-endian.  This is the default when targeting a little-
           endian platform.  This option is currently ignored when targeting a big-endian
           platform.

           The element order is used to interpret element numbers in Altivec intrinsics such as
           "vec_splat", "vec_extract", and "vec_insert".  By default, these match array element
           order corresponding to the endianness for the target.

       -mvrsave
       -mno-vrsave
           Generate VRSAVE instructions when generating AltiVec code.

       -mgen-cell-microcode
           Generate Cell microcode instructions.

       -mwarn-cell-microcode
           Warn when a Cell microcode instruction is emitted.  An example of a Cell microcode
           instruction is a variable shift.

       -msecure-plt
           Generate code that allows ld and ld.so to build executables and shared libraries with
           non-executable ".plt" and ".got" sections.  This is a PowerPC 32-bit SYSV ABI option.

       -mbss-plt
           Generate code that uses a BSS ".plt" section that ld.so fills in, and requires ".plt"
           and ".got" sections that are both writable and executable.  This is a PowerPC 32-bit
           SYSV ABI option.

       -misel
       -mno-isel
           This switch enables or disables the generation of ISEL instructions.

       -misel=yes/no
           This switch has been deprecated.  Use -misel and -mno-isel instead.

       -mspe
       -mno-spe
           This switch enables or disables the generation of SPE simd instructions.

       -mpaired
       -mno-paired
           This switch enables or disables the generation of PAIRED simd instructions.

       -mspe=yes/no
           This option has been deprecated.  Use -mspe and -mno-spe instead.

       -mvsx
       -mno-vsx
           Generate code that uses (does not use) vector/scalar (VSX) instructions, and also
           enable the use of built-in functions that allow more direct access to the VSX
           instruction set.

       -mcrypto
       -mno-crypto
           Enable the use (disable) of the built-in functions that allow direct access to the
           cryptographic instructions that were added in version 2.07 of the PowerPC ISA.

       -mdirect-move
       -mno-direct-move
           Generate code that uses (does not use) the instructions to move data between the
           general purpose registers and the vector/scalar (VSX) registers that were added in
           version 2.07 of the PowerPC ISA.

       -mpower8-fusion
       -mno-power8-fusion
           Generate code that keeps (does not keeps) some integer operations adjacent so that the
           instructions can be fused together on power8 and later processors.

       -mpower8-vector
       -mno-power8-vector
           Generate code that uses (does not use) the vector and scalar instructions that were
           added in version 2.07 of the PowerPC ISA.  Also enable the use of built-in functions
           that allow more direct access to the vector instructions.

       -mquad-memory
       -mno-quad-memory
           Generate code that uses (does not use) the non-atomic quad word memory instructions.
           The -mquad-memory option requires use of 64-bit mode.

       -mquad-memory-atomic
       -mno-quad-memory-atomic
           Generate code that uses (does not use) the atomic quad word memory instructions.  The
           -mquad-memory-atomic option requires use of 64-bit mode.

       -mupper-regs-df
       -mno-upper-regs-df
           Generate code that uses (does not use) the scalar double precision instructions that
           target all 64 registers in the vector/scalar floating point register set that were
           added in version 2.06 of the PowerPC ISA.  -mupper-regs-df is turned on by default if
           you use any of the -mcpu=power7, -mcpu=power8, or -mvsx options.

       -mupper-regs-sf
       -mno-upper-regs-sf
           Generate code that uses (does not use) the scalar single precision instructions that
           target all 64 registers in the vector/scalar floating point register set that were
           added in version 2.07 of the PowerPC ISA.  -mupper-regs-sf is turned on by default if
           you use either of the -mcpu=power8 or -mpower8-vector options.

       -mupper-regs
       -mno-upper-regs
           Generate code that uses (does not use) the scalar instructions that target all 64
           registers in the vector/scalar floating point register set, depending on the model of
           the machine.

           If the -mno-upper-regs option is used, it turns off both -mupper-regs-sf and
           -mupper-regs-df options.

       -mfloat-gprs=yes/single/double/no
       -mfloat-gprs
           This switch enables or disables the generation of floating-point operations on the
           general-purpose registers for architectures that support it.

           The argument yes or single enables the use of single-precision floating-point
           operations.

           The argument double enables the use of single and double-precision floating-point
           operations.

           The argument no disables floating-point operations on the general-purpose registers.

           This option is currently only available on the MPC854x.

       -m32
       -m64
           Generate code for 32-bit or 64-bit environments of Darwin and SVR4 targets (including
           GNU/Linux).  The 32-bit environment sets int, long and pointer to 32 bits and
           generates code that runs on any PowerPC variant.  The 64-bit environment sets int to
           32 bits and long and pointer to 64 bits, and generates code for PowerPC64, as for
           -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
           Modify generation of the TOC (Table Of Contents), which is created for every
           executable file.  The -mfull-toc option is selected by default.  In that case, GCC
           allocates at least one TOC entry for each unique non-automatic variable reference in
           your program.  GCC also places floating-point constants in the TOC.  However, only
           16,384 entries are available in the TOC.

           If you receive a linker error message that saying you have overflowed the available
           TOC space, you can reduce the amount of TOC space used with the -mno-fp-in-toc and
           -mno-sum-in-toc options.  -mno-fp-in-toc prevents GCC from putting floating-point
           constants in the TOC and -mno-sum-in-toc forces GCC to generate code to calculate the
           sum of an address and a constant at run time instead of putting that sum into the TOC.
           You may specify one or both of these options.  Each causes GCC to produce very
           slightly slower and larger code at the expense of conserving TOC space.

           If you still run out of space in the TOC even when you specify both of these options,
           specify -mminimal-toc instead.  This option causes GCC to make only one TOC entry for
           every file.  When you specify this option, GCC produces code that is slower and larger
           but which uses extremely little TOC space.  You may wish to use this option only on
           files that contain less frequently-executed code.

       -maix64
       -maix32
           Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit "long" type, and
           the infrastructure needed to support them.  Specifying -maix64 implies -mpowerpc64,
           while -maix32 disables the 64-bit ABI and implies -mno-powerpc64.  GCC defaults to
           -maix32.

       -mxl-compat
       -mno-xl-compat
           Produce code that conforms more closely to IBM XL compiler semantics when using AIX-
           compatible ABI.  Pass floating-point arguments to prototyped functions beyond the
           register save area (RSA) on the stack in addition to argument FPRs.  Do not assume
           that most significant double in 128-bit long double value is properly rounded when
           comparing values and converting to double.  Use XL symbol names for long double
           support routines.

           The AIX calling convention was extended but not initially documented to handle an
           obscure K&R C case of calling a function that takes the address of its arguments with
           fewer arguments than declared.  IBM XL compilers access floating-point arguments that
           do not fit in the RSA from the stack when a subroutine is compiled without
           optimization.  Because always storing floating-point arguments on the stack is
           inefficient and rarely needed, this option is not enabled by default and only is
           necessary when calling subroutines compiled by IBM XL compilers without optimization.

       -mpe
           Support IBM RS/6000 SP Parallel Environment (PE).  Link an application written to use
           message passing with special startup code to enable the application to run.  The
           system must have PE installed in the standard location (/usr/lpp/ppe.poe/), or the
           specs file must be overridden with the -specs= option to specify the appropriate
           directory location.  The Parallel Environment does not support threads, so the -mpe
           option and the -pthread option are incompatible.

       -malign-natural
       -malign-power
           On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option -malign-natural
           overrides the ABI-defined alignment of larger types, such as floating-point doubles,
           on their natural size-based boundary.  The option -malign-power instructs GCC to
           follow the ABI-specified alignment rules.  GCC defaults to the standard alignment
           defined in the ABI.

           On 64-bit Darwin, natural alignment is the default, and -malign-power is not
           supported.

       -msoft-float
       -mhard-float
           Generate code that does not use (uses) the floating-point register set.  Software
           floating-point emulation is provided if you use the -msoft-float option, and pass the
           option to GCC when linking.

       -msingle-float
       -mdouble-float
           Generate code for single- or double-precision floating-point operations.
           -mdouble-float implies -msingle-float.

       -msimple-fpu
           Do not generate "sqrt" and "div" instructions for hardware floating-point unit.

       -mfpu=name
           Specify type of floating-point unit.  Valid values for name are sp_lite (equivalent to
           -msingle-float -msimple-fpu), dp_lite (equivalent to -mdouble-float -msimple-fpu),
           sp_full (equivalent to -msingle-float), and dp_full (equivalent to -mdouble-float).

       -mxilinx-fpu
           Perform optimizations for the floating-point unit on Xilinx PPC 405/440.

       -mmultiple
       -mno-multiple
           Generate code that uses (does not use) the load multiple word instructions and the
           store multiple word instructions.  These instructions are generated by default on
           POWER systems, and not generated on PowerPC systems.  Do not use -mmultiple on little-
           endian PowerPC systems, since those instructions do not work when the processor is in
           little-endian mode.  The exceptions are PPC740 and PPC750 which permit these
           instructions in little-endian mode.

       -mstring
       -mno-string
           Generate code that uses (does not use) the load string instructions and the store
           string word instructions to save multiple registers and do small block moves.  These
           instructions are generated by default on POWER systems, and not generated on PowerPC
           systems.  Do not use -mstring on little-endian PowerPC systems, since those
           instructions do not work when the processor is in little-endian mode.  The exceptions
           are PPC740 and PPC750 which permit these instructions in little-endian mode.

       -mupdate
       -mno-update
           Generate code that uses (does not use) the load or store instructions that update the
           base register to the address of the calculated memory location.  These instructions
           are generated by default.  If you use -mno-update, there is a small window between the
           time that the stack pointer is updated and the address of the previous frame is
           stored, which means code that walks the stack frame across interrupts or signals may
           get corrupted data.

       -mavoid-indexed-addresses
       -mno-avoid-indexed-addresses
           Generate code that tries to avoid (not avoid) the use of indexed load or store
           instructions. These instructions can incur a performance penalty on Power6 processors
           in certain situations, such as when stepping through large arrays that cross a 16M
           boundary.  This option is enabled by default when targeting Power6 and disabled
           otherwise.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point multiply and accumulate
           instructions.  These instructions are generated by default if hardware floating point
           is used.  The machine-dependent -mfused-madd option is now mapped to the machine-
           independent -ffp-contract=fast option, and -mno-fused-madd is mapped to
           -ffp-contract=off.

       -mmulhw
       -mno-mulhw
           Generate code that uses (does not use) the half-word multiply and multiply-accumulate
           instructions on the IBM 405, 440, 464 and 476 processors.  These instructions are
           generated by default when targeting those processors.

       -mdlmzb
       -mno-dlmzb
           Generate code that uses (does not use) the string-search dlmzb instruction on the IBM
           405, 440, 464 and 476 processors.  This instruction is generated by default when
           targeting those processors.

       -mno-bit-align
       -mbit-align
           On System V.4 and embedded PowerPC systems do not (do) force structures and unions
           that contain bit-fields to be aligned to the base type of the bit-field.

           For example, by default a structure containing nothing but 8 "unsigned" bit-fields of
           length 1 is aligned to a 4-byte boundary and has a size of 4 bytes.  By using
           -mno-bit-align, the structure is aligned to a 1-byte boundary and is 1 byte in size.

       -mno-strict-align
       -mstrict-align
           On System V.4 and embedded PowerPC systems do not (do) assume that unaligned memory
           references are handled by the system.

       -mrelocatable
       -mno-relocatable
           Generate code that allows (does not allow) a static executable to be relocated to a
           different address at run time.  A simple embedded PowerPC system loader should
           relocate the entire contents of ".got2" and 4-byte locations listed in the ".fixup"
           section, a table of 32-bit addresses generated by this option.  For this to work, all
           objects linked together must be compiled with -mrelocatable or -mrelocatable-lib.
           -mrelocatable code aligns the stack to an 8-byte boundary.

       -mrelocatable-lib
       -mno-relocatable-lib
           Like -mrelocatable, -mrelocatable-lib generates a ".fixup" section to allow static
           executables to be relocated at run time, but -mrelocatable-lib does not use the
           smaller stack alignment of -mrelocatable.  Objects compiled with -mrelocatable-lib may
           be linked with objects compiled with any combination of the -mrelocatable options.

       -mno-toc
       -mtoc
           On System V.4 and embedded PowerPC systems do not (do) assume that register 2 contains
           a pointer to a global area pointing to the addresses used in the program.

       -mlittle
       -mlittle-endian
           On System V.4 and embedded PowerPC systems compile code for the processor in little-
           endian mode.  The -mlittle-endian option is the same as -mlittle.

       -mbig
       -mbig-endian
           On System V.4 and embedded PowerPC systems compile code for the processor in big-
           endian mode.  The -mbig-endian option is the same as -mbig.

       -mdynamic-no-pic
           On Darwin and Mac OS X systems, compile code so that it is not relocatable, but that
           its external references are relocatable.  The resulting code is suitable for
           applications, but not shared libraries.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather than loading it in the
           prologue for each function.  The runtime system is responsible for initializing this
           register with an appropriate value before execution begins.

       -mprioritize-restricted-insns=priority
           This option controls the priority that is assigned to dispatch-slot restricted
           instructions during the second scheduling pass.  The argument priority takes the value
           0, 1, or 2 to assign no, highest, or second-highest (respectively) priority to
           dispatch-slot restricted instructions.

       -msched-costly-dep=dependence_type
           This option controls which dependences are considered costly by the target during
           instruction scheduling.  The argument dependence_type takes one of the following
           values:

           no  No dependence is costly.

           all All dependences are costly.

           true_store_to_load
               A true dependence from store to load is costly.

           store_to_load
               Any dependence from store to load is costly.

           number
               Any dependence for which the latency is greater than or equal to number is costly.

       -minsert-sched-nops=scheme
           This option controls which NOP insertion scheme is used during the second scheduling
           pass.  The argument scheme takes one of the following values:

           no  Don't insert NOPs.

           pad Pad with NOPs any dispatch group that has vacant issue slots, according to the
               scheduler's grouping.

           regroup_exact
               Insert NOPs to force costly dependent insns into separate groups.  Insert exactly
               as many NOPs as needed to force an insn to a new group, according to the estimated
               processor grouping.

           number
               Insert NOPs to force costly dependent insns into separate groups.  Insert number
               NOPs to force an insn to a new group.

       -mcall-sysv
           On System V.4 and embedded PowerPC systems compile code using calling conventions that
           adhere to the March 1995 draft of the System V Application Binary Interface, PowerPC
           processor supplement.  This is the default unless you configured GCC using
           powerpc-*-eabiaix.

       -mcall-sysv-eabi
       -mcall-eabi
           Specify both -mcall-sysv and -meabi options.

       -mcall-sysv-noeabi
           Specify both -mcall-sysv and -mno-eabi options.

       -mcall-aixdesc
           On System V.4 and embedded PowerPC systems compile code for the AIX operating system.

       -mcall-linux
           On System V.4 and embedded PowerPC systems compile code for the Linux-based GNU
           system.

       -mcall-freebsd
           On System V.4 and embedded PowerPC systems compile code for the FreeBSD operating
           system.

       -mcall-netbsd
           On System V.4 and embedded PowerPC systems compile code for the NetBSD operating
           system.

       -mcall-openbsd
           On System V.4 and embedded PowerPC systems compile code for the OpenBSD operating
           system.

       -maix-struct-return
           Return all structures in memory (as specified by the AIX ABI).

       -msvr4-struct-return
           Return structures smaller than 8 bytes in registers (as specified by the SVR4 ABI).

       -mabi=abi-type
           Extend the current ABI with a particular extension, or remove such extension.  Valid
           values are altivec, no-altivec, spe, no-spe, ibmlongdouble, ieeelongdouble, elfv1,
           elfv2.

       -mabi=spe
           Extend the current ABI with SPE ABI extensions.  This does not change the default ABI,
           instead it adds the SPE ABI extensions to the current ABI.

       -mabi=no-spe
           Disable Book-E SPE ABI extensions for the current ABI.

       -mabi=ibmlongdouble
           Change the current ABI to use IBM extended-precision long double.  This is a PowerPC
           32-bit SYSV ABI option.

       -mabi=ieeelongdouble
           Change the current ABI to use IEEE extended-precision long double.  This is a PowerPC
           32-bit Linux ABI option.

       -mabi=elfv1
           Change the current ABI to use the ELFv1 ABI.  This is the default ABI for big-endian
           PowerPC 64-bit Linux.  Overriding the default ABI requires special system support and
           is likely to fail in spectacular ways.

       -mabi=elfv2
           Change the current ABI to use the ELFv2 ABI.  This is the default ABI for little-
           endian PowerPC 64-bit Linux.  Overriding the default ABI requires special system
           support and is likely to fail in spectacular ways.

       -mprototype
       -mno-prototype
           On System V.4 and embedded PowerPC systems assume that all calls to variable argument
           functions are properly prototyped.  Otherwise, the compiler must insert an instruction
           before every non-prototyped call to set or clear bit 6 of the condition code register
           ("CR") to indicate whether floating-point values are passed in the floating-point
           registers in case the function takes variable arguments.  With -mprototype, only calls
           to prototyped variable argument functions set or clear the bit.

       -msim
           On embedded PowerPC systems, assume that the startup module is called sim-crt0.o and
           that the standard C libraries are libsim.a and libc.a.  This is the default for
           powerpc-*-eabisim configurations.

       -mmvme
           On embedded PowerPC systems, assume that the startup module is called crt0.o and the
           standard C libraries are libmvme.a and libc.a.

       -mads
           On embedded PowerPC systems, assume that the startup module is called crt0.o and the
           standard C libraries are libads.a and libc.a.

       -myellowknife
           On embedded PowerPC systems, assume that the startup module is called crt0.o and the
           standard C libraries are libyk.a and libc.a.

       -mvxworks
           On System V.4 and embedded PowerPC systems, specify that you are compiling for a
           VxWorks system.

       -memb
           On embedded PowerPC systems, set the "PPC_EMB" bit in the ELF flags header to indicate
           that eabi extended relocations are used.

       -meabi
       -mno-eabi
           On System V.4 and embedded PowerPC systems do (do not) adhere to the Embedded
           Applications Binary Interface (EABI), which is a set of modifications to the System
           V.4 specifications.  Selecting -meabi means that the stack is aligned to an 8-byte
           boundary, a function "__eabi" is called from "main" to set up the EABI environment,
           and the -msdata option can use both "r2" and "r13" to point to two separate small data
           areas.  Selecting -mno-eabi means that the stack is aligned to a 16-byte boundary, no
           EABI initialization function is called from "main", and the -msdata option only uses
           "r13" to point to a single small data area.  The -meabi option is on by default if you
           configured GCC using one of the powerpc*-*-eabi* options.

       -msdata=eabi
           On System V.4 and embedded PowerPC systems, put small initialized "const" global and
           static data in the ".sdata2" section, which is pointed to by register "r2".  Put small
           initialized non-"const" global and static data in the ".sdata" section, which is
           pointed to by register "r13".  Put small uninitialized global and static data in the
           ".sbss" section, which is adjacent to the ".sdata" section.  The -msdata=eabi option
           is incompatible with the -mrelocatable option.  The -msdata=eabi option also sets the
           -memb option.

       -msdata=sysv
           On System V.4 and embedded PowerPC systems, put small global and static data in the
           ".sdata" section, which is pointed to by register "r13".  Put small uninitialized
           global and static data in the ".sbss" section, which is adjacent to the ".sdata"
           section.  The -msdata=sysv option is incompatible with the -mrelocatable option.

       -msdata=default
       -msdata
           On System V.4 and embedded PowerPC systems, if -meabi is used, compile code the same
           as -msdata=eabi, otherwise compile code the same as -msdata=sysv.

       -msdata=data
           On System V.4 and embedded PowerPC systems, put small global data in the ".sdata"
           section.  Put small uninitialized global data in the ".sbss" section.  Do not use
           register "r13" to address small data however.  This is the default behavior unless
           other -msdata options are used.

       -msdata=none
       -mno-sdata
           On embedded PowerPC systems, put all initialized global and static data in the ".data"
           section, and all uninitialized data in the ".bss" section.

       -mblock-move-inline-limit=num
           Inline all block moves (such as calls to "memcpy" or structure copies) less than or
           equal to num bytes.  The minimum value for num is 32 bytes on 32-bit targets and 64
           bytes on 64-bit targets.  The default value is target-specific.

       -G num
           On embedded PowerPC systems, put global and static items less than or equal to num
           bytes into the small data or BSS sections instead of the normal data or BSS section.
           By default, num is 8.  The -G num switch is also passed to the linker.  All modules
           should be compiled with the same -G num value.

       -mregnames
       -mno-regnames
           On System V.4 and embedded PowerPC systems do (do not) emit register names in the
           assembly language output using symbolic forms.

       -mlongcall
       -mno-longcall
           By default assume that all calls are far away so that a longer and more expensive
           calling sequence is required.  This is required for calls farther than 32 megabytes
           (33,554,432 bytes) from the current location.  A short call is generated if the
           compiler knows the call cannot be that far away.  This setting can be overridden by
           the "shortcall" function attribute, or by "#pragma longcall(0)".

           Some linkers are capable of detecting out-of-range calls and generating glue code on
           the fly.  On these systems, long calls are unnecessary and generate slower code.  As
           of this writing, the AIX linker can do this, as can the GNU linker for PowerPC/64.  It
           is planned to add this feature to the GNU linker for 32-bit PowerPC systems as well.

           On Darwin/PPC systems, "#pragma longcall" generates "jbsr callee, L42", plus a branch
           island (glue code).  The two target addresses represent the callee and the branch
           island.  The Darwin/PPC linker prefers the first address and generates a "bl callee"
           if the PPC "bl" instruction reaches the callee directly; otherwise, the linker
           generates "bl L42" to call the branch island.  The branch island is appended to the
           body of the calling function; it computes the full 32-bit address of the callee and
           jumps to it.

           On Mach-O (Darwin) systems, this option directs the compiler emit to the glue for
           every direct call, and the Darwin linker decides whether to use or discard it.

           In the future, GCC may ignore all longcall specifications when the linker is known to
           generate glue.

       -mtls-markers
       -mno-tls-markers
           Mark (do not mark) calls to "__tls_get_addr" with a relocation specifying the function
           argument.  The relocation allows the linker to reliably associate function call with
           argument setup instructions for TLS optimization, which in turn allows GCC to better
           schedule the sequence.

       -pthread
           Adds support for multithreading with the pthreads library.  This option sets flags for
           both the preprocessor and linker.

       -mrecip
       -mno-recip
           This option enables use of the reciprocal estimate and reciprocal square root estimate
           instructions with additional Newton-Raphson steps to increase precision instead of
           doing a divide or square root and divide for floating-point arguments.  You should use
           the -ffast-math option when using -mrecip (or at least -funsafe-math-optimizations,
           -finite-math-only, -freciprocal-math and -fno-trapping-math).  Note that while the
           throughput of the sequence is generally higher than the throughput of the non-
           reciprocal instruction, the precision of the sequence can be decreased by up to 2 ulp
           (i.e. the inverse of 1.0 equals 0.99999994) for reciprocal square roots.

       -mrecip=opt
           This option controls which reciprocal estimate instructions may be used.  opt is a
           comma-separated list of options, which may be preceded by a "!" to invert the option:

           all Enable all estimate instructions.

           default
               Enable the default instructions, equivalent to -mrecip.

           none
               Disable all estimate instructions, equivalent to -mno-recip.

           div Enable the reciprocal approximation instructions for both single and double
               precision.

           divf
               Enable the single-precision reciprocal approximation instructions.

           divd
               Enable the double-precision reciprocal approximation instructions.

           rsqrt
               Enable the reciprocal square root approximation instructions for both single and
               double precision.

           rsqrtf
               Enable the single-precision reciprocal square root approximation instructions.

           rsqrtd
               Enable the double-precision reciprocal square root approximation instructions.

           So, for example, -mrecip=all,!rsqrtd enables all of the reciprocal estimate
           instructions, except for the "FRSQRTE", "XSRSQRTEDP", and "XVRSQRTEDP" instructions
           which handle the double-precision reciprocal square root calculations.

       -mrecip-precision
       -mno-recip-precision
           Assume (do not assume) that the reciprocal estimate instructions provide higher-
           precision estimates than is mandated by the PowerPC ABI.  Selecting -mcpu=power6,
           -mcpu=power7 or -mcpu=power8 automatically selects -mrecip-precision.  The double-
           precision square root estimate instructions are not generated by default on low-
           precision machines, since they do not provide an estimate that converges after three
           steps.

       -mveclibabi=type
           Specifies the ABI type to use for vectorizing intrinsics using an external library.
           The only type supported at present is mass, which specifies to use IBM's Mathematical
           Acceleration Subsystem (MASS) libraries for vectorizing intrinsics using external
           libraries.  GCC currently emits calls to "acosd2", "acosf4", "acoshd2", "acoshf4",
           "asind2", "asinf4", "asinhd2", "asinhf4", "atan2d2", "atan2f4", "atand2", "atanf4",
           "atanhd2", "atanhf4", "cbrtd2", "cbrtf4", "cosd2", "cosf4", "coshd2", "coshf4",
           "erfcd2", "erfcf4", "erfd2", "erff4", "exp2d2", "exp2f4", "expd2", "expf4", "expm1d2",
           "expm1f4", "hypotd2", "hypotf4", "lgammad2", "lgammaf4", "log10d2", "log10f4",
           "log1pd2", "log1pf4", "log2d2", "log2f4", "logd2", "logf4", "powd2", "powf4", "sind2",
           "sinf4", "sinhd2", "sinhf4", "sqrtd2", "sqrtf4", "tand2", "tanf4", "tanhd2", and
           "tanhf4" when generating code for power7.  Both -ftree-vectorize and
           -funsafe-math-optimizations must also be enabled.  The MASS libraries must be
           specified at link time.

       -mfriz
       -mno-friz
           Generate (do not generate) the "friz" instruction when the -funsafe-math-optimizations
           option is used to optimize rounding of floating-point values to 64-bit integer and
           back to floating point.  The "friz" instruction does not return the same value if the
           floating-point number is too large to fit in an integer.

       -mpointers-to-nested-functions
       -mno-pointers-to-nested-functions
           Generate (do not generate) code to load up the static chain register ("r11") when
           calling through a pointer on AIX and 64-bit Linux systems where a function pointer
           points to a 3-word descriptor giving the function address, TOC value to be loaded in
           register "r2", and static chain value to be loaded in register "r11".  The
           -mpointers-to-nested-functions is on by default.  You cannot call through pointers to
           nested functions or pointers to functions compiled in other languages that use the
           static chain if you use -mno-pointers-to-nested-functions.

       -msave-toc-indirect
       -mno-save-toc-indirect
           Generate (do not generate) code to save the TOC value in the reserved stack location
           in the function prologue if the function calls through a pointer on AIX and 64-bit
           Linux systems.  If the TOC value is not saved in the prologue, it is saved just before
           the call through the pointer.  The -mno-save-toc-indirect option is the default.

       -mcompat-align-parm
       -mno-compat-align-parm
           Generate (do not generate) code to pass structure parameters with a maximum alignment
           of 64 bits, for compatibility with older versions of GCC.

           Older versions of GCC (prior to 4.9.0) incorrectly did not align a structure parameter
           on a 128-bit boundary when that structure contained a member requiring 128-bit
           alignment.  This is corrected in more recent versions of GCC.  This option may be used
           to generate code that is compatible with functions compiled with older versions of
           GCC.

           The -mno-compat-align-parm option is the default.

       RX Options

       These command-line options are defined for RX targets:

       -m64bit-doubles
       -m32bit-doubles
           Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits (-m32bit-doubles)
           in size.  The default is -m32bit-doubles.  Note RX floating-point hardware only works
           on 32-bit values, which is why the default is -m32bit-doubles.

       -fpu
       -nofpu
           Enables (-fpu) or disables (-nofpu) the use of RX floating-point hardware.  The
           default is enabled for the RX600 series and disabled for the RX200 series.

           Floating-point instructions are only generated for 32-bit floating-point values,
           however, so the FPU hardware is not used for doubles if the -m64bit-doubles option is
           used.

           Note If the -fpu option is enabled then -funsafe-math-optimizations is also enabled
           automatically.  This is because the RX FPU instructions are themselves unsafe.

       -mcpu=name
           Selects the type of RX CPU to be targeted.  Currently three types are supported, the
           generic RX600 and RX200 series hardware and the specific RX610 CPU.  The default is
           RX600.

           The only difference between RX600 and RX610 is that the RX610 does not support the
           "MVTIPL" instruction.

           The RX200 series does not have a hardware floating-point unit and so -nofpu is enabled
           by default when this type is selected.

       -mbig-endian-data
       -mlittle-endian-data
           Store data (but not code) in the big-endian format.  The default is
           -mlittle-endian-data, i.e. to store data in the little-endian format.

       -msmall-data-limit=N
           Specifies the maximum size in bytes of global and static variables which can be placed
           into the small data area.  Using the small data area can lead to smaller and faster
           code, but the size of area is limited and it is up to the programmer to ensure that
           the area does not overflow.  Also when the small data area is used one of the RX's
           registers (usually "r13") is reserved for use pointing to this area, so it is no
           longer available for use by the compiler.  This could result in slower and/or larger
           code if variables are pushed onto the stack instead of being held in this register.

           Note, common variables (variables that have not been initialized) and constants are
           not placed into the small data area as they are assigned to other sections in the
           output executable.

           The default value is zero, which disables this feature.  Note, this feature is not
           enabled by default with higher optimization levels (-O2 etc) because of the
           potentially detrimental effects of reserving a register.  It is up to the programmer
           to experiment and discover whether this feature is of benefit to their program.  See
           the description of the -mpid option for a description of how the actual register to
           hold the small data area pointer is chosen.

       -msim
       -mno-sim
           Use the simulator runtime.  The default is to use the libgloss board-specific runtime.

       -mas100-syntax
       -mno-as100-syntax
           When generating assembler output use a syntax that is compatible with Renesas's AS100
           assembler.  This syntax can also be handled by the GAS assembler, but it has some
           restrictions so it is not generated by default.

       -mmax-constant-size=N
           Specifies the maximum size, in bytes, of a constant that can be used as an operand in
           a RX instruction.  Although the RX instruction set does allow constants of up to 4
           bytes in length to be used in instructions, a longer value equates to a longer
           instruction.  Thus in some circumstances it can be beneficial to restrict the size of
           constants that are used in instructions.  Constants that are too big are instead
           placed into a constant pool and referenced via register indirection.

           The value N can be between 0 and 4.  A value of 0 (the default) or 4 means that
           constants of any size are allowed.

       -mrelax
           Enable linker relaxation.  Linker relaxation is a process whereby the linker attempts
           to reduce the size of a program by finding shorter versions of various instructions.
           Disabled by default.

       -mint-register=N
           Specify the number of registers to reserve for fast interrupt handler functions.  The
           value N can be between 0 and 4.  A value of 1 means that register "r13" is reserved
           for the exclusive use of fast interrupt handlers.  A value of 2 reserves "r13" and
           "r12".  A value of 3 reserves "r13", "r12" and "r11", and a value of 4 reserves "r13"
           through "r10".  A value of 0, the default, does not reserve any registers.

       -msave-acc-in-interrupts
           Specifies that interrupt handler functions should preserve the accumulator register.
           This is only necessary if normal code might use the accumulator register, for example
           because it performs 64-bit multiplications.  The default is to ignore the accumulator
           as this makes the interrupt handlers faster.

       -mpid
       -mno-pid
           Enables the generation of position independent data.  When enabled any access to
           constant data is done via an offset from a base address held in a register.  This
           allows the location of constant data to be determined at run time without requiring
           the executable to be relocated, which is a benefit to embedded applications with tight
           memory constraints.  Data that can be modified is not affected by this option.

           Note, using this feature reserves a register, usually "r13", for the constant data
           base address.  This can result in slower and/or larger code, especially in complicated
           functions.

           The actual register chosen to hold the constant data base address depends upon whether
           the -msmall-data-limit and/or the -mint-register command-line options are enabled.
           Starting with register "r13" and proceeding downwards, registers are allocated first
           to satisfy the requirements of -mint-register, then -mpid and finally
           -msmall-data-limit.  Thus it is possible for the small data area register to be "r8"
           if both -mint-register=4 and -mpid are specified on the command line.

           By default this feature is not enabled.  The default can be restored via the -mno-pid
           command-line option.

       -mno-warn-multiple-fast-interrupts
       -mwarn-multiple-fast-interrupts
           Prevents GCC from issuing a warning message if it finds more than one fast interrupt
           handler when it is compiling a file.  The default is to issue a warning for each extra
           fast interrupt handler found, as the RX only supports one such interrupt.

       Note: The generic GCC command-line option -ffixed-reg has special significance to the RX
       port when used with the "interrupt" function attribute.  This attribute indicates a
       function intended to process fast interrupts.  GCC ensures that it only uses the registers
       "r10", "r11", "r12" and/or "r13" and only provided that the normal use of the
       corresponding registers have been restricted via the -ffixed-reg or -mint-register
       command-line options.

       S/390 and zSeries Options

       These are the -m options defined for the S/390 and zSeries architecture.

       -mhard-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions and registers for floating-
           point operations.  When -msoft-float is specified, functions in libgcc.a are used to
           perform floating-point operations.  When -mhard-float is specified, the compiler
           generates IEEE floating-point instructions.  This is the default.

       -mhard-dfp
       -mno-hard-dfp
           Use (do not use) the hardware decimal-floating-point instructions for decimal-
           floating-point operations.  When -mno-hard-dfp is specified, functions in libgcc.a are
           used to perform decimal-floating-point operations.  When -mhard-dfp is specified, the
           compiler generates decimal-floating-point hardware instructions.  This is the default
           for -march=z9-ec or higher.

       -mlong-double-64
       -mlong-double-128
           These switches control the size of "long double" type. A size of 64 bits makes the
           "long double" type equivalent to the "double" type. This is the default.

       -mbackchain
       -mno-backchain
           Store (do not store) the address of the caller's frame as backchain pointer into the
           callee's stack frame.  A backchain may be needed to allow debugging using tools that
           do not understand DWARF 2 call frame information.  When -mno-packed-stack is in
           effect, the backchain pointer is stored at the bottom of the stack frame; when
           -mpacked-stack is in effect, the backchain is placed into the topmost word of the
           96/160 byte register save area.

           In general, code compiled with -mbackchain is call-compatible with code compiled with
           -mmo-backchain; however, use of the backchain for debugging purposes usually requires
           that the whole binary is built with -mbackchain.  Note that the combination of
           -mbackchain, -mpacked-stack and -mhard-float is not supported.  In order to build a
           linux kernel use -msoft-float.

           The default is to not maintain the backchain.

       -mpacked-stack
       -mno-packed-stack
           Use (do not use) the packed stack layout.  When -mno-packed-stack is specified, the
           compiler uses the all fields of the 96/160 byte register save area only for their
           default purpose; unused fields still take up stack space.  When -mpacked-stack is
           specified, register save slots are densely packed at the top of the register save
           area; unused space is reused for other purposes, allowing for more efficient use of
           the available stack space.  However, when -mbackchain is also in effect, the topmost
           word of the save area is always used to store the backchain, and the return address
           register is always saved two words below the backchain.

           As long as the stack frame backchain is not used, code generated with -mpacked-stack
           is call-compatible with code generated with -mno-packed-stack.  Note that some non-FSF
           releases of GCC 2.95 for S/390 or zSeries generated code that uses the stack frame
           backchain at run time, not just for debugging purposes.  Such code is not call-
           compatible with code compiled with -mpacked-stack.  Also, note that the combination of
           -mbackchain, -mpacked-stack and -mhard-float is not supported.  In order to build a
           linux kernel use -msoft-float.

           The default is to not use the packed stack layout.

       -msmall-exec
       -mno-small-exec
           Generate (or do not generate) code using the "bras" instruction to do subroutine
           calls.  This only works reliably if the total executable size does not exceed 64k.
           The default is to use the "basr" instruction instead, which does not have this
           limitation.

       -m64
       -m31
           When -m31 is specified, generate code compliant to the GNU/Linux for S/390 ABI.  When
           -m64 is specified, generate code compliant to the GNU/Linux for zSeries ABI.  This
           allows GCC in particular to generate 64-bit instructions.  For the s390 targets, the
           default is -m31, while the s390x targets default to -m64.

       -mzarch
       -mesa
           When -mzarch is specified, generate code using the instructions available on
           z/Architecture.  When -mesa is specified, generate code using the instructions
           available on ESA/390.  Note that -mesa is not possible with -m64.  When generating
           code compliant to the GNU/Linux for S/390 ABI, the default is -mesa.  When generating
           code compliant to the GNU/Linux for zSeries ABI, the default is -mzarch.

       -mmvcle
       -mno-mvcle
           Generate (or do not generate) code using the "mvcle" instruction to perform block
           moves.  When -mno-mvcle is specified, use a "mvc" loop instead.  This is the default
           unless optimizing for size.

       -mdebug
       -mno-debug
           Print (or do not print) additional debug information when compiling.  The default is
           to not print debug information.

       -march=cpu-type
           Generate code that runs on cpu-type, which is the name of a system representing a
           certain processor type.  Possible values for cpu-type are g5, g6, z900, z990, z9-109,
           z9-ec, z10,  z196, zEC12, and z13.  When generating code using the instructions
           available on z/Architecture, the default is -march=z900.  Otherwise, the default is
           -march=g5.

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code, except for the ABI
           and the set of available instructions.  The list of cpu-type values is the same as for
           -march.  The default is the value used for -march.

       -mtpf-trace
       -mno-tpf-trace
           Generate code that adds (does not add) in TPF OS specific branches to trace routines
           in the operating system.  This option is off by default, even when compiling for the
           TPF OS.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point multiply and accumulate
           instructions.  These instructions are generated by default if hardware floating point
           is used.

       -mwarn-framesize=framesize
           Emit a warning if the current function exceeds the given frame size.  Because this is
           a compile-time check it doesn't need to be a real problem when the program runs.  It
           is intended to identify functions that most probably cause a stack overflow.  It is
           useful to be used in an environment with limited stack size e.g. the linux kernel.

       -mwarn-dynamicstack
           Emit a warning if the function calls "alloca" or uses dynamically-sized arrays.  This
           is generally a bad idea with a limited stack size.

       -mstack-guard=stack-guard
       -mstack-size=stack-size
           If these options are provided the S/390 back end emits additional instructions in the
           function prologue that trigger a trap if the stack size is stack-guard bytes above the
           stack-size (remember that the stack on S/390 grows downward).  If the stack-guard
           option is omitted the smallest power of 2 larger than the frame size of the compiled
           function is chosen.  These options are intended to be used to help debugging stack
           overflow problems.  The additionally emitted code causes only little overhead and
           hence can also be used in production-like systems without greater performance
           degradation.  The given values have to be exact powers of 2 and stack-size has to be
           greater than stack-guard without exceeding 64k.  In order to be efficient the extra
           code makes the assumption that the stack starts at an address aligned to the value
           given by stack-size.  The stack-guard option can only be used in conjunction with
           stack-size.

       -mhotpatch=pre-halfwords,post-halfwords
           If the hotpatch option is enabled, a "hot-patching" function prologue is generated for
           all functions in the compilation unit.  The funtion label is prepended with the given
           number of two-byte NOP instructions (pre-halfwords, maximum 1000000).  After the
           label, 2 * post-halfwords bytes are appended, using the largest NOP like instructions
           the architecture allows (maximum 1000000).

           If both arguments are zero, hotpatching is disabled.

           This option can be overridden for individual functions with the "hotpatch" attribute.

       Score Options

       These options are defined for Score implementations:

       -meb
           Compile code for big-endian mode.  This is the default.

       -mel
           Compile code for little-endian mode.

       -mnhwloop
           Disable generation of "bcnz" instructions.

       -muls
           Enable generation of unaligned load and store instructions.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mscore5
           Specify the SCORE5 as the target architecture.

       -mscore5u
           Specify the SCORE5U of the target architecture.

       -mscore7
           Specify the SCORE7 as the target architecture. This is the default.

       -mscore7d
           Specify the SCORE7D as the target architecture.

       SH Options

       These -m options are defined for the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m2e
           Generate code for the SH2e.

       -m2a-nofpu
           Generate code for the SH2a without FPU, or for a SH2a-FPU in such a way that the
           floating-point unit is not used.

       -m2a-single-only
           Generate code for the SH2a-FPU, in such a way that no double-precision floating-point
           operations are used.

       -m2a-single
           Generate code for the SH2a-FPU assuming the floating-point unit is in single-precision
           mode by default.

       -m2a
           Generate code for the SH2a-FPU assuming the floating-point unit is in double-precision
           mode by default.

       -m3 Generate code for the SH3.

       -m3e
           Generate code for the SH3e.

       -m4-nofpu
           Generate code for the SH4 without a floating-point unit.

       -m4-single-only
           Generate code for the SH4 with a floating-point unit that only supports single-
           precision arithmetic.

       -m4-single
           Generate code for the SH4 assuming the floating-point unit is in single-precision mode
           by default.

       -m4 Generate code for the SH4.

       -m4-100
           Generate code for SH4-100.

       -m4-100-nofpu
           Generate code for SH4-100 in such a way that the floating-point unit is not used.

       -m4-100-single
           Generate code for SH4-100 assuming the floating-point unit is in single-precision mode
           by default.

       -m4-100-single-only
           Generate code for SH4-100 in such a way that no double-precision floating-point
           operations are used.

       -m4-200
           Generate code for SH4-200.

       -m4-200-nofpu
           Generate code for SH4-200 without in such a way that the floating-point unit is not
           used.

       -m4-200-single
           Generate code for SH4-200 assuming the floating-point unit is in single-precision mode
           by default.

       -m4-200-single-only
           Generate code for SH4-200 in such a way that no double-precision floating-point
           operations are used.

       -m4-300
           Generate code for SH4-300.

       -m4-300-nofpu
           Generate code for SH4-300 without in such a way that the floating-point unit is not
           used.

       -m4-300-single
           Generate code for SH4-300 in such a way that no double-precision floating-point
           operations are used.

       -m4-300-single-only
           Generate code for SH4-300 in such a way that no double-precision floating-point
           operations are used.

       -m4-340
           Generate code for SH4-340 (no MMU, no FPU).

       -m4-500
           Generate code for SH4-500 (no FPU).  Passes -isa=sh4-nofpu to the assembler.

       -m4a-nofpu
           Generate code for the SH4al-dsp, or for a SH4a in such a way that the floating-point
           unit is not used.

       -m4a-single-only
           Generate code for the SH4a, in such a way that no double-precision floating-point
           operations are used.

       -m4a-single
           Generate code for the SH4a assuming the floating-point unit is in single-precision
           mode by default.

       -m4a
           Generate code for the SH4a.

       -m4al
           Same as -m4a-nofpu, except that it implicitly passes -dsp to the assembler.  GCC
           doesn't generate any DSP instructions at the moment.

       -m5-32media
           Generate 32-bit code for SHmedia.

       -m5-32media-nofpu
           Generate 32-bit code for SHmedia in such a way that the floating-point unit is not
           used.

       -m5-64media
           Generate 64-bit code for SHmedia.

       -m5-64media-nofpu
           Generate 64-bit code for SHmedia in such a way that the floating-point unit is not
           used.

       -m5-compact
           Generate code for SHcompact.

       -m5-compact-nofpu
           Generate code for SHcompact in such a way that the floating-point unit is not used.

       -mb Compile code for the processor in big-endian mode.

       -ml Compile code for the processor in little-endian mode.

       -mdalign
           Align doubles at 64-bit boundaries.  Note that this changes the calling conventions,
           and thus some functions from the standard C library do not work unless you recompile
           it first with -mdalign.

       -mrelax
           Shorten some address references at link time, when possible; uses the linker option
           -relax.

       -mbigtable
           Use 32-bit offsets in "switch" tables.  The default is to use 16-bit offsets.

       -mbitops
           Enable the use of bit manipulation instructions on SH2A.

       -mfmovd
           Enable the use of the instruction "fmovd".  Check -mdalign for alignment constraints.

       -mrenesas
           Comply with the calling conventions defined by Renesas.

       -mno-renesas
           Comply with the calling conventions defined for GCC before the Renesas conventions
           were available.  This option is the default for all targets of the SH toolchain.

       -mnomacsave
           Mark the "MAC" register as call-clobbered, even if -mrenesas is given.

       -mieee
       -mno-ieee
           Control the IEEE compliance of floating-point comparisons, which affects the handling
           of cases where the result of a comparison is unordered.  By default -mieee is
           implicitly enabled.  If -ffinite-math-only is enabled -mno-ieee is implicitly set,
           which results in faster floating-point greater-equal and less-equal comparisons.  The
           implcit settings can be overridden by specifying either -mieee or -mno-ieee.

       -minline-ic_invalidate
           Inline code to invalidate instruction cache entries after setting up nested function
           trampolines.  This option has no effect if -musermode is in effect and the selected
           code generation option (e.g. -m4) does not allow the use of the "icbi" instruction.
           If the selected code generation option does not allow the use of the "icbi"
           instruction, and -musermode is not in effect, the inlined code manipulates the
           instruction cache address array directly with an associative write.  This not only
           requires privileged mode at run time, but it also fails if the cache line had been
           mapped via the TLB and has become unmapped.

       -misize
           Dump instruction size and location in the assembly code.

       -mpadstruct
           This option is deprecated.  It pads structures to multiple of 4 bytes, which is
           incompatible with the SH ABI.

       -matomic-model=model
           Sets the model of atomic operations and additional parameters as a comma separated
           list.  For details on the atomic built-in functions see __atomic Builtins.  The
           following models and parameters are supported:

           none
               Disable compiler generated atomic sequences and emit library calls for atomic
               operations.  This is the default if the target is not "sh*-*-linux*".

           soft-gusa
               Generate GNU/Linux compatible gUSA software atomic sequences for the atomic built-
               in functions.  The generated atomic sequences require additional support from the
               interrupt/exception handling code of the system and are only suitable for SH3* and
               SH4* single-core systems.  This option is enabled by default when the target is
               "sh*-*-linux*" and SH3* or SH4*.  When the target is SH4A, this option also
               partially utilizes the hardware atomic instructions "movli.l" and "movco.l" to
               create more efficient code, unless strict is specified.

           soft-tcb
               Generate software atomic sequences that use a variable in the thread control
               block.  This is a variation of the gUSA sequences which can also be used on SH1*
               and SH2* targets.  The generated atomic sequences require additional support from
               the interrupt/exception handling code of the system and are only suitable for
               single-core systems.  When using this model, the gbr-offset= parameter has to be
               specified as well.

           soft-imask
               Generate software atomic sequences that temporarily disable interrupts by setting
               "SR.IMASK = 1111".  This model works only when the program runs in privileged mode
               and is only suitable for single-core systems.  Additional support from the
               interrupt/exception handling code of the system is not required.  This model is
               enabled by default when the target is "sh*-*-linux*" and SH1* or SH2*.

           hard-llcs
               Generate hardware atomic sequences using the "movli.l" and "movco.l" instructions
               only.  This is only available on SH4A and is suitable for multi-core systems.
               Since the hardware instructions support only 32 bit atomic variables access to 8
               or 16 bit variables is emulated with 32 bit accesses.  Code compiled with this
               option is also compatible with other software atomic model interrupt/exception
               handling systems if executed on an SH4A system.  Additional support from the
               interrupt/exception handling code of the system is not required for this model.

           gbr-offset=
               This parameter specifies the offset in bytes of the variable in the thread control
               block structure that should be used by the generated atomic sequences when the
               soft-tcb model has been selected.  For other models this parameter is ignored.
               The specified value must be an integer multiple of four and in the range 0-1020.

           strict
               This parameter prevents mixed usage of multiple atomic models, even if they are
               compatible, and makes the compiler generate atomic sequences of the specified
               model only.

       -mtas
           Generate the "tas.b" opcode for "__atomic_test_and_set".  Notice that depending on the
           particular hardware and software configuration this can degrade overall performance
           due to the operand cache line flushes that are implied by the "tas.b" instruction.  On
           multi-core SH4A processors the "tas.b" instruction must be used with caution since it
           can result in data corruption for certain cache configurations.

       -mprefergot
           When generating position-independent code, emit function calls using the Global Offset
           Table instead of the Procedure Linkage Table.

       -musermode
       -mno-usermode
           Don't allow (allow) the compiler generating privileged mode code.  Specifying
           -musermode also implies -mno-inline-ic_invalidate if the inlined code would not work
           in user mode.  -musermode is the default when the target is "sh*-*-linux*".  If the
           target is SH1* or SH2* -musermode has no effect, since there is no user mode.

       -multcost=number
           Set the cost to assume for a multiply insn.

       -mdiv=strategy
           Set the division strategy to be used for integer division operations.  For SHmedia
           strategy can be one of:

           fp  Performs the operation in floating point.  This has a very high latency, but needs
               only a few instructions, so it might be a good choice if your code has enough
               easily-exploitable ILP to allow the compiler to schedule the floating-point
               instructions together with other instructions.  Division by zero causes a
               floating-point exception.

           inv Uses integer operations to calculate the inverse of the divisor, and then
               multiplies the dividend with the inverse.  This strategy allows CSE and hoisting
               of the inverse calculation.  Division by zero calculates an unspecified result,
               but does not trap.

           inv:minlat
               A variant of inv where, if no CSE or hoisting opportunities have been found, or if
               the entire operation has been hoisted to the same place, the last stages of the
               inverse calculation are intertwined with the final multiply to reduce the overall
               latency, at the expense of using a few more instructions, and thus offering fewer
               scheduling opportunities with other code.

           call
               Calls a library function that usually implements the inv:minlat strategy.  This
               gives high code density for "m5-*media-nofpu" compilations.

           call2
               Uses a different entry point of the same library function, where it assumes that a
               pointer to a lookup table has already been set up, which exposes the pointer load
               to CSE and code hoisting optimizations.

           inv:call
           inv:call2
           inv:fp
               Use the inv algorithm for initial code generation, but if the code stays
               unoptimized, revert to the call, call2, or fp strategies, respectively.  Note that
               the potentially-trapping side effect of division by zero is carried by a separate
               instruction, so it is possible that all the integer instructions are hoisted out,
               but the marker for the side effect stays where it is.  A recombination to
               floating-point operations or a call is not possible in that case.

           inv20u
           inv20l
               Variants of the inv:minlat strategy.  In the case that the inverse calculation is
               not separated from the multiply, they speed up division where the dividend fits
               into 20 bits (plus sign where applicable) by inserting a test to skip a number of
               operations in this case; this test slows down the case of larger dividends.
               inv20u assumes the case of a such a small dividend to be unlikely, and inv20l
               assumes it to be likely.

           For targets other than SHmedia strategy can be one of:

           call-div1
               Calls a library function that uses the single-step division instruction "div1" to
               perform the operation.  Division by zero calculates an unspecified result and does
               not trap.  This is the default except for SH4, SH2A and SHcompact.

           call-fp
               Calls a library function that performs the operation in double precision floating
               point.  Division by zero causes a floating-point exception.  This is the default
               for SHcompact with FPU.  Specifying this for targets that do not have a double
               precision FPU defaults to "call-div1".

           call-table
               Calls a library function that uses a lookup table for small divisors and the
               "div1" instruction with case distinction for larger divisors.  Division by zero
               calculates an unspecified result and does not trap.  This is the default for SH4.
               Specifying this for targets that do not have dynamic shift instructions defaults
               to "call-div1".

           When a division strategy has not been specified the default strategy is selected based
           on the current target.  For SH2A the default strategy is to use the "divs" and "divu"
           instructions instead of library function calls.

       -maccumulate-outgoing-args
           Reserve space once for outgoing arguments in the function prologue rather than around
           each call.  Generally beneficial for performance and size.  Also needed for unwinding
           to avoid changing the stack frame around conditional code.

       -mdivsi3_libfunc=name
           Set the name of the library function used for 32-bit signed division to name.  This
           only affects the name used in the call and inv:call division strategies, and the
           compiler still expects the same sets of input/output/clobbered registers as if this
           option were not present.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed register
           is one that the register allocator can not use.  This is useful when compiling kernel
           code.  A register range is specified as two registers separated by a dash.  Multiple
           register ranges can be specified separated by a comma.

       -mindexed-addressing
           Enable the use of the indexed addressing mode for SHmedia32/SHcompact.  This is only
           safe if the hardware and/or OS implement 32-bit wrap-around semantics for the indexed
           addressing mode.  The architecture allows the implementation of processors with 64-bit
           MMU, which the OS could use to get 32-bit addressing, but since no current hardware
           implementation supports this or any other way to make the indexed addressing mode safe
           to use in the 32-bit ABI, the default is -mno-indexed-addressing.

       -mgettrcost=number
           Set the cost assumed for the "gettr" instruction to number.  The default is 2 if
           -mpt-fixed is in effect, 100 otherwise.

       -mpt-fixed
           Assume "pt*" instructions won't trap.  This generally generates better-scheduled code,
           but is unsafe on current hardware.  The current architecture definition says that
           "ptabs" and "ptrel" trap when the target anded with 3 is 3.  This has the
           unintentional effect of making it unsafe to schedule these instructions before a
           branch, or hoist them out of a loop.  For example, "__do_global_ctors", a part of
           libgcc that runs constructors at program startup, calls functions in a list which is
           delimited by -1.  With the -mpt-fixed option, the "ptabs" is done before testing
           against -1.  That means that all the constructors run a bit more quickly, but when the
           loop comes to the end of the list, the program crashes because "ptabs" loads -1 into a
           target register.

           Since this option is unsafe for any hardware implementing the current architecture
           specification, the default is -mno-pt-fixed.  Unless specified explicitly with
           -mgettrcost, -mno-pt-fixed also implies -mgettrcost=100; this deters register
           allocation from using target registers for storing ordinary integers.

       -minvalid-symbols
           Assume symbols might be invalid.  Ordinary function symbols generated by the compiler
           are always valid to load with "movi"/"shori"/"ptabs" or "movi"/"shori"/"ptrel", but
           with assembler and/or linker tricks it is possible to generate symbols that cause
           "ptabs" or "ptrel" to trap.  This option is only meaningful when -mno-pt-fixed is in
           effect.  It prevents cross-basic-block CSE, hoisting and most scheduling of symbol
           loads.  The default is -mno-invalid-symbols.

       -mbranch-cost=num
           Assume num to be the cost for a branch instruction.  Higher numbers make the compiler
           try to generate more branch-free code if possible.  If not specified the value is
           selected depending on the processor type that is being compiled for.

       -mzdcbranch
       -mno-zdcbranch
           Assume (do not assume) that zero displacement conditional branch instructions "bt" and
           "bf" are fast.  If -mzdcbranch is specified, the compiler prefers zero displacement
           branch code sequences.  This is enabled by default when generating code for SH4 and
           SH4A.  It can be explicitly disabled by specifying -mno-zdcbranch.

       -mcbranch-force-delay-slot
           Force the usage of delay slots for conditional branches, which stuffs the delay slot
           with a "nop" if a suitable instruction can't be found.  By default this option is
           disabled.  It can be enabled to work around hardware bugs as found in the original
           SH7055.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point multiply and accumulate
           instructions.  These instructions are generated by default if hardware floating point
           is used.  The machine-dependent -mfused-madd option is now mapped to the machine-
           independent -ffp-contract=fast option, and -mno-fused-madd is mapped to
           -ffp-contract=off.

       -mfsca
       -mno-fsca
           Allow or disallow the compiler to emit the "fsca" instruction for sine and cosine
           approximations.  The option -mfsca must be used in combination with
           -funsafe-math-optimizations.  It is enabled by default when generating code for SH4A.
           Using -mno-fsca disables sine and cosine approximations even if
           -funsafe-math-optimizations is in effect.

       -mfsrra
       -mno-fsrra
           Allow or disallow the compiler to emit the "fsrra" instruction for reciprocal square
           root approximations.  The option -mfsrra must be used in combination with
           -funsafe-math-optimizations and -ffinite-math-only.  It is enabled by default when
           generating code for SH4A.  Using -mno-fsrra disables reciprocal square root
           approximations even if -funsafe-math-optimizations and -ffinite-math-only are in
           effect.

       -mpretend-cmove
           Prefer zero-displacement conditional branches for conditional move instruction
           patterns.  This can result in faster code on the SH4 processor.

       Solaris 2 Options

       These -m options are supported on Solaris 2:

       -mclear-hwcap
           -mclear-hwcap tells the compiler to remove the hardware capabilities generated by the
           Solaris assembler.  This is only necessary when object files use ISA extensions not
           supported by the current machine, but check at runtime whether or not to use them.

       -mimpure-text
           -mimpure-text, used in addition to -shared, tells the compiler to not pass -z text to
           the linker when linking a shared object.  Using this option, you can link position-
           dependent code into a shared object.

           -mimpure-text suppresses the "relocations remain against allocatable but non-writable
           sections" linker error message.  However, the necessary relocations trigger copy-on-
           write, and the shared object is not actually shared across processes.  Instead of
           using -mimpure-text, you should compile all source code with -fpic or -fPIC.

       These switches are supported in addition to the above on Solaris 2:

       -pthreads
           Add support for multithreading using the POSIX threads library.  This option sets
           flags for both the preprocessor and linker.  This option does not affect the thread
           safety of object code produced  by the compiler or that of libraries supplied with it.

       -pthread
           This is a synonym for -pthreads.

       SPARC Options

       These -m options are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
           Specify -mapp-regs to generate output using the global registers 2 through 4, which
           the SPARC SVR4 ABI reserves for applications.  Like the global register 1, each global
           register 2 through 4 is then treated as an allocable register that is clobbered by
           function calls.  This is the default.

           To be fully SVR4 ABI-compliant at the cost of some performance loss, specify
           -mno-app-regs.  You should compile libraries and system software with this option.

       -mflat
       -mno-flat
           With -mflat, the compiler does not generate save/restore instructions and uses a
           "flat" or single register window model.  This model is compatible with the regular
           register window model.  The local registers and the input registers (0--5) are still
           treated as "call-saved" registers and are saved on the stack as needed.

           With -mno-flat (the default), the compiler generates save/restore instructions (except
           for leaf functions).  This is the normal operating mode.

       -mfpu
       -mhard-float
           Generate output containing floating-point instructions.  This is the default.

       -mno-fpu
       -msoft-float
           Generate output containing library calls for floating point.  Warning: the requisite
           libraries are not available for all SPARC targets.  Normally the facilities of the
           machine's usual C compiler are used, but this cannot be done directly in cross-
           compilation.  You must make your own arrangements to provide suitable library
           functions for cross-compilation.  The embedded targets sparc-*-aout and sparclite-*-*
           do provide software floating-point support.

           -msoft-float changes the calling convention in the output file; therefore, it is only
           useful if you compile all of a program with this option.  In particular, you need to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this
           to work.

       -mhard-quad-float
           Generate output containing quad-word (long double) floating-point instructions.

       -msoft-quad-float
           Generate output containing library calls for quad-word (long double) floating-point
           instructions.  The functions called are those specified in the SPARC ABI.  This is the
           default.

           As of this writing, there are no SPARC implementations that have hardware support for
           the quad-word floating-point instructions.  They all invoke a trap handler for one of
           these instructions, and then the trap handler emulates the effect of the instruction.
           Because of the trap handler overhead, this is much slower than calling the ABI library
           routines.  Thus the -msoft-quad-float option is the default.

       -mno-unaligned-doubles
       -munaligned-doubles
           Assume that doubles have 8-byte alignment.  This is the default.

           With -munaligned-doubles, GCC assumes that doubles have 8-byte alignment only if they
           are contained in another type, or if they have an absolute address.  Otherwise, it
           assumes they have 4-byte alignment.  Specifying this option avoids some rare
           compatibility problems with code generated by other compilers.  It is not the default
           because it results in a performance loss, especially for floating-point code.

       -muser-mode
       -mno-user-mode
           Do not generate code that can only run in supervisor mode.  This is relevant only for
           the "casa" instruction emitted for the LEON3 processor.  This is the default.

       -mno-faster-structs
       -mfaster-structs
           With -mfaster-structs, the compiler assumes that structures should have 8-byte
           alignment.  This enables the use of pairs of "ldd" and "std" instructions for copies
           in structure assignment, in place of twice as many "ld" and "st" pairs.  However, the
           use of this changed alignment directly violates the SPARC ABI.  Thus, it's intended
           only for use on targets where the developer acknowledges that their resulting code is
           not directly in line with the rules of the ABI.

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling parameters for
           machine type cpu_type.  Supported values for cpu_type are v7, cypress, v8, supersparc,
           hypersparc, leon, leon3, leon3v7, sparclite, f930, f934, sparclite86x, sparclet,
           tsc701, v9, ultrasparc, ultrasparc3, niagara, niagara2, niagara3 and niagara4.

           Native Solaris and GNU/Linux toolchains also support the value native, which selects
           the best architecture option for the host processor.  -mcpu=native has no effect if
           GCC does not recognize the processor.

           Default instruction scheduling parameters are used for values that select an
           architecture and not an implementation.  These are v7, v8, sparclite, sparclet, v9.

           Here is a list of each supported architecture and their supported implementations.

           v7  cypress, leon3v7

           v8  supersparc, hypersparc, leon, leon3

           sparclite
               f930, f934, sparclite86x

           sparclet
               tsc701

           v9  ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4

           By default (unless configured otherwise), GCC generates code for the V7 variant of the
           SPARC architecture.  With -mcpu=cypress, the compiler additionally optimizes it for
           the Cypress CY7C602 chip, as used in the SPARCStation/SPARCServer 3xx series.  This is
           also appropriate for the older SPARCStation 1, 2, IPX etc.

           With -mcpu=v8, GCC generates code for the V8 variant of the SPARC architecture.  The
           only difference from V7 code is that the compiler emits the integer multiply and
           integer divide instructions which exist in SPARC-V8 but not in SPARC-V7.  With
           -mcpu=supersparc, the compiler additionally optimizes it for the SuperSPARC chip, as
           used in the SPARCStation 10, 1000 and 2000 series.

           With -mcpu=sparclite, GCC generates code for the SPARClite variant of the SPARC
           architecture.  This adds the integer multiply, integer divide step and scan ("ffs")
           instructions which exist in SPARClite but not in SPARC-V7.  With -mcpu=f930, the
           compiler additionally optimizes it for the Fujitsu MB86930 chip, which is the original
           SPARClite, with no FPU.  With -mcpu=f934, the compiler additionally optimizes it for
           the Fujitsu MB86934 chip, which is the more recent SPARClite with FPU.

           With -mcpu=sparclet, GCC generates code for the SPARClet variant of the SPARC
           architecture.  This adds the integer multiply, multiply/accumulate, integer divide
           step and scan ("ffs") instructions which exist in SPARClet but not in SPARC-V7.  With
           -mcpu=tsc701, the compiler additionally optimizes it for the TEMIC SPARClet chip.

           With -mcpu=v9, GCC generates code for the V9 variant of the SPARC architecture.  This
           adds 64-bit integer and floating-point move instructions, 3 additional floating-point
           condition code registers and conditional move instructions.  With -mcpu=ultrasparc,
           the compiler additionally optimizes it for the Sun UltraSPARC I/II/IIi chips.  With
           -mcpu=ultrasparc3, the compiler additionally optimizes it for the Sun UltraSPARC
           III/III+/IIIi/IIIi+/IV/IV+ chips.  With -mcpu=niagara, the compiler additionally
           optimizes it for Sun UltraSPARC T1 chips.  With -mcpu=niagara2, the compiler
           additionally optimizes it for Sun UltraSPARC T2 chips. With -mcpu=niagara3, the
           compiler additionally optimizes it for Sun UltraSPARC T3 chips.  With -mcpu=niagara4,
           the compiler additionally optimizes it for Sun UltraSPARC T4 chips.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not set
           the instruction set or register set that the option -mcpu=cpu_type does.

           The same values for -mcpu=cpu_type can be used for -mtune=cpu_type, but the only
           useful values are those that select a particular CPU implementation.  Those are
           cypress, supersparc, hypersparc, leon, leon3, leon3v7, f930, f934, sparclite86x,
           tsc701, ultrasparc, ultrasparc3, niagara, niagara2, niagara3 and niagara4.  With
           native Solaris and GNU/Linux toolchains, native can also be used.

       -mv8plus
       -mno-v8plus
           With -mv8plus, GCC generates code for the SPARC-V8+ ABI.  The difference from the V8
           ABI is that the global and out registers are considered 64 bits wide.  This is enabled
           by default on Solaris in 32-bit mode for all SPARC-V9 processors.

       -mvis
       -mno-vis
           With -mvis, GCC generates code that takes advantage of the UltraSPARC Visual
           Instruction Set extensions.  The default is -mno-vis.

       -mvis2
       -mno-vis2
           With -mvis2, GCC generates code that takes advantage of version 2.0 of the UltraSPARC
           Visual Instruction Set extensions.  The default is -mvis2 when targeting a cpu that
           supports such instructions, such as UltraSPARC-III and later.  Setting -mvis2 also
           sets -mvis.

       -mvis3
       -mno-vis3
           With -mvis3, GCC generates code that takes advantage of version 3.0 of the UltraSPARC
           Visual Instruction Set extensions.  The default is -mvis3 when targeting a cpu that
           supports such instructions, such as niagara-3 and later.  Setting -mvis3 also sets
           -mvis2 and -mvis.

       -mcbcond
       -mno-cbcond
           With -mcbcond, GCC generates code that takes advantage of compare-and-branch
           instructions, as defined in the Sparc Architecture 2011.  The default is -mcbcond when
           targeting a cpu that supports such instructions, such as niagara-4 and later.

       -mpopc
       -mno-popc
           With -mpopc, GCC generates code that takes advantage of the UltraSPARC population
           count instruction.  The default is -mpopc when targeting a cpu that supports such
           instructions, such as Niagara-2 and later.

       -mfmaf
       -mno-fmaf
           With -mfmaf, GCC generates code that takes advantage of the UltraSPARC Fused Multiply-
           Add Floating-point extensions.  The default is -mfmaf when targeting a cpu that
           supports such instructions, such as Niagara-3 and later.

       -mfix-at697f
           Enable the documented workaround for the single erratum of the Atmel AT697F processor
           (which corresponds to erratum #13 of the AT697E processor).

       -mfix-ut699
           Enable the documented workarounds for the floating-point errata and the data cache
           nullify errata of the UT699 processor.

       These -m options are supported in addition to the above on SPARC-V9 processors in 64-bit
       environments:

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int,
           long and pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and
           pointer to 64 bits.

       -mcmodel=which
           Set the code model to one of

           medlow
               The Medium/Low code model: 64-bit addresses, programs must be linked in the low 32
               bits of memory.  Programs can be statically or dynamically linked.

           medmid
               The Medium/Middle code model: 64-bit addresses, programs must be linked in the low
               44 bits of memory, the text and data segments must be less than 2GB in size and
               the data segment must be located within 2GB of the text segment.

           medany
               The Medium/Anywhere code model: 64-bit addresses, programs may be linked anywhere
               in memory, the text and data segments must be less than 2GB in size and the data
               segment must be located within 2GB of the text segment.

           embmedany
               The Medium/Anywhere code model for embedded systems: 64-bit addresses, the text
               and data segments must be less than 2GB in size, both starting anywhere in memory
               (determined at link time).  The global register %g4 points to the base of the data
               segment.  Programs are statically linked and PIC is not supported.

       -mmemory-model=mem-model
           Set the memory model in force on the processor to one of

           default
               The default memory model for the processor and operating system.

           rmo Relaxed Memory Order

           pso Partial Store Order

           tso Total Store Order

           sc  Sequential Consistency

           These memory models are formally defined in Appendix D of the Sparc V9 architecture
           manual, as set in the processor's "PSTATE.MM" field.

       -mstack-bias
       -mno-stack-bias
           With -mstack-bias, GCC assumes that the stack pointer, and frame pointer if present,
           are offset by -2047 which must be added back when making stack frame references.  This
           is the default in 64-bit mode.  Otherwise, assume no such offset is present.

       SPU Options

       These -m options are supported on the SPU:

       -mwarn-reloc
       -merror-reloc
           The loader for SPU does not handle dynamic relocations.  By default, GCC gives an
           error when it generates code that requires a dynamic relocation.  -mno-error-reloc
           disables the error, -mwarn-reloc generates a warning instead.

       -msafe-dma
       -munsafe-dma
           Instructions that initiate or test completion of DMA must not be reordered with
           respect to loads and stores of the memory that is being accessed.  With -munsafe-dma
           you must use the "volatile" keyword to protect memory accesses, but that can lead to
           inefficient code in places where the memory is known to not change.  Rather than mark
           the memory as volatile, you can use -msafe-dma to tell the compiler to treat the DMA
           instructions as potentially affecting all memory.

       -mbranch-hints
           By default, GCC generates a branch hint instruction to avoid pipeline stalls for
           always-taken or probably-taken branches.  A hint is not generated closer than 8
           instructions away from its branch.  There is little reason to disable them, except for
           debugging purposes, or to make an object a little bit smaller.

       -msmall-mem
       -mlarge-mem
           By default, GCC generates code assuming that addresses are never larger than 18 bits.
           With -mlarge-mem code is generated that assumes a full 32-bit address.

       -mstdmain
           By default, GCC links against startup code that assumes the SPU-style main function
           interface (which has an unconventional parameter list).  With -mstdmain, GCC links
           your program against startup code that assumes a C99-style interface to "main",
           including a local copy of "argv" strings.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed registers.  A fixed register
           is one that the register allocator cannot use.  This is useful when compiling kernel
           code.  A register range is specified as two registers separated by a dash.  Multiple
           register ranges can be specified separated by a comma.

       -mea32
       -mea64
           Compile code assuming that pointers to the PPU address space accessed via the "__ea"
           named address space qualifier are either 32 or 64 bits wide.  The default is 32 bits.
           As this is an ABI-changing option, all object code in an executable must be compiled
           with the same setting.

       -maddress-space-conversion
       -mno-address-space-conversion
           Allow/disallow treating the "__ea" address space as superset of the generic address
           space.  This enables explicit type casts between "__ea" and generic pointer as well as
           implicit conversions of generic pointers to "__ea" pointers.  The default is to allow
           address space pointer conversions.

       -mcache-size=cache-size
           This option controls the version of libgcc that the compiler links to an executable
           and selects a software-managed cache for accessing variables in the "__ea" address
           space with a particular cache size.  Possible options for cache-size are 8, 16, 32, 64
           and 128.  The default cache size is 64KB.

       -matomic-updates
       -mno-atomic-updates
           This option controls the version of libgcc that the compiler links to an executable
           and selects whether atomic updates to the software-managed cache of PPU-side variables
           are used.  If you use atomic updates, changes to a PPU variable from SPU code using
           the "__ea" named address space qualifier do not interfere with changes to other PPU
           variables residing in the same cache line from PPU code.  If you do not use atomic
           updates, such interference may occur; however, writing back cache lines is more
           efficient.  The default behavior is to use atomic updates.

       -mdual-nops
       -mdual-nops=n
           By default, GCC inserts nops to increase dual issue when it expects it to increase
           performance.  n can be a value from 0 to 10.  A smaller n inserts fewer nops.  10 is
           the default, 0 is the same as -mno-dual-nops.  Disabled with -Os.

       -mhint-max-nops=n
           Maximum number of nops to insert for a branch hint.  A branch hint must be at least 8
           instructions away from the branch it is affecting.  GCC inserts up to n nops to
           enforce this, otherwise it does not generate the branch hint.

       -mhint-max-distance=n
           The encoding of the branch hint instruction limits the hint to be within 256
           instructions of the branch it is affecting.  By default, GCC makes sure it is within
           125.

       -msafe-hints
           Work around a hardware bug that causes the SPU to stall indefinitely.  By default, GCC
           inserts the "hbrp" instruction to make sure this stall won't happen.

       Options for System V

       These additional options are available on System V Release 4 for compatibility with other
       compilers on those systems:

       -G  Create a shared object.  It is recommended that -symbolic or -shared be used instead.

       -Qy Identify the versions of each tool used by the compiler, in a ".ident" assembler
           directive in the output.

       -Qn Refrain from adding ".ident" directives to the output file (this is the default).

       -YP,dirs
           Search the directories dirs, and no others, for libraries specified with -l.

       -Ym,dir
           Look in the directory dir to find the M4 preprocessor.  The assembler uses this
           option.

       TILE-Gx Options

       These -m options are supported on the TILE-Gx:

       -mcmodel=small
           Generate code for the small model.  The distance for direct calls is limited to 500M
           in either direction.  PC-relative addresses are 32 bits.  Absolute addresses support
           the full address range.

       -mcmodel=large
           Generate code for the large model.  There is no limitation on call distance, pc-
           relative addresses, or absolute addresses.

       -mcpu=name
           Selects the type of CPU to be targeted.  Currently the only supported type is tilegx.

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit environment sets int,
           long, and pointer to 32 bits.  The 64-bit environment sets int to 32 bits and long and
           pointer to 64 bits.

       -mbig-endian
       -mlittle-endian
           Generate code in big/little endian mode, respectively.

       TILEPro Options

       These -m options are supported on the TILEPro:

       -mcpu=name
           Selects the type of CPU to be targeted.  Currently the only supported type is tilepro.

       -m32
           Generate code for a 32-bit environment, which sets int, long, and pointer to 32 bits.
           This is the only supported behavior so the flag is essentially ignored.

       V850 Options

       These -m options are defined for V850 implementations:

       -mlong-calls
       -mno-long-calls
           Treat all calls as being far away (near).  If calls are assumed to be far away, the
           compiler always loads the function's address into a register, and calls indirect
           through the pointer.

       -mno-ep
       -mep
           Do not optimize (do optimize) basic blocks that use the same index pointer 4 or more
           times to copy pointer into the "ep" register, and use the shorter "sld" and "sst"
           instructions.  The -mep option is on by default if you optimize.

       -mno-prolog-function
       -mprolog-function
           Do not use (do use) external functions to save and restore registers at the prologue
           and epilogue of a function.  The external functions are slower, but use less code
           space if more than one function saves the same number of registers.  The
           -mprolog-function option is on by default if you optimize.

       -mspace
           Try to make the code as small as possible.  At present, this just turns on the -mep
           and -mprolog-function options.

       -mtda=n
           Put static or global variables whose size is n bytes or less into the tiny data area
           that register "ep" points to.  The tiny data area can hold up to 256 bytes in total
           (128 bytes for byte references).

       -msda=n
           Put static or global variables whose size is n bytes or less into the small data area
           that register "gp" points to.  The small data area can hold up to 64 kilobytes.

       -mzda=n
           Put static or global variables whose size is n bytes or less into the first 32
           kilobytes of memory.

       -mv850
           Specify that the target processor is the V850.

       -mv850e3v5
           Specify that the target processor is the V850E3V5.  The preprocessor constant
           "__v850e3v5__" is defined if this option is used.

       -mv850e2v4
           Specify that the target processor is the V850E3V5.  This is an alias for the
           -mv850e3v5 option.

       -mv850e2v3
           Specify that the target processor is the V850E2V3.  The preprocessor constant
           "__v850e2v3__" is defined if this option is used.

       -mv850e2
           Specify that the target processor is the V850E2.  The preprocessor constant
           "__v850e2__" is defined if this option is used.

       -mv850e1
           Specify that the target processor is the V850E1.  The preprocessor constants
           "__v850e1__" and "__v850e__" are defined if this option is used.

       -mv850es
           Specify that the target processor is the V850ES.  This is an alias for the -mv850e1
           option.

       -mv850e
           Specify that the target processor is the V850E.  The preprocessor constant "__v850e__"
           is defined if this option is used.

           If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2 nor -mv850e2v3 nor -mv850e3v5
           are defined then a default target processor is chosen and the relevant __v850*__
           preprocessor constant is defined.

           The preprocessor constants "__v850" and "__v851__" are always defined, regardless of
           which processor variant is the target.

       -mdisable-callt
       -mno-disable-callt
           This option suppresses generation of the "CALLT" instruction for the v850e, v850e1,
           v850e2, v850e2v3 and v850e3v5 flavors of the v850 architecture.

           This option is enabled by default when the RH850 ABI is in use (see -mrh850-abi), and
           disabled by default when the GCC ABI is in use.  If "CALLT" instructions are being
           generated then the C preprocessor symbol "__V850_CALLT__" is defined.

       -mrelax
       -mno-relax
           Pass on (or do not pass on) the -mrelax command-line option to the assembler.

       -mlong-jumps
       -mno-long-jumps
           Disable (or re-enable) the generation of PC-relative jump instructions.

       -msoft-float
       -mhard-float
           Disable (or re-enable) the generation of hardware floating point instructions.  This
           option is only significant when the target architecture is V850E2V3 or higher.  If
           hardware floating point instructions are being generated then the C preprocessor
           symbol "__FPU_OK__" is defined, otherwise the symbol "__NO_FPU__" is defined.

       -mloop
           Enables the use of the e3v5 LOOP instruction.  The use of this instruction is not
           enabled by default when the e3v5 architecture is selected because its use is still
           experimental.

       -mrh850-abi
       -mghs
           Enables support for the RH850 version of the V850 ABI.  This is the default.  With
           this version of the ABI the following rules apply:

           *   Integer sized structures and unions are returned via a memory pointer rather than
               a register.

           *   Large structures and unions (more than 8 bytes in size) are passed by value.

           *   Functions are aligned to 16-bit boundaries.

           *   The -m8byte-align command-line option is supported.

           *   The -mdisable-callt command-line option is enabled by default.  The
               -mno-disable-callt command-line option is not supported.

           When this version of the ABI is enabled the C preprocessor symbol "__V850_RH850_ABI__"
           is defined.

       -mgcc-abi
           Enables support for the old GCC version of the V850 ABI.  With this version of the ABI
           the following rules apply:

           *   Integer sized structures and unions are returned in register "r10".

           *   Large structures and unions (more than 8 bytes in size) are passed by reference.

           *   Functions are aligned to 32-bit boundaries, unless optimizing for size.

           *   The -m8byte-align command-line option is not supported.

           *   The -mdisable-callt command-line option is supported but not enabled by default.

           When this version of the ABI is enabled the C preprocessor symbol "__V850_GCC_ABI__"
           is defined.

       -m8byte-align
       -mno-8byte-align
           Enables support for "double" and "long long" types to be aligned on 8-byte boundaries.
           The default is to restrict the alignment of all objects to at most 4-bytes.  When
           -m8byte-align is in effect the C preprocessor symbol "__V850_8BYTE_ALIGN__" is
           defined.

       -mbig-switch
           Generate code suitable for big switch tables.  Use this option only if the
           assembler/linker complain about out of range branches within a switch table.

       -mapp-regs
           This option causes r2 and r5 to be used in the code generated by the compiler.  This
           setting is the default.

       -mno-app-regs
           This option causes r2 and r5 to be treated as fixed registers.

       VAX Options

       These -m options are defined for the VAX:

       -munix
           Do not output certain jump instructions ("aobleq" and so on) that the Unix assembler
           for the VAX cannot handle across long ranges.

       -mgnu
           Do output those jump instructions, on the assumption that the GNU assembler is being
           used.

       -mg Output code for G-format floating-point numbers instead of D-format.

       Visium Options

       -mdebug
           A program which performs file I/O and is destined to run on an MCM target should be
           linked with this option.  It causes the libraries libc.a and libdebug.a to be linked.
           The program should be run on the target under the control of the GDB remote debugging
           stub.

       -msim
           A program which performs file I/O and is destined to run on the simulator should be
           linked with option.  This causes libraries libc.a and libsim.a to be linked.

       -mfpu
       -mhard-float
           Generate code containing floating-point instructions.  This is the default.

       -mno-fpu
       -msoft-float
           Generate code containing library calls for floating-point.

           -msoft-float changes the calling convention in the output file; therefore, it is only
           useful if you compile all of a program with this option.  In particular, you need to
           compile libgcc.a, the library that comes with GCC, with -msoft-float in order for this
           to work.

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling parameters for
           machine type cpu_type.  Supported values for cpu_type are mcm, gr5 and gr6.

           mcm is a synonym of gr5 present for backward compatibility.

           By default (unless configured otherwise), GCC generates code for the GR5 variant of
           the Visium architecture.

           With -mcpu=gr6, GCC generates code for the GR6 variant of the Visium architecture.
           The only difference from GR5 code is that the compiler will generate block move
           instructions.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type cpu_type, but do not set
           the instruction set or register set that the option -mcpu=cpu_type would.

       -msv-mode
           Generate code for the supervisor mode, where there are no restrictions on the access
           to general registers.  This is the default.

       -muser-mode
           Generate code for the user mode, where the access to some general registers is
           forbidden: on the GR5, registers r24 to r31 cannot be accessed in this mode; on the
           GR6, only registers r29 to r31 are affected.

       VMS Options

       These -m options are defined for the VMS implementations:

       -mvms-return-codes
           Return VMS condition codes from "main". The default is to return POSIX-style condition
           (e.g. error) codes.

       -mdebug-main=prefix
           Flag the first routine whose name starts with prefix as the main routine for the
           debugger.

       -mmalloc64
           Default to 64-bit memory allocation routines.

       -mpointer-size=size
           Set the default size of pointers. Possible options for size are 32 or short for 32 bit
           pointers, 64 or long for 64 bit pointers, and no for supporting only 32 bit pointers.
           The later option disables "pragma pointer_size".

       VxWorks Options

       The options in this section are defined for all VxWorks targets.  Options specific to the
       target hardware are listed with the other options for that target.

       -mrtp
           GCC can generate code for both VxWorks kernels and real time processes (RTPs).  This
           option switches from the former to the latter.  It also defines the preprocessor macro
           "__RTP__".

       -non-static
           Link an RTP executable against shared libraries rather than static libraries.  The
           options -static and -shared can also be used for RTPs; -static is the default.

       -Bstatic
       -Bdynamic
           These options are passed down to the linker.  They are defined for compatibility with
           Diab.

       -Xbind-lazy
           Enable lazy binding of function calls.  This option is equivalent to -Wl,-z,now and is
           defined for compatibility with Diab.

       -Xbind-now
           Disable lazy binding of function calls.  This option is the default and is defined for
           compatibility with Diab.

       x86 Options

       These -m options are defined for the x86 family of computers.

       -march=cpu-type
           Generate instructions for the machine type cpu-type.  In contrast to -mtune=cpu-type,
           which merely tunes the generated code for the specified cpu-type, -march=cpu-type
           allows GCC to generate code that may not run at all on processors other than the one
           indicated.  Specifying -march=cpu-type implies -mtune=cpu-type.

           The choices for cpu-type are:

           native
               This selects the CPU to generate code for at compilation time by determining the
               processor type of the compiling machine.  Using -march=native enables all
               instruction subsets supported by the local machine (hence the result might not run
               on different machines).  Using -mtune=native produces code optimized for the local
               machine under the constraints of the selected instruction set.

           i386
               Original Intel i386 CPU.

           i486
               Intel i486 CPU.  (No scheduling is implemented for this chip.)

           i586
           pentium
               Intel Pentium CPU with no MMX support.

           pentium-mmx
               Intel Pentium MMX CPU, based on Pentium core with MMX instruction set support.

           pentiumpro
               Intel Pentium Pro CPU.

           i686
               When used with -march, the Pentium Pro instruction set is used, so the code runs
               on all i686 family chips.  When used with -mtune, it has the same meaning as
               generic.

           pentium2
               Intel Pentium II CPU, based on Pentium Pro core with MMX instruction set support.

           pentium3
           pentium3m
               Intel Pentium III CPU, based on Pentium Pro core with MMX and SSE instruction set
               support.

           pentium-m
               Intel Pentium M; low-power version of Intel Pentium III CPU with MMX, SSE and SSE2
               instruction set support.  Used by Centrino notebooks.

           pentium4
           pentium4m
               Intel Pentium 4 CPU with MMX, SSE and SSE2 instruction set support.

           prescott
               Improved version of Intel Pentium 4 CPU with MMX, SSE, SSE2 and SSE3 instruction
               set support.

           nocona
               Improved version of Intel Pentium 4 CPU with 64-bit extensions, MMX, SSE, SSE2 and
               SSE3 instruction set support.

           core2
               Intel Core 2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3
               instruction set support.

           nehalem
               Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2 and POPCNT instruction set support.

           westmere
               Intel Westmere CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AES and PCLMUL instruction set support.

           sandybridge
               Intel Sandy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AVX, AES and PCLMUL instruction set support.

           ivybridge
               Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, POPCNT, AVX, AES, PCLMUL, FSGSBASE, RDRND and F16C instruction set
               support.

           haswell
               Intel Haswell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2
               and F16C instruction set support.

           broadwell
               Intel Broadwell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2,
               F16C, RDSEED, ADCX and PREFETCHW instruction set support.

           bonnell
               Intel Bonnell CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3 and SSSE3
               instruction set support.

           silvermont
               Intel Silvermont CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4.1, SSE4.2, POPCNT, AES, PCLMUL and RDRND instruction set support.

           knl Intel Knight's Landing CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2, SSE3,
               SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI,
               BMI2, F16C, RDSEED, ADCX, PREFETCHW, AVX512F, AVX512PF, AVX512ER and AVX512CD
               instruction set support.

           k6  AMD K6 CPU with MMX instruction set support.

           k6-2
           k6-3
               Improved versions of AMD K6 CPU with MMX and 3DNow! instruction set support.

           athlon
           athlon-tbird
               AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow! and SSE prefetch instructions
               support.

           athlon-4
           athlon-xp
           athlon-mp
               Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow! and full SSE instruction
               set support.

           k8
           opteron
           athlon64
           athlon-fx
               Processors based on the AMD K8 core with x86-64 instruction set support, including
               the AMD Opteron, Athlon 64, and Athlon 64 FX processors.  (This supersets MMX,
               SSE, SSE2, 3DNow!, enhanced 3DNow! and 64-bit instruction set extensions.)

           k8-sse3
           opteron-sse3
           athlon64-sse3
               Improved versions of AMD K8 cores with SSE3 instruction set support.

           amdfam10
           barcelona
               CPUs based on AMD Family 10h cores with x86-64 instruction set support.  (This
               supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!, enhanced 3DNow!, ABM and 64-bit
               instruction set extensions.)

           bdver1
               CPUs based on AMD Family 15h cores with x86-64 instruction set support.  (This
               supersets FMA4, AVX, XOP, LWP, AES, PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A,
               SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

           bdver2
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This
               supersets BMI, TBM, F16C, FMA, FMA4, AVX, XOP, LWP, AES, PCL_MUL, CX16, MMX, SSE,
               SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set
               extensions.)

           bdver3
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This
               supersets BMI, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, XOP, LWP, AES, PCL_MUL, CX16,
               MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set
               extensions.

           bdver4
               AMD Family 15h core based CPUs with x86-64 instruction set support.  (This
               supersets BMI, BMI2, TBM, F16C, FMA, FMA4, FSGSBASE, AVX, AVX2, XOP, LWP, AES,
               PCL_MUL, CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and
               64-bit instruction set extensions.

           btver1
               CPUs based on AMD Family 14h cores with x86-64 instruction set support.  (This
               supersets MMX, SSE, SSE2, SSE3, SSSE3, SSE4A, CX16, ABM and 64-bit instruction set
               extensions.)

           btver2
               CPUs based on AMD Family 16h cores with x86-64 instruction set support. This
               includes MOVBE, F16C, BMI, AVX, PCL_MUL, AES, SSE4.2, SSE4.1, CX16, ABM, SSE4A,
               SSSE3, SSE3, SSE2, SSE, MMX and 64-bit instruction set extensions.

           winchip-c6
               IDT WinChip C6 CPU, dealt in same way as i486 with additional MMX instruction set
               support.

           winchip2
               IDT WinChip 2 CPU, dealt in same way as i486 with additional MMX and 3DNow!
               instruction set support.

           c3  VIA C3 CPU with MMX and 3DNow! instruction set support.  (No scheduling is
               implemented for this chip.)

           c3-2
               VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE instruction set support.  (No
               scheduling is implemented for this chip.)

           geode
               AMD Geode embedded processor with MMX and 3DNow! instruction set support.

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code, except for the ABI
           and the set of available instructions.  While picking a specific cpu-type schedules
           things appropriately for that particular chip, the compiler does not generate any code
           that cannot run on the default machine type unless you use a -march=cpu-type option.
           For example, if GCC is configured for i686-pc-linux-gnu then -mtune=pentium4 generates
           code that is tuned for Pentium 4 but still runs on i686 machines.

           The choices for cpu-type are the same as for -march.  In addition, -mtune supports 2
           extra choices for cpu-type:

           generic
               Produce code optimized for the most common IA32/AMD64/EM64T processors.  If you
               know the CPU on which your code will run, then you should use the corresponding
               -mtune or -march option instead of -mtune=generic.  But, if you do not know
               exactly what CPU users of your application will have, then you should use this
               option.

               As new processors are deployed in the marketplace, the behavior of this option
               will change.  Therefore, if you upgrade to a newer version of GCC, code generation
               controlled by this option will change to reflect the processors that are most
               common at the time that version of GCC is released.

               There is no -march=generic option because -march indicates the instruction set the
               compiler can use, and there is no generic instruction set applicable to all
               processors.  In contrast, -mtune indicates the processor (or, in this case,
               collection of processors) for which the code is optimized.

           intel
               Produce code optimized for the most current Intel processors, which are Haswell
               and Silvermont for this version of GCC.  If you know the CPU on which your code
               will run, then you should use the corresponding -mtune or -march option instead of
               -mtune=intel.  But, if you want your application performs better on both Haswell
               and Silvermont, then you should use this option.

               As new Intel processors are deployed in the marketplace, the behavior of this
               option will change.  Therefore, if you upgrade to a newer version of GCC, code
               generation controlled by this option will change to reflect the most current Intel
               processors at the time that version of GCC is released.

               There is no -march=intel option because -march indicates the instruction set the
               compiler can use, and there is no common instruction set applicable to all
               processors.  In contrast, -mtune indicates the processor (or, in this case,
               collection of processors) for which the code is optimized.

       -mcpu=cpu-type
           A deprecated synonym for -mtune.

       -mfpmath=unit
           Generate floating-point arithmetic for selected unit unit.  The choices for unit are:

           387 Use the standard 387 floating-point coprocessor present on the majority of chips
               and emulated otherwise.  Code compiled with this option runs almost everywhere.
               The temporary results are computed in 80-bit precision instead of the precision
               specified by the type, resulting in slightly different results compared to most of
               other chips.  See -ffloat-store for more detailed description.

               This is the default choice for x86-32 targets.

           sse Use scalar floating-point instructions present in the SSE instruction set.  This
               instruction set is supported by Pentium III and newer chips, and in the AMD line
               by Athlon-4, Athlon XP and Athlon MP chips.  The earlier version of the SSE
               instruction set supports only single-precision arithmetic, thus the double and
               extended-precision arithmetic are still done using 387.  A later version, present
               only in Pentium 4 and AMD x86-64 chips, supports double-precision arithmetic too.

               For the x86-32 compiler, you must use -march=cpu-type, -msse or -msse2 switches to
               enable SSE extensions and make this option effective.  For the x86-64 compiler,
               these extensions are enabled by default.

               The resulting code should be considerably faster in the majority of cases and
               avoid the numerical instability problems of 387 code, but may break some existing
               code that expects temporaries to be 80 bits.

               This is the default choice for the x86-64 compiler.

           sse,387
           sse+387
           both
               Attempt to utilize both instruction sets at once.  This effectively doubles the
               amount of available registers, and on chips with separate execution units for 387
               and SSE the execution resources too.  Use this option with care, as it is still
               experimental, because the GCC register allocator does not model separate
               functional units well, resulting in unstable performance.

       -masm=dialect
           Output assembly instructions using selected dialect.  Also affects which dialect is
           used for basic "asm" and extended "asm". Supported choices (in dialect order) are att
           or intel. The default is att. Darwin does not support intel.

       -mieee-fp
       -mno-ieee-fp
           Control whether or not the compiler uses IEEE floating-point comparisons.  These
           correctly handle the case where the result of a comparison is unordered.

       -msoft-float
           Generate output containing library calls for floating point.

           Warning: the requisite libraries are not part of GCC.  Normally the facilities of the
           machine's usual C compiler are used, but this can't be done directly in cross-
           compilation.  You must make your own arrangements to provide suitable library
           functions for cross-compilation.

           On machines where a function returns floating-point results in the 80387 register
           stack, some floating-point opcodes may be emitted even if -msoft-float is used.

       -mno-fp-ret-in-387
           Do not use the FPU registers for return values of functions.

           The usual calling convention has functions return values of types "float" and "double"
           in an FPU register, even if there is no FPU.  The idea is that the operating system
           should emulate an FPU.

           The option -mno-fp-ret-in-387 causes such values to be returned in ordinary CPU
           registers instead.

       -mno-fancy-math-387
           Some 387 emulators do not support the "sin", "cos" and "sqrt" instructions for the
           387.  Specify this option to avoid generating those instructions.  This option is the
           default on OpenBSD and NetBSD.  This option is overridden when -march indicates that
           the target CPU always has an FPU and so the instruction does not need emulation.
           These instructions are not generated unless you also use the
           -funsafe-math-optimizations switch.

       -malign-double
       -mno-align-double
           Control whether GCC aligns "double", "long double", and "long long" variables on a
           two-word boundary or a one-word boundary.  Aligning "double" variables on a two-word
           boundary produces code that runs somewhat faster on a Pentium at the expense of more
           memory.

           On x86-64, -malign-double is enabled by default.

           Warning: if you use the -malign-double switch, structures containing the above types
           are aligned differently than the published application binary interface specifications
           for the x86-32 and are not binary compatible with structures in code compiled without
           that switch.

       -m96bit-long-double
       -m128bit-long-double
           These switches control the size of "long double" type.  The x86-32 application binary
           interface specifies the size to be 96 bits, so -m96bit-long-double is the default in
           32-bit mode.

           Modern architectures (Pentium and newer) prefer "long double" to be aligned to an 8-
           or 16-byte boundary.  In arrays or structures conforming to the ABI, this is not
           possible.  So specifying -m128bit-long-double aligns "long double" to a 16-byte
           boundary by padding the "long double" with an additional 32-bit zero.

           In the x86-64 compiler, -m128bit-long-double is the default choice as its ABI
           specifies that "long double" is aligned on 16-byte boundary.

           Notice that neither of these options enable any extra precision over the x87 standard
           of 80 bits for a "long double".

           Warning: if you override the default value for your target ABI, this changes the size
           of structures and arrays containing "long double" variables, as well as modifying the
           function calling convention for functions taking "long double".  Hence they are not
           binary-compatible with code compiled without that switch.

       -mlong-double-64
       -mlong-double-80
       -mlong-double-128
           These switches control the size of "long double" type. A size of 64 bits makes the
           "long double" type equivalent to the "double" type. This is the default for 32-bit
           Bionic C library.  A size of 128 bits makes the "long double" type equivalent to the
           "__float128" type. This is the default for 64-bit Bionic C library.

           Warning: if you override the default value for your target ABI, this changes the size
           of structures and arrays containing "long double" variables, as well as modifying the
           function calling convention for functions taking "long double".  Hence they are not
           binary-compatible with code compiled without that switch.

       -malign-data=type
           Control how GCC aligns variables.  Supported values for type are compat uses increased
           alignment value compatible uses GCC 4.8 and earlier, abi uses alignment value as
           specified by the psABI, and cacheline uses increased alignment value to match the
           cache line size.  compat is the default.

       -mlarge-data-threshold=threshold
           When -mcmodel=medium is specified, data objects larger than threshold are placed in
           the large data section.  This value must be the same across all objects linked into
           the binary, and defaults to 65535.

       -mrtd
           Use a different function-calling convention, in which functions that take a fixed
           number of arguments return with the "ret num" instruction, which pops their arguments
           while returning.  This saves one instruction in the caller since there is no need to
           pop the arguments there.

           You can specify that an individual function is called with this calling sequence with
           the function attribute "stdcall".  You can also override the -mrtd option by using the
           function attribute "cdecl".

           Warning: this calling convention is incompatible with the one normally used on Unix,
           so you cannot use it if you need to call libraries compiled with the Unix compiler.

           Also, you must provide function prototypes for all functions that take variable
           numbers of arguments (including "printf"); otherwise incorrect code is generated for
           calls to those functions.

           In addition, seriously incorrect code results if you call a function with too many
           arguments.  (Normally, extra arguments are harmlessly ignored.)

       -mregparm=num
           Control how many registers are used to pass integer arguments.  By default, no
           registers are used to pass arguments, and at most 3 registers can be used.  You can
           control this behavior for a specific function by using the function attribute
           "regparm".

           Warning: if you use this switch, and num is nonzero, then you must build all modules
           with the same value, including any libraries.  This includes the system libraries and
           startup modules.

       -msseregparm
           Use SSE register passing conventions for float and double arguments and return values.
           You can control this behavior for a specific function by using the function attribute
           "sseregparm".

           Warning: if you use this switch then you must build all modules with the same value,
           including any libraries.  This includes the system libraries and startup modules.

       -mvect8-ret-in-mem
           Return 8-byte vectors in memory instead of MMX registers.  This is the default on
           Solaris@tie{}8 and 9 and VxWorks to match the ABI of the Sun Studio compilers until
           version 12.  Later compiler versions (starting with Studio 12 Update@tie{}1) follow
           the ABI used by other x86 targets, which is the default on Solaris@tie{}10 and later.
           Only use this option if you need to remain compatible with existing code produced by
           those previous compiler versions or older versions of GCC.

       -mpc32
       -mpc64
       -mpc80
           Set 80387 floating-point precision to 32, 64 or 80 bits.  When -mpc32 is specified,
           the significands of results of floating-point operations are rounded to 24 bits
           (single precision); -mpc64 rounds the significands of results of floating-point
           operations to 53 bits (double precision) and -mpc80 rounds the significands of results
           of floating-point operations to 64 bits (extended double precision), which is the
           default.  When this option is used, floating-point operations in higher precisions are
           not available to the programmer without setting the FPU control word explicitly.

           Setting the rounding of floating-point operations to less than the default 80 bits can
           speed some programs by 2% or more.  Note that some mathematical libraries assume that
           extended-precision (80-bit) floating-point operations are enabled by default; routines
           in such libraries could suffer significant loss of accuracy, typically through so-
           called "catastrophic cancellation", when this option is used to set the precision to
           less than extended precision.

       -mstackrealign
           Realign the stack at entry.  On the x86, the -mstackrealign option generates an
           alternate prologue and epilogue that realigns the run-time stack if necessary.  This
           supports mixing legacy codes that keep 4-byte stack alignment with modern codes that
           keep 16-byte stack alignment for SSE compatibility.  See also the attribute
           "force_align_arg_pointer", applicable to individual functions.

       -mpreferred-stack-boundary=num
           Attempt to keep the stack boundary aligned to a 2 raised to num byte boundary.  If
           -mpreferred-stack-boundary is not specified, the default is 4 (16 bytes or 128 bits).

           Warning: When generating code for the x86-64 architecture with SSE extensions
           disabled, -mpreferred-stack-boundary=3 can be used to keep the stack boundary aligned
           to 8 byte boundary.  Since x86-64 ABI require 16 byte stack alignment, this is ABI
           incompatible and intended to be used in controlled environment where stack space is
           important limitation.  This option leads to wrong code when functions compiled with 16
           byte stack alignment (such as functions from a standard library) are called with
           misaligned stack.  In this case, SSE instructions may lead to misaligned memory access
           traps.  In addition, variable arguments are handled incorrectly for 16 byte aligned
           objects (including x87 long double and __int128), leading to wrong results.  You must
           build all modules with -mpreferred-stack-boundary=3, including any libraries.  This
           includes the system libraries and startup modules.

       -mincoming-stack-boundary=num
           Assume the incoming stack is aligned to a 2 raised to num byte boundary.  If
           -mincoming-stack-boundary is not specified, the one specified by
           -mpreferred-stack-boundary is used.

           On Pentium and Pentium Pro, "double" and "long double" values should be aligned to an
           8-byte boundary (see -malign-double) or suffer significant run time performance
           penalties.  On Pentium III, the Streaming SIMD Extension (SSE) data type "__m128" may
           not work properly if it is not 16-byte aligned.

           To ensure proper alignment of this values on the stack, the stack boundary must be as
           aligned as that required by any value stored on the stack.  Further, every function
           must be generated such that it keeps the stack aligned.  Thus calling a function
           compiled with a higher preferred stack boundary from a function compiled with a lower
           preferred stack boundary most likely misaligns the stack.  It is recommended that
           libraries that use callbacks always use the default setting.

           This extra alignment does consume extra stack space, and generally increases code
           size.  Code that is sensitive to stack space usage, such as embedded systems and
           operating system kernels, may want to reduce the preferred alignment to
           -mpreferred-stack-boundary=2.

       -mmmx
       -msse
       -msse2
       -msse3
       -mssse3
       -msse4
       -msse4a
       -msse4.1
       -msse4.2
       -mavx
       -mavx2
       -mavx512f
       -mavx512pf
       -mavx512er
       -mavx512cd
       -msha
       -maes
       -mpclmul
       -mclfushopt
       -mfsgsbase
       -mrdrnd
       -mf16c
       -mfma
       -mfma4
       -mno-fma4
       -mprefetchwt1
       -mxop
       -mlwp
       -m3dnow
       -mpopcnt
       -mabm
       -mbmi
       -mbmi2
       -mlzcnt
       -mfxsr
       -mxsave
       -mxsaveopt
       -mxsavec
       -mxsaves
       -mrtm
       -mtbm
       -mmpx
       -mmwaitx
           These switches enable the use of instructions in the MMX, SSE, SSE2, SSE3, SSSE3,
           SSE4.1, AVX, AVX2, AVX512F, AVX512PF, AVX512ER, AVX512CD, SHA, AES, PCLMUL, FSGSBASE,
           RDRND, F16C, FMA, SSE4A, FMA4, XOP, LWP, ABM, BMI, BMI2, FXSR, XSAVE, XSAVEOPT, LZCNT,
           RTM, MPX, MWAITX or 3DNow!  extended instruction sets.  Each has a corresponding -mno-
           option to disable use of these instructions.

           These extensions are also available as built-in functions: see x86 Built-in Functions,
           for details of the functions enabled and disabled by these switches.

           To generate SSE/SSE2 instructions automatically from floating-point code (as opposed
           to 387 instructions), see -mfpmath=sse.

           GCC depresses SSEx instructions when -mavx is used. Instead, it generates new AVX
           instructions or AVX equivalence for all SSEx instructions when needed.

           These options enable GCC to use these extended instructions in generated code, even
           without -mfpmath=sse.  Applications that perform run-time CPU detection must compile
           separate files for each supported architecture, using the appropriate flags.  In
           particular, the file containing the CPU detection code should be compiled without
           these options.

       -mdump-tune-features
           This option instructs GCC to dump the names of the x86 performance tuning features and
           default settings. The names can be used in -mtune-ctrl=feature-list.

       -mtune-ctrl=feature-list
           This option is used to do fine grain control of x86 code generation features.
           feature-list is a comma separated list of feature names. See also
           -mdump-tune-features. When specified, the feature is turned on if it is not preceded
           with ^, otherwise, it is turned off.  -mtune-ctrl=feature-list is intended to be used
           by GCC developers. Using it may lead to code paths not covered by testing and can
           potentially result in compiler ICEs or runtime errors.

       -mno-default
           This option instructs GCC to turn off all tunable features. See also
           -mtune-ctrl=feature-list and -mdump-tune-features.

       -mcld
           This option instructs GCC to emit a "cld" instruction in the prologue of functions
           that use string instructions.  String instructions depend on the DF flag to select
           between autoincrement or autodecrement mode.  While the ABI specifies the DF flag to
           be cleared on function entry, some operating systems violate this specification by not
           clearing the DF flag in their exception dispatchers.  The exception handler can be
           invoked with the DF flag set, which leads to wrong direction mode when string
           instructions are used.  This option can be enabled by default on 32-bit x86 targets by
           configuring GCC with the --enable-cld configure option.  Generation of "cld"
           instructions can be suppressed with the -mno-cld compiler option in this case.

       -mvzeroupper
           This option instructs GCC to emit a "vzeroupper" instruction before a transfer of
           control flow out of the function to minimize the AVX to SSE transition penalty as well
           as remove unnecessary "zeroupper" intrinsics.

       -mprefer-avx128
           This option instructs GCC to use 128-bit AVX instructions instead of 256-bit AVX
           instructions in the auto-vectorizer.

       -mcx16
           This option enables GCC to generate "CMPXCHG16B" instructions.  "CMPXCHG16B" allows
           for atomic operations on 128-bit double quadword (or oword) data types.  This is
           useful for high-resolution counters that can be updated by multiple processors (or
           cores).  This instruction is generated as part of atomic built-in functions: see
           __sync Builtins or __atomic Builtins for details.

       -msahf
           This option enables generation of "SAHF" instructions in 64-bit code.  Early Intel
           Pentium 4 CPUs with Intel 64 support, prior to the introduction of Pentium 4 G1 step
           in December 2005, lacked the "LAHF" and "SAHF" instructions which are supported by
           AMD64.  These are load and store instructions, respectively, for certain status flags.
           In 64-bit mode, the "SAHF" instruction is used to optimize "fmod", "drem", and
           "remainder" built-in functions; see Other Builtins for details.

       -mmovbe
           This option enables use of the "movbe" instruction to implement "__builtin_bswap32"
           and "__builtin_bswap64".

       -mcrc32
           This option enables built-in functions "__builtin_ia32_crc32qi",
           "__builtin_ia32_crc32hi", "__builtin_ia32_crc32si" and "__builtin_ia32_crc32di" to
           generate the "crc32" machine instruction.

       -mrecip
           This option enables use of "RCPSS" and "RSQRTSS" instructions (and their vectorized
           variants "RCPPS" and "RSQRTPS") with an additional Newton-Raphson step to increase
           precision instead of "DIVSS" and "SQRTSS" (and their vectorized variants) for single-
           precision floating-point arguments.  These instructions are generated only when
           -funsafe-math-optimizations is enabled together with -finite-math-only and
           -fno-trapping-math.  Note that while the throughput of the sequence is higher than the
           throughput of the non-reciprocal instruction, the precision of the sequence can be
           decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994).

           Note that GCC implements "1.0f/sqrtf(x)" in terms of "RSQRTSS" (or "RSQRTPS") already
           with -ffast-math (or the above option combination), and doesn't need -mrecip.

           Also note that GCC emits the above sequence with additional Newton-Raphson step for
           vectorized single-float division and vectorized "sqrtf(x)" already with -ffast-math
           (or the above option combination), and doesn't need -mrecip.

       -mrecip=opt
           This option controls which reciprocal estimate instructions may be used.  opt is a
           comma-separated list of options, which may be preceded by a ! to invert the option:

           all Enable all estimate instructions.

           default
               Enable the default instructions, equivalent to -mrecip.

           none
               Disable all estimate instructions, equivalent to -mno-recip.

           div Enable the approximation for scalar division.

           vec-div
               Enable the approximation for vectorized division.

           sqrt
               Enable the approximation for scalar square root.

           vec-sqrt
               Enable the approximation for vectorized square root.

           So, for example, -mrecip=all,!sqrt enables all of the reciprocal approximations,
           except for square root.

       -mveclibabi=type
           Specifies the ABI type to use for vectorizing intrinsics using an external library.
           Supported values for type are svml for the Intel short vector math library and acml
           for the AMD math core library.  To use this option, both -ftree-vectorize and
           -funsafe-math-optimizations have to be enabled, and an SVML or ACML ABI-compatible
           library must be specified at link time.

           GCC currently emits calls to "vmldExp2", "vmldLn2", "vmldLog102", "vmldLog102",
           "vmldPow2", "vmldTanh2", "vmldTan2", "vmldAtan2", "vmldAtanh2", "vmldCbrt2",
           "vmldSinh2", "vmldSin2", "vmldAsinh2", "vmldAsin2", "vmldCosh2", "vmldCos2",
           "vmldAcosh2", "vmldAcos2", "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsLog104",
           "vmlsPow4", "vmlsTanh4", "vmlsTan4", "vmlsAtan4", "vmlsAtanh4", "vmlsCbrt4",
           "vmlsSinh4", "vmlsSin4", "vmlsAsinh4", "vmlsAsin4", "vmlsCosh4", "vmlsCos4",
           "vmlsAcosh4" and "vmlsAcos4" for corresponding function type when -mveclibabi=svml is
           used, and "__vrd2_sin", "__vrd2_cos", "__vrd2_exp", "__vrd2_log", "__vrd2_log2",
           "__vrd2_log10", "__vrs4_sinf", "__vrs4_cosf", "__vrs4_expf", "__vrs4_logf",
           "__vrs4_log2f", "__vrs4_log10f" and "__vrs4_powf" for the corresponding function type
           when -mveclibabi=acml is used.

       -mabi=name
           Generate code for the specified calling convention.  Permissible values are sysv for
           the ABI used on GNU/Linux and other systems, and ms for the Microsoft ABI.  The
           default is to use the Microsoft ABI when targeting Microsoft Windows and the SysV ABI
           on all other systems.  You can control this behavior for specific functions by using
           the function attributes "ms_abi" and "sysv_abi".

       -mtls-dialect=type
           Generate code to access thread-local storage using the gnu or gnu2 conventions.  gnu
           is the conservative default; gnu2 is more efficient, but it may add compile- and run-
           time requirements that cannot be satisfied on all systems.

       -mpush-args
       -mno-push-args
           Use PUSH operations to store outgoing parameters.  This method is shorter and usually
           equally fast as method using SUB/MOV operations and is enabled by default.  In some
           cases disabling it may improve performance because of improved scheduling and reduced
           dependencies.

       -maccumulate-outgoing-args
           If enabled, the maximum amount of space required for outgoing arguments is computed in
           the function prologue.  This is faster on most modern CPUs because of reduced
           dependencies, improved scheduling and reduced stack usage when the preferred stack
           boundary is not equal to 2.  The drawback is a notable increase in code size.  This
           switch implies -mno-push-args.

       -mthreads
           Support thread-safe exception handling on MinGW.  Programs that rely on thread-safe
           exception handling must compile and link all code with the -mthreads option.  When
           compiling, -mthreads defines -D_MT; when linking, it links in a special thread helper
           library -lmingwthrd which cleans up per-thread exception-handling data.

       -mno-align-stringops
           Do not align the destination of inlined string operations.  This switch reduces code
           size and improves performance in case the destination is already aligned, but GCC
           doesn't know about it.

       -minline-all-stringops
           By default GCC inlines string operations only when the destination is known to be
           aligned to least a 4-byte boundary.  This enables more inlining and increases code
           size, but may improve performance of code that depends on fast "memcpy", "strlen", and
           "memset" for short lengths.

       -minline-stringops-dynamically
           For string operations of unknown size, use run-time checks with inline code for small
           blocks and a library call for large blocks.

       -mstringop-strategy=alg
           Override the internal decision heuristic for the particular algorithm to use for
           inlining string operations.  The allowed values for alg are:

           rep_byte
           rep_4byte
           rep_8byte
               Expand using i386 "rep" prefix of the specified size.

           byte_loop
           loop
           unrolled_loop
               Expand into an inline loop.

           libcall
               Always use a library call.

       -mmemcpy-strategy=strategy
           Override the internal decision heuristic to decide if "__builtin_memcpy" should be
           inlined and what inline algorithm to use when the expected size of the copy operation
           is known. strategy is a comma-separated list of alg:max_size:dest_align triplets.  alg
           is specified in -mstringop-strategy, max_size specifies the max byte size with which
           inline algorithm alg is allowed.  For the last triplet, the max_size must be "-1". The
           max_size of the triplets in the list must be specified in increasing order.  The
           minimal byte size for alg is 0 for the first triplet and "max_size + 1" of the
           preceding range.

       -mmemset-strategy=strategy
           The option is similar to -mmemcpy-strategy= except that it is to control
           "__builtin_memset" expansion.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf functions.  This avoids the
           instructions to save, set up, and restore frame pointers and makes an extra register
           available in leaf functions.  The option -fomit-leaf-frame-pointer removes the frame
           pointer for leaf functions, which might make debugging harder.

       -mtls-direct-seg-refs
       -mno-tls-direct-seg-refs
           Controls whether TLS variables may be accessed with offsets from the TLS segment
           register (%gs for 32-bit, %fs for 64-bit), or whether the thread base pointer must be
           added.  Whether or not this is valid depends on the operating system, and whether it
           maps the segment to cover the entire TLS area.

           For systems that use the GNU C Library, the default is on.

       -msse2avx
       -mno-sse2avx
           Specify that the assembler should encode SSE instructions with VEX prefix.  The option
           -mavx turns this on by default.

       -mfentry
       -mno-fentry
           If profiling is active (-pg), put the profiling counter call before the prologue.
           Note: On x86 architectures the attribute "ms_hook_prologue" isn't possible at the
           moment for -mfentry and -pg.

       -mrecord-mcount
       -mno-record-mcount
           If profiling is active (-pg), generate a __mcount_loc section that contains pointers
           to each profiling call. This is useful for automatically patching and out calls.

       -mnop-mcount
       -mno-nop-mcount
           If profiling is active (-pg), generate the calls to the profiling functions as nops.
           This is useful when they should be patched in later dynamically. This is likely only
           useful together with -mrecord-mcount.

       -mskip-rax-setup
       -mno-skip-rax-setup
           When generating code for the x86-64 architecture with SSE extensions disabled,
           -skip-rax-setup can be used to skip setting up RAX register when there are no variable
           arguments passed in vector registers.

           Warning: Since RAX register is used to avoid unnecessarily saving vector registers on
           stack when passing variable arguments, the impacts of this option are callees may
           waste some stack space, misbehave or jump to a random location.  GCC 4.4 or newer
           don't have those issues, regardless the RAX register value.

       -m8bit-idiv
       -mno-8bit-idiv
           On some processors, like Intel Atom, 8-bit unsigned integer divide is much faster than
           32-bit/64-bit integer divide.  This option generates a run-time check.  If both
           dividend and divisor are within range of 0 to 255, 8-bit unsigned integer divide is
           used instead of 32-bit/64-bit integer divide.

       -mavx256-split-unaligned-load
       -mavx256-split-unaligned-store
           Split 32-byte AVX unaligned load and store.

       -mstack-protector-guard=guard
           Generate stack protection code using canary at guard.  Supported locations are global
           for global canary or tls for per-thread canary in the TLS block (the default).  This
           option has effect only when -fstack-protector or -fstack-protector-all is specified.

       These -m switches are supported in addition to the above on x86-64 processors in 64-bit
       environments.

       -m32
       -m64
       -mx32
       -m16
           Generate code for a 16-bit, 32-bit or 64-bit environment.  The -m32 option sets "int",
           "long", and pointer types to 32 bits, and generates code that runs on any i386 system.

           The -m64 option sets "int" to 32 bits and "long" and pointer types to 64 bits, and
           generates code for the x86-64 architecture.  For Darwin only the -m64 option also
           turns off the -fno-pic and -mdynamic-no-pic options.

           The -mx32 option sets "int", "long", and pointer types to 32 bits, and generates code
           for the x86-64 architecture.

           The -m16 option is the same as -m32, except for that it outputs the ".code16gcc"
           assembly directive at the beginning of the assembly output so that the binary can run
           in 16-bit mode.

       -mno-red-zone
           Do not use a so-called "red zone" for x86-64 code.  The red zone is mandated by the
           x86-64 ABI; it is a 128-byte area beyond the location of the stack pointer that is not
           modified by signal or interrupt handlers and therefore can be used for temporary data
           without adjusting the stack pointer.  The flag -mno-red-zone disables this red zone.

       -mcmodel=small
           Generate code for the small code model: the program and its symbols must be linked in
           the lower 2 GB of the address space.  Pointers are 64 bits.  Programs can be
           statically or dynamically linked.  This is the default code model.

       -mcmodel=kernel
           Generate code for the kernel code model.  The kernel runs in the negative 2 GB of the
           address space.  This model has to be used for Linux kernel code.

       -mcmodel=medium
           Generate code for the medium model: the program is linked in the lower 2 GB of the
           address space.  Small symbols are also placed there.  Symbols with sizes larger than
           -mlarge-data-threshold are put into large data or BSS sections and can be located
           above 2GB.  Programs can be statically or dynamically linked.

       -mcmodel=large
           Generate code for the large model.  This model makes no assumptions about addresses
           and sizes of sections.

       -maddress-mode=long
           Generate code for long address mode.  This is only supported for 64-bit and x32
           environments.  It is the default address mode for 64-bit environments.

       -maddress-mode=short
           Generate code for short address mode.  This is only supported for 32-bit and x32
           environments.  It is the default address mode for 32-bit and x32 environments.

       x86 Windows Options

       These additional options are available for Microsoft Windows targets:

       -mconsole
           This option specifies that a console application is to be generated, by instructing
           the linker to set the PE header subsystem type required for console applications.
           This option is available for Cygwin and MinGW targets and is enabled by default on
           those targets.

       -mdll
           This option is available for Cygwin and MinGW targets.  It specifies that a DLL---a
           dynamic link library---is to be generated, enabling the selection of the required
           runtime startup object and entry point.

       -mnop-fun-dllimport
           This option is available for Cygwin and MinGW targets.  It specifies that the
           "dllimport" attribute should be ignored.

       -mthread
           This option is available for MinGW targets. It specifies that MinGW-specific thread
           support is to be used.

       -municode
           This option is available for MinGW-w64 targets.  It causes the "UNICODE" preprocessor
           macro to be predefined, and chooses Unicode-capable runtime startup code.

       -mwin32
           This option is available for Cygwin and MinGW targets.  It specifies that the typical
           Microsoft Windows predefined macros are to be set in the pre-processor, but does not
           influence the choice of runtime library/startup code.

       -mwindows
           This option is available for Cygwin and MinGW targets.  It specifies that a GUI
           application is to be generated by instructing the linker to set the PE header
           subsystem type appropriately.

       -fno-set-stack-executable
           This option is available for MinGW targets. It specifies that the executable flag for
           the stack used by nested functions isn't set. This is necessary for binaries running
           in kernel mode of Microsoft Windows, as there the User32 API, which is used to set
           executable privileges, isn't available.

       -fwritable-relocated-rdata
           This option is available for MinGW and Cygwin targets.  It specifies that relocated-
           data in read-only section is put into .data section.  This is a necessary for older
           runtimes not supporting modification of .rdata sections for pseudo-relocation.

       -mpe-aligned-commons
           This option is available for Cygwin and MinGW targets.  It specifies that the GNU
           extension to the PE file format that permits the correct alignment of COMMON variables
           should be used when generating code.  It is enabled by default if GCC detects that the
           target assembler found during configuration supports the feature.

       See also under x86 Options for standard options.

       Xstormy16 Options

       These options are defined for Xstormy16:

       -msim
           Choose startup files and linker script suitable for the simulator.

       Xtensa Options

       These options are supported for Xtensa targets:

       -mconst16
       -mno-const16
           Enable or disable use of "CONST16" instructions for loading constant values.  The
           "CONST16" instruction is currently not a standard option from Tensilica.  When
           enabled, "CONST16" instructions are always used in place of the standard "L32R"
           instructions.  The use of "CONST16" is enabled by default only if the "L32R"
           instruction is not available.

       -mfused-madd
       -mno-fused-madd
           Enable or disable use of fused multiply/add and multiply/subtract instructions in the
           floating-point option.  This has no effect if the floating-point option is not also
           enabled.  Disabling fused multiply/add and multiply/subtract instructions forces the
           compiler to use separate instructions for the multiply and add/subtract operations.
           This may be desirable in some cases where strict IEEE 754-compliant results are
           required: the fused multiply add/subtract instructions do not round the intermediate
           result, thereby producing results with more bits of precision than specified by the
           IEEE standard.  Disabling fused multiply add/subtract instructions also ensures that
           the program output is not sensitive to the compiler's ability to combine multiply and
           add/subtract operations.

       -mserialize-volatile
       -mno-serialize-volatile
           When this option is enabled, GCC inserts "MEMW" instructions before "volatile" memory
           references to guarantee sequential consistency.  The default is -mserialize-volatile.
           Use -mno-serialize-volatile to omit the "MEMW" instructions.

       -mforce-no-pic
           For targets, like GNU/Linux, where all user-mode Xtensa code must be position-
           independent code (PIC), this option disables PIC for compiling kernel code.

       -mtext-section-literals
       -mno-text-section-literals
           These options control the treatment of literal pools.  The default is
           -mno-text-section-literals, which places literals in a separate section in the output
           file.  This allows the literal pool to be placed in a data RAM/ROM, and it also allows
           the linker to combine literal pools from separate object files to remove redundant
           literals and improve code size.  With -mtext-section-literals, the literals are
           interspersed in the text section in order to keep them as close as possible to their
           references.  This may be necessary for large assembly files.

       -mtarget-align
       -mno-target-align
           When this option is enabled, GCC instructs the assembler to automatically align
           instructions to reduce branch penalties at the expense of some code density.  The
           assembler attempts to widen density instructions to align branch targets and the
           instructions following call instructions.  If there are not enough preceding safe
           density instructions to align a target, no widening is performed.  The default is
           -mtarget-align.  These options do not affect the treatment of auto-aligned
           instructions like "LOOP", which the assembler always aligns, either by widening
           density instructions or by inserting NOP instructions.

       -mlongcalls
       -mno-longcalls
           When this option is enabled, GCC instructs the assembler to translate direct calls to
           indirect calls unless it can determine that the target of a direct call is in the
           range allowed by the call instruction.  This translation typically occurs for calls to
           functions in other source files.  Specifically, the assembler translates a direct
           "CALL" instruction into an "L32R" followed by a "CALLX" instruction.  The default is
           -mno-longcalls.  This option should be used in programs where the call target can
           potentially be out of range.  This option is implemented in the assembler, not the
           compiler, so the assembly code generated by GCC still shows direct call
           instructions---look at the disassembled object code to see the actual instructions.
           Note that the assembler uses an indirect call for every cross-file call, not just
           those that really are out of range.

       zSeries Options

       These are listed under

   Options for Code Generation Conventions
       These machine-independent options control the interface conventions used in code
       generation.

       Most of them have both positive and negative forms; the negative form of -ffoo is
       -fno-foo.  In the table below, only one of the forms is listed---the one that is not the
       default.  You can figure out the other form by either removing no- or adding it.

       -fbounds-check
           For front ends that support it, generate additional code to check that indices used to
           access arrays are within the declared range.  This is currently only supported by the
           Java and Fortran front ends, where this option defaults to true and false
           respectively.

       -fstack-reuse=reuse-level
           This option controls stack space reuse for user declared local/auto variables and
           compiler generated temporaries.  reuse_level can be all, named_vars, or none. all
           enables stack reuse for all local variables and temporaries, named_vars enables the
           reuse only for user defined local variables with names, and none disables stack reuse
           completely. The default value is all. The option is needed when the program extends
           the lifetime of a scoped local variable or a compiler generated temporary beyond the
           end point defined by the language.  When a lifetime of a variable ends, and if the
           variable lives in memory, the optimizing compiler has the freedom to reuse its stack
           space with other temporaries or scoped local variables whose live range does not
           overlap with it. Legacy code extending local lifetime is likely to break with the
           stack reuse optimization.

           For example,

                      int *p;
                      {
                        int local1;

                        p = &local1;
                        local1 = 10;
                        ....
                      }
                      {
                         int local2;
                         local2 = 20;
                         ...
                      }

                      if (*p == 10)  // out of scope use of local1
                        {

                        }

           Another example:

                      struct A
                      {
                          A(int k) : i(k), j(k) { }
                          int i;
                          int j;
                      };

                      A *ap;

                      void foo(const A& ar)
                      {
                         ap = &ar;
                      }

                      void bar()
                      {
                         foo(A(10)); // temp object's lifetime ends when foo returns

                         {
                           A a(20);
                           ....
                         }
                         ap->i+= 10;  // ap references out of scope temp whose space
                                      // is reused with a. What is the value of ap->i?
                      }

           The lifetime of a compiler generated temporary is well defined by the C++ standard.
           When a lifetime of a temporary ends, and if the temporary lives in memory, the
           optimizing compiler has the freedom to reuse its stack space with other temporaries or
           scoped local variables whose live range does not overlap with it. However some of the
           legacy code relies on the behavior of older compilers in which temporaries' stack
           space is not reused, the aggressive stack reuse can lead to runtime errors. This
           option is used to control the temporary stack reuse optimization.

       -ftrapv
           This option generates traps for signed overflow on addition, subtraction,
           multiplication operations.

       -fwrapv
           This option instructs the compiler to assume that signed arithmetic overflow of
           addition, subtraction and multiplication wraps around using twos-complement
           representation.  This flag enables some optimizations and disables others.  This
           option is enabled by default for the Java front end, as required by the Java language
           specification.

       -fexceptions
           Enable exception handling.  Generates extra code needed to propagate exceptions.  For
           some targets, this implies GCC generates frame unwind information for all functions,
           which can produce significant data size overhead, although it does not affect
           execution.  If you do not specify this option, GCC enables it by default for languages
           like C++ that normally require exception handling, and disables it for languages like
           C that do not normally require it.  However, you may need to enable this option when
           compiling C code that needs to interoperate properly with exception handlers written
           in C++.  You may also wish to disable this option if you are compiling older C++
           programs that don't use exception handling.

       -fnon-call-exceptions
           Generate code that allows trapping instructions to throw exceptions.  Note that this
           requires platform-specific runtime support that does not exist everywhere.  Moreover,
           it only allows trapping instructions to throw exceptions, i.e. memory references or
           floating-point instructions.  It does not allow exceptions to be thrown from arbitrary
           signal handlers such as "SIGALRM".

       -fdelete-dead-exceptions
           Consider that instructions that may throw exceptions but don't otherwise contribute to
           the execution of the program can be optimized away.  This option is enabled by default
           for the Ada front end, as permitted by the Ada language specification.  Optimization
           passes that cause dead exceptions to be removed are enabled independently at different
           optimization levels.

       -funwind-tables
           Similar to -fexceptions, except that it just generates any needed static data, but
           does not affect the generated code in any other way.  You normally do not need to
           enable this option; instead, a language processor that needs this handling enables it
           on your behalf.

       -fasynchronous-unwind-tables
           Generate unwind table in DWARF 2 format, if supported by target machine.  The table is
           exact at each instruction boundary, so it can be used for stack unwinding from
           asynchronous events (such as debugger or garbage collector).

       -fno-gnu-unique
           On systems with recent GNU assembler and C library, the C++ compiler uses the
           "STB_GNU_UNIQUE" binding to make sure that definitions of template static data members
           and static local variables in inline functions are unique even in the presence of
           "RTLD_LOCAL"; this is necessary to avoid problems with a library used by two different
           "RTLD_LOCAL" plugins depending on a definition in one of them and therefore
           disagreeing with the other one about the binding of the symbol.  But this causes
           "dlclose" to be ignored for affected DSOs; if your program relies on reinitialization
           of a DSO via "dlclose" and "dlopen", you can use -fno-gnu-unique.

       -fpcc-struct-return
           Return "short" "struct" and "union" values in memory like longer ones, rather than in
           registers.  This convention is less efficient, but it has the advantage of allowing
           intercallability between GCC-compiled files and files compiled with other compilers,
           particularly the Portable C Compiler (pcc).

           The precise convention for returning structures in memory depends on the target
           configuration macros.

           Short structures and unions are those whose size and alignment match that of some
           integer type.

           Warning: code compiled with the -fpcc-struct-return switch is not binary compatible
           with code compiled with the -freg-struct-return switch.  Use it to conform to a non-
           default application binary interface.

       -freg-struct-return
           Return "struct" and "union" values in registers when possible.  This is more efficient
           for small structures than -fpcc-struct-return.

           If you specify neither -fpcc-struct-return nor -freg-struct-return, GCC defaults to
           whichever convention is standard for the target.  If there is no standard convention,
           GCC defaults to -fpcc-struct-return, except on targets where GCC is the principal
           compiler.  In those cases, we can choose the standard, and we chose the more efficient
           register return alternative.

           Warning: code compiled with the -freg-struct-return switch is not binary compatible
           with code compiled with the -fpcc-struct-return switch.  Use it to conform to a non-
           default application binary interface.

       -fshort-enums
           Allocate to an "enum" type only as many bytes as it needs for the declared range of
           possible values.  Specifically, the "enum" type is equivalent to the smallest integer
           type that has enough room.

           Warning: the -fshort-enums switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Use it to conform to a non-
           default application binary interface.

       -fshort-double
           Use the same size for "double" as for "float".

           Warning: the -fshort-double switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Use it to conform to a non-
           default application binary interface.

       -fshort-wchar
           Override the underlying type for "wchar_t" to be "short unsigned int" instead of the
           default for the target.  This option is useful for building programs to run under
           WINE.

           Warning: the -fshort-wchar switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Use it to conform to a non-
           default application binary interface.

       -fno-common
           In C code, controls the placement of uninitialized global variables.  Unix C compilers
           have traditionally permitted multiple definitions of such variables in different
           compilation units by placing the variables in a common block.  This is the behavior
           specified by -fcommon, and is the default for GCC on most targets.  On the other hand,
           this behavior is not required by ISO C, and on some targets may carry a speed or code
           size penalty on variable references.  The -fno-common option specifies that the
           compiler should place uninitialized global variables in the data section of the object
           file, rather than generating them as common blocks.  This has the effect that if the
           same variable is declared (without "extern") in two different compilations, you get a
           multiple-definition error when you link them.  In this case, you must compile with
           -fcommon instead.  Compiling with -fno-common is useful on targets for which it
           provides better performance, or if you wish to verify that the program will work on
           other systems that always treat uninitialized variable declarations this way.

       -fno-ident
           Ignore the "#ident" directive.

       -finhibit-size-directive
           Don't output a ".size" assembler directive, or anything else that would cause trouble
           if the function is split in the middle, and the two halves are placed at locations far
           apart in memory.  This option is used when compiling crtstuff.c; you should not need
           to use it for anything else.

       -fverbose-asm
           Put extra commentary information in the generated assembly code to make it more
           readable.  This option is generally only of use to those who actually need to read the
           generated assembly code (perhaps while debugging the compiler itself).

           -fno-verbose-asm, the default, causes the extra information to be omitted and is
           useful when comparing two assembler files.

       -frecord-gcc-switches
           This switch causes the command line used to invoke the compiler to be recorded into
           the object file that is being created.  This switch is only implemented on some
           targets and the exact format of the recording is target and binary file format
           dependent, but it usually takes the form of a section containing ASCII text.  This
           switch is related to the -fverbose-asm switch, but that switch only records
           information in the assembler output file as comments, so it never reaches the object
           file.  See also -grecord-gcc-switches for another way of storing compiler options into
           the object file.

       -fpic
           Generate position-independent code (PIC) suitable for use in a shared library, if
           supported for the target machine.  Such code accesses all constant addresses through a
           global offset table (GOT).  The dynamic loader resolves the GOT entries when the
           program starts (the dynamic loader is not part of GCC; it is part of the operating
           system).  If the GOT size for the linked executable exceeds a machine-specific maximum
           size, you get an error message from the linker indicating that -fpic does not work; in
           that case, recompile with -fPIC instead.  (These maximums are 8k on the SPARC and 32k
           on the m68k and RS/6000.  The x86 has no such limit.)

           Position-independent code requires special support, and therefore works only on
           certain machines.  For the x86, GCC supports PIC for System V but not for the Sun
           386i.  Code generated for the IBM RS/6000 is always position-independent.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined to 1.

       -fPIC
           If supported for the target machine, emit position-independent code, suitable for
           dynamic linking and avoiding any limit on the size of the global offset table.  This
           option makes a difference on the m68k, PowerPC and SPARC.

           Position-independent code requires special support, and therefore works only on
           certain machines.

           When this flag is set, the macros "__pic__" and "__PIC__" are defined to 2.

       -fpie
       -fPIE
           These options are similar to -fpic and -fPIC, but generated position independent code
           can be only linked into executables.  Usually these options are used when -pie GCC
           option is used during linking.

           -fpie and -fPIE both define the macros "__pie__" and "__PIE__".  The macros have the
           value 1 for -fpie and 2 for -fPIE.

       -fno-jump-tables
           Do not use jump tables for switch statements even where it would be more efficient
           than other code generation strategies.  This option is of use in conjunction with
           -fpic or -fPIC for building code that forms part of a dynamic linker and cannot
           reference the address of a jump table.  On some targets, jump tables do not require a
           GOT and this option is not needed.

       -ffixed-reg
           Treat the register named reg as a fixed register; generated code should never refer to
           it (except perhaps as a stack pointer, frame pointer or in some other fixed role).

           reg must be the name of a register.  The register names accepted are machine-specific
           and are defined in the "REGISTER_NAMES" macro in the machine description macro file.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fcall-used-reg
           Treat the register named reg as an allocable register that is clobbered by function
           calls.  It may be allocated for temporaries or variables that do not live across a
           call.  Functions compiled this way do not save and restore the register reg.

           It is an error to use this flag with the frame pointer or stack pointer.  Use of this
           flag for other registers that have fixed pervasive roles in the machine's execution
           model produces disastrous results.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fcall-saved-reg
           Treat the register named reg as an allocable register saved by functions.  It may be
           allocated even for temporaries or variables that live across a call.  Functions
           compiled this way save and restore the register reg if they use it.

           It is an error to use this flag with the frame pointer or stack pointer.  Use of this
           flag for other registers that have fixed pervasive roles in the machine's execution
           model produces disastrous results.

           A different sort of disaster results from the use of this flag for a register in which
           function values may be returned.

           This flag does not have a negative form, because it specifies a three-way choice.

       -fpack-struct[=n]
           Without a value specified, pack all structure members together without holes.  When a
           value is specified (which must be a small power of two), pack structure members
           according to this value, representing the maximum alignment (that is, objects with
           default alignment requirements larger than this are output potentially unaligned at
           the next fitting location.

           Warning: the -fpack-struct switch causes GCC to generate code that is not binary
           compatible with code generated without that switch.  Additionally, it makes the code
           suboptimal.  Use it to conform to a non-default application binary interface.

       -finstrument-functions
           Generate instrumentation calls for entry and exit to functions.  Just after function
           entry and just before function exit, the following profiling functions are called with
           the address of the current function and its call site.  (On some platforms,
           "__builtin_return_address" does not work beyond the current function, so the call site
           information may not be available to the profiling functions otherwise.)

                   void __cyg_profile_func_enter (void *this_fn,
                                                  void *call_site);
                   void __cyg_profile_func_exit  (void *this_fn,
                                                  void *call_site);

           The first argument is the address of the start of the current function, which may be
           looked up exactly in the symbol table.

           This instrumentation is also done for functions expanded inline in other functions.
           The profiling calls indicate where, conceptually, the inline function is entered and
           exited.  This means that addressable versions of such functions must be available.  If
           all your uses of a function are expanded inline, this may mean an additional expansion
           of code size.  If you use "extern inline" in your C code, an addressable version of
           such functions must be provided.  (This is normally the case anyway, but if you get
           lucky and the optimizer always expands the functions inline, you might have gotten
           away without providing static copies.)

           A function may be given the attribute "no_instrument_function", in which case this
           instrumentation is not done.  This can be used, for example, for the profiling
           functions listed above, high-priority interrupt routines, and any functions from which
           the profiling functions cannot safely be called (perhaps signal handlers, if the
           profiling routines generate output or allocate memory).

       -finstrument-functions-exclude-file-list=file,file,...
           Set the list of functions that are excluded from instrumentation (see the description
           of -finstrument-functions).  If the file that contains a function definition matches
           with one of file, then that function is not instrumented.  The match is done on
           substrings: if the file parameter is a substring of the file name, it is considered to
           be a match.

           For example:

                   -finstrument-functions-exclude-file-list=/bits/stl,include/sys

           excludes any inline function defined in files whose pathnames contain /bits/stl or
           include/sys.

           If, for some reason, you want to include letter , in one of sym, write ,. For example,
           -finstrument-functions-exclude-file-list=',,tmp' (note the single quote surrounding
           the option).

       -finstrument-functions-exclude-function-list=sym,sym,...
           This is similar to -finstrument-functions-exclude-file-list, but this option sets the
           list of function names to be excluded from instrumentation.  The function name to be
           matched is its user-visible name, such as "vector<int> blah(const vector<int> &)", not
           the internal mangled name (e.g., "_Z4blahRSt6vectorIiSaIiEE").  The match is done on
           substrings: if the sym parameter is a substring of the function name, it is considered
           to be a match.  For C99 and C++ extended identifiers, the function name must be given
           in UTF-8, not using universal character names.

       -fstack-check
           Generate code to verify that you do not go beyond the boundary of the stack.  You
           should specify this flag if you are running in an environment with multiple threads,
           but you only rarely need to specify it in a single-threaded environment since stack
           overflow is automatically detected on nearly all systems if there is only one stack.

           Note that this switch does not actually cause checking to be done; the operating
           system or the language runtime must do that.  The switch causes generation of code to
           ensure that they see the stack being extended.

           You can additionally specify a string parameter: no means no checking, generic means
           force the use of old-style checking, specific means use the best checking method and
           is equivalent to bare -fstack-check.

           Old-style checking is a generic mechanism that requires no specific target support in
           the compiler but comes with the following drawbacks:

           1.  Modified allocation strategy for large objects: they are always allocated
               dynamically if their size exceeds a fixed threshold.

           2.  Fixed limit on the size of the static frame of functions: when it is topped by a
               particular function, stack checking is not reliable and a warning is issued by the
               compiler.

           3.  Inefficiency: because of both the modified allocation strategy and the generic
               implementation, code performance is hampered.

           Note that old-style stack checking is also the fallback method for specific if no
           target support has been added in the compiler.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
           Generate code to ensure that the stack does not grow beyond a certain value, either
           the value of a register or the address of a symbol.  If a larger stack is required, a
           signal is raised at run time.  For most targets, the signal is raised before the stack
           overruns the boundary, so it is possible to catch the signal without taking special
           precautions.

           For instance, if the stack starts at absolute address 0x80000000 and grows downwards,
           you can use the flags -fstack-limit-symbol=__stack_limit and
           -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of 128KB.  Note that
           this may only work with the GNU linker.

       -fsplit-stack
           Generate code to automatically split the stack before it overflows.  The resulting
           program has a discontiguous stack which can only overflow if the program is unable to
           allocate any more memory.  This is most useful when running threaded programs, as it
           is no longer necessary to calculate a good stack size to use for each thread.  This is
           currently only implemented for the x86 targets running GNU/Linux.

           When code compiled with -fsplit-stack calls code compiled without -fsplit-stack, there
           may not be much stack space available for the latter code to run.  If compiling all
           code, including library code, with -fsplit-stack is not an option, then the linker can
           fix up these calls so that the code compiled without -fsplit-stack always has a large
           stack.  Support for this is implemented in the gold linker in GNU binutils release
           2.21 and later.

       -fleading-underscore
           This option and its counterpart, -fno-leading-underscore, forcibly change the way C
           symbols are represented in the object file.  One use is to help link with legacy
           assembly code.

           Warning: the -fleading-underscore switch causes GCC to generate code that is not
           binary compatible with code generated without that switch.  Use it to conform to a
           non-default application binary interface.  Not all targets provide complete support
           for this switch.

       -ftls-model=model
           Alter the thread-local storage model to be used.  The model argument should be one of
           global-dynamic, local-dynamic, initial-exec or local-exec.  Note that the choice is
           subject to optimization: the compiler may use a more efficient model for symbols not
           visible outside of the translation unit, or if -fpic is not given on the command line.

           The default without -fpic is initial-exec; with -fpic the default is global-dynamic.

       -fvisibility=[default|internal|hidden|protected]
           Set the default ELF image symbol visibility to the specified option---all symbols are
           marked with this unless overridden within the code.  Using this feature can very
           substantially improve linking and load times of shared object libraries, produce more
           optimized code, provide near-perfect API export and prevent symbol clashes.  It is
           strongly recommended that you use this in any shared objects you distribute.

           Despite the nomenclature, default always means public; i.e., available to be linked
           against from outside the shared object.  protected and internal are pretty useless in
           real-world usage so the only other commonly used option is hidden.  The default if
           -fvisibility isn't specified is default, i.e., make every symbol public.

           A good explanation of the benefits offered by ensuring ELF symbols have the correct
           visibility is given by "How To Write Shared Libraries" by Ulrich Drepper (which can be
           found at <http://www.akkadia.org/drepper/>)---however a superior solution made
           possible by this option to marking things hidden when the default is public is to make
           the default hidden and mark things public.  This is the norm with DLLs on Windows and
           with -fvisibility=hidden and "__attribute__ ((visibility("default")))" instead of
           "__declspec(dllexport)" you get almost identical semantics with identical syntax.
           This is a great boon to those working with cross-platform projects.

           For those adding visibility support to existing code, you may find "#pragma GCC
           visibility" of use.  This works by you enclosing the declarations you wish to set
           visibility for with (for example) "#pragma GCC visibility push(hidden)" and "#pragma
           GCC visibility pop".  Bear in mind that symbol visibility should be viewed as part of
           the API interface contract and thus all new code should always specify visibility when
           it is not the default; i.e., declarations only for use within the local DSO should
           always be marked explicitly as hidden as so to avoid PLT indirection
           overheads---making this abundantly clear also aids readability and self-documentation
           of the code.  Note that due to ISO C++ specification requirements, "operator new" and
           "operator delete" must always be of default visibility.

           Be aware that headers from outside your project, in particular system headers and
           headers from any other library you use, may not be expecting to be compiled with
           visibility other than the default.  You may need to explicitly say "#pragma GCC
           visibility push(default)" before including any such headers.

           "extern" declarations are not affected by -fvisibility, so a lot of code can be
           recompiled with -fvisibility=hidden with no modifications.  However, this means that
           calls to "extern" functions with no explicit visibility use the PLT, so it is more
           effective to use "__attribute ((visibility))" and/or "#pragma GCC visibility" to tell
           the compiler which "extern" declarations should be treated as hidden.

           Note that -fvisibility does affect C++ vague linkage entities. This means that, for
           instance, an exception class that is be thrown between DSOs must be explicitly marked
           with default visibility so that the type_info nodes are unified between the DSOs.

           An overview of these techniques, their benefits and how to use them is at
           <http://gcc.gnu.org/wiki/Visibility>.

       -fstrict-volatile-bitfields
           This option should be used if accesses to volatile bit-fields (or other structure
           fields, although the compiler usually honors those types anyway) should use a single
           access of the width of the field's type, aligned to a natural alignment if possible.
           For example, targets with memory-mapped peripheral registers might require all such
           accesses to be 16 bits wide; with this flag you can declare all peripheral bit-fields
           as "unsigned short" (assuming short is 16 bits on these targets) to force GCC to use
           16-bit accesses instead of, perhaps, a more efficient 32-bit access.

           If this option is disabled, the compiler uses the most efficient instruction.  In the
           previous example, that might be a 32-bit load instruction, even though that accesses
           bytes that do not contain any portion of the bit-field, or memory-mapped registers
           unrelated to the one being updated.

           In some cases, such as when the "packed" attribute is applied to a structure field, it
           may not be possible to access the field with a single read or write that is correctly
           aligned for the target machine.  In this case GCC falls back to generating multiple
           accesses rather than code that will fault or truncate the result at run time.

           Note:  Due to restrictions of the C/C++11 memory model, write accesses are not allowed
           to touch non bit-field members.  It is therefore recommended to define all bits of the
           field's type as bit-field members.

           The default value of this option is determined by the application binary interface for
           the target processor.

       -fsync-libcalls
           This option controls whether any out-of-line instance of the "__sync" family of
           functions may be used to implement the C++11 "__atomic" family of functions.

           The default value of this option is enabled, thus the only useful form of the option
           is -fno-sync-libcalls.  This option is used in the implementation of the libatomic
           runtime library.

ENVIRONMENT

       This section describes several environment variables that affect how GCC operates.  Some
       of them work by specifying directories or prefixes to use when searching for various kinds
       of files.  Some are used to specify other aspects of the compilation environment.

       Note that you can also specify places to search using options such as -B, -I and -L.
       These take precedence over places specified using environment variables, which in turn
       take precedence over those specified by the configuration of GCC.

       LANG
       LC_CTYPE
       LC_MESSAGES
       LC_ALL
           These environment variables control the way that GCC uses localization information
           which allows GCC to work with different national conventions.  GCC inspects the locale
           categories LC_CTYPE and LC_MESSAGES if it has been configured to do so.  These locale
           categories can be set to any value supported by your installation.  A typical value is
           en_GB.UTF-8 for English in the United Kingdom encoded in UTF-8.

           The LC_CTYPE environment variable specifies character classification.  GCC uses it to
           determine the character boundaries in a string; this is needed for some multibyte
           encodings that contain quote and escape characters that are otherwise interpreted as a
           string end or escape.

           The LC_MESSAGES environment variable specifies the language to use in diagnostic
           messages.

           If the LC_ALL environment variable is set, it overrides the value of LC_CTYPE and
           LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES default to the value of the LANG
           environment variable.  If none of these variables are set, GCC defaults to traditional
           C English behavior.

       TMPDIR
           If TMPDIR is set, it specifies the directory to use for temporary files.  GCC uses
           temporary files to hold the output of one stage of compilation which is to be used as
           input to the next stage: for example, the output of the preprocessor, which is the
           input to the compiler proper.

       GCC_COMPARE_DEBUG
           Setting GCC_COMPARE_DEBUG is nearly equivalent to passing -fcompare-debug to the
           compiler driver.  See the documentation of this option for more details.

       GCC_EXEC_PREFIX
           If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the names of the
           subprograms executed by the compiler.  No slash is added when this prefix is combined
           with the name of a subprogram, but you can specify a prefix that ends with a slash if
           you wish.

           If GCC_EXEC_PREFIX is not set, GCC attempts to figure out an appropriate prefix to use
           based on the pathname it is invoked with.

           If GCC cannot find the subprogram using the specified prefix, it tries looking in the
           usual places for the subprogram.

           The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ where prefix is the prefix to
           the installed compiler. In many cases prefix is the value of "prefix" when you ran the
           configure script.

           Other prefixes specified with -B take precedence over this prefix.

           This prefix is also used for finding files such as crt0.o that are used for linking.

           In addition, the prefix is used in an unusual way in finding the directories to search
           for header files.  For each of the standard directories whose name normally begins
           with /usr/local/lib/gcc (more precisely, with the value of GCC_INCLUDE_DIR), GCC tries
           replacing that beginning with the specified prefix to produce an alternate directory
           name.  Thus, with -Bfoo/, GCC searches foo/bar just before it searches the standard
           directory /usr/local/lib/bar.  If a standard directory begins with the configured
           prefix then the value of prefix is replaced by GCC_EXEC_PREFIX when looking for header
           files.

       COMPILER_PATH
           The value of COMPILER_PATH is a colon-separated list of directories, much like PATH.
           GCC tries the directories thus specified when searching for subprograms, if it can't
           find the subprograms using GCC_EXEC_PREFIX.

       LIBRARY_PATH
           The value of LIBRARY_PATH is a colon-separated list of directories, much like PATH.
           When configured as a native compiler, GCC tries the directories thus specified when
           searching for special linker files, if it can't find them using GCC_EXEC_PREFIX.
           Linking using GCC also uses these directories when searching for ordinary libraries
           for the -l option (but directories specified with -L come first).

       LANG
           This variable is used to pass locale information to the compiler.  One way in which
           this information is used is to determine the character set to be used when character
           literals, string literals and comments are parsed in C and C++.  When the compiler is
           configured to allow multibyte characters, the following values for LANG are
           recognized:

           C-JIS
               Recognize JIS characters.

           C-SJIS
               Recognize SJIS characters.

           C-EUCJP
               Recognize EUCJP characters.

           If LANG is not defined, or if it has some other value, then the compiler uses "mblen"
           and "mbtowc" as defined by the default locale to recognize and translate multibyte
           characters.

       Some additional environment variables affect the behavior of the preprocessor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
           Each variable's value is a list of directories separated by a special character, much
           like PATH, in which to look for header files.  The special character,
           "PATH_SEPARATOR", is target-dependent and determined at GCC build time.  For Microsoft
           Windows-based targets it is a semicolon, and for almost all other targets it is a
           colon.

           CPATH specifies a list of directories to be searched as if specified with -I, but
           after any paths given with -I options on the command line.  This environment variable
           is used regardless of which language is being preprocessed.

           The remaining environment variables apply only when preprocessing the particular
           language indicated.  Each specifies a list of directories to be searched as if
           specified with -isystem, but after any paths given with -isystem options on the
           command line.

           In all these variables, an empty element instructs the compiler to search its current
           working directory.  Empty elements can appear at the beginning or end of a path.  For
           instance, if the value of CPATH is ":/special/include", that has the same effect as
           -I. -I/special/include.

       DEPENDENCIES_OUTPUT
           If this variable is set, its value specifies how to output dependencies for Make based
           on the non-system header files processed by the compiler.  System header files are
           ignored in the dependency output.

           The value of DEPENDENCIES_OUTPUT can be just a file name, in which case the Make rules
           are written to that file, guessing the target name from the source file name.  Or the
           value can have the form file target, in which case the rules are written to file file
           using target as the target name.

           In other words, this environment variable is equivalent to combining the options -MM
           and -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
           This variable is the same as DEPENDENCIES_OUTPUT (see above), except that system
           header files are not ignored, so it implies -M rather than -MM.  However, the
           dependence on the main input file is omitted.

BUGS

       For instructions on reporting bugs, see <file:///usr/share/doc/gcc-5/README.Bugs>.

FOOTNOTES

       1.  On some systems, gcc -shared needs to build supplementary stub code for constructors
           to work.  On multi-libbed systems, gcc -shared must select the correct support
           libraries to link against.  Failing to supply the correct flags may lead to subtle
           defects.  Supplying them in cases where they are not necessary is innocuous.

SEE ALSO

       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1), adb(1), dbx(1),
       sdb(1) and the Info entries for gcc, cpp, as, ld, binutils and gdb.

AUTHOR

       See the Info entry for gcc, or <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for
       contributors to GCC.

COPYRIGHT

       Copyright (c) 1988-2015 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document under the terms of
       the GNU Free Documentation License, Version 1.3 or any later version published by the Free
       Software Foundation; with the Invariant Sections being "GNU General Public License" and
       "Funding Free Software", the Front-Cover texts being (a) (see below), and with the Back-
       Cover Texts being (b) (see below).  A copy of the license is included in the gfdl(7) man
       page.

       (a) The FSF's Front-Cover Text is:

            A GNU Manual

       (b) The FSF's Back-Cover Text is:

            You have freedom to copy and modify this GNU Manual, like GNU
            software.  Copies published by the Free Software Foundation raise
            funds for GNU development.