xenial (1) gcc.1.gz

Provided by: gcc-5_5.4.0-6ubuntu1~16.04.12_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=string -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 -mindirect-branch=choice -mfunction-return=choice
           -mindirect-branch-register

           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.

           Version 9, which first appeared in G++ 5.2, corrects the alignment of "nullptr_t".

           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, the default for GCC 5.1.

           *   "decltype(nullptr)" incorrectly had an alignment of 1, leading to unaligned accesses.  Note that
               this did not affect the ABI of a function with a "nullptr_t" parameter, as parameters have a
               minimum alignment.

               This was fixed in -fabi-version=9, the default for GCC 5.2.

           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.

               NOTE: In Ubuntu 8.10 and later versions this option is enabled by default for C, C++, ObjC,
               ObjC++.  To disable, use -Wno-format-security, or disable all format warnings with -Wformat=0.
               To make format security warnings fatal, specify -Werror=format-security.

           -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=string
           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 string can either be a number (decimal, octal or hex) or an arbitrary string (in which case it's
           converted to a number by computing CRC32).

           The string 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.

           NOTE: In Ubuntu 14.10 and later versions, -fstack-protector-strong is enabled by default for C, C++,
           ObjC, ObjC++, if none of -fno-stack-protector, -nostdlib, nor -ffreestanding are found.

       -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.

               This default before Ubuntu 10.10 was "8". Currently it is "4", to increase the number of
               functions protected by the stack protector.

           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.

       -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, -mskip-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.

       -mindirect-branch=choice
           Convert indirect call and jump with choice.  The default is keep, which keeps indirect call and jump
           unmodified.  thunk converts indirect call and jump to call and return thunk.  thunk-inline converts
           indirect call and jump to inlined call and return thunk.  thunk-extern converts indirect call and
           jump to external call and return thunk provided in a separate object file.  You can control this
           behavior for a specific function by using the function attribute "indirect_branch".

           Note that -mcmodel=large is incompatible with -mindirect-branch=thunk nor
           -mindirect-branch=thunk-extern since the thunk function may not be reachable in large code model.

       -mfunction-return=choice
           Convert function return with choice.  The default is keep, which keeps function return unmodified.
           thunk converts function return to call and return thunk.  thunk-inline converts function return to
           inlined call and return thunk.  thunk-extern converts function return to external call and return
           thunk provided in a separate object file.  You can control this behavior for a specific function by
           using the function attribute "function_return".

           Note that -mcmodel=large is incompatible with -mfunction-return=thunk nor
           -mfunction-return=thunk-extern since the thunk function may not be reachable in large code model.

       -mindirect-branch-register
           Force indirect call and jump via register.

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.

       SOURCE_DATE_EPOCH
           If this variable is set, its value specifies a UNIX timestamp to be used in replacement of the
           current date and time in the "__DATE__" and "__TIME__" macros, so that the embedded timestamps become
           reproducible.

           The value of SOURCE_DATE_EPOCH must be a UNIX timestamp, defined as the number of seconds (excluding
           leap seconds) since 01 Jan 1970 00:00:00 represented in ASCII; identical to the output of
           @command{date +%s} on GNU/Linux and other systems that support the %s extension in the "date"
           command.

           The value should be a known timestamp such as the last modification time of the source or package and
           it should be set by the build process.

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 (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.