Provided by: gcc-4.6_4.6.3-1ubuntu5_amd64 bug

NAME

       gcc - GNU project C and C++ compiler

SYNOPSIS

       gcc [-c|-S|-E] [-std=standard]
           [-g] [-pg] [-Olevel]
           [-Wwarn...] [-pedantic]
           [-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 would be -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] -fdump-go-spec=file

       C Language Options
           -ansi  -std=standard  -fgnu89-inline -aux-info filename -fno-asm  -fno-builtin
           -fno-builtin-function -fhosted  -ffreestanding -fopenmp -fms-extensions
           -fplan9-extensions -trigraphs  -no-integrated-cpp  -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 -fconserve-space
           -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  -fstats  -ftemplate-depth=n
           -fno-threadsafe-statics -fuse-cxa-atexit  -fno-weak  -nostdinc++ -fno-default-inline
           -fvisibility-inlines-hidden -fvisibility-ms-compat -Wabi  -Wconversion-null
           -Wctor-dtor-privacy -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 -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]
           -fno-diagnostics-show-option

       Warning Options
           -fsyntax-only  -fmax-errors=n  -pedantic -pedantic-errors -w  -Wextra  -Wall
           -Waddress  -Waggregate-return  -Warray-bounds -Wno-attributes
           -Wno-builtin-macro-redefined -Wc++-compat -Wc++0x-compat -Wcast-align  -Wcast-qual
           -Wchar-subscripts -Wclobbered  -Wcomment -Wconversion  -Wcoverage-mismatch  -Wno-cpp
           -Wno-deprecated -Wno-deprecated-declarations -Wdisabled-optimization -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-y2k
           -Wframe-larger-than=len -Wjump-misses-init -Wignored-qualifiers -Wimplicit
           -Wimplicit-function-declaration  -Wimplicit-int -Winit-self  -Winline
           -Wno-int-to-pointer-cast -Wno-invalid-offsetof -Winvalid-pch -Wlarger-than=len
           -Wunsafe-loop-optimizations -Wlogical-op -Wlong-long -Wmain  -Wmissing-braces
           -Wmissing-field-initializers -Wmissing-format-attribute  -Wmissing-include-dirs
           -Wno-mudflap -Wno-multichar  -Wnonnull  -Wno-overflow -Woverlength-strings  -Wpacked
           -Wpacked-bitfield-compat  -Wpadded -Wparentheses  -Wpedantic-ms-format
           -Wno-pedantic-ms-format -Wpointer-arith  -Wno-pointer-to-int-cast -Wredundant-decls
           -Wreturn-type  -Wsequence-point  -Wshadow -Wsign-compare  -Wsign-conversion
           -Wstack-protector -Wstrict-aliasing -Wstrict-aliasing=n -Wstrict-overflow
           -Wstrict-overflow=n -Wsuggest-attribute=[pure|const|noreturn] -Wswitch
           -Wswitch-default  -Wswitch-enum -Wsync-nand -Wsystem-headers  -Wtrampolines
           -Wtrigraphs  -Wtype-limits  -Wundef -Wuninitialized  -Wunknown-pragmas  -Wno-pragmas
           -Wunsuffixed-float-constants  -Wunused  -Wunused-function -Wunused-label
           -Wunused-parameter -Wno-unused-result -Wunused-value -Wunused-variable
           -Wunused-but-set-parameter -Wunused-but-set-variable -Wvariadic-macros -Wvla
           -Wvolatile-register-var  -Wwrite-strings

       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 -fdbg-cnt-list -fdbg-cnt=counter-
           value-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-statistics -fdump-tree-all
           -fdump-tree-original[-n] -fdump-tree-optimized[-n] -fdump-tree-cfg -fdump-tree-vcg
           -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-mudflap[-n] -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-vrp[-n]
           -ftree-vectorizer-verbose=n -fdump-tree-storeccp[-n] -fdump-final-insns=file
           -fcompare-debug[=opts]  -fcompare-debug-second -feliminate-dwarf2-dups
           -feliminate-unused-debug-types -feliminate-unused-debug-symbols
           -femit-class-debug-always -fenable-icf-debug -fmem-report -fpre-ipa-mem-report
           -fpost-ipa-mem-report -fprofile-arcs -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
           -gstabs  -gstabs+  -gstrict-dwarf  -gno-strict-dwarf -gvms  -gxcoff  -gxcoff+
           -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
           -falign-functions[=n] -falign-jumps[=n] -falign-labels[=n] -falign-loops[=n]
           -fassociative-math -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 -fdce -fdelayed-branch
           -fdelete-null-pointer-checks -fdse -fdevirtualize -fdse -fearly-inlining -fipa-sra
           -fexpensive-optimizations -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
           -fif-conversion -fif-conversion2 -findirect-inlining -finline-functions
           -finline-functions-called-once -finline-limit=n -finline-small-functions -fipa-cp
           -fipa-cp-clone -fipa-matrix-reorg -fipa-pta -fipa-profile -fipa-pure-const
           -fipa-reference -fipa-struct-reorg -fira-algorithm=algorithm -fira-region=region
           -fira-loop-pressure -fno-ira-share-save-slots -fno-ira-share-spill-slots
           -fira-verbose=n -fivopts -fkeep-inline-functions -fkeep-static-consts -floop-block
           -floop-flatten -floop-interchange -floop-strip-mine -floop-parallelize-all -flto
           -flto-compression-level -flto-partition=alg -flto-report -fmerge-all-constants
           -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves -fmove-loop-invariants
           fmudflap -fmudflapir -fmudflapth -fno-branch-count-reg -fno-default-inline
           -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-register-move
           -foptimize-sibling-calls -fpartial-inlining -fpeel-loops -fpredictive-commoning
           -fprefetch-loop-arrays -fprofile-correction -fprofile-dir=path -fprofile-generate
           -fprofile-generate=path -fprofile-use -fprofile-use=path -fprofile-values
           -freciprocal-math -fregmove -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-insns
           -fschedule-insns2 -fsection-anchors -fselective-scheduling -fselective-scheduling2
           -fsel-sched-pipelining -fsel-sched-pipelining-outer-loops -fsignaling-nans
           -fsingle-precision-constant -fsplit-ivs-in-unroller -fsplit-wide-types
           -fstack-protector -fstack-protector-all -fstrict-aliasing -fstrict-overflow
           -fthread-jumps -ftracer -ftree-bit-ccp -ftree-builtin-call-dce -ftree-ccp -ftree-ch
           -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-parallelize-loops=n
           -ftree-pre -ftree-pta -ftree-reassoc -ftree-sink -ftree-sra -ftree-switch-conversion
           -ftree-ter -ftree-vect-loop-version -ftree-vectorize -ftree-vrp -funit-at-a-time
           -funroll-all-loops -funroll-loops -funsafe-loop-optimizations
           -funsafe-math-optimizations -funswitch-loops -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

       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  -fworking-directory  -remap -trigraphs  -undef  -Umacro
           -Wp,option -Xpreprocessor option

       Assembler Option
           -Wa,option  -Xassembler option

       Linker Options
           object-file-name  -llibrary -nostartfiles  -nodefaultlibs  -nostdlib -pie -rdynamic -s
           -static  -static-libgcc  -static-libstdc++ -shared -shared-libgcc  -symbolic -T script
           -Wl,option  -Xlinker option -u symbol

       Directory Options
           -Bprefix -Idir -iplugindir=dir -iquotedir -Ldir -specs=file -I- --sysroot=dir

       Machine Dependent Options
           ARC Options -EB  -EL -mmangle-cpu  -mcpu=cpu  -mtext=text-section -mdata=data-section
           -mrodata=readonly-data-section

           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
           -mwords-little-endian -mfloat-abi=name  -msoft-float  -mhard-float  -mfpe
           -mfp16-format=name -mthumb-interwork  -mno-thumb-interwork -mcpu=name  -march=name
           -mfpu=name -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 -mcirrus-fix-invalid-insns -mno-cirrus-fix-invalid-insns
           -mpoke-function-name -mthumb  -marm -mtpcs-frame  -mtpcs-leaf-frame
           -mcaller-super-interworking  -mcallee-super-interworking -mtp=name -mword-relocations
           -mfix-cortex-m3-ldrd

           AVR Options -mmcu=mcu  -mno-interrupts -mcall-prologues  -mtiny-stack  -mint8

           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

           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

           CRX Options -mmac -mpush-args

           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  -malpha-as  -mgas -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

           DEC Alpha/VMS Options -mvms-return-codes -mdebug-main=prefix -mmalloc64

           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  -mint32  -malign-300

           HPPA Options -march=architecture-type -mbig-switch  -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-big-switch  -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

           i386 and x86-64 Options -mtune=cpu-type  -march=cpu-type -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 -mvzeroupper -mmmx  -msse  -msse2 -msse3 -mssse3
           -msse4.1 -msse4.2 -msse4 -mavx -maes -mpclmul -mfsgsbase -mrdrnd -mf16c -mfused-madd
           -msse4a -m3dnow -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop -mlwp -mthreads
           -mno-align-stringops  -minline-all-stringops -minline-stringops-dynamically
           -mstringop-strategy=alg -mpush-args  -maccumulate-outgoing-args  -m128bit-long-double
           -m96bit-long-double  -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 -m32  -m64
           -mlarge-data-threshold=num -msse2avx -mfentry -m8bit-idiv
           -mavx256-split-unaligned-load -mavx256-split-unaligned-store

           i386 and x86-64 Windows Options -mconsole -mcygwin -mno-cygwin -mdll
           -mnop-fun-dllimport -mthread -municode -mwin32 -mwindows -fno-set-stack-executable

           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

           IA-64/VMS Options -mvms-return-codes -mdebug-main=prefix -mmalloc64

           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

           M68hc1x Options -m6811  -m6812  -m68hc11  -m68hc12   -m68hcs12 -mauto-incdec  -minmax
           -mlong-calls  -mshort -msoft-reg-count=count

           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
           -mxl-mode-app-model

           MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2  -mips3  -mips4
           -mips32  -mips32r2 -mips64  -mips64r2 -mips16  -mno-mips16  -mflip-mips16
           -minterlink-mips16  -mno-interlink-mips16 -mabi=abi  -mabicalls  -mno-abicalls
           -mshared  -mno-shared  -mplt  -mno-plt  -mxgot  -mno-xgot -mgp32  -mgp64  -mfp32
           -mfp64  -mhard-float  -msoft-float -msingle-float  -mdouble-float  -mdsp  -mno-dsp
           -mdspr2  -mno-dspr2 -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
           -mfused-madd  -mno-fused-madd  -nocpp -mfix-r4000  -mno-fix-r4000  -mfix-r4400
           -mno-fix-r4400 -mfix-r10000 -mno-fix-r10000  -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

           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.

           RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -mpower
           -mno-power  -mpower2  -mno-power2 -mpowerpc  -mpowerpc64  -mno-powerpc -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
           -mnew-mnemonics  -mold-mnemonics -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

           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= -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

           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  -mbitops  -misize  -minline-ic_invalidate -mpadstruct
           -mspace -mprefergot  -musermode -multcost=number -mdiv=strategy -mdivsi3_libfunc=name
           -mfixed-range=register-range -madjust-unroll -mindexed-addressing -mgettrcost=number
           -mpt-fixed -maccumulate-outgoing-args -minvalid-symbols

           Solaris 2 Options -mimpure-text  -mno-impure-text -threads -pthreads -pthread

           SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model -m32  -m64
           -mapp-regs  -mno-app-regs -mfaster-structs  -mno-faster-structs -mfpu  -mno-fpu
           -mhard-float  -msoft-float -mhard-quad-float  -msoft-quad-float -mlittle-endian
           -mstack-bias  -mno-stack-bias -munaligned-doubles  -mno-unaligned-doubles -mv8plus
           -mno-v8plus  -mvis  -mno-vis -mfix-at697f

           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

           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  -mbig-switch

           VAX Options -mg  -mgnu  -munix

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

           x86-64 Options See i386 and x86-64 Options.

           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
           -funwind-tables -fasynchronous-unwind-tables -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 -ftrapv
           -fwrapv  -fbounds-check -fvisibility -fstrict-volatile-bitfields

   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 which must be preprocessed.

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

       file.ii
           C++ source code which 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 which 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 which 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 which 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 which must be preprocessed.

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

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

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

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

       file.go
           Go source code.

       file.ads
           Ada source code file which 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 which 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 will exit 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
           will instead return with numerically highest error produced by any phase that returned
           an error indication.  The C, C++, and Fortran frontends 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 which don't require preprocessing are ignored.

       -o file
           Place output in file file.  This applies regardless 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 will also be 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 which have no documentation associated with them
           will also be 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
               This will display all of the optimization options supported by the compiler.

           warnings
               This will display all of the options controlling warning messages produced by the
               compiler.

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

           params
               This will display the values recognized by the --param option.

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

           common
               This will display the options that are common to all languages.

           These are the supported qualifiers:

           undocumented
               Display only those options which are undocumented.

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

           separate
               Display options which take 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 the following can be used:

                   --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), which have a description the following can be used:

                   --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 by
           so much that there is nothing to display.  One case where it does work however is when
           one of the classes is target.  So for example to display all the target-specific
           optimization options the following can be used:

                   --help=target,optimizers

           The --help= option can be repeated on the command line.  Each successive use will
           display 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 will invoke all subprograms of gcc under gdb --args, thus the invocation of cc1
           will be 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.

       -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
       treats .c, .h and .i files as C++ source files instead of C source files unless -x is
       used, and automatically specifies linking against the C++ library.  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, -pedantic 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 would normally be 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.  By specifying a base standard, the
           compiler will accept all programs following that standard and 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, by specifying a GNU
           dialect of a standard, all features the compiler support are enabled, even when those
           features change the meaning of the base standard and some strict-conforming programs
           may be rejected.  The particular standard is used by -pedantic to identify which
           features are GNU extensions given that version of the standard. For example -std=gnu90
           -pedantic would warn about C++ style // comments, while -std=gnu99 -pedantic would
           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.  Note that this standard is not yet fully supported; see
               <http://gcc.gnu.org/gcc-4.6/c99status.html> for more information.  The names c9x
               and iso9899:199x are deprecated.

           c1x ISO C1X, the draft of the next revision of the ISO C standard.  Support is limited
               and experimental and features enabled by this option may be changed or removed if
               changed in or removed from the standard draft.

           gnu90
           gnu89
               GNU dialect of ISO C90 (including some C99 features). This is the default for C
               code.

           gnu99
           gnu9x
               GNU dialect of ISO C99.  When ISO C99 is fully implemented in GCC, this will
               become the default.  The name gnu9x is deprecated.

           gnu1x
               GNU dialect of ISO C1X.  Support is limited and experimental and features enabled
               by this option may be changed or removed if changed in or removed from the
               standard draft.

           c++98
               The 1998 ISO C++ standard plus amendments. Same as -ansi for C++ code.

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

           c++0x
               The working draft of the upcoming ISO C++0x standard. This option enables
               experimental features that are likely to be included in C++0x. The working draft
               is constantly changing, and any feature that is enabled by this flag may be
               removed from future versions of GCC if it is not part of the C++0x standard.

           gnu++0x
               GNU dialect of -std=c++0x. This option enables experimental features that may be
               removed in future versions of GCC.

       -fgnu89-inline
           The option -fgnu89-inline tells GCC to use the traditional GNU semantics for "inline"
           functions when in C99 mode.
             This option is accepted and ignored by GCC versions 4.1.3 up to but not including
           4.3.  In GCC versions 4.3 and later it changes the behavior of GCC 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 was first supported in GCC 4.3.  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.

       -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 that
           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 takes place in 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 takes place in 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.

       -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 v3.0 <http://www.openmp.org/>.  This option
           implies -pthread, and thus is only supported on targets that have support for
           -pthread.

       -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.

       -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 which 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.

       -no-integrated-cpp
           Performs a compilation in two passes: preprocessing and compiling.  This option allows
           a user supplied "cc1", "cc1plus", or "cc1obj" via the -B option.  The user supplied
           compilation step can then add in an additional preprocessing step after normal
           preprocessing but before compiling.  The default is to use the integrated cpp
           (internal cpp)

           The semantics of this option will change if "cc1", "cc1plus", and "cc1obj" are merged.

       -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;
       but 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.  Version 2 is the version of the C++ ABI that first
           appeared in G++ 3.4.  Version 1 is the version of the C++ ABI that first appeared in
           G++ 3.2.  Version 0 will always be the version that conforms most closely to the C++
           ABI specification.  Therefore, the ABI obtained using version 0 will change as ABI
           bugs are fixed.

           The default is version 2.

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

           Version 4 implements a standard mangling for vector types.

           Version 5 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.

           See also -Wabi.

       -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" will only return 0 if it is declared throw(),
           in which case the compiler will always check 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).

       -fconserve-space
           Put uninitialized or runtime-initialized global variables into the common segment, as
           C does.  This saves space in the executable at the cost of not diagnosing duplicate
           definitions.  If you compile with this flag and your program mysteriously crashes
           after "main()" has completed, you may have an object that is being destroyed twice
           because two definitions were merged.

           This option is no longer useful on most targets, now that support has been added for
           putting variables into BSS without making them common.

       -fconstexpr-depth=n
           Set the maximum nested evaluation depth for C++0x constexpr functions to n.  A limit
           is needed to detect endless recursion during constant expression evaluation.  The
           minimum specified by the standard is 512.

       -fno-deduce-init-list
           Disable 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 option is present because this deduction is an extension to the current
           specification in the C++0x working draft, and there was some concern about potential
           overload resolution problems.

       -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, and versions of G++ before
           4.1 always worked that way.  However, in ISO C++ a friend function which is not
           declared in an enclosing scope can only be found using argument dependent lookup.
           This option causes friends to be injected as they were in earlier releases.

           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 which 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 runtime.
           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 will
           still optimize based on the specifications, so throwing an unexpected exception will
           result in undefined behavior.

       -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++.

           The default if neither flag is given 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 which 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 will
           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 will cause linker errors if these functions are not
           inlined everywhere they are called.

       -fms-extensions
           Disable pedantic 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 though 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 will actually make 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 will result 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 will allow some nonconforming code to compile.

       -fno-pretty-templates
           When an error message refers to a specialization of a function template, the compiler
           will normally print 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 will omit any
           template arguments which match the default template arguments for that template.  If
           either of these behaviors make it harder to understand the error message rather than
           easier, using -fno-pretty-templates will 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++ runtime 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 it will generate it as needed.
           The dynamic_cast operator can still be used for casts that do not require runtime type
           information, i.e. casts to "void *" or to unambiguous base classes.

       -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 enumeration type
           can only be one of the values of the enumeration (as defined in the C++ standard;
           basically, a value which 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 enumeration type.

       -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++0x).

       -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 will only work if your C
           library supports "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
           Don't use the "__cxa_get_exception_ptr" runtime routine.  This will cause
           "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
           methods where the addresses of the two functions were 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 will have 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 which are defined in more than one different shared object: those
               declarations are permitted if they would have been permitted when this option was
               not used.

           In new code it is better to use -fvisibility=hidden and export those classes which 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 will be different, so
           changing one will 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.

       -fno-weak
           Do not use weak symbol support, even if it is provided by the linker.  By default, G++
           will use weak symbols if they are available.  This option exists only for testing, and
           should not be used by end-users; it will result 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:

       -fno-default-inline
           Do not assume inline for functions defined inside a class scope.
             Note that these functions will have linkage like inline functions; they just won't
           be inlined by default.

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
           Warn when G++ generates code that is probably not compatible with the vendor-neutral
           C++ ABI.  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 will be 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.

           The known incompatibilities in -fabi-version=2 (the default) include:

           ·   A template with a non-type template parameter of reference type is mangled
               incorrectly:

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

               This is fixed in -fabi-version=3.

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

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

           The known incompatibilities in -fabi-version=1 include:

           ·   Incorrect handling of tail-padding for bit-fields.  G++ may attempt to pack data
               into the same byte as a base class.  For example:

                       struct A { virtual void f(); int f1 : 1; };
                       struct B : public A { int f2 : 1; };

               In this case, G++ will place "B::f2" into the same byte as"A::f1"; other compilers
               will not.  You can avoid this problem by explicitly padding "A" so that its size
               is a multiple of the byte size on your platform; that will cause G++ and other
               compilers to layout "B" identically.

           ·   Incorrect handling of tail-padding for virtual bases.  G++ does not use tail
               padding when laying out virtual bases.  For example:

                       struct A { virtual void f(); char c1; };
                       struct B { B(); char c2; };
                       struct C : public A, public virtual B {};

               In this case, G++ will not place "B" into the tail-padding for "A"; other
               compilers will.  You can avoid this problem by explicitly padding "A" so that its
               size is a multiple of its alignment (ignoring virtual base classes); that will
               cause G++ and other compilers to layout "C" identically.

           ·   Incorrect handling of bit-fields with declared widths greater than that of their
               underlying types, when the bit-fields appear in a union.  For example:

                       union U { int i : 4096; };

               Assuming that an "int" does not have 4096 bits, G++ will make the union too small
               by the number of bits in an "int".

           ·   Empty classes can be placed at incorrect offsets.  For example:

                       struct A {};

                       struct B {
                         A a;
                         virtual void f ();
                       };

                       struct C : public B, public A {};

               G++ will place the "A" base class of "C" at a nonzero offset; it should be placed
               at offset zero.  G++ mistakenly believes that the "A" data member of "B" is
               already at offset zero.

           ·   Names of template functions whose types involve "typename" or template template
               parameters can be mangled incorrectly.

                       template <typename Q>
                       void f(typename Q::X) {}

                       template <template <typename> class Q>
                       void f(typename Q<int>::X) {}

               Instantiations of these templates may be mangled incorrectly.

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

           ·   For SYSV/x86-64, when passing union with long double, it is changed to pass in
               memory as specified in psABI.  For example:

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

               "union U" will always be passed in memory.

       -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.

       -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 accessible non-virtual destructor, in
           which case it would be possible but unsafe to delete an instance of a derived class
           through a pointer to the base class.  This warning is also 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 will rearrange 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.

       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++ book:

           ·   Item 11:  Define a copy constructor and an assignment operator for classes with
               dynamically allocated memory.

           ·   Item 12:  Prefer initialization to assignment in constructors.

           ·   Item 14:  Make destructors virtual in base classes.

           ·   Item 15:  Have "operator=" return a reference to *this.

           ·   Item 23:  Don't try to return a reference when you must return an object.

           Also warn about violations of the following style guidelines from Scott Meyers' More
           Effective C++ book:

           ·   Item 6:  Distinguish between prefix and postfix forms of increment and decrement
               operators.

           ·   Item 7:  Never overload "&&", "||", or ",".

           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 also 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 not 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();

           will fail 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++ would try to preserve unsignedness, but the standard mandates the
           current behavior.

                   struct A {
                     operator int ();
                     A& operator = (int);
                   };

                   main ()
                   {
                     A a,b;
                     a = b;
                   }

           In this example, G++ will synthesize a default A& operator = (const A&);, while cfront
           will use the user-defined operator =.

   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, but 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, will override 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 that will run 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 that will run all such default destructors,
           in reverse order.

           The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods thusly generated will
           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 will be invoked by the runtime immediately after a new object
           instance is allocated; the "- (void) .cxx_destruct" methods will be 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.

       -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 will omit such warnings if any differences found are confined to types which
           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, ...).  The options described below can be used to control the
       diagnostic messages formatting algorithm, e.g. how many characters per line, how often
       source location information should be reported.  Right now, only the C++ front end can
       honor these options.  However it is expected, in the near future, that the remaining front
       ends would be able to digest them correctly.

       -fmessage-length=n
           Try to format error messages so that they fit on lines of about n characters.  The
           default is 72 characters for g++ and 0 for the rest of the front ends supported by
           GCC.  If n is zero, then no line-wrapping will be done; each error message will appear
           on a single line.

       -fdiagnostics-show-location=once
           Only meaningful in line-wrapping mode.  Instructs the diagnostic messages reporter to
           emit once source location information; 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.

       -fno-diagnostics-show-option
           By default, each diagnostic emitted includes text which indicates 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.

       -Wcoverage-mismatch
           Warn if feedback profiles do not match when using the -fprofile-use option.  If a
           source file was changed between -fprofile-gen and -fprofile-use, the files with the
           profile feedback can fail to match the source file and GCC can not 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.  Disable the error for
           this warning can result in poorly optimized code, so disabling the error 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.

   Options to Request or Suppress Warnings
       Warnings are diagnostic messages that report constructions which are not inherently
       erroneous but which 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 which 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 -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.

       When an unrecognized warning option is requested (e.g., -Wunknown-warning), GCC will emit
       a diagnostic stating that the option is not recognized.  However, if the -Wno- form is
       used, the behavior is slightly different: No diagnostic will be 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 will warn
       that an unrecognized option was used.

       -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 will 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.

           -pedantic 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 -pedantic 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
           -pedantic.  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 -pedantic are given where they are
           required by the base standard.  (It would 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
           Like -pedantic, except that errors are produced rather than warnings.

       -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 (only with -O2) -Wc++0x-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) -Wmissing-braces -Wnonnull
           -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 which has been declared register.

           ·   (C++ only) Taking the address of a variable which has been declared register.

           ·   (C++ only) A base class is not initialized in a derived class' 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-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 will perform the entire computation with "double" because the floating-
           point literal is a "double".

       -Wformat
           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 -pedantic is used with -Wformat,
           warnings will be 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).

           Since -Wformat also checks for null format arguments for several functions, -Wformat
           also implies -Wnonnull.

           -Wformat is included in -Wall.  For more control over some aspects of format checking,
           the options -Wformat-y2k, -Wno-format-extra-args, -Wno-format-zero-length,
           -Wformat-nonliteral, -Wformat-security, and -Wformat=2 are available, but are not
           included in -Wall.

           NOTE: In Ubuntu 8.10 and later versions this option is enabled by default for C, C++,
           ObjC, ObjC++.  To disable, use -Wformat=0.

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

       -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 will suppress 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 (C and Objective-C only)
           If -Wformat is specified, do not warn about zero-length formats.  The C standard
           specifies that zero-length formats are allowed.

       -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.)

           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=2
           Enable -Wformat plus format checks not included in -Wformat.  Currently equivalent to
           -Wformat -Wformat-nonliteral -Wformat-security -Wformat-y2k.

       -Wnonnull (C and Objective-C only)
           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 which are initialized with themselves.  Note this
           option can only be used with the -Wuninitialized option.

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

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

       -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 -pedantic.

       -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.

                   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 will issue 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" could belong to the enclosing "if".  The
           resulting code would look like this:

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

           Also warn for dangerous uses of the ?: with omitted middle operand GNU extension. When
           the condition in the ?: operator is a boolean expression the omitted value will be
           always 1. Often the user expects 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 defines 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++.

       -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.

       -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.

       -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-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] will cause a warning, while x[(void)i,j] will
           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 which 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 which 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 will depend 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.

           These warnings are made optional because GCC is not smart enough to see all the
           reasons why the code might be correct despite 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.  Here is another common case:

                   {
                     int save_y;
                     if (change_y) save_y = y, y = new_y;
                     ...
                     if (change_y) y = save_y;
                   }

           This has no bug because "save_y" is used only if it is set.

           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 which 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 which is not understood by GCC.  If this
           command line option is used, warnings will even be issued for unknown pragmas in
           system header files.  This is not the case if the warnings were 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
           which 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
           which 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=n, with n=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 frontend
           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 frontend 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 frontend:
           "*(int*)&some_float".  If optimization is enabled, it also runs in the backend, 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 which 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
           which 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 will require, in particular when
           determining whether a loop will be executed at all.

           -Wstrict-overflow=1
               Warn about cases which are both questionable and easy to avoid.  For example: "x +
               1 > x"; with -fstrict-overflow, the compiler will simplify this 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" will be simplified to "x > 0".

           -Wstrict-overflow=4
               Also warn about other simplifications not covered by the above cases.  For
               example: "(x * 10) / 5" will be 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" will be 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 will give a very
               large number of false positives.

       -Wsuggest-attribute=[pure|const|noreturn]
           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 which 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 nor returns 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.

       -Warray-bounds
           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.

       -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
           will 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 would 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 which 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 does not
               in ISO C.

           ·   In traditional C, some preprocessor directives did not exist.  Traditional
               preprocessors would only consider 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 would ignore 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 would not recognize #elif, so it 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 would cause 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 will
               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 and was not supported by GCC versions before GCC 3.0.

       -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, or class member (in C++), or whenever a built-in function is
           shadowed. Note that in C++, the compiler will not warn if a local variable shadows a
           struct/class/enum, but will warn if it shadows an explicit typedef.

       -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.

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

       -Wno-pedantic-ms-format (MinGW targets only)
           Disables the warnings about non-ISO "printf" / "scanf" format width specifiers "I32",
           "I64", and "I" used on Windows targets depending on the MS runtime, when you are using
           the options -Wformat and -pedantic without gnu-extensions.

       -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 -pedantic.

       -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 whenever a function call is cast to a non-matching type.  For example, warn if
           "int malloc()" is cast to "anything *".

       -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++0x-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++ 1998 and ISO C++ 200x,
           e.g., identifiers in ISO C++ 1998 that will become keywords in ISO C++ 200x.  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 which 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 will get a warning.  These
           warnings will 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 will just be 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.

       -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 will 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.

       -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 enum types. In C++ this 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 which 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.

       -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.

       -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-attributes
           Do not warn if an unexpected "__attribute__" is used, such as unrecognized attributes,
           function attributes applied to variables, etc.  This will 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 which 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.  The aim is to
           detect global functions that fail to be declared in header files.

       -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
           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 would cause 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
           would not trigger a warning:

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

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

       -Wmissing-format-attribute
           Warn about function pointers which might be candidates for "format" attributes.  Note
           these are only possible candidates, not absolute ones.  GCC will guess 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 will also warn about function definitions which might be candidates for "format"
           attributes.  Again, these are only possible candidates.  GCC will guess 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.

       -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 which have not been normalized; this option
           controls that warning.

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

           Unfortunately, there are some characters which ISO C and ISO C++ allow in identifiers
           that when turned into NFC aren't allowable as 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.  You
           would only want to do this if you were 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", will display just like a regular "n"
           which 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 will warn 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 is unable to 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.

       -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" will
           be 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.

       -Winline
           Warn if a function can not be inlined and it was declared as inline.  Even with this
           option, the compiler will 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 1998 ISO C++ standard, applying offsetof to a non-POD type is undefined.  In
           existing C++ implementations, however, offsetof typically gives meaningful results
           even when applied to certain kinds of non-POD types. (Such as a simple struct that
           fails to be a POD type only by virtue of having a constructor.)  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 -pedantic 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 pedantic ISO C90 mode, or the GNU alternate syntax
           when in pedantic ISO C99 mode.  This is default.  To inhibit the warning messages, use
           -Wno-variadic-macros.

       -Wvla
           Warn if variable length array is used in the code.  -Wno-vla will prevent the
           -pedantic 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 were unable to handle the code effectively.  Often, the problem is that
           your code is too big or too complex; GCC will refuse 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
           -pedantic, 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 will not be protected against stack smashing.

       -Wno-mudflap
           Suppress warnings about constructs that cannot be instrumented by -fmudflap.

       -Woverlength-strings
           Warn about string constants which are longer than the "minimum maximum" length
           specified in the C standard.  Modern compilers generally allow string constants which
           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 -pedantic, and can be disabled with -Wno-overlength-strings.

       -Wunsuffixed-float-constants (C and Objective-C only)
           GCC will issue a warning for any floating constant that does not have a suffix.  When
           used together with -Wsystem-headers it will warn 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.

   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
           will probably make 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 were already at
           hand; some statements may execute in different places because they were 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.

       -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.

       -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 which 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 will increase the size of debugging information
           by as much as a factor of two.

       -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).  This is the
           format used by DBX on IRIX 6.  The value of version may be either 2, 3 or 4; the
           default version is 2.

           Note that with DWARF version 2 some ports require, and will 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.

       -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.

       -gvms
           Produce debugging information in VMS debug format (if that is supported).  This is the
           format used by DEBUG on 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, but no information about local variables and no line numbers.

           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 would have generated 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.

       -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 will be 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 will reject 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 DWARF2 debugging information by eliminating duplicated information about each
           symbol.  This option only makes sense when generating DWARF2 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 was 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 was 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 will generate 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 will serve 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 would be legal, 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
           will 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 types declared in foo.c and foo.h will have debug information, but
           types declared in other header will not.  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.

       -fenable-icf-debug
           Generate additional debug information to support identical code folding (ICF).  This
           option only works with DWARF version 2 or higher.

       -fno-merge-debug-strings
           Direct the linker to not merge together strings in the debugging information which 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.

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

       -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 will match 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.  e.g. With
           -fdbg-cnt=dce:10,tail_call:0 dbg_cnt(dce) will return true only for first 10
           invocations and dbg_cnt(tail_call) will return false always.

       -dletters
       -fdump-rtl-pass
           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.  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 sub-
               expression 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 pro and epilogues.

           -fdump-rtl-regmove
               Dump after the register move pass.

           -fdump-rtl-sched1
           -fdump-rtl-sched2
               -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after the basic block
               scheduling passes.

           -fdump-rtl-see
               Dump after sign 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
               -fdump-rtl-split1, -fdump-rtl-split2, -fdump-rtl-split3, -fdump-rtl-split4 and
               -fdump-rtl-split5 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.

           -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.

           -dm Print statistics on memory usage, at the end of the run, to standard error.

           -dp Annotate the assembler output with a comment indicating which pattern and
               alternative was 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.

           -dv For each of the other indicated dump files (-fdump-rtl-pass), dump a
               representation of the control flow graph suitable for viewing with VCG to
               file.pass.vcg.

           -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.

       -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-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 will cause counters to be summed over the whole compilation unit while
           -details will dump 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
           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.
           If the -options form is used, options is a list of - separated options that control
           the details of the dump.  Not all options are applicable to all dumps, those which are
           not meaningful will be 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
               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.

           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).

           stats
               Enable dumping various statistics about the pass (not honored by every dump
               option).

           blocks
               Enable showing basic block boundaries (disabled in raw dumps).

           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.

           all Turn on all options, except raw, slim, verbose and lineno.

           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.

           vcg Dump the control flow graph of each function to a file in VCG format.  The file
               name is made by appending .vcg to the source file name.  Note that if the file
               contains more than one function, the generated file cannot be used directly by
               VCG.  You will need to cut and paste each function's graph into its own separate
               file first.

           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.

           mudflap
               Dump each function after adding mudflap instrumentation.  The file name is made by
               appending .mudflap 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.

       -ftree-vectorizer-verbose=n
           This option controls the amount of debugging output the vectorizer prints.  This
           information is written to standard error, unless -fdump-tree-all or -fdump-tree-vect
           is specified, in which case it is output to the usual dump listing file, .vect.  For
           n=0 no diagnostic information is reported.  If n=1 the vectorizer reports each loop
           that got vectorized, and the total number of loops that got vectorized.  If n=2 the
           vectorizer also reports non-vectorized loops that passed the first analysis phase
           (vect_analyze_loop_form) - i.e. countable, inner-most, single-bb, single-entry/exit
           loops.  This is the same verbosity level that -fdump-tree-vect-stats uses.  Higher
           verbosity levels mean either more information dumped for each reported loop, or same
           amount of information reported for more loops: if n=3, vectorizer cost model
           information is reported.  If n=4, alignment related information is added to the
           reports.  If n=5, data-references related information (e.g. memory dependences, memory
           access-patterns) is added to the reports.  If n=6, the vectorizer reports also non-
           vectorized inner-most loops that did not pass the first analysis phase (i.e., may not
           be countable, or may have complicated control-flow).  If n=7, the vectorizer reports
           also non-vectorized nested loops.  If n=8, SLP related information is added to the
           reports.  For n=9, all the information the vectorizer generates during its analysis
           and transformation is reported.  This is the same verbosity level that
           -fdump-tree-vect-details uses.

       -frandom-seed=string
           This option provides a seed that GCC uses when it would otherwise use random numbers.
           It is used to generate 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 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 would produce 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

           would create 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 will be
           created and maintained, but discarded at the end.

       -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 will search---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 will be 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.)

       -feliminate-unused-debug-types
           Normally, when producing DWARF2 output, GCC will emit debugging information for all
           types declared in a compilation unit, regardless of whether or not they are actually
           used in that compilation unit.  Sometimes this is useful, such as 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.
           With this option, GCC will avoid producing debug symbol output for types that are
           nowhere used in the source file being compiled.

   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 would 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 -fcompare-elim -fcprop-registers -fdce -fdefer-pop -fdelayed-branch
           -fdse -fguess-branch-probability -fif-conversion2 -fif-conversion -fipa-pure-const
           -fipa-profile -fipa-reference -fmerge-constants -fsplit-wide-types -ftree-bit-ccp
           -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-copyrename -ftree-dce
           -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre -ftree-phiprop -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 -fexpensive-optimizations -fgcse
           -fgcse-lm -finline-small-functions -findirect-inlining -fipa-sra
           -foptimize-sibling-calls -fpartial-inlining -fpeephole2 -fregmove -freorder-blocks
           -freorder-functions -frerun-cse-after-loop -fsched-interblock  -fsched-spec
           -fschedule-insns  -fschedule-insns2 -fstrict-aliasing -fstrict-overflow
           -ftree-switch-conversion -ftree-pre -ftree-vrp

           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-vectorize 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  -ftree-vect-loop-version

       -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.

           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 would be -fno-foo.  In the table
       below, only one of the forms is listed---the one you typically will 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-default-inline
           Do not make member functions inline by default merely because they are defined inside
           the class scope (C++ only).  Otherwise, when you specify -O, member functions defined
           inside class scope are compiled inline by default; i.e., you don't need to add inline
           in front of the member function name.

       -fno-defer-pop
           Always pop the arguments to each function call as soon as that function returns.  For
           machines which 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.

           Starting with GCC version 4.6, the default setting (when not optimizing for size) for
           32-bit Linux x86 and 32-bit Darwin x86 targets has been changed to
           -fomit-frame-pointer.  The default can be reverted to -fno-omit-frame-pointer by
           configuring GCC with the --enable-frame-pointer configure option.

           Enabled at levels -O, -O2, -O3, -Os.

       -foptimize-sibling-calls
           Optimize sibling and tail recursive calls.

           Enabled at levels -O2, -O3, -Os.

       -fno-inline
           Don't pay attention to the "inline" keyword.  Normally this option is used to keep the
           compiler from expanding any functions inline.  Note that if you are not optimizing, no
           functions can be expanded inline.

       -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.

           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
           Integrate all simple functions into their callers.  The compiler heuristically decides
           which functions are simple enough to be 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 the
           variable was 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 will result 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 will be deleted which will trigger
           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.

           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.

       -fmudflap -fmudflapth -fmudflapir
           For front-ends that support it (C and C++), instrument all risky pointer/array
           dereferencing operations, some standard library string/heap functions, and some other
           associated constructs with range/validity tests.  Modules so instrumented should be
           immune to buffer overflows, invalid heap use, and some other classes of C/C++
           programming errors.  The instrumentation relies on a separate runtime library
           (libmudflap), which will be linked into a program if -fmudflap is given at link time.
           Run-time behavior of the instrumented program is controlled by the MUDFLAP_OPTIONS
           environment variable.  See "env MUDFLAP_OPTIONS=-help a.out" for its options.

           Use -fmudflapth instead of -fmudflap to compile and to link if your program is multi-
           threaded.  Use -fmudflapir, in addition to -fmudflap or -fmudflapth, if
           instrumentation should ignore pointer reads.  This produces less instrumentation (and
           therefore faster execution) and still provides some protection against outright memory
           corrupting writes, but allows erroneously read data to propagate within a program.

       -fthread-jumps
           Perform optimizations where we 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 will follow 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 which
           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 has been 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 runtime 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 will attempt to
           move loads which 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 gcse is enabled.

       -fgcse-sm
           When -fgcse-sm is enabled, a store motion pass is run after global common
           subexpression elimination.  This pass will attempt 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 cleanup redundant spilling.

       -funsafe-loop-optimizations
           If given, the loop optimizer will assume that loop indices do not overflow, and that
           the 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.  Using -Wunsafe-loop-optimizations, the compiler will warn you
           if it finds this kind of loop.

       -fcrossjumping
           Perform cross-jumping transformation.  This transformation unifies equivalent code and
           save 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 include 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 "if-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.

       -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 which 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.

       -fexpensive-optimizations
           Perform a number of minor optimizations that are relatively expensive.

           Enabled at levels -O2, -O3, -Os.

       -foptimize-register-move
       -fregmove
           Attempt to reassign register numbers in move instructions and as operands of other
           simple instructions in order to maximize the amount of register tying.  This is
           especially helpful on machines with two-operand instructions.

           Note -fregmove and -foptimize-register-move are the same optimization.

           Enabled at levels -O2, -O3, -Os.

       -fira-algorithm=algorithm
           Use specified coloring algorithm for the integrated register allocator.  The algorithm
           argument should be "priority" or "CB".  The first algorithm specifies Chow's priority
           coloring, the second one specifies Chaitin-Briggs coloring.  The second algorithm can
           be unimplemented for some architectures.  If it is implemented, it is the default
           because Chaitin-Briggs coloring as a rule generates a better code.

       -fira-region=region
           Use specified regions for the integrated register allocator.  The region argument
           should be one of "all", "mixed", or "one".  The first value means using all loops as
           register allocation regions, the second value which is the default means using all
           loops except for loops with small register pressure as the regions, and third one
           means using all function as a single region.  The first value can give best result for
           machines with small size and irregular register set, the third one results in faster
           and generates decent code and the smallest size code, and the default value usually
           give the best results in most cases and for most architectures.

       -fira-loop-pressure
           Use IRA to evaluate register pressure in loops for decision to move loop invariants.
           Usage of this option usually results in generation of faster and smaller code on
           machines with big register files (>= 32 registers) but it can slow compiler down.

           This option is enabled at level -O3 for some targets.

       -fno-ira-share-save-slots
           Switch off sharing stack slots used for saving call used hard registers living through
           a call.  Each hard register will get a separate stack slot and as a result function
           stack frame will be bigger.

       -fno-ira-share-spill-slots
           Switch off sharing stack slots allocated for pseudo-registers.  Each pseudo-register
           which did not get a hard register will get a separate stack slot and as a result
           function stack frame will be bigger.

       -fira-verbose=n
           Set up how verbose dump file for the integrated register allocator will be.  Default
           value is 5.  If the value is greater or equal to 10, the dump file will be stderr as
           if the value were n minus 10.

       -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 the 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 as a consequence register spills in the 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 will be 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) will be examined for a dependency on a stalled
           insn that is 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, do use superblock scheduling algorithm.
           Superblock scheduling allows motion across basic block boundaries resulting on 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
           The modulo scheduling comes before the traditional scheduling, if a loop was modulo
           scheduled we may want to prevent the later scheduling passes from changing its
           schedule, we use this option to control that.

       -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 until 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 until -fsel-sched-pipelining is turned on.

       -fcaller-saves
           Enable values to be allocated in registers that will be 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 than would
           otherwise be produced.

           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.

       -fconserve-stack
           Attempt to minimize stack usage.  The compiler will attempt 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-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.

       -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 cannot escape the compilation unit.
           Enabled by default at -O and higher.

       -fipa-struct-reorg
           Perform structure reorganization optimization, that change C-like structures layout in
           order to better utilize spatial locality.  This transformation is affective for
           programs containing arrays of structures.  Available in two compilation modes:
           profile-based (enabled with -fprofile-generate) or static (which uses built-in
           heuristics).  It works only in whole program mode, so it requires -fwhole-program to
           be enabled.  Structures considered cold by this transformation are not affected (see
           --param struct-reorg-cold-struct-ratio=value).

           With this flag, the program debug info reflects a new structure layout.

       -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 will perform 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-matrix-reorg
           Perform matrix flattening and transposing.  Matrix flattening tries to replace an
           m-dimensional matrix with its equivalent n-dimensional matrix, where n < m.  This
           reduces the level of indirection needed for accessing the elements of the matrix. The
           second optimization is matrix transposing that attempts to change the order of the
           matrix's dimensions in order to improve cache locality.  Both optimizations need the
           -fwhole-program flag.  Transposing is enabled only if profiling information is
           available.

       -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.

       -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-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 builtin 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 which will later be 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-ppl and --with-cloog 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 will transform the loop as if the user had 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-ppl
           and --with-cloog 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 will transform the loop as if the user had 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-ppl
           and --with-cloog 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 will transform the loop as if the user had 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
           will iterate over a smaller amount of data that 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-ppl
           and --with-cloog 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 CLooG, like index
           splitting and dead code elimination in loops.

       -floop-flatten
           Removes the loop nesting structure: transforms the loop nest into a single loop.  This
           transformation can be useful to vectorize all the levels of the loop nest.

       -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;

           would be 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 would be
           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 the loop for that 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-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-vectorize
           Perform loop vectorization on trees. This flag is enabled by default at -O3.

       -ftree-slp-vectorize
           Perform basic block vectorization on trees. This flag is enabled by default at -O3 and
           when -ftree-vectorize is enabled.

       -ftree-vect-loop-version
           Perform loop versioning when doing loop vectorization on trees.  When a loop appears
           to be vectorizable except that data alignment or data dependence cannot be determined
           at compile time then vectorized and non-vectorized versions of the loop are generated
           along with runtime checks for alignment or dependence to control which version is
           executed.  This option is enabled by default except at level -Os where it is disabled.

       -fvect-cost-model
           Enable cost model for vectorization.

       -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.

       -ftracer
           Perform tail duplication to enlarge superblock size.  This transformation simplifies
           the control flow of the function allowing other optimizations to do better job.

       -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.  This option makes
           code larger, and may or may not make it run faster.

       -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,

       -fsplit-ivs-in-unroller
           Enables expressing 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.

           Combination of -fweb and CSE is often sufficient to obtain the same effect.  However
           in cases the loop body is more complicated than a single basic block, this is not
           reliable.  It also does not work at all on some of the architectures due to
           restrictions in the CSE pass.

           This optimization is enabled by default.

       -fvariable-expansion-in-unroller
           With this option, the compiler will create 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 will use 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 will be 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.

       -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 in 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 will work 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 will not
           happen.  This permits various optimizations.  For example, the compiler will assume
           that an expression like "i + 10 > i" will always be 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 will overflow
           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 would align 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
           will not be 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 will not be
           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.
           The hope is that the loop will be executed many times, which will make up for any
           execution of the dummy operations.

           -fno-align-loops and -falign-loops=1 are equivalent and mean that loops will not be
           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 will not be
           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 will not be removed.  This option is intended to support
           existing code which relies on a particular ordering.  For new code, it is better to
           use attributes.

           Enabled at level -O0.  When disabled explicitly, it also imply -fno-section-anchors
           that 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 will 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. If gold is used as the linker plugin,
           "externally_visible" attributes are automatically added to functions (not variable yet
           due to a current gold issue) that are accessed outside of LTO objects according to
           resolution file produced by gold.  For other linkers that cannot generate resolution
           file, explicit "externally_visible" attributes are still necessary.  While this option
           is equivalent to proper use of the "static" keyword for programs consisting of a
           single file, in combination with option -flto this flag can be used to compile many
           smaller scale programs since the functions and variables become local for the whole
           combined compilation unit, not for the single source file itself.

           This option implies -fwhole-file for Fortran programs.

       -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 needs to 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 the
           -flto flag needs to be passed to both the compile and the link commands.

           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.

           Note that 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.
           This means that object files with LTO information can be linked as normal object
           files; if -flto is not passed to the linker, no interprocedural optimizations are
           applied.

           Additionally, the optimization flags used to compile individual files are not
           necessarily related to those used at link time.  For instance,

                   gcc -c -O0 -flto foo.c
                   gcc -c -O0 -flto bar.c
                   gcc -o myprog -flto -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 without -flto, then myprog is not optimized.

           When producing the final binary with -flto, 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 that GCC preserves when generating bytecodes, as
           they need to be used during the final link stage.  Currently, the following options
           are saved into the GIMPLE bytecode files: -fPIC, -fcommon and all the -m target flags.

           At link time, these options are read in and reapplied.  Note that the current
           implementation makes no attempt to recognize conflicting values for these options.  If
           different files have conflicting option values (e.g., one file is compiled with -fPIC
           and another isn't), the compiler simply uses the last value read from the bytecode
           files.  It is recommended, then, that you compile all the files participating in the
           same link with the same options.

           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
           runtime.

           Another feature of LTO is that it is possible to apply interprocedural optimizations
           on files written in different languages.  This requires support in the language front
           end.  Currently, the C, C++ and Fortran front ends are capable of emitting GIMPLE
           bytecodes, so something like this should work:

                   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; all you need to add is -flto to all the
           compile and link commands.

           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 enable this feature, use the flag -fuse-linker-plugin
           at link time:

                   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.

           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 will not
           work with an older/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 wrong
           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.

           This option is disabled by default.

       -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).
           Specifying "none" as an algorithm disables partitioning and streaming completely. The
           default value is "balanced".

       -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.

       -fuse-linker-plugin
           Enables the use of a linker plugin during link-time optimization.  This option relies
           on the linker plugin support in linker that 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).

       -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, we
           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 will
           use heuristics to correct or smooth out such inconsistencies. By default, GCC will
           emit 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.  By default, GCC will use the current directory as path, thus the profile
           data file will appear 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 will look at the path to find the profile feedback data
           files. See -fprofile-dir.

       -fprofile-use
       -fprofile-use=path
           Enable profile feedback directed optimizations, and optimizations generally profitable
           only with profile feedback available.

           The following options are enabled: "-fbranch-probabilities", "-fvpt",
           "-funroll-loops", "-fpeel-loops", "-ftracer"

           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 will look at the path to find the profile feedback data
           files. See -fprofile-dir.

       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 will follow 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 -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 which 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 which 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 which 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 a code which 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 which 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 which 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 constant as single precision constant instead of implicitly
           converting it to double precision constant.

       -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 the 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.

       -fvpt
           If combined with -fprofile-arcs, it instructs the compiler to add a 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 operation 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 will most benefit processors with
           lots of registers.  Depending on the debug information format adopted by the target,
           however, it can make debugging impossible, since variables will no longer stay in a
           "home register".

           Enabled by default with -funroll-loops and -fpeel-loops.

       -ftracer
           Perform tail duplication to enlarge superblock size.  This transformation simplifies
           the control flow of the function allowing other optimizations to do 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 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 the loops for that 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 will create larger object and
           executable files and will also be slower.  You will not be able to 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 in 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.

           NOTE: In Ubuntu 6.10 and later versions this option is enabled by default for C, C++,
           ObjC, ObjC++, if none of -fno-stack-protector, -nostdlib, nor -ffreestanding are
           found.

       -fstack-protector-all
           Like -fstack-protector except that all functions are protected.

       -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; }

           would usually calculate the addresses of all three variables, but if you compile it
           with -fsection-anchors, it will access 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 will not inline functions that contain more that 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 given in
           the following table:

           struct-reorg-cold-struct-ratio
               The threshold ratio (as a percentage) between a structure frequency and the
               frequency of the hottest structure in the program.  This parameter is used by
               struct-reorg optimization enabled by -fipa-struct-reorg.  We say that if the ratio
               of a structure frequency, calculated by profiling, to the hottest structure
               frequency in the program is less than this parameter, then structure
               reorganization is not applied to this structure.  The default is 10.

           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 crossjumping.  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 compile time
               increase with probably small improvement in executable size.

           min-crossjump-insns
               The minimum number of instructions which must be matched at the end of two blocks
               before crossjumping will be performed on them.  This value is ignored in the case
               where all instructions in the block being crossjumped 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 is
               searched, the time savings from filling the delay slot will be minimal so stop
               searching.  Increasing values mean more aggressive optimization, making the
               compile time increase with probably small improvement in executable run 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
               compile 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 will be allocated in order to
               perform the global common subexpression elimination optimization.  If more memory
               than specified is required, the optimization will not be done.

           max-gcse-insertion-ratio
               If the ratio of expression insertions to deletions is larger than this value for
               any expression, then RTL PRE will insert or remove the expression and thus leave
               partially redundant computations in the instruction stream.  The default value is
               20.

           max-pending-list-length
               The maximum number of pending dependencies scheduling will allow 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-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 will consider 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 will be investigated.  To
               those functions, a different (more restrictive) limit compared to functions
               declared inline can be applied.  The default value is 40.

           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 backend.  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 (consider unit consisting of function A that is inline and
               B that just calls A three time.  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 30 which limits unit growth to 1.3 times the original 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.  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 maximum number of instructions out-of-line copy of self recursive inline
               function can grow into by performing recursive inlining.

               For functions declared inline --param max-inline-insns-recursive is taken into
               account.  For function not declared inline, recursive inlining happens only when
               -finline-functions (included in -O3) is enabled and --param max-inline-insns-
               recursive-auto is used.  The default value is 450.

           max-inline-recursive-depth
           max-inline-recursive-depth-auto
               Specifies maximum recursion depth used by the recursive inlining.

               For functions declared inline --param max-inline-recursive-depth is taken into
               account.  For function not declared inline, recursive inlining happens only when
               -finline-functions (included in -O3) is enabled and --param max-inline-recursive-
               depth-auto is used.  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 will recurse via given call
               expression.  This parameter limits inlining only to call expression whose
               probability exceeds given threshold (in percents).  The default value is 10.

           early-inlining-insns
               Specify growth that early inliner can make.  In effect it increases amount of
               inlining for code having large abstraction penalty.  The default value is 10.

           max-early-inliner-iterations
           max-early-inliner-iterations
               Limit of iterations of early inliner.  This basically bounds number of nested
               indirect calls early inliner can resolve.  Deeper chains are still handled by late
               inlining.

           comdat-sharing-probability
           comdat-sharing-probability
               Probability (in percent) that C++ inline function with comdat visibility will be
               shared across multiple compilation units.  The default value is 20.

           min-vect-loop-bound
               The minimum number of iterations under which a loop will not get 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 will be with simple
               expressions, i.e., the expressions which have cost less than gcse-unrestricted-
               cost.  Specifying 0 will disable 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 will 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 will be.  Specifying 0 will allow 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 will avoid
               limiting the search, but may slow down compilation of huge functions.  The default
               value is 30.

           max-unrolled-insns
               The maximum number of instructions that a loop should have if that loop is
               unrolled, and if the loop is unrolled, it 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 should have if that loop is unrolled, and if the loop is unrolled, it
               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 should have if that loop is peeled,
               and if the loop is peeled, it determines how many times the loop code is peeled.

           max-peel-times
               The maximum number of peelings of a single loop.

           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 that all candidates
               are considered for each use in induction variable optimizations.  Only the most
               relevant candidates are considered if there are more candidates, 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 number of candidates in the set is smaller than this value, we always try to
               remove unnecessary ivs from the set during its optimization when a new iv is added
               to the set.

           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 will be 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 runtime checks that can be performed when doing loop
               versioning for alignment in the vectorizer.  See option ftree-vect-loop-version
               for more information.

           vect-max-version-for-alias-checks
               The maximum number of runtime checks that can be performed when doing loop
               versioning for alias in the vectorizer.  See option ftree-vect-loop-version for
               more information.

           max-iterations-to-track
               The maximum number of iterations of a loop the brute force algorithm for analysis
               of # of iterations of the loop tries to evaluate.

           hot-bb-count-fraction
               Select fraction of the maximal count of repetitions of basic block in program
               given basic block needs to have to be considered hot.

           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 function contain single loop with known bound and other loop with
               unknown.  We predict the known number of iterations correctly, while the unknown
               number of iterations average to roughly 10.  This means that the loop without
               bounds would appear artificially cold relative to the other one.

           align-threshold
               Select fraction of the maximal frequency of executions of basic block in function
               given basic block will get aligned.

           align-loop-iterations
               A loop expected to iterate at lest the selected number of iterations will get
               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 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
               rather hokey argument, as most of the duplicates will be 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 do have 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
               Maximum number of basic blocks on path that cse considers.  The default is 10.

           max-cse-insns
               The maximum instructions CSE process 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 which 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 compile
               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 compile time
               increase with probably slightly better performance.  The default value is 500.

           reorder-blocks-duplicate
           reorder-blocks-duplicate-feedback
               Used by 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 is used only when profile feedback is
               available and 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.  0 - disable
               region extension, N - do at most N iterations.  The default value is 0.

           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
               insn will be scheduled.  The default value is 40.

           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 will be 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 will generate.  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.

           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.

           min-virtual-mappings
               Specifies the minimum number of virtual mappings in the incremental SSA updater
               that should be registered to trigger the virtual mappings heuristic defined by
               virtual-mappings-ratio.  The default value is 100.

           virtual-mappings-ratio
               If the number of virtual mappings is virtual-mappings-ratio bigger than the number
               of virtual symbols to be updated, then the incremental SSA updater switches to a
               full update for those symbols.  The default ratio is 3.

           ssp-buffer-size
               The minimum size of buffers (i.e. arrays) that will receive stack smashing
               protection when -fstack-protection is used.

           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 we will treat 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 we prefetch 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 will refuse 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 will
               allow 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 will not be done and
               optimizations depending on it will be disabled.  The default maximum SCC size is
               10000.

           ira-max-loops-num
               IRA uses a regional register allocation by default.  If a function contains loops
               more than number given by the parameter, only at most given number of the most
               frequently executed loops will form regions for the regional register allocation.
               The default value of the parameter is 100.

           ira-max-conflict-table-size
               Although IRA uses a sophisticated algorithm of compression conflict table, the
               table can be still big for huge functions.  If the conflict table for a function
               could be more than size in MB given by the parameter, the conflict table is not
               built and faster, simpler, and lower quality register allocation algorithm will be
               used.  The algorithm do not use pseudo-register conflicts.  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 decision
               to move loop invariants (see -O3).  The number of available registers reserved for
               some other purposes is described by this parameter.  The default value of the
               parameter is 2 which is minimal number of registers needed for execution of
               typical instruction.  This value is the best found from numerous experiments.

           loop-invariant-max-bbs-in-loop
               Loop invariant motion can be very expensive, both in compile 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.

           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.

           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 will replace 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.

           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 compile 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.

           devirt-type-list-size
               IPA-CP attempts to track all possible types passed to a function's parameter in
               order to perform devirtualization.  devirt-type-list-size is the maximum number of
               types it stores per a single formal parameter of a function.

           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.

           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.

   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 which GCC does not know how to 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.

       -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.

           "c1x"
               The next version of the ISO C standard, still under development.

           "gnu90"
           "gnu89"
               The 1990 C standard plus GNU extensions.  This is the default.

           "gnu99"
           "gnu9x"
               The 1999 C standard plus GNU extensions.

           "gnu1x"
               The next version of the ISO C standard, still under development, 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 experimental; in a
           future version of GCC, it will be enabled by default for C99 and C++.

       -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.

       -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 which GCC does not know how to 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.

       -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
           will be passed to the linker, options specifying linkage of the system libraries, such
           as "-static-libgcc" or "-shared-libgcc", will be 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 will be passed to the linker, options
           specifying linkage of the system libraries, such as "-static-libgcc" or
           "-shared-libgcc", will be 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 that 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.  (For example, __main, used to ensure C++
           constructors will be called.)

       -pie
           Produce a position independent executable on targets which support it.  For
           predictable results, you must also specify the same set of options that were used to
           generate code (-fpie, -fPIE, or model suboptions) when you specify this option.

       -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 that were used to generate code (-fpic, -fPIC, or
           model suboptions) when you specify this 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
           will not always be 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 will link the shared version of libgcc into shared libraries by
           default.  Otherwise, it will take advantage of the linker and optimize 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-libstdc++
           When the g++ program is used to link a C++ program, it will normally automatically
           link against libstdc++.  If libstdc++ is available as a shared library, and the
           -static option is not used, then this will link 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 which GCC does not know how to 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.

   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 will be ignored.  The directory will still be
           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 which 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 was not specified, the driver tries two standard
           prefixes, which are /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 will check to see if the path provided by the -B refers to a directory,
           and if necessary it will add 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 includes 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 run-time 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 will be 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 that 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 would normally search for headers in /usr/include and libraries in /usr/lib,
           it will instead search dir/usr/include and dir/usr/lib.

           If you use both this option and the -isysroot option, then the --sysroot option will
           apply to libraries, but the -isysroot option will apply 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 will still work, but the library aspect will not.

       -I- This option has been deprecated.  Please use -iquote instead for -I directories before
           the -I- and remove the -I-.  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-, 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 which was current when the compiler was 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.

       ARC Options

       These options are defined for ARC implementations:

       -EL Compile code for little endian mode.  This is the default.

       -EB Compile code for big endian mode.

       -mmangle-cpu
           Prepend the name of the CPU to all public symbol names.  In multiple-processor
           systems, there are many ARC variants with different instruction and register set
           characteristics.  This flag prevents code compiled for one CPU to be linked with code
           compiled for another.  No facility exists for handling variants that are "almost
           identical".  This is an all or nothing option.

       -mcpu=cpu
           Compile code for ARC variant cpu.  Which variants are supported depend on the
           configuration.  All variants support -mcpu=base, this is the default.

       -mtext=text-section
       -mdata=data-section
       -mrodata=readonly-data-section
           Put functions, data, and readonly data in text-section, data-section, and readonly-
           data-section respectively by default.  This can be overridden with the "section"
           attribute.

       ARM Options

       These -m options are defined for Advanced RISC Machines (ARM) architectures:

       -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 will cause the stack frames not to be
           generated for leaf functions.  The default is -mno-apcs-frame.

       -mapcs
           This is a synonym for -mapcs-frame.

       -mthumb-interwork
           Generate code which supports calling between the ARM and Thumb instruction sets.
           Without this option 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.

       -mno-sched-prolog
           Prevent the reordering of instructions in the function prolog, or the merging of those
           instruction with the instructions in the function's body.  This means that all
           functions will 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 if 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.

       -mhard-float
           Equivalent to -mfloat-abi=hard.

       -msoft-float
           Equivalent to -mfloat-abi=soft.

       -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.

       -mwords-little-endian
           This option only applies when generating code for big-endian processors.  Generate
           code for a little-endian word order but a big-endian byte order.  That is, a byte
           order of the form 32107654.  Note: this option should only be used if you require
           compatibility with code for big-endian ARM processors generated by versions of the
           compiler prior to 2.8.

       -mcpu=name
           This specifies the name of the target ARM processor.  GCC uses this name to determine
           what kind of instructions it can emit when generating assembly code.  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-a15, cortex-r4,
           cortex-r4f, cortex-r5, cortex-m4, cortex-m3, cortex-m1, cortex-m0, xscale, iwmmxt,
           iwmmxt2, ep9312.

           -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 Linux, and not all architectures are
           recognised.  If the auto-detect is unsuccessful the option has no effect.

       -mtune=name
           This option is very similar to the -mcpu= option, except that instead of specifying
           the actual target processor type, and hence restricting which instructions can be
           used, it specifies that GCC should tune the performance of the code as if the target
           were of the type specified in this option, but still choosing the instructions that it
           will generate based on the CPU specified by a -mcpu= option.  For some ARM
           implementations better performance can be obtained by using this option.

           -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 Linux, and not all architectures are
           recognised.  If the auto-detect is unsuccessful the option has no effect.

       -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, iwmmxt, iwmmxt2, ep9312.

           -march=native causes the compiler to auto-detect the architecture of the build
           computer.  At present, this feature is only supported on Linux, and not all
           architectures are recognised.  If the auto-detect is unsuccessful the option has no
           effect.

       -mfpu=name
       -mfpe=number
       -mfp=number
           This specifies what floating point hardware (or hardware emulation) is available on
           the target.  Permissible names are: fpa, fpe2, fpe3, maverick, vfp, vfpv3, vfpv3-fp16,
           vfpv3-d16, vfpv3-d16-fp16, vfpv3xd, vfpv3xd-fp16, neon, neon-fp16, vfpv4, vfpv4-d16,
           fpv4-sp-d16 and neon-vfpv4.  -mfp and -mfpe are synonyms for -mfpu=fpenumber, for
           compatibility with older versions of GCC.

           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 will not be used 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 size of all structures and unions will be 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 the 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 will
           be 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 will lie 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 will be turned into long calls.
           The heuristic is that static functions, functions which 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, will
           not be turned into long calls.  The exception to this rule is 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, will always be
           turned into long calls.

           This feature is not enabled by default.  Specifying -mno-long-calls will restore the
           default behavior, as will 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 run-time 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.  The default is R10 unless stack-
           checking is enabled, when R9 is used.

       -mcirrus-fix-invalid-insns
           Insert NOPs into the instruction stream to in order to work around problems with
           invalid Maverick instruction combinations.  This option is only valid if the
           -mcpu=ep9312 option has been used to enable generation of instructions for the Cirrus
           Maverick floating point co-processor.  This option is not enabled by default, since
           the problem is only present in older Maverick implementations.  The default can be re-
           enabled by use of the -mno-cirrus-fix-invalid-insns switch.

       -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
           Generate code for the Thumb instruction set.  The default is to use the 32-bit ARM
           instruction set.  This option automatically enables either 16-bit Thumb-1 or mixed
           16/32-bit Thumb-2 instructions based on the -mcpu=name and -march=name options.  This
           option is not passed to the assembler. If you want to force assembler files to be
           interpreted as Thumb code, either add a .thumb directive to the source or pass the
           -mthumb option directly to the assembler by prefixing it with -Wa.

       -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.

       -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.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
           Specify ATMEL AVR instruction set or MCU type.

           Instruction set avr1 is for the minimal AVR core, not supported by the C compiler,
           only for assembler programs (MCU types: at90s1200, attiny10, attiny11, attiny12,
           attiny15, attiny28).

           Instruction set avr2 (default) is for the classic AVR core with up to 8K program
           memory space (MCU types: at90s2313, at90s2323, attiny22, at90s2333, at90s2343,
           at90s4414, at90s4433, at90s4434, at90s8515, at90c8534, at90s8535).

           Instruction set avr3 is for the classic AVR core with up to 128K program memory space
           (MCU types: atmega103, atmega603, at43usb320, at76c711).

           Instruction set avr4 is for the enhanced AVR core with up to 8K program memory space
           (MCU types: atmega8, atmega83, atmega85).

           Instruction set avr5 is for the enhanced AVR core with up to 128K program memory space
           (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323, atmega64, atmega128,
           at43usb355, at94k).

       -mno-interrupts
           Generated code is not compatible with hardware interrupts.  Code size will be smaller.

       -mcall-prologues
           Functions prologues/epilogues expanded as call to appropriate subroutines.  Code size
           will be smaller.

       -mtiny-stack
           Change only the low 8 bits of the stack pointer.

       -mint8
           Assume int to be 8 bit integer.  This affects the sizes of all types: A char will be 1
           byte, an int will be 1 byte, a long will be 2 bytes and long long will be 4 bytes.
           Please note that this option does not comply to the C standards, but it will provide
           you with smaller code size.

       "EIND" and Devices with more than 128k Bytes of Flash

       Pointers in the implementation are 16 bits wide.  The address of a function or label is
       represented as word address so that indirect jumps and calls can address any code address
       in the range of 64k words.

       In order to faciliate indirect jump on devices with more than 128k 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 and are subject to some
       limitations:

       ·   The compiler never sets "EIND".

       ·   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").

       ·   The compiler uses "EIND" implicitely in "EICALL"/"EIJMP" instructions or might read
           "EIND" directly.

       ·   The compiler assumes that "EIND" never changes during the startup code or run of the
           application. In particular, "EIND" is not saved/restored in function or interrupt
           service routine prologue/epilogue.

       ·   It is legitimate for user-specific startup code to set up "EIND" early, for example by
           means of initialization code located in section ".init3", and thus prior to general
           startup code that initializes RAM and calls constructors.

       ·   For indirect calls to functions and computed goto, the linker will generate stubs.
           Stubs are jump pads sometimes also called trampolines. Thus, the indirect call/jump
           will jump to such a stub.  The stub contains a direct jump to the desired address.

       ·   Stubs will be 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 will emit 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.>
       ·   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.

       ·   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:

                   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.

       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.  The optional sirevision specifies the silicon
           revision of the target Blackfin processor.  Any workarounds available for the targeted
           silicon revision will be enabled.  If sirevision is none, no workarounds are enabled.
           If sirevision is any, all workarounds for the targeted processor will be 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.

           Support for bf561 is incomplete.  For bf561, Only the processor macro is defined.
           Without this option, bf532 is used as the processor by default.  The corresponding
           predefined processor macros for cpu is to be defined.  And for bfin-elf toolchain,
           this causes the hardware BSP provided by libgloss to be linked in if -msim is not
           given.

       -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 will ensure 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 will ensure 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 will be generated for jump and call insns.

       -mshared-library-id=n
           Specified the identification number of the ID based shared library being compiled.
           Specifying a value of 0 will generate more compact code, specifying other values will
           force 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 will lie 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 will restore 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 standalone application for multicore Blackfin processor. Proper start files and
           link scripts will be used to support multicore.  This option defines
           "__BFIN_MULTICORE". It can only be used with -mcpu=bf561[-sirevision]. It can be used
           with -mcorea or -mcoreb. If it's used without -mcorea or -mcoreb, single
           application/dual core programming model is used. In this model, the main function of
           Core B should be named as coreb_main. If it's used with -mcorea or -mcoreb, one
           application per core programming model is used.  If this option is not used, single
           core application programming model is used.

       -mcorea
           Build standalone application for Core A of BF561 when using one application per core
           programming model. Proper start files and link scripts will be used to support Core A.
           This option defines "__BFIN_COREA". It must be used with -mmulticore.

       -mcoreb
           Build standalone application for Core B of BF561 when using one application per core
           programming model. Proper start files and link scripts will be used to support Core B.
           This option defines "__BFIN_COREB". When this option is used, coreb_main should be
           used instead of main. It must be used with -mmulticore.

       -msdram
           Build standalone application for SDRAM. Proper start files and link scripts will be
           used to put the application into SDRAM.  Loader should initialize SDRAM before loading
           the application into SDRAM. This option defines "__BFIN_SDRAM".

       -micplb
           Assume that ICPLBs are enabled at runtime.  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.

       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 to turn 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) arranges (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 that sets 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 variable 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.

       CRX Options

       These options are defined specifically for the CRX ports.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by default.

       -mpush-args
           Push instructions will be used to pass outgoing arguments when functions are called.
           Enabled by default.

       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 will create an object file for
       the single architecture that it 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 targetting, 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, will only permit 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, will fail and print 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, will quietly give 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 will be 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 which are compatible with as many systems and code bases as
           possible.

       -mkernel
           Enable kernel development mode.  The -mkernel option sets -static, -fno-common,
           -fno-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 turn around development.  Needed to enable 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 be loading the build output file being
           linked.  See man ld(1) for more information.

       -dynamiclib
           When passed this option, GCC will produce 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 will be 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 will 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.  Under DEC Unix, this has the effect that
           IEEE-conformant math library routines will be linked in.

       -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 will output the
           constant as a literal and generate code to load it from the data segment at runtime.

           Use this option to require GCC to construct all integer constants using code, even if
           it takes more instructions (the maximum is six).

           You would 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.

       -malpha-as
       -mgas
           Select whether to generate code to be assembled by the vendor-supplied assembler
           (-malpha-as) or by the GNU assembler -mgas.

       -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 was
           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
           will choose the default values for the instruction set from the processor you specify.
           If you do not specify a processor type, GCC will default 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 Linux/GNU 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 Linux/GNU 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.

       DEC Alpha/VMS Options

       These -m options are defined for the DEC Alpha/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 64bit memory allocation routines.

       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 will fit into a 20-bit range.

       -mno-lsim
           Assume that run-time 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, that 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.

       -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 will run 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.

       -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.

       -mjump-in-delay
           Fill delay slots of function calls with unconditional jump instructions by modifying
           the return pointer for the function call to be the target of the conditional jump.

       -mdisable-fpregs
           Prevent floating point registers from being used in any manner.  This is necessary for
           compiling kernels which perform lazy context switching of floating point registers.
           If you use this option and attempt to perform floating point operations, the compiler
           will abort.

       -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 which performs faster indirect calls.

           This option will 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 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.

       -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 GNU ld specific options.  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 have any affect on 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 HP ld specific options.  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 have
           any affect on 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 will degrade 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.

       Intel 386 and AMD x86-64 Options

       These -m options are defined for the i386 and x86-64 family of computers:

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code, except for the ABI
           and the set of available instructions.  The choices for cpu-type are:

           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 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, the code
               generated option will change to reflect the processors that were most common when
               that version of GCC was 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.

           native
               This selects the CPU to tune for at compilation time by determining the processor
               type of the compiling machine.  Using -mtune=native will produce code optimized
               for the local machine under the constraints of the selected instruction set.
               Using -march=native will enable all instruction subsets supported by the local
               machine (hence the result might not run on different machines).

           i386
               Original Intel's i386 CPU.

           i486
               Intel's i486 CPU.  (No scheduling is implemented for this chip.)

           i586, pentium
               Intel Pentium CPU with no MMX support.

           pentium-mmx
               Intel PentiumMMX CPU based on Pentium core with MMX instruction set support.

           pentiumpro
               Intel PentiumPro CPU.

           i686
               Same as "generic", but when used as "march" option, PentiumPro instruction set
               will be used, so the code will run on all i686 family chips.

           pentium2
               Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support.

           pentium3, pentium3m
               Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set
               support.

           pentium-m
               Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set
               support.  Used by Centrino notebooks.

           pentium4, pentium4m
               Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.

           prescott
               Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction
               set support.

           nocona
               Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, SSE2 and
               SSE3 instruction set support.

           core2
               Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 instruction
               set support.

           corei7
               Intel Core i7 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1 and
               SSE4.2 instruction set support.

           corei7-avx
               Intel Core i7 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, AVX, AES and PCLMUL instruction set support.

           core-avx-i
               Intel Core CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1,
               SSE4.2, AVX, AES, PCLMUL, FSGSBASE, RDRND and F16C instruction set support.

           atom
               Intel Atom CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 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
               AMD K8 core based CPUs with x86-64 instruction set support.  (This supersets MMX,
               SSE, SSE2, 3DNow!, enhanced 3DNow! and 64-bit instruction set extensions.)

           k8-sse3, opteron-sse3, athlon64-sse3
               Improved versions of k8, opteron and athlon64 with SSE3 instruction set support.

           amdfam10, barcelona
               AMD Family 10h core based CPUs with x86-64 instruction set support.  (This
               supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!, enhanced 3DNow!, ABM 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 Winchip2 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 CPU with MMX and SSE instruction set support.  (No scheduling is
               implemented for this chip.)

           geode
               Embedded AMD CPU with MMX and 3DNow! instruction set support.

           While picking a specific cpu-type will schedule things appropriately for that
           particular chip, the compiler will not generate any code that does not run on the i386
           without the -march=cpu-type option being used.

       -march=cpu-type
           Generate instructions for the machine type cpu-type.  The choices for cpu-type are the
           same as for -mtune.  Moreover, specifying -march=cpu-type implies -mtune=cpu-type.

       -mcpu=cpu-type
           A deprecated synonym for -mtune.

       -mfpmath=unit
           Generate floating point arithmetics for selected unit unit.  The choices for unit are:

           387 Use the standard 387 floating point coprocessor present majority of chips and
               emulated otherwise.  Code compiled with this option will run almost everywhere.
               The temporary results are computed in 80bit precision instead of 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 i386 compiler.

           sse Use scalar floating point instructions present in the SSE instruction set.  This
               instruction set is supported by Pentium3 and newer chips, in the AMD line by
               Athlon-4, Athlon-xp and Athlon-mp chips.  The earlier version of SSE instruction
               set supports only single precision arithmetics, thus the double and extended
               precision arithmetics is still done using 387.  Later version, present only in
               Pentium4 and the future AMD x86-64 chips supports double precision arithmetics
               too.

               For the i386 compiler, you need to 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 80bit.

               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 double 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 instable performance.

       -masm=dialect
           Output asm instructions using selected dialect.  Supported choices are intel or att
           (the default one).  Darwin does not support intel.

       -mieee-fp
       -mno-ieee-fp
           Control whether or not the compiler uses IEEE floating point comparisons.  These
           handle correctly 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 FreeBSD, OpenBSD and NetBSD.  This option is overridden when -march
           indicates that the target CPU will always have an FPU and so the instruction will not
           need emulation.  As of revision 2.6.1, 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 will produce 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
           will be aligned differently than the published application binary interface
           specifications for the 386 and will not be 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 i386 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) would prefer "long double" to be aligned to
           an 8 or 16 byte boundary.  In arrays or structures conforming to the ABI, this would
           not be possible.  So specifying a -m128bit-long-double will align "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 to be 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, the structures and
           arrays containing "long double" variables will change their size as well as function
           calling convention for function taking "long double" will be modified.  Hence they
           will not be binary compatible with arrays or structures in code compiled without that
           switch.

       -mlarge-data-threshold=number
           When -mcmodel=medium is specified, the data greater than threshold are placed in large
           data section.  This value must be the same across all object 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 will be generated
           for calls to those functions.

           In addition, seriously incorrect code will result 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 Intel x86, the -mstackrealign option will generate
           an alternate prologue and epilogue that realigns the runtime stack if necessary.  This
           supports mixing legacy codes that keep a 4-byte aligned stack with modern codes that
           keep a 16-byte stack 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).

       -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 will be used.

           On Pentium and PentiumPro, "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 will most likely misalign 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
       -mno-mmx
       -msse
       -mno-sse
       -msse2
       -mno-sse2
       -msse3
       -mno-sse3
       -mssse3
       -mno-ssse3
       -msse4.1
       -mno-sse4.1
       -msse4.2
       -mno-sse4.2
       -msse4
       -mno-sse4
       -mavx
       -mno-avx
       -maes
       -mno-aes
       -mpclmul
       -mno-pclmul
       -mfsgsbase
       -mno-fsgsbase
       -mrdrnd
       -mno-rdrnd
       -mf16c
       -mno-f16c
       -msse4a
       -mno-sse4a
       -mfma4
       -mno-fma4
       -mxop
       -mno-xop
       -mlwp
       -mno-lwp
       -m3dnow
       -mno-3dnow
       -mpopcnt
       -mno-popcnt
       -mabm
       -mno-abm
       -mbmi
       -mno-bmi
       -mtbm
       -mno-tbm
           These switches enable or disable the use of instructions in the MMX, SSE, SSE2, SSE3,
           SSSE3, SSE4.1, AVX, AES, PCLMUL, FSGSBASE, RDRND, F16C, SSE4A, FMA4, XOP, LWP, ABM,
           BMI, or 3DNow! extended instruction sets.  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 have SSE/SSE2 instructions generated 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 will enable GCC to use these extended instructions in generated code,
           even without -mfpmath=sse.  Applications which perform runtime 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.

       -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.

       -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 AVX to SSE transition penalty as well as
           remove unnecessary zeroupper intrinsics.

       -mcx16
           This option will enable GCC to use CMPXCHG16B instruction in generated code.
           CMPXCHG16B allows for atomic operations on 128-bit double quadword (or oword) data
           types.  This is useful for high resolution counters that could be updated by multiple
           processors (or cores).  This instruction is generated as part of atomic built-in
           functions: see Atomic Builtins for details.

       -msahf
           This option will enable GCC to use SAHF instruction in generated 64-bit code.  Early
           Intel CPUs with Intel 64 lacked LAHF and SAHF instructions supported by AMD64 until
           introduction of Pentium 4 G1 step in December 2005.  LAHF and SAHF are load and store
           instructions, respectively, for certain status flags.  In 64-bit mode, SAHF
           instruction is used to optimize "fmod", "drem" or "remainder" built-in functions: see
           Other Builtins for details.

       -mmovbe
           This option will enable GCC to use movbe instruction to implement "__builtin_bswap32"
           and "__builtin_bswap64".

       -mcrc32
           This option will enable 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 will enable GCC to use 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.

       -mveclibabi=type
           Specifies the ABI type to use for vectorizing intrinsics using an external library.
           Supported types are "svml" for the Intel short vector math library and "acml" for the
           AMD math core library style of interfacing.  GCC will currently emit 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 corresponding function type when
           -mveclibabi=acml is used. Both -ftree-vectorize and -funsafe-math-optimizations have
           to be enabled. A SVML or ACML ABI compatible library will have to be specified at link
           time.

       -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 Windows.  On all other systems, the default
           is the SYSV ABI.  You can control this behavior for a specific function by using the
           function attribute ms_abi/sysv_abi.

       -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 will be
           computed in the function prologue.  This is faster on most modern CPUs because of
           reduced dependencies, improved scheduling and reduced stack usage when 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 Mingw32.  Code that relies 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 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 destination is known to be aligned
           at least to 4 byte boundary.  This enables more inlining, increase code size, but may
           improve performance of code that depends on fast memcpy, strlen and memset for short
           lengths.

       -minline-stringops-dynamically
           For string operation of unknown size, inline runtime checks so for small blocks inline
           code is used, while for large blocks library call is used.

       -mstringop-strategy=alg
           Overwrite internal decision heuristic about particular algorithm to inline string
           operation with.  The allowed values are "rep_byte", "rep_4byte", "rep_8byte" for
           expanding using i386 "rep" prefix of specified size, "byte_loop", "loop",
           "unrolled_loop" for expanding inline loop, "libcall" for always expanding library
           call.

       -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.

       -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 legal depends on the operating system, and whether it
           maps the segment to cover the entire TLS area.

           For systems that use GNU libc, 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 prologue.  Note: On
           x86 architectures the attribute "ms_hook_prologue" isn't possible at the moment for
           -mfentry and -pg.

       -m8bit-idiv
       -mno-8bit-idiv
           On some processors, like Intel Atom, 8bit unsigned integer divide is much faster than
           32bit/64bit integer divide.  This option will generate a runt-time check.  If both
           dividend and divisor are within range of 0 to 255, 8bit unsigned integer divide will
           be used instead of 32bit/64bit integer divide.

       -mavx256-split-unaligned-load
       -mavx256-split-unaligned-store
           Split 32-byte AVX unaligned load and store.

       These -m switches are supported in addition to the above on AMD x86-64 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 and generates code that runs on any i386 system.  The
           64-bit environment sets int to 32 bits and long and pointer to 64 bits and generates
           code for AMD's x86-64 architecture. For darwin only the -m64 option turns off the
           -fno-pic and -mdynamic-no-pic options.

       -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 will
           not be 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.

       i386 and x86-64 Windows Options

       These additional options are available for Windows targets:

       -mconsole
           This option is available for Cygwin and MinGW targets.  It 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 is the default behavior for
           Cygwin and MinGW 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 specifies that the UNICODE macro
           is getting pre-defined and that the unicode capable runtime startup code is chosen.

       -mwin32
           This option is available for Cygwin and MinGW targets.  It specifies that the typical
           Windows pre-defined 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
           stack used by nested functions isn't set. This is necessary for binaries running in
           kernel mode of Windows, as there the user32 API, which is used to set executable
           privileges, isn't available.

       -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 will be enabled by default if GCC detects
           that the target assembler found during configuration supports the feature.

       See also under i386 and x86-64 Options for standard options.

       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 DWARF2 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 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.

       -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 will result in
           generation of the 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 will result in generation
           of the 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 will result 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 will be chosen for schedule only if there
           are no other choices at the moment.  This will make 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 will be chosen for schedule only if there
           are no other choices at the moment.  This will make 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 will be considered during computation of the
           instructions priorities.  This will make 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
           Disallow more than `msched-max-memory-insns' in instruction group.  Otherwise, limit
           is `soft' meaning that we would prefer non-memory operations when limit is reached but
           may still schedule memory operations.

       IA-64/VMS Options

       These -m options are defined for the IA-64/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 64bit memory allocation routines.

       LM32 Options

       These -m options are defined for the Lattice Mico32 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 will use during code
           generation.  These pseudo-registers will be 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 the default runtime libraries gcc builds.

       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 will generate
           "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 will generate
           "seth/add3" instructions to load their addresses), and assume subroutines may not be
           reachable with the "bl" instruction (the compiler will generate the much slower
           "seth/add3/jl" instruction sequence).

       -msdata=none
           Disable use of the small data area.  Variables will be 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 will give an error
           message---incorrect code will not be 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 will be preferred over
           conditional code, if it is 2, then the opposite will apply.

       -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 will only be 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 51cn 51em 51qe
           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 which 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 which 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 will be generated
           for calls to those functions.

           In addition, seriously incorrect code will result 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 will align 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 will be 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
           Specified the identification number of the ID based shared library being compiled.
           Specifying a value of 0 will generate more compact code, specifying other values will
           force 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.

       M68hc1x Options

       These are the -m options defined for the 68hc11 and 68hc12 microcontrollers.  The default
       values for these options depends on which style of microcontroller was selected when the
       compiler was configured; the defaults for the most common choices are given below.

       -m6811
       -m68hc11
           Generate output for a 68HC11.  This is the default when the compiler is configured for
           68HC11-based systems.

       -m6812
       -m68hc12
           Generate output for a 68HC12.  This is the default when the compiler is configured for
           68HC12-based systems.

       -m68S12
       -m68hcs12
           Generate output for a 68HCS12.

       -mauto-incdec
           Enable the use of 68HC12 pre and post auto-increment and auto-decrement addressing
           modes.

       -minmax
       -mnominmax
           Enable the use of 68HC12 min and max instructions.

       -mlong-calls
       -mno-long-calls
           Treat all calls as being far away (near).  If calls are assumed to be far away, the
           compiler will use the "call" instruction to call a function and the "rtc" instruction
           for returning.

       -mshort
           Consider type "int" to be 16 bits wide, like "short int".

       -msoft-reg-count=count
           Specify the number of pseudo-soft registers which are used for the code generation.
           The maximum number is 32.  Using more pseudo-soft register may or may not result in
           better code depending on the program.  The default is 4 for 68HC11 and 2 for 68HC12.

       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 four 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 run-time 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 which 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 will be 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 will be 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 build-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 runtime 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 will be 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 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.

       -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 be 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 will run 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, mips64 and mips64r2.  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, 74kc, 74kf2_1, 74kf1_1, 74kf3_2, 1004kc, 1004kf2_1,
           1004kf1_1, loongson2e, loongson2f, loongson3a, m4k, octeon, orion, r2000, r3000,
           r3900, r4000, r4400, r4600, r4650, r6000, r8000, rm7000, rm9000, r10000, r12000,
           r14000, r16000, sb1, sr71000, vr4100, vr4111, vr4120, vr4130, vr4300, vr5000, vr5400,
           vr5500 and xlr.  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).

           Native Linux/GNU toolchains also support 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 will set _MIPS_ARCH to "r2000" and define the macro _MIPS_ARCH_R2000.

           Note that the _MIPS_ARCH macro uses the processor names given above.  In other words,
           it will have the full prefix and will 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 will optimize for the processor specified by -march.
           By using -march and -mtune together, it is possible to generate code that will run 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.

       -mips32r2
           Equivalent to -march=mips32r2.

       -mips64
           Equivalent to -march=mips64.

       -mips64r2
           Equivalent to -march=mips64r2.

       -mips16
       -mno-mips16
           Generate (do not generate) MIPS16 code.  If GCC is targetting a MIPS32 or MIPS64
           architecture, it will make 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-mips16
       -mno-interlink-mips16
           Require (do not require) that non-MIPS16 code be link-compatible with MIPS16 code.

           For example, non-MIPS16 code cannot jump directly to MIPS16 code; it must either use a
           call or an indirect jump.  -minterlink-mips16 therefore disables direct jumps unless
           GCC knows that the target of the jump is not MIPS16.

       -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 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, but all 64 bits
           are saved.

       -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 will
           generally make 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 will only work if the GOT is smaller than about 64k.
           Anything larger will cause 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.  It should then work with
           very large GOTs, although it will also be less efficient, since it will take 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.

       -mhard-float
           Use floating-point coprocessor instructions.

       -msoft-float
           Do not use floating-point coprocessor instructions.  Implement floating-point
           calculations using library calls instead.

       -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.

       -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 will use 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.

       -mmt
       -mno-mt
           Use (do not use) MT Multithreading 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 access the data more efficiently; 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 will be in a small data section if
           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 will pass an unknown value in $gp.
           (In such situations, the boot monitor itself would usually be 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.

       -mfused-madd
       -mno-fused-madd
           Enable (disable) use of the floating point multiply-accumulate instructions, when they
           are available.  The default is -mfused-madd.

           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.

       -nocpp
           Tell the MIPS assembler to not run its preprocessor over user assembler files (with a
           .s suffix) when assembling them.

       -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-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 will avoid 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 was 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 will overwrite 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 will 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 which implement those architectures; for those,
           Branch Likely instructions will 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 we schedule FP
           instructions 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 will
           align 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) will be generated when
           "__builtin___clear_cache()" is compiled.

           This option defaults to "-mno-synci", but the default can be overridden by configuring
           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 will 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 supports 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 which uses features specific to the AM33 processor.

       -mno-am33
           Do not generate code which uses features specific to the AM33 processor.  This is the
           default.

       -mam33-2
           Generate code which uses features specific to the AM33/2.0 processor.

       -mam34
           Generate code which uses 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 which 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 would 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__.

       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 will
           run on any of the other AE types.  The code will not be as efficient as it would be if
           compiled for a specific AE type, and some types of operation (e.g., multiplication)
           will 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 will generate 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 which 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 will be generated indicating to the
           programmer that they should rewrite the code to avoid byte operations, or to target an
           AE type which has the necessary hardware support.  This option enables the warning to
           be turned off.

       PowerPC Options

       These are listed under

       IBM RS/6000 and PowerPC Options

       These -m options are defined for the IBM RS/6000 and PowerPC:

       -mpower
       -mno-power
       -mpower2
       -mno-power2
       -mpowerpc
       -mno-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
           GCC supports two related instruction set architectures for the RS/6000 and PowerPC.
           The POWER instruction set are those instructions supported by the rios chip set used
           in the original RS/6000 systems and the PowerPC instruction set is the architecture of
           the Freescale MPC5xx, MPC6xx, MPC8xx microprocessors, and the IBM 4xx, 6xx, and
           follow-on microprocessors.

           Neither architecture is a subset of the other.  However there is a large common subset
           of instructions supported by both.  An MQ register is included in processors
           supporting the POWER architecture.

           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.

           The -mpower option allows GCC to generate instructions that are found only in the
           POWER architecture and to use the MQ register.  Specifying -mpower2 implies -power and
           also allows GCC to generate instructions that are present in the POWER2 architecture
           but not the original POWER architecture.

           The -mpowerpc option allows GCC to generate instructions that are found only in the
           32-bit subset of the PowerPC architecture.  Specifying -mpowerpc-gpopt implies
           -mpowerpc and also allows GCC to use the optional PowerPC architecture instructions in
           the General Purpose group, including floating-point square root.  Specifying
           -mpowerpc-gfxopt implies -mpowerpc and also 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.

           If you specify both -mno-power and -mno-powerpc, GCC will use only the instructions in
           the common subset of both architectures plus some special AIX common-mode calls, and
           will not use the MQ register.  Specifying both -mpower and -mpowerpc permits GCC to
           use any instruction from either architecture and to allow use of the MQ register;
           specify this for the Motorola MPC601.

       -mnew-mnemonics
       -mold-mnemonics
           Select which mnemonics to use in the generated assembler code.  With -mnew-mnemonics,
           GCC uses the assembler mnemonics defined for the PowerPC architecture.  With
           -mold-mnemonics it uses the assembler mnemonics defined for the POWER architecture.
           Instructions defined in only one architecture have only one mnemonic; GCC uses that
           mnemonic irrespective of which of these options is specified.

           GCC defaults to the mnemonics appropriate for the architecture in use.  Specifying
           -mcpu=cpu_type sometimes overrides the value of these option.  Unless you are building
           a cross-compiler, you should normally not specify either -mnew-mnemonics or
           -mold-mnemonics, but should instead accept the default.

       -mcpu=cpu_type
           Set architecture type, register usage, choice of mnemonics, 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, ec603e, G3, G4, G5, titan, power, power2, power3, power4, power5,
           power5+, power6, power6x, power7, common, powerpc, powerpc64, rios, rios1, rios2, rsc,
           and rs64.

           -mcpu=common selects a completely generic processor.  Code generated under this option
           will run on any POWER or PowerPC processor.  GCC will use only the instructions in the
           common subset of both architectures, and will not use the MQ register.  GCC assumes a
           generic processor model for scheduling purposes.

           -mcpu=power, -mcpu=power2, -mcpu=powerpc, and -mcpu=powerpc64 specify generic POWER,
           POWER2, pure 32-bit PowerPC (i.e., not MPC601), and 64-bit 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
           will run 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 -mnew-mnemonics  -mpopcntb
           -mpopcntd  -mpower  -mpower2  -mpowerpc64 -mpowerpc-gpopt  -mpowerpc-gfxopt
           -msingle-float -mdouble-float -msimple-fpu -mstring  -mmulhw  -mdlmzb  -mmfpgpr -mvsx

           The particular options set for any particular CPU will vary 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, register usage, or choice of mnemonics, as -mcpu=cpu_type
           would.  The same values for cpu_type are used for -mtune as for -mcpu.  If both are
           specified, the code generated will use the architecture, registers, and mnemonics 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.

       -mvrsave
       -mno-vrsave
           Generate VRSAVE instructions when generating AltiVec code.

       -mgen-cell-microcode
           Generate Cell microcode instructions

       -mwarn-cell-microcode
           Warning when a Cell microcode instruction is going to 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-exec .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.

       -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
           will allocate at least one TOC entry for each unique non-automatic variable reference
           in your program.  GCC will also place 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 will produce 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 and
           -mpowerpc, 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 which
           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
           Specify type of floating point unit.  Valid values 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 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 the
           instructions usage 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 the instructions usage 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 targetting 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 targetting 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
           targetting 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 would be aligned to a 4 byte boundary and have a size of 4 bytes.  By using
           -mno-bit-align, the structure would be aligned to a 1 byte boundary and be one byte in
           size.

       -mno-strict-align
       -mstrict-align
           On System V.4 and embedded PowerPC systems do not (do) assume that unaligned memory
           references will be 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 runtime.  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 runtime, 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 run-time 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
           0/1/2 to assign no/highest/second-highest 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 which latency >=
           number is costly.

       -minsert-sched-nops=scheme
           This option controls which nop insertion scheme will be 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 which 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
           adheres 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-gnu
           On System V.4 and embedded PowerPC systems compile code for the Hurd-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.

       -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 Booke 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.

       -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 were passed in the floating point
           registers in case the function takes a variable arguments.  With -mprototype, only
           calls to prototyped variable argument functions will 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 to 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, do
           not call an initialization function from "main", and the -msdata option will only use
           "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 more expensive calling
           sequence is required.  This is required for calls further than 32 megabytes
           (33,554,432 bytes) from the current location.  A short call will be 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" will generate "jbsr callee, L42", plus a
           "branch island" (glue code).  The two target addresses represent the callee and the
           "branch island".  The Darwin/PPC linker will prefer the first address and generate a
           "bl callee" if the PPC "bl" instruction will reach the callee directly; otherwise, the
           linker will generate "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, we may cause GCC to 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 ld 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 will enable GCC to use 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 allows to control which reciprocal estimate instructions may be used.  opt
           is a comma separated list of options, that 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 would enable the 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 or
           -mcpu=power7 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 will currently emit 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 have to be enabled.  The MASS libraries will have to 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 a floating point value 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.

       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 will only be generated for 32-bit floating point values
           however, so if the -m64bit-doubles option is in use then the FPU hardware will not be
           used for doubles.

           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 ("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 which once could have been held in "r13" are now pushed onto the stack.

           Note, common variables (variables which have not been initialised) 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 register "r13".  It is up to the
           programmer to experiment and discover whether this feature is of benefit to their
           program.

       -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 generating it is not the default option.

       -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 will
           attempt 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" will be
           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.

       Note: The generic GCC command line -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 will will ensure 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 will be 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
           will be 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 64bit 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 will run 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 and z10.  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 which 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 s390 back end emits additional instructions in the
           function prologue which trigger a trap if the stack size is stack-guard bytes above
           the stack-size (remember that the stack on s390 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.

       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 generate bcnz instruction.

       -muls
           Enable generate unaligned load and store instruction.

       -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.

       -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.

       -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 will 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.

       -mhitachi
           Comply with the calling conventions defined by Renesas.

       -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 except
           for sh-symbianelf.

       -mnomacsave
           Mark the "MAC" register as call-clobbered, even if -mhitachi is given.

       -mieee
           Increase IEEE-compliance of floating-point code.  At the moment, this is equivalent to
           -fno-finite-math-only.  When generating 16 bit SH opcodes, getting IEEE-conforming
           results for comparisons of NANs / infinities incurs extra overhead in every floating
           point comparison, therefore the default is set to -ffinite-math-only.

       -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 will manipulate the instruction
           cache address array directly with an associative write.  This not only requires
           privileged mode, but it will also fail 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.

       -mspace
           Optimize for space instead of speed.  Implied by -Os.

       -mprefergot
           When generating position-independent code, emit function calls using the Global Offset
           Table instead of the Procedure Linkage Table.

       -musermode
           Don't generate privileged mode only code; implies -mno-inline-ic_invalidate if the
           inlined code would not work in user mode.  This is the default when the target is
           "sh-*-linux*".

       -multcost=number
           Set the cost to assume for a multiply insn.

       -mdiv=strategy
           Set the division strategy to use for SHmedia code.  strategy must be one of: call,
           call2, fp, inv, inv:minlat, inv20u, inv20l, inv:call, inv:call2, inv:fp .  "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" is a variant of "inv" where if no cse / 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 / code hoisting optimizations.
           "inv:call", "inv:call2" and "inv:fp" all 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 fp operations or a call is not possible in that case.  "inv20u" and
           "inv20l" are variants of the "inv:minlat" strategy.  In the case that the inverse
           calculation was nor 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.

       -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 affect the name used in the call and inv:call division strategies, and the
           compiler will still expect the same sets of input/output/clobbered registers as if
           this option was 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.

       -madjust-unroll
           Throttle unrolling to avoid thrashing target registers.  This option only has an
           effect if the gcc code base supports the TARGET_ADJUST_UNROLL_MAX target hook.

       -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 will generally generate 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 ptabs / ptrel before a branch, or
           hoist it 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 will be done before testing against -1.  That
           means that all the constructors will be run a bit quicker, 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 the user specifies a
           specific cost with -mgettrcost, -mno-pt-fixed also implies -mgettrcost=100; this
           deters register allocation using target registers for storing ordinary integers.

       -minvalid-symbols
           Assume symbols might be invalid.  Ordinary function symbols generated by the compiler
           will always be 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 will cause
           ptabs / ptrel to trap.  This option is only meaningful when -mno-pt-fixed is in
           effect.  It will then prevent cross-basic-block cse, hoisting and most scheduling of
           symbol loads.  The default is -mno-invalid-symbols.

       Solaris 2 Options

       These -m options are supported on Solaris 2:

       -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 will 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:

       -threads
           Add support for multithreading using the Solaris 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.

       -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.  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.

       -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.

       -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
           will not be 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, sparclite, f930, f934, sparclite86x, sparclet, tsc701, v9,
           ultrasparc, ultrasparc3, niagara and niagara2.

           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
                       v8:             supersparc, hypersparc, leon
                       sparclite:      f930, f934, sparclite86x
                       sparclet:       tsc701
                       v9:             ultrasparc, ultrasparc3, niagara, niagara2

           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.

       -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.

           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, f930, f934, sparclite86x, tsc701, ultrasparc,
           ultrasparc3, niagara, and niagara2.

       -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-bit 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.

       -mfix-at697f
           Enable the documented workaround for the single erratum of the Atmel AT697F processor
           (which corresponds to erratum #13 of the AT697E processor).

       These -m options are supported in addition to the above on SPARC-V9 processors in 64-bit
       environments:

       -mlittle-endian
           Generate code for a processor running in little-endian mode.  It is only available for
           a few configurations and most notably not on Solaris and Linux.

       -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=medlow
           Generate code for 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.

       -mcmodel=medmid
           Generate code for 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.

       -mcmodel=medany
           Generate code for 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.

       -mcmodel=embmedany
           Generate code for 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.

       -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 will give an
           error when it generates code that requires a dynamic relocation.  -mno-error-reloc
           disables the error, -mwarn-reloc will generate a warning instead.

       -msafe-dma
       -munsafe-dma
           Instructions which initiate or test completion of DMA must not be reordered with
           respect to loads and stores of the memory which is being accessed.  Users typically
           address this problem using the volatile keyword, but that can lead to inefficient code
           in places where the memory is known to not change.  Rather than mark the memory as
           volatile we treat the DMA instructions as potentially effecting all memory.  With
           -munsafe-dma users must use the volatile keyword to protect memory accesses.

       -mbranch-hints
           By default, GCC will generate a branch hint instruction to avoid pipeline stalls for
           always taken or probably taken branches.  A hint will not be 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 will link
           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 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.

       -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 will 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 will be more
           efficient.  The default behavior is to use atomic updates.

       -mdual-nops
       -mdual-nops=n
           By default, GCC will insert nops to increase dual issue when it expects it to increase
           performance.  n can be a value from 0 to 10.  A smaller n will insert 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 effecting.  GCC will insert up to n nops to
           enforce this, otherwise it will 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 effecting.  By default, GCC makes sure it is within
           125.

       -msafe-hints
           Work around a hardware bug which causes the SPU to stall indefinitely.  By default,
           GCC will insert 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.

       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 will always load the functions address up into a register, and call 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.

       -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 will cause r2 and r5 to be used in the code generated by the compiler.
           This setting is the default.

       -mno-app-regs
           This option will cause r2 and r5 to be treated as fixed registers.

       -mv850e2v3
           Specify that the target processor is the V850E2V3.  The preprocessor constants
           __v850e2v3__ will be defined if this option is used.

       -mv850e2
           Specify that the target processor is the V850E2.  The preprocessor constants
           __v850e2__ will be defined if

       -mv850e1
           Specify that the target processor is the V850E1.  The preprocessor constants
           __v850e1__ and __v850e__ will be defined if

       -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__
           will be defined if this option is used.

           If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2 nor -mv850e2v3 are defined
           then a default target processor will be chosen and the relevant __v850*__ preprocessor
           constant will be defined.

           The preprocessor constants __v850 and __v851__ are always defined, regardless of which
           processor variant is the target.

       -mdisable-callt
           This option will suppress generation of the CALLT instruction for the v850e, v850e1,
           v850e2 and v850e2v3 flavors of the v850 architecture.  The default is
           -mno-disable-callt which allows the CALLT instruction to be used.

       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 you will assemble with the
           GNU assembler.

       -mg Output code for g-format floating point numbers instead of d-format.

       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.

       x86-64 Options

       These are listed under

       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
           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 will be performed.  The default is
           -mtarget-align.  These options do not affect the treatment of auto-aligned
           instructions like "LOOP", which the assembler will always align, either by widening
           density instructions or by inserting no-op 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 will still show direct call
           instructions---look at the disassembled object code to see the actual instructions.
           Note that the assembler will use an indirect call for every cross-file call, not just
           those that really will be 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 would be
       -fno-foo.  In the table below, only one of the forms is listed---the one which 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.

       -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 will generate 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 will enable it by default
           for languages like C++ which normally require exception handling, and disable 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".

       -funwind-tables
           Similar to -fexceptions, except that it will just generate any needed static data, but
           will not affect the generated code in any other way.  You will normally not enable
           this option; instead, a language processor that needs this handling would enable it on
           your behalf.

       -fasynchronous-unwind-tables
           Generate unwind table in dwarf2 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).

       -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 will be equivalent to the smallest
           integer type which 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 will
           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 which 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 that was 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.

       -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 386 has no such limit.)

           Position-independent code requires special support, and therefore works only on
           certain machines.  For the 386, 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 will be 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 which 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 will not save and restore the register reg.

           It is an error to used 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 will produce 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 will save and restore the register reg if they use it.

           It is an error to used 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 will produce disastrous results.

           A different sort of disaster will result 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 will be 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 will be 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 will 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 anyways, 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 will not be 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

           will exclude 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 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 will always be 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, the performances of the code are 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 the stack would grow beyond
           the value, a signal is raised.  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 i386 and x86_64 backends 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".

           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 will
           be 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 will be "hidden".  The
           default if -fvisibility isn't specified is "default", i.e., make every symbol
           public---this causes the same behavior as previous versions of GCC.

           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://people.redhat.com/~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 DLL's 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 will 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 will be thrown between DSOs must be explicitly
           marked with default visibility so that the type_info nodes will be 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 bitfields (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 the user could declare all peripheral
           bitfields 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 will use the most efficient instruction.  In
           the previous example, that might be a 32-bit load instruction, even though that will
           access bytes that do not contain any portion of the bitfield, or memory-mapped
           registers unrelated to the one being updated.

           If the target requires strict alignment, and honoring the field type would require
           violating this alignment, a warning is issued.  If the field has "packed" attribute,
           the access is done without honoring the field type.  If the field doesn't have
           "packed" attribute, the access is done honoring the field type.  In both cases, GCC
           assumes that the user knows something about the target hardware that it is unaware of.

           The default value of this option is determined by the application binary interface for
           the target processor.

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
           that allow 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 would otherwise be 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_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 will attempt to figure out an appropriate prefix to
           use based on the pathname it was 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 will search foo/bar where it would normally search
           /usr/local/lib/bar.  These alternate directories are searched first; the standard
           directories come next. 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 will use
           mblen and mbtowc as defined by the default locale to recognize and translate multibyte
           characters.

       Some additional environments variables affect the behavior of the preprocessor.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
           Each variable's value is a list of directories separated by a special character, much
           like PATH, in which to look for header files.  The special character,
           "PATH_SEPARATOR", is target-dependent and determined at GCC build time.  For Microsoft
           Windows-based targets it is a semicolon, and for almost all other targets it is a
           colon.

           CPATH specifies a list of directories to be searched as if specified with -I, but
           after any paths given with -I options on the command line.  This environment variable
           is used regardless of which language is being preprocessed.

           The remaining environment variables apply only when preprocessing the particular
           language indicated.  Each specifies a list of directories to be searched as if
           specified with -isystem, but after any paths given with -isystem options on the
           command line.

           In all these variables, an empty element instructs the compiler to search its current
           working directory.  Empty elements can appear at the beginning or end of a path.  For
           instance, if the value of CPATH is ":/special/include", that has the same effect as
           -I. -I/special/include.

       DEPENDENCIES_OUTPUT
           If this variable is set, its value specifies how to output dependencies for Make based
           on the non-system header files processed by the compiler.  System header files are
           ignored in the dependency output.

           The value of DEPENDENCIES_OUTPUT can be just a file name, in which case the Make rules
           are written to that file, guessing the target name from the source file name.  Or the
           value can have the form file target, in which case the rules are written to file file
           using target as the target name.

           In other words, this environment variable is equivalent to combining the options -MM
           and -MF, with an optional -MT switch too.

       SUNPRO_DEPENDENCIES
           This variable is the same as DEPENDENCIES_OUTPUT (see above), except that system
           header files are not ignored, so it implies -M rather than -MM.  However, the
           dependence on the main input file is omitted.

BUGS

       For instructions on reporting bugs, see <file:///usr/share/doc/gcc-4.6/README.Bugs>.

FOOTNOTES

       1.  On some systems, gcc -shared needs to build supplementary stub code for constructors
           to work.  On multi-libbed systems, gcc -shared must select the correct support
           libraries to link against.  Failing to supply the correct flags may lead to subtle
           defects.  Supplying them in cases where they are not necessary is innocuous.

SEE ALSO

       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1), adb(1), dbx(1),
       sdb(1) and the Info entries for gcc, cpp, as, ld, binutils and gdb.

AUTHOR

       See the Info entry for gcc, or <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for
       contributors to GCC.

COPYRIGHT

       Copyright (c) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001,
       2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 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.