Overview - Using as

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1 Overview

Here is a brief summary of how to invoke as. For details, see Command-Line Options.

     
     as [-a[cdghlns][=file]] [--alternate] [-D]
      [--compress-debug-sections]  [--nocompress-debug-sections]
      [--debug-prefix-map old=new]
      [--defsym sym=val] [-f] [-g] [--gstabs]
      [--gstabs+] [--gdwarf-2] [--gdwarf-sections]
      [--help] [-I dir] [-J]
      [-K] [-L] [--listing-lhs-width=NUM]
      [--listing-lhs-width2=NUM] [--listing-rhs-width=NUM]
      [--listing-cont-lines=NUM] [--keep-locals]
      [--no-pad-sections]
      [-o objfile] [-R]
      [--hash-size=NUM] [--reduce-memory-overheads]
      [--statistics]
      [-v] [-version] [--version]
      [-W] [--warn] [--fatal-warnings] [-w] [-x]
      [-Z] [@FILE]
      [--sectname-subst] [--size-check=[error|warning]]
      [--elf-stt-common=[no|yes]]
      [--target-help] [target-options]
      [--|files ...]
     
     
     
     
     
     Target AArch64 options:
        [-EB|-EL]
        [-mabi=ABI]
     
     Target Alpha options:
        [-mcpu]
        [-mdebug | -no-mdebug]
        [-replace | -noreplace]
        [-relax] [-g] [-Gsize]
        [-F] [-32addr]
     
     Target ARC options:
        [-mcpu=cpu]
        [-mA6|-mARC600|-mARC601|-mA7|-mARC700|-mEM|-mHS]
        [-mcode-density]
        [-mrelax]
        [-EB|-EL]
     
     Target ARM options:
     
        [-mcpu=processor[+extension...]]
        [-march=architecture[+extension...]]
        [-mfpu=floating-point-format]
        [-mfloat-abi=abi]
        [-meabi=ver]
        [-mthumb]
        [-EB|-EL]
        [-mapcs-32|-mapcs-26|-mapcs-float|
         -mapcs-reentrant]
        [-mthumb-interwork] [-k]
     
     Target Blackfin options:
        [-mcpu=processor[-sirevision]]
        [-mfdpic]
        [-mno-fdpic]
        [-mnopic]
     
     Target CRIS options:
        [--underscore | --no-underscore]
        [--pic] [-N]
        [--emulation=criself | --emulation=crisaout]
        [--march=v0_v10 | --march=v10 | --march=v32 | --march=common_v10_v32]
     
     
     
     Target D10V options:
        [-O]
     
     Target D30V options:
        [-O|-n|-N]
     
     Target EPIPHANY options:
        [-mepiphany|-mepiphany16]
     
     Target H8/300 options:
        [-h-tick-hex]
     
     
     Target i386 options:
        [--32|--x32|--64] [-n]
        [-march=CPU[+EXTENSION...]] [-mtune=CPU]
     
     Target i960 options:
     
        [-ACA|-ACA_A|-ACB|-ACC|-AKA|-AKB|
         -AKC|-AMC]
        [-b] [-no-relax]
     
     Target IA-64 options:
        [-mconstant-gp|-mauto-pic]
        [-milp32|-milp64|-mlp64|-mp64]
        [-mle|mbe]
        [-mtune=itanium1|-mtune=itanium2]
        [-munwind-check=warning|-munwind-check=error]
        [-mhint.b=ok|-mhint.b=warning|-mhint.b=error]
        [-x|-xexplicit] [-xauto] [-xdebug]
     
     Target IP2K options:
        [-mip2022|-mip2022ext]
     
     Target M32C options:
        [-m32c|-m16c] [-relax] [-h-tick-hex]
     
     Target M32R options:
        [--m32rx|--[no-]warn-explicit-parallel-conflicts|
        --W[n]p]
     
     Target M680X0 options:
        [-l] [-m68000|-m68010|-m68020|...]
     
     Target M68HC11 options:
        [-m68hc11|-m68hc12|-m68hcs12|-mm9s12x|-mm9s12xg]
        [-mshort|-mlong]
        [-mshort-double|-mlong-double]
        [--force-long-branches] [--short-branches]
        [--strict-direct-mode] [--print-insn-syntax]
        [--print-opcodes] [--generate-example]
     
     Target MCORE options:
        [-jsri2bsr] [-sifilter] [-relax]
        [-mcpu=[210|340]]
     
     Target Meta options:
        [-mcpu=cpu] [-mfpu=cpu] [-mdsp=cpu]
     Target MICROBLAZE options:
     
     
     Target MIPS options:
        [-nocpp] [-EL] [-EB] [-O[optimization level]]
        [-g[debug level]] [-G num] [-KPIC] [-call_shared]
        [-non_shared] [-xgot [-mvxworks-pic]
        [-mabi=ABI] [-32] [-n32] [-64] [-mfp32] [-mgp32]
        [-mfp64] [-mgp64] [-mfpxx]
        [-modd-spreg] [-mno-odd-spreg]
        [-march=CPU] [-mtune=CPU] [-mips1] [-mips2]
        [-mips3] [-mips4] [-mips5] [-mips32] [-mips32r2]
        [-mips32r3] [-mips32r5] [-mips32r6] [-mips64] [-mips64r2]
        [-mips64r3] [-mips64r5] [-mips64r6]
        [-construct-floats] [-no-construct-floats]
        [-mnan=encoding]
        [-trap] [-no-break] [-break] [-no-trap]
        [-mips16] [-no-mips16]
        [-mmicromips] [-mno-micromips]
        [-msmartmips] [-mno-smartmips]
        [-mips3d] [-no-mips3d]
        [-mdmx] [-no-mdmx]
        [-mdsp] [-mno-dsp]
        [-mdspr2] [-mno-dspr2]
        [-mdspr3] [-mno-dspr3]
        [-mmsa] [-mno-msa]
        [-mxpa] [-mno-xpa]
        [-mmt] [-mno-mt]
        [-mmcu] [-mno-mcu]
        [-minsn32] [-mno-insn32]
        [-mfix7000] [-mno-fix7000]
        [-mfix-rm7000] [-mno-fix-rm7000]
        [-mfix-vr4120] [-mno-fix-vr4120]
        [-mfix-vr4130] [-mno-fix-vr4130]
        [-mdebug] [-no-mdebug]
        [-mpdr] [-mno-pdr]
     
     Target MMIX options:
        [--fixed-special-register-names] [--globalize-symbols]
        [--gnu-syntax] [--relax] [--no-predefined-symbols]
        [--no-expand] [--no-merge-gregs] [-x]
        [--linker-allocated-gregs]
     
     Target Nios II options:
        [-relax-all] [-relax-section] [-no-relax]
        [-EB] [-EL]
     
     Target NDS32 options:
         [-EL] [-EB] [-O] [-Os] [-mcpu=cpu]
         [-misa=isa] [-mabi=abi] [-mall-ext]
         [-m[no-]16-bit]  [-m[no-]perf-ext] [-m[no-]perf2-ext]
         [-m[no-]string-ext] [-m[no-]dsp-ext] [-m[no-]mac] [-m[no-]div]
         [-m[no-]audio-isa-ext] [-m[no-]fpu-sp-ext] [-m[no-]fpu-dp-ext]
         [-m[no-]fpu-fma] [-mfpu-freg=FREG] [-mreduced-regs]
         [-mfull-regs] [-m[no-]dx-regs] [-mpic] [-mno-relax]
         [-mb2bb]
     
     Target PDP11 options:
        [-mpic|-mno-pic] [-mall] [-mno-extensions]
        [-mextension|-mno-extension]
        [-mcpu] [-mmachine]
     
     Target picoJava options:
        [-mb|-me]
     
     Target PowerPC options:
        [-a32|-a64]
        [-mpwrx|-mpwr2|-mpwr|-m601|-mppc|-mppc32|-m603|-m604|-m403|-m405|
         -m440|-m464|-m476|-m7400|-m7410|-m7450|-m7455|-m750cl|-mppc64|
         -m620|-me500|-e500x2|-me500mc|-me500mc64|-me5500|-me6500|-mppc64bridge|
         -mbooke|-mpower4|-mpwr4|-mpower5|-mpwr5|-mpwr5x|-mpower6|-mpwr6|
         -mpower7|-mpwr7|-mpower8|-mpwr8|-mpower9|-mpwr9-ma2|
         -mcell|-mspe|-mtitan|-me300|-mcom]
        [-many] [-maltivec|-mvsx|-mhtm|-mvle]
        [-mregnames|-mno-regnames]
        [-mrelocatable|-mrelocatable-lib|-K PIC] [-memb]
        [-mlittle|-mlittle-endian|-le|-mbig|-mbig-endian|-be]
        [-msolaris|-mno-solaris]
        [-nops=count]
     
     Target RL78 options:
        [-mg10]
        [-m32bit-doubles|-m64bit-doubles]
     
     Target RX options:
        [-mlittle-endian|-mbig-endian]
        [-m32bit-doubles|-m64bit-doubles]
        [-muse-conventional-section-names]
        [-msmall-data-limit]
        [-mpid]
        [-mrelax]
        [-mint-register=number]
        [-mgcc-abi|-mrx-abi]
     
     Target s390 options:
        [-m31|-m64] [-mesa|-mzarch] [-march=CPU]
        [-mregnames|-mno-regnames]
        [-mwarn-areg-zero]
     
     Target SCORE options:
        [-EB][-EL][-FIXDD][-NWARN]
        [-SCORE5][-SCORE5U][-SCORE7][-SCORE3]
        [-march=score7][-march=score3]
        [-USE_R1][-KPIC][-O0][-G num][-V]
     
     Target SPARC options:
     
        [-Av6|-Av7|-Av8|-Asparclet|-Asparclite
         -Av8plus|-Av8plusa|-Av9|-Av9a]
        [-xarch=v8plus|-xarch=v8plusa] [-bump]
        [-32|-64]
     
     Target TIC54X options:
      [-mcpu=54[123589]|-mcpu=54[56]lp] [-mfar-mode|-mf]
      [-merrors-to-file <filename>|-me <filename>]
     
     Target TIC6X options:
        [-march=arch] [-mbig-endian|-mlittle-endian]
        [-mdsbt|-mno-dsbt] [-mpid=no|-mpid=near|-mpid=far]
        [-mpic|-mno-pic]
     
     Target TILE-Gx options:
        [-m32|-m64][-EB][-EL]
     
     
     Target Visium options:
        [-mtune=arch]
     
     Target Xtensa options:
      [--[no-]text-section-literals] [--[no-]auto-litpools]
      [--[no-]absolute-literals]
      [--[no-]target-align] [--[no-]longcalls]
      [--[no-]transform]
      [--rename-section oldname=newname]
      [--[no-]trampolines]
     
     Target Z80 options:
       [-z80] [-r800]
       [ -ignore-undocumented-instructions] [-Wnud]
       [ -ignore-unportable-instructions] [-Wnup]
       [ -warn-undocumented-instructions] [-Wud]
       [ -warn-unportable-instructions] [-Wup]
       [ -forbid-undocumented-instructions] [-Fud]
       [ -forbid-unportable-instructions] [-Fup]

@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.

-a[cdghlmns]

Turn on listings, in any of a variety of ways:

-ac: omit false conditionals
-ad: omit debugging directives
-ag: include general information, like as version and options passed
-ah: include high-level source
-al: include assembly
-am: include macro expansions
-an: omit forms processing
-as: include symbols
=file: set the name of the listing file

You may combine these options; for example, use `-aln' for assembly listing without forms processing. The `=file' option, if used, must be the last one. By itself, `-a' defaults to `-ahls'.

--alternate

Begin in alternate macro mode. See .altmacro.

--compress-debug-sections

Compress DWARF debug sections using zlib with SHF_COMPRESSED from the ELF ABI. The resulting object file may not be compatible with older linkers and object file utilities. Note if compression would make a given section larger then it is not compressed.

--compress-debug-sections=none

--compress-debug-sections=zlib

--compress-debug-sections=zlib-gnu

--compress-debug-sections=zlib-gabi

These options control how DWARF debug sections are compressed. --compress-debug-sections=none is equivalent to --nocompress-debug-sections. --compress-debug-sections=zlib and --compress-debug-sections=zlib-gabi are equivalent to --compress-debug-sections. --compress-debug-sections=zlib-gnu compresses DWARF debug sections using zlib. The debug sections are renamed to begin with `.zdebug'. Note if compression would make a given section larger then it is not compressed nor renamed.

--nocompress-debug-sections

Do not compress DWARF debug sections. This is usually the default for all targets except the x86/x86_64, but a configure time option can be used to override this.

-D

Ignored. This option is accepted for script compatibility with calls to other assemblers.

--debug-prefix-map old=new

When assembling files in directory old, record debugging information describing them as in new instead.

--defsym sym=value

Define the symbol sym to be value before assembling the input file. value must be an integer constant. As in C, a leading `0x' indicates a hexadecimal value, and a leading `0' indicates an octal value. The value of the symbol can be overridden inside a source file via the use of a .set pseudo-op.

-f

“fast”—skip whitespace and comment preprocessing (assume source is compiler output).

-g

--gen-debug

Generate debugging information for each assembler source line using whichever debug format is preferred by the target. This currently means either STABS, ECOFF or DWARF2.

--gstabs

Generate stabs debugging information for each assembler line. This may help debugging assembler code, if the debugger can handle it.

--gstabs+

Generate stabs debugging information for each assembler line, with GNU extensions that probably only gdb can handle, and that could make other debuggers crash or refuse to read your program. This may help debugging assembler code. Currently the only GNU extension is the location of the current working directory at assembling time.

--gdwarf-2

Generate DWARF2 debugging information for each assembler line. This may help debugging assembler code, if the debugger can handle it. Note—this option is only supported by some targets, not all of them.

--gdwarf-sections

Instead of creating a .debug_line section, create a series of .debug_line.foo sections where foo is the name of the corresponding code section. For example a code section called .text.func will have its dwarf line number information placed into a section called .debug_line.text.func. If the code section is just called .text then debug line section will still be called just .debug_line without any suffix.

--size-check=error

--size-check=warning

Issue an error or warning for invalid ELF .size directive.

--elf-stt-common=no

--elf-stt-common=yes

These options control whether the ELF assembler should generate common symbols with the STT_COMMON type. The default can be controlled by a configure option --enable-elf-stt-common.

--help

Print a summary of the command line options and exit.

--target-help

Print a summary of all target specific options and exit.

-I dir

Add directory dir to the search list for .include directives.

-J

Don't warn about signed overflow.

-K

Issue warnings when difference tables altered for long displacements.

-L

--keep-locals

Keep (in the symbol table) local symbols. These symbols start with system-specific local label prefixes, typically `.L' for ELF systems or `L' for traditional a.out systems. See Symbol Names.

--listing-lhs-width=number

Set the maximum width, in words, of the output data column for an assembler listing to number.

--listing-lhs-width2=number

Set the maximum width, in words, of the output data column for continuation lines in an assembler listing to number.

--listing-rhs-width=number

Set the maximum width of an input source line, as displayed in a listing, to number bytes.

--listing-cont-lines=number

Set the maximum number of lines printed in a listing for a single line of input to number + 1.

--no-pad-sections

Stop the assembler for padding the ends of output sections to the alignment of that section. The default is to pad the sections, but this can waste space which might be needed on targets which have tight memory constraints.

-o objfile

Name the object-file output from as objfile.

-R

Fold the data section into the text section.

--hash-size=number

Set the default size of GAS's hash tables to a prime number close to number. Increasing this value can reduce the length of time it takes the assembler to perform its tasks, at the expense of increasing the assembler's memory requirements. Similarly reducing this value can reduce the memory requirements at the expense of speed.

--reduce-memory-overheads

This option reduces GAS's memory requirements, at the expense of making the assembly processes slower. Currently this switch is a synonym for `--hash-size=4051', but in the future it may have other effects as well.

--sectname-subst

Honor substitution sequences in section names. See .section name.

--statistics

Print the maximum space (in bytes) and total time (in seconds) used by assembly.

--strip-local-absolute

Remove local absolute symbols from the outgoing symbol table.

-v

-version

Print the as version.

--version

Print the as version and exit.

-W

--no-warn

Suppress warning messages.

--fatal-warnings

Treat warnings as errors.

--warn

Don't suppress warning messages or treat them as errors.

-w

Ignored.

-x

Ignored.

-Z

Generate an object file even after errors.

-- | files ...

Standard input, or source files to assemble.

See AArch64 Options, for the options available when as is configured for the 64-bit mode of the ARM Architecture (AArch64).

See Alpha Options, for the options available when as is configured for an Alpha processor.

The following options are available when as is configured for an ARC processor.

-mcpu=cpu: This option selects the core processor variant.
-EB | -EL: Select either big-endian (-EB) or little-endian (-EL) output.
-mcode-density: Enable Code Density extenssion instructions.

The following options are available when as is configured for the ARM processor family.

-mcpu=processor[+extension...]: Specify which ARM processor variant is the target.
-march=architecture[+extension...]: Specify which ARM architecture variant is used by the target.
-mfpu=floating-point-format: Select which Floating Point architecture is the target.
-mfloat-abi=abi: Select which floating point ABI is in use.
-mthumb: Enable Thumb only instruction decoding.
-mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant: Select which procedure calling convention is in use.
-EB | -EL: Select either big-endian (-EB) or little-endian (-EL) output.
-mthumb-interwork: Specify that the code has been generated with interworking between Thumb and ARM code in mind.
-mccs: Turns on CodeComposer Studio assembly syntax compatibility mode.
-k: Specify that PIC code has been generated.

See Blackfin Options, for the options available when as is configured for the Blackfin processor family.

See the info pages for documentation of the CRIS-specific options.

The following options are available when as is configured for a D10V processor.

-O: Optimize output by parallelizing instructions.

The following options are available when as is configured for a D30V processor.

-O: Optimize output by parallelizing instructions.
-n: Warn when nops are generated.
-N: Warn when a nop after a 32-bit multiply instruction is generated.

The following options are available when as is configured for the Adapteva EPIPHANY series.

See Epiphany Options, for the options available when as is configured for an Epiphany processor.

See i386-Options, for the options available when as is configured for an i386 processor.

The following options are available when as is configured for the Intel 80960 processor.

-ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC: Specify which variant of the 960 architecture is the target.
-b: Add code to collect statistics about branches taken.
-no-relax: Do not alter compare-and-branch instructions for long displacements; error if necessary.

The following options are available when as is configured for the Ubicom IP2K series.

-mip2022ext: Specifies that the extended IP2022 instructions are allowed.
-mip2022: Restores the default behaviour, which restricts the permitted instructions to just the basic IP2022 ones.

The following options are available when as is configured for the Renesas M32C and M16C processors.

-m32c: Assemble M32C instructions.
-m16c: Assemble M16C instructions (the default).
-relax: Enable support for link-time relaxations.
-h-tick-hex: Support H'00 style hex constants in addition to 0x00 style.

The following options are available when as is configured for the Renesas M32R (formerly Mitsubishi M32R) series.

--m32rx: Specify which processor in the M32R family is the target. The default is normally the M32R, but this option changes it to the M32RX.
--warn-explicit-parallel-conflicts or --Wp: Produce warning messages when questionable parallel constructs are encountered.
--no-warn-explicit-parallel-conflicts or --Wnp: Do not produce warning messages when questionable parallel constructs are encountered.

The following options are available when as is configured for the Motorola 68000 series.

-l: Shorten references to undefined symbols, to one word instead of two.
-m68000 | -m68008 | -m68010 | -m68020 | -m68030
| -m68040 | -m68060 | -m68302 | -m68331 | -m68332
| -m68333 | -m68340 | -mcpu32 | -m5200: Specify what processor in the 68000 family is the target. The default is normally the 68020, but this can be changed at configuration time.
-m68881 | -m68882 | -mno-68881 | -mno-68882: The target machine does (or does not) have a floating-point coprocessor. The default is to assume a coprocessor for 68020, 68030, and cpu32. Although the basic 68000 is not compatible with the 68881, a combination of the two can be specified, since it's possible to do emulation of the coprocessor instructions with the main processor.
-m68851 | -mno-68851: The target machine does (or does not) have a memory-management unit coprocessor. The default is to assume an MMU for 68020 and up.

See Nios II Options, for the options available when as is configured for an Altera Nios II processor.

For details about the PDP-11 machine dependent features options, see PDP-11-Options.

-mpic | -mno-pic: Generate position-independent (or position-dependent) code. The default is -mpic.
-mall
-mall-extensions: Enable all instruction set extensions. This is the default.
-mno-extensions: Disable all instruction set extensions.
-mextension | -mno-extension: Enable (or disable) a particular instruction set extension.
-mcpu: Enable the instruction set extensions supported by a particular CPU, and disable all other extensions.
-mmachine: Enable the instruction set extensions supported by a particular machine model, and disable all other extensions.

The following options are available when as is configured for a picoJava processor.

-mb: Generate “big endian” format output.
-ml: Generate “little endian” format output.

The following options are available when as is configured for the Motorola 68HC11 or 68HC12 series.

-m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg: Specify what processor is the target. The default is defined by the configuration option when building the assembler.
--xgate-ramoffset: Instruct the linker to offset RAM addresses from S12X address space into XGATE address space.
-mshort: Specify to use the 16-bit integer ABI.
-mlong: Specify to use the 32-bit integer ABI.
-mshort-double: Specify to use the 32-bit double ABI.
-mlong-double: Specify to use the 64-bit double ABI.
--force-long-branches: Relative branches are turned into absolute ones. This concerns conditional branches, unconditional branches and branches to a sub routine.
-S | --short-branches: Do not turn relative branches into absolute ones when the offset is out of range.
--strict-direct-mode: Do not turn the direct addressing mode into extended addressing mode when the instruction does not support direct addressing mode.
--print-insn-syntax: Print the syntax of instruction in case of error.
--print-opcodes: Print the list of instructions with syntax and then exit.
--generate-example: Print an example of instruction for each possible instruction and then exit. This option is only useful for testing as.

The following options are available when as is configured for the SPARC architecture:

-Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite

-Av8plus | -Av8plusa | -Av9 | -Av9a

Explicitly select a variant of the SPARC architecture.

`-Av8plus' and `-Av8plusa' select a 32 bit environment. `-Av9' and `-Av9a' select a 64 bit environment.

`-Av8plusa' and `-Av9a' enable the SPARC V9 instruction set with UltraSPARC extensions.

-xarch=v8plus | -xarch=v8plusa

For compatibility with the Solaris v9 assembler. These options are equivalent to -Av8plus and -Av8plusa, respectively.

-bump

Warn when the assembler switches to another architecture.

The following options are available when as is configured for the 'c54x architecture.

-mfar-mode: Enable extended addressing mode. All addresses and relocations will assume extended addressing (usually 23 bits).
-mcpu=CPU_VERSION: Sets the CPU version being compiled for.
-merrors-to-file FILENAME: Redirect error output to a file, for broken systems which don't support such behaviour in the shell.

The following options are available when as is configured for a MIPS processor.

-G num: This option sets the largest size of an object that can be referenced implicitly with the gp register. It is only accepted for targets that use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
-EB: Generate “big endian” format output.
-EL: Generate “little endian” format output.
-mips1
-mips2
-mips3
-mips4
-mips5
-mips32
-mips32r2
-mips32r3
-mips32r5
-mips32r6
-mips64
-mips64r2
-mips64r3
-mips64r5
-mips64r6: Generate code for a particular MIPS Instruction Set Architecture level. `-mips1' is an alias for `-march=r3000', `-mips2' is an alias for `-march=r6000', `-mips3' is an alias for `-march=r4000' and `-mips4' is an alias for `-march=r8000'. `-mips5', `-mips32', `-mips32r2', `-mips32r3', `-mips32r5', `-mips32r6', `-mips64', `-mips64r2', `-mips64r3', `-mips64r5', and `-mips64r6' correspond to generic MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and MIPS64 Release 6 ISA processors, respectively.
-march=cpu: Generate code for a particular MIPS CPU.
-mtune=cpu: Schedule and tune for a particular MIPS CPU.
-mfix7000
-mno-fix7000: Cause nops to be inserted if the read of the destination register of an mfhi or mflo instruction occurs in the following two instructions.
-mfix-rm7000
-mno-fix-rm7000: Cause nops to be inserted if a dmult or dmultu instruction is followed by a load instruction.
-mdebug
-no-mdebug: Cause stabs-style debugging output to go into an ECOFF-style .mdebug section instead of the standard ELF .stabs sections.
-mpdr
-mno-pdr: Control generation of .pdr sections.
-mgp32
-mfp32: The register sizes are normally inferred from the ISA and ABI, but these flags force a certain group of registers to be treated as 32 bits wide at all times. `-mgp32' controls the size of general-purpose registers and `-mfp32' controls the size of floating-point registers.
-mgp64
-mfp64: The register sizes are normally inferred from the ISA and ABI, but these flags force a certain group of registers to be treated as 64 bits wide at all times. `-mgp64' controls the size of general-purpose registers and `-mfp64' controls the size of floating-point registers.
-mfpxx: The register sizes are normally inferred from the ISA and ABI, but using this flag in combination with `-mabi=32' enables an ABI variant which will operate correctly with floating-point registers which are 32 or 64 bits wide.
-modd-spreg
-mno-odd-spreg: Enable use of floating-point operations on odd-numbered single-precision registers when supported by the ISA. `-mfpxx' implies `-mno-odd-spreg', otherwise the default is `-modd-spreg'.
-mips16
-no-mips16: Generate code for the MIPS 16 processor. This is equivalent to putting .set mips16 at the start of the assembly file. `-no-mips16' turns off this option.
-mmicromips
-mno-micromips: Generate code for the microMIPS processor. This is equivalent to putting .set micromips at the start of the assembly file. `-mno-micromips' turns off this option. This is equivalent to putting .set nomicromips at the start of the assembly file.
-msmartmips
-mno-smartmips: Enables the SmartMIPS extension to the MIPS32 instruction set. This is equivalent to putting .set smartmips at the start of the assembly file. `-mno-smartmips' turns off this option.
-mips3d
-no-mips3d: Generate code for the MIPS-3D Application Specific Extension. This tells the assembler to accept MIPS-3D instructions. `-no-mips3d' turns off this option.
-mdmx
-no-mdmx: Generate code for the MDMX Application Specific Extension. This tells the assembler to accept MDMX instructions. `-no-mdmx' turns off this option.
-mdsp
-mno-dsp: Generate code for the DSP Release 1 Application Specific Extension. This tells the assembler to accept DSP Release 1 instructions. `-mno-dsp' turns off this option.
-mdspr2
-mno-dspr2: Generate code for the DSP Release 2 Application Specific Extension. This option implies `-mdsp'. This tells the assembler to accept DSP Release 2 instructions. `-mno-dspr2' turns off this option.
-mdspr3
-mno-dspr3: Generate code for the DSP Release 3 Application Specific Extension. This option implies `-mdsp' and `-mdspr2'. This tells the assembler to accept DSP Release 3 instructions. `-mno-dspr3' turns off this option.
-mmsa
-mno-msa: Generate code for the MIPS SIMD Architecture Extension. This tells the assembler to accept MSA instructions. `-mno-msa' turns off this option.
-mxpa
-mno-xpa: Generate code for the MIPS eXtended Physical Address (XPA) Extension. This tells the assembler to accept XPA instructions. `-mno-xpa' turns off this option.
-mmt
-mno-mt: Generate code for the MT Application Specific Extension. This tells the assembler to accept MT instructions. `-mno-mt' turns off this option.
-mmcu
-mno-mcu: Generate code for the MCU Application Specific Extension. This tells the assembler to accept MCU instructions. `-mno-mcu' turns off this option.
-minsn32
-mno-insn32: Only use 32-bit instruction encodings when generating code for the microMIPS processor. This option inhibits the use of any 16-bit instructions. This is equivalent to putting .set insn32 at the start of the assembly file. `-mno-insn32' turns off this option. This is equivalent to putting .set noinsn32 at the start of the assembly file. By default `-mno-insn32' is selected, allowing all instructions to be used.
--construct-floats
--no-construct-floats: The `--no-construct-floats' option disables the construction of double width floating point constants by loading the two halves of the value into the two single width floating point registers that make up the double width register. By default `--construct-floats' is selected, allowing construction of these floating point constants.
--relax-branch
--no-relax-branch: The `--relax-branch' option enables the relaxation of out-of-range branches. By default `--no-relax-branch' is selected, causing any out-of-range branches to produce an error.
-mnan=encoding: Select between the IEEE 754-2008 (-mnan=2008) or the legacy (-mnan=legacy) NaN encoding format. The latter is the default.
--emulation=name: This option was formerly used to switch between ELF and ECOFF output on targets like IRIX 5 that supported both. MIPS ECOFF support was removed in GAS 2.24, so the option now serves little purpose. It is retained for backwards compatibility.
The available configuration names are: `mipself', `mipslelf' and `mipsbelf'. Choosing `mipself' now has no effect, since the output is always ELF. `mipslelf' and `mipsbelf' select little- and big-endian output respectively, but `-EL' and `-EB' are now the preferred options instead.
-nocpp: as ignores this option. It is accepted for compatibility with the native tools.
--trap
--no-trap
--break
--no-break: Control how to deal with multiplication overflow and division by zero. `--trap' or `--no-break' (which are synonyms) take a trap exception (and only work for Instruction Set Architecture level 2 and higher); `--break' or `--no-trap' (also synonyms, and the default) take a break exception.
-n: When this option is used, as will issue a warning every time it generates a nop instruction from a macro.

The following options are available when as is configured for an MCore processor.

-jsri2bsr
-nojsri2bsr: Enable or disable the JSRI to BSR transformation. By default this is enabled. The command line option `-nojsri2bsr' can be used to disable it.
-sifilter
-nosifilter: Enable or disable the silicon filter behaviour. By default this is disabled. The default can be overridden by the `-sifilter' command line option.
-relax: Alter jump instructions for long displacements.
-mcpu=[210|340]: Select the cpu type on the target hardware. This controls which instructions can be assembled.
-EB: Assemble for a big endian target.
-EL: Assemble for a little endian target.

See Meta Options, for the options available when as is configured for a Meta processor.

See the info pages for documentation of the MMIX-specific options.

See NDS32 Options, for the options available when as is configured for a NDS32 processor.

See PowerPC-Opts, for the options available when as is configured for a PowerPC processor.

See the info pages for documentation of the RX-specific options.

The following options are available when as is configured for the s390 processor family.

-m31
-m64: Select the word size, either 31/32 bits or 64 bits.
-mesa
-mzarch: Select the architecture mode, either the Enterprise System Architecture (esa) or the z/Architecture mode (zarch).
-march=processor: Specify which s390 processor variant is the target, `g6', `g6', `z900', `z990', `z9-109', `z9-ec', `z10', `z196', `zEC12', or `z13'.
-mregnames
-mno-regnames: Allow or disallow symbolic names for registers.
-mwarn-areg-zero: Warn whenever the operand for a base or index register has been specified but evaluates to zero.

See TIC6X Options, for the options available when as is configured for a TMS320C6000 processor.

See TILE-Gx Options, for the options available when as is configured for a TILE-Gx processor.

See Visium Options, for the options available when as is configured for a Visium processor.

See Xtensa Options, for the options available when as is configured for an Xtensa processor.

The following options are available when as is configured for a Z80 family processor.

-z80: Assemble for Z80 processor.
-r800: Assemble for R800 processor.
-ignore-undocumented-instructions
-Wnud: Assemble undocumented Z80 instructions that also work on R800 without warning.
-ignore-unportable-instructions
-Wnup: Assemble all undocumented Z80 instructions without warning.
-warn-undocumented-instructions
-Wud: Issue a warning for undocumented Z80 instructions that also work on R800.
-warn-unportable-instructions
-Wup: Issue a warning for undocumented Z80 instructions that do not work on R800.
-forbid-undocumented-instructions
-Fud: Treat all undocumented instructions as errors.
-forbid-unportable-instructions
-Fup: Treat undocumented Z80 instructions that do not work on R800 as errors.