1 Overview

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

     
     as [-a[cdghlns][=file]] [--alternate] [-D]
      [--debug-prefix-map old=new]
      [--defsym sym=val] [-f] [-g] [--gstabs]
      [--gstabs+] [--gdwarf-2] [--help] [-I dir] [-J]
      [-K] [-L] [--listing-lhs-width=NUM]
      [--listing-lhs-width2=NUM] [--listing-rhs-width=NUM]
      [--listing-cont-lines=NUM] [--keep-locals] [-o
      objfile] [-R] [--reduce-memory-overheads] [--statistics]
      [-v] [-version] [--version] [-W] [--warn]
      [--fatal-warnings] [-w] [-x] [-Z] [@FILE]
      [--target-help] [target-options]
      [--|files ...]
     
     
     
     Target Alpha options:
        [-mcpu]
        [-mdebug | -no-mdebug]
        [-relax] [-g] [-Gsize]
        [-F] [-32addr]
     
     Target ARC options:
        [-marc[5|6|7|8]]
        [-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 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 H8/300 options:
        [-h-tick-hex]
     
     
     Target i386 options:
        [--32|--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]
        [-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 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]
        [-march=CPU] [-mtune=CPU] [-mips1] [-mips2]
        [-mips3] [-mips4] [-mips5] [-mips32] [-mips32r2]
        [-mips64] [-mips64r2]
        [-construct-floats] [-no-construct-floats]
        [-trap] [-no-break] [-break] [-no-trap]
        [-mfix7000] [-mno-fix7000]
        [-mips16] [-no-mips16]
        [-msmartmips] [-mno-smartmips]
        [-mips3d] [-no-mips3d]
        [-mdmx] [-no-mdmx]
        [-mdsp] [-mno-dsp]
        [-mdspr2] [-mno-dspr2]
        [-mmt] [-mno-mt]
        [-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 PDP11 options:
        [-mpic|-mno-pic] [-mall] [-mno-extensions]
        [-mextension|-mno-extension]
        [-mcpu] [-mmachine]
     
     Target picoJava options:
        [-mb|-me]
     
     Target PowerPC options:
        [-mpwrx|-mpwr2|-mpwr|-m601|-mppc|-mppc32|-m603|-m604|
         -m403|-m405|-mppc64|-m620|-mppc64bridge|-mbooke|
         -mbooke32|-mbooke64]
        [-mcom|-many|-maltivec|-mvsx] [-memb]
        [-mregnames|-mno-regnames]
        [-mrelocatable|-mrelocatable-lib]
        [-mlittle|-mlittle-endian|-mbig|-mbig-endian]
        [-msolaris|-mno-solaris]
     
     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 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]
     
     
     
     Target Xtensa options:
      [--[no-]text-section-literals] [--[no-]absolute-literals]
      [--[no-]target-align] [--[no-]longcalls]
      [--[no-]transform]
      [--rename-section oldname=newname]
     

@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.

-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.

--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.

-o objfile

Name the object-file output from as objfile.

-R

Fold the data section into the text section.

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.

--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.

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

-marc[5|6|7|8]

This option selects the core processor variant.

-EB | -EL

Select either big-endian (-EB) or little-endian (-EL) output.

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.

-k

Specify that PIC code has been generated.

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 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.

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

Specify what processor is the target. The default is defined by the configuration option when building the assembler.

-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

-mips64

-mips64r2

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, -mips64, and -mips64r2 correspond to generic MIPS V, MIPS32, MIPS32 Release 2, MIPS64, and MIPS64 Release 2 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.

-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.

-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.

-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.

-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.

--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.

--emulation=name

This option causes as to emulate as configured for some other target, in all respects, including output format (choosing between ELF and ECOFF only), handling of pseudo-opcodes which may generate debugging information or store symbol table information, and default endianness. The available configuration names are: mipsecoff, mipself, mipslecoff, mipsbecoff, mipslelf, mipsbelf. The first two do not alter the default endianness from that of the primary target for which the assembler was configured; the others change the default to little- or big-endian as indicated by the b or l in the name. Using -EB or -EL will override the endianness selection in any case.

This option is currently supported only when the primary target as is configured for is a mips ELF or ECOFF target. Furthermore, the primary target or others specified with --enable-targets=... at configuration time must include support for the other format, if both are to be available. For example, the Irix 5 configuration includes support for both.

Eventually, this option will support more configurations, with more fine-grained control over the assembler's behavior, and will be supported for more processors.

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

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

--text-section-literals | --no-text-section-literals

With --text-section-literals, literal pools are interspersed in the text section. The default is --no-text-section-literals, which places literals in a separate section in the output file. These options only affect literals referenced via PC-relative L32R instructions; literals for absolute mode L32R instructions are handled separately.

--absolute-literals | --no-absolute-literals

Indicate to the assembler whether L32R instructions use absolute or PC-relative addressing. The default is to assume absolute addressing if the Xtensa processor includes the absolute L32R addressing option. Otherwise, only the PC-relative L32R mode can be used.

--target-align | --no-target-align

Enable or disable automatic alignment to reduce branch penalties at the expense of some code density. The default is --target-align.

--longcalls | --no-longcalls

Enable or disable transformation of call instructions to allow calls across a greater range of addresses. The default is --no-longcalls.

--transform | --no-transform

Enable or disable all assembler transformations of Xtensa instructions. The default is --transform; --no-transform should be used only in the rare cases when the instructions must be exactly as specified in the assembly source.

--rename-section oldname=newname

When generating output sections, rename the oldname section to newname.

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.

• Manual: Structure of this Manual
• GNU Assembler: The GNU Assembler
• Object Formats: Object File Formats
• Command Line: Command Line
• Input Files: Input Files
• Object: Output (Object) File
• Errors: Error and Warning Messages