This is as.info, produced by makeinfo version 6.5 from as.texi. This file documents the GNU Assembler "as". Copyright (C) 1991-2018 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 no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". INFO-DIR-SECTION Software development START-INFO-DIR-ENTRY * As: (as). The GNU assembler. * Gas: (as). The GNU assembler. END-INFO-DIR-ENTRY  File: as.info, Node: Top, Next: Overview, Up: (dir) Using as ******** This file is a user guide to the GNU assembler 'as' (GNU Binutils) version 2.31.1. This document is distributed under the terms of the GNU Free Documentation License. A copy of the license is included in the section entitled "GNU Free Documentation License". * Menu: * Overview:: Overview * Invoking:: Command-Line Options * Syntax:: Syntax * Sections:: Sections and Relocation * Symbols:: Symbols * Expressions:: Expressions * Pseudo Ops:: Assembler Directives * Object Attributes:: Object Attributes * Machine Dependencies:: Machine Dependent Features * Reporting Bugs:: Reporting Bugs * Acknowledgements:: Who Did What * GNU Free Documentation License:: GNU Free Documentation License * AS Index:: AS Index  File: as.info, Node: Overview, Next: Invoking, Prev: Top, Up: Top 1 Overview ********** Here is a brief summary of how to invoke 'as'. For details, see *note Command-Line Options: Invoking. 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]] [-generate-missing-build-notes=[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 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] [-mignore-branch-isa] [-mno-ignore-branch-isa] [-mnan=ENCODING] [-trap] [-no-break] [-break] [-no-trap] [-mips16] [-no-mips16] [-mmips16e2] [-mno-mips16e2] [-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] [-mcrc] [-mno-crc] [-mginv] [-mno-ginv] [-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|-mspe2|-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 PRU options:_ [-link-relax] [-mnolink-relax] [-mno-warn-regname-label] _Target RISC-V options:_ [-fpic|-fPIC|-fno-pic] [-march=ISA] [-mabi=ABI] _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|-Aleon|-Asparclet|-Asparclite -Av8plus|-Av8plusa|-Av8plusb|-Av8plusc|-Av8plusd -Av8plusv|-Av8plusm|-Av9|-Av9a|-Av9b|-Av9c -Av9d|-Av9e|-Av9v|-Av9m|-Asparc|-Asparcvis -Asparcvis2|-Asparcfmaf|-Asparcima|-Asparcvis3 -Asparcvisr|-Asparc5] [-xarch=v8plus|-xarch=v8plusa]|-xarch=v8plusb|-xarch=v8plusc -xarch=v8plusd|-xarch=v8plusv|-xarch=v8plusm|-xarch=v9 -xarch=v9a|-xarch=v9b|-xarch=v9c|-xarch=v9d|-xarch=v9e -xarch=v9v|-xarch=v9m|-xarch=sparc|-xarch=sparcvis -xarch=sparcvis2|-xarch=sparcfmaf|-xarch=sparcima -xarch=sparcvis3|-xarch=sparcvisr|-xarch=sparc5 -bump] [-32|-64] [-enforce-aligned-data][-dcti-couples-detect] _Target TIC54X options:_ [-mcpu=54[123589]|-mcpu=54[56]lp] [-mfar-mode|-mf] [-merrors-to-file |-me ] _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. *Note '.altmacro': 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'. '--generate-missing-build-notes=yes' '--generate-missing-build-notes=no' These options control whether the ELF assembler should generate GNU Build attribute notes if none are present in the input sources. The default can be controlled by the '--enable-generate-build-notes' configure option. '--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. *Note 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. *Note '.section NAME': Section Name Substitutions. '--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. *Note AArch64 Options::, for the options available when as is configured for the 64-bit mode of the ARM Architecture (AArch64). *Note 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. *Note 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. *Note Epiphany Options::, for the options available when as is configured for an Epiphany processor. *Note 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 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. *Note 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 *note 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. *Note PRU Options::, for the options available when as is configured for a PRU processor. 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 '.module mips16' at the start of the assembly file. '-no-mips16' turns off this option. '-mmips16e2' '-mno-mips16e2' Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent to putting '.module mips16e2' at the start of the assembly file. '-mno-mips16e2' turns off this option. '-mmicromips' '-mno-micromips' Generate code for the microMIPS processor. This is equivalent to putting '.module micromips' at the start of the assembly file. '-mno-micromips' turns off this option. This is equivalent to putting '.module 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 '.module 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. '-mcrc' '-mno-crc' Generate code for the MIPS cyclic redundancy check (CRC) Application Specific Extension. This tells the assembler to accept CRC instructions. '-mno-crc' turns off this option. '-mginv' '-mno-ginv' Generate code for the Global INValidate (GINV) Application Specific Extension. This tells the assembler to accept GINV instructions. '-mno-ginv' 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. '-mignore-branch-isa' '-mno-ignore-branch-isa' Ignore branch checks for invalid transitions between ISA modes. The semantics of branches does not provide for an ISA mode switch, so in most cases the ISA mode a branch has been encoded for has to be the same as the ISA mode of the branch's target label. Therefore GAS has checks implemented that verify in branch assembly that the two ISA modes match. '-mignore-branch-isa' disables these checks. By default '-mno-ignore-branch-isa' is selected, causing any invalid branch requiring a transition between ISA modes 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. *Note 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. *Note NDS32 Options::, for the options available when as is configured for a NDS32 processor. *Note PowerPC-Opts::, for the options available when as is configured for a PowerPC processor. *Note RISC-V-Options::, for the options available when as is configured for a RISC-V 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, 'g5' (or 'arch3'), 'g6', 'z900' (or 'arch5'), 'z990' (or 'arch6'), 'z9-109', 'z9-ec' (or 'arch7'), 'z10' (or 'arch8'), 'z196' (or 'arch9'), 'zEC12' (or 'arch10'), 'z13' (or 'arch11'), or 'z14' (or 'arch12'). '-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. *Note TIC6X Options::, for the options available when as is configured for a TMS320C6000 processor. *Note TILE-Gx Options::, for the options available when as is configured for a TILE-Gx processor. *Note Visium Options::, for the options available when as is configured for a Visium processor. *Note 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. * Menu: * 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  File: as.info, Node: Manual, Next: GNU Assembler, Up: Overview 1.1 Structure of this Manual ============================ This manual is intended to describe what you need to know to use GNU 'as'. We cover the syntax expected in source files, including notation for symbols, constants, and expressions; the directives that 'as' understands; and of course how to invoke 'as'. This manual also describes some of the machine-dependent features of various flavors of the assembler. On the other hand, this manual is _not_ intended as an introduction to programming in assembly language--let alone programming in general! In a similar vein, we make no attempt to introduce the machine architecture; we do _not_ describe the instruction set, standard mnemonics, registers or addressing modes that are standard to a particular architecture. You may want to consult the manufacturer's machine architecture manual for this information.  File: as.info, Node: GNU Assembler, Next: Object Formats, Prev: Manual, Up: Overview 1.2 The GNU Assembler ===================== GNU 'as' is really a family of assemblers. If you use (or have used) the GNU assembler on one architecture, you should find a fairly similar environment when you use it on another architecture. Each version has much in common with the others, including object file formats, most assembler directives (often called "pseudo-ops") and assembler syntax. 'as' is primarily intended to assemble the output of the GNU C compiler 'gcc' for use by the linker 'ld'. Nevertheless, we've tried to make 'as' assemble correctly everything that other assemblers for the same machine would assemble. Any exceptions are documented explicitly (*note Machine Dependencies::). This doesn't mean 'as' always uses the same syntax as another assembler for the same architecture; for example, we know of several incompatible versions of 680x0 assembly language syntax. Unlike older assemblers, 'as' is designed to assemble a source program in one pass of the source file. This has a subtle impact on the '.org' directive (*note '.org': Org.).  File: as.info, Node: Object Formats, Next: Command Line, Prev: GNU Assembler, Up: Overview 1.3 Object File Formats ======================= The GNU assembler can be configured to produce several alternative object file formats. For the most part, this does not affect how you write assembly language programs; but directives for debugging symbols are typically different in different file formats. *Note Symbol Attributes: Symbol Attributes.  File: as.info, Node: Command Line, Next: Input Files, Prev: Object Formats, Up: Overview 1.4 Command Line ================ After the program name 'as', the command line may contain options and file names. Options may appear in any order, and may be before, after, or between file names. The order of file names is significant. '--' (two hyphens) by itself names the standard input file explicitly, as one of the files for 'as' to assemble. Except for '--' any command line argument that begins with a hyphen ('-') is an option. Each option changes the behavior of 'as'. No option changes the way another option works. An option is a '-' followed by one or more letters; the case of the letter is important. All options are optional. Some options expect exactly one file name to follow them. The file name may either immediately follow the option's letter (compatible with older assemblers) or it may be the next command argument (GNU standard). These two command lines are equivalent: as -o my-object-file.o mumble.s as -omy-object-file.o mumble.s  File: as.info, Node: Input Files, Next: Object, Prev: Command Line, Up: Overview 1.5 Input Files =============== We use the phrase "source program", abbreviated "source", to describe the program input to one run of 'as'. The program may be in one or more files; how the source is partitioned into files doesn't change the meaning of the source. The source program is a concatenation of the text in all the files, in the order specified. Each time you run 'as' it assembles exactly one source program. The source program is made up of one or more files. (The standard input is also a file.) You give 'as' a command line that has zero or more input file names. The input files are read (from left file name to right). A command line argument (in any position) that has no special meaning is taken to be an input file name. If you give 'as' no file names it attempts to read one input file from the 'as' standard input, which is normally your terminal. You may have to type to tell 'as' there is no more program to assemble. Use '--' if you need to explicitly name the standard input file in your command line. If the source is empty, 'as' produces a small, empty object file. Filenames and Line-numbers -------------------------- There are two ways of locating a line in the input file (or files) and either may be used in reporting error messages. One way refers to a line number in a physical file; the other refers to a line number in a "logical" file. *Note Error and Warning Messages: Errors. "Physical files" are those files named in the command line given to 'as'. "Logical files" are simply names declared explicitly by assembler directives; they bear no relation to physical files. Logical file names help error messages reflect the original source file, when 'as' source is itself synthesized from other files. 'as' understands the '#' directives emitted by the 'gcc' preprocessor. See also *note '.file': File.  File: as.info, Node: Object, Next: Errors, Prev: Input Files, Up: Overview 1.6 Output (Object) File ======================== Every time you run 'as' it produces an output file, which is your assembly language program translated into numbers. This file is the object file. Its default name is 'a.out'. You can give it another name by using the '-o' option. Conventionally, object file names end with '.o'. The default name is used for historical reasons: older assemblers were capable of assembling self-contained programs directly into a runnable program. (For some formats, this isn't currently possible, but it can be done for the 'a.out' format.) The object file is meant for input to the linker 'ld'. It contains assembled program code, information to help 'ld' integrate the assembled program into a runnable file, and (optionally) symbolic information for the debugger.  File: as.info, Node: Errors, Prev: Object, Up: Overview 1.7 Error and Warning Messages ============================== 'as' may write warnings and error messages to the standard error file (usually your terminal). This should not happen when a compiler runs 'as' automatically. Warnings report an assumption made so that 'as' could keep assembling a flawed program; errors report a grave problem that stops the assembly. Warning messages have the format file_name:NNN:Warning Message Text (where NNN is a line number). If both a logical file name (*note '.file': File.) and a logical line number (*note '.line': Line.) have been given then they will be used, otherwise the file name and line number in the current assembler source file will be used. The message text is intended to be self explanatory (in the grand Unix tradition). Note the file name must be set via the logical version of the '.file' directive, not the DWARF2 version of the '.file' directive. For example: .file 2 "bar.c" error_assembler_source .file "foo.c" .line 30 error_c_source produces this output: Assembler messages: asm.s:2: Error: no such instruction: `error_assembler_source' foo.c:31: Error: no such instruction: `error_c_source' Error messages have the format file_name:NNN:FATAL:Error Message Text The file name and line number are derived as for warning messages. The actual message text may be rather less explanatory because many of them aren't supposed to happen.  File: as.info, Node: Invoking, Next: Syntax, Prev: Overview, Up: Top 2 Command-Line Options ********************** This chapter describes command-line options available in _all_ versions of the GNU assembler; see *note Machine Dependencies::, for options specific to particular machine architectures. If you are invoking 'as' via the GNU C compiler, you can use the '-Wa' option to pass arguments through to the assembler. The assembler arguments must be separated from each other (and the '-Wa') by commas. For example: gcc -c -g -O -Wa,-alh,-L file.c This passes two options to the assembler: '-alh' (emit a listing to standard output with high-level and assembly source) and '-L' (retain local symbols in the symbol table). Usually you do not need to use this '-Wa' mechanism, since many compiler command-line options are automatically passed to the assembler by the compiler. (You can call the GNU compiler driver with the '-v' option to see precisely what options it passes to each compilation pass, including the assembler.) * Menu: * a:: -a[cdghlns] enable listings * alternate:: -alternate enable alternate macro syntax * D:: -D for compatibility * f:: -f to work faster * I:: -I for .include search path * K:: -K for difference tables * L:: -L to retain local symbols * listing:: -listing-XXX to configure listing output * M:: -M or -mri to assemble in MRI compatibility mode * MD:: -MD for dependency tracking * no-pad-sections:: -no-pad-sections to stop section padding * o:: -o to name the object file * R:: -R to join data and text sections * statistics:: -statistics to see statistics about assembly * traditional-format:: -traditional-format for compatible output * v:: -v to announce version * W:: -W, -no-warn, -warn, -fatal-warnings to control warnings * Z:: -Z to make object file even after errors  File: as.info, Node: a, Next: alternate, Up: Invoking 2.1 Enable Listings: '-a[cdghlns]' ================================== These options enable listing output from the assembler. By itself, '-a' requests high-level, assembly, and symbols listing. You can use other letters to select specific options for the list: '-ah' requests a high-level language listing, '-al' requests an output-program assembly listing, and '-as' requests a symbol table listing. High-level listings require that a compiler debugging option like '-g' be used, and that assembly listings ('-al') be requested also. Use the '-ag' option to print a first section with general assembly information, like as version, switches passed, or time stamp. Use the '-ac' option to omit false conditionals from a listing. Any lines which are not assembled because of a false '.if' (or '.ifdef', or any other conditional), or a true '.if' followed by an '.else', will be omitted from the listing. Use the '-ad' option to omit debugging directives from the listing. Once you have specified one of these options, you can further control listing output and its appearance using the directives '.list', '.nolist', '.psize', '.eject', '.title', and '.sbttl'. The '-an' option turns off all forms processing. If you do not request listing output with one of the '-a' options, the listing-control directives have no effect. The letters after '-a' may be combined into one option, _e.g._, '-aln'. Note if the assembler source is coming from the standard input (e.g., because it is being created by 'gcc' and the '-pipe' command line switch is being used) then the listing will not contain any comments or preprocessor directives. This is because the listing code buffers input source lines from stdin only after they have been preprocessed by the assembler. This reduces memory usage and makes the code more efficient.  File: as.info, Node: alternate, Next: D, Prev: a, Up: Invoking 2.2 '--alternate' ================= Begin in alternate macro mode, see *note '.altmacro': Altmacro.  File: as.info, Node: D, Next: f, Prev: alternate, Up: Invoking 2.3 '-D' ======== This option has no effect whatsoever, but it is accepted to make it more likely that scripts written for other assemblers also work with 'as'.  File: as.info, Node: f, Next: I, Prev: D, Up: Invoking 2.4 Work Faster: '-f' ===================== '-f' should only be used when assembling programs written by a (trusted) compiler. '-f' stops the assembler from doing whitespace and comment preprocessing on the input file(s) before assembling them. *Note Preprocessing: Preprocessing. _Warning:_ if you use '-f' when the files actually need to be preprocessed (if they contain comments, for example), 'as' does not work correctly.  File: as.info, Node: I, Next: K, Prev: f, Up: Invoking 2.5 '.include' Search Path: '-I' PATH ===================================== Use this option to add a PATH to the list of directories 'as' searches for files specified in '.include' directives (*note '.include': Include.). You may use '-I' as many times as necessary to include a variety of paths. The current working directory is always searched first; after that, 'as' searches any '-I' directories in the same order as they were specified (left to right) on the command line.  File: as.info, Node: K, Next: L, Prev: I, Up: Invoking 2.6 Difference Tables: '-K' =========================== 'as' sometimes alters the code emitted for directives of the form '.word SYM1-SYM2'. *Note '.word': Word. You can use the '-K' option if you want a warning issued when this is done.  File: as.info, Node: L, Next: listing, Prev: K, Up: Invoking 2.7 Include Local Symbols: '-L' =============================== Symbols beginning with system-specific local label prefixes, typically '.L' for ELF systems or 'L' for traditional a.out systems, are called "local symbols". *Note Symbol Names::. Normally you do not see such symbols when debugging, because they are intended for the use of programs (like compilers) that compose assembler programs, not for your notice. Normally both 'as' and 'ld' discard such symbols, so you do not normally debug with them. This option tells 'as' to retain those local symbols in the object file. Usually if you do this you also tell the linker 'ld' to preserve those symbols.  File: as.info, Node: listing, Next: M, Prev: L, Up: Invoking 2.8 Configuring listing output: '--listing' =========================================== The listing feature of the assembler can be enabled via the command line switch '-a' (*note a::). This feature combines the input source file(s) with a hex dump of the corresponding locations in the output object file, and displays them as a listing file. The format of this listing can be controlled by directives inside the assembler source (i.e., '.list' (*note List::), '.title' (*note Title::), '.sbttl' (*note Sbttl::), '.psize' (*note Psize::), and '.eject' (*note Eject::) and also by the following switches: '--listing-lhs-width='number'' Sets the maximum width, in words, of the first line of the hex byte dump. This dump appears on the left hand side of the listing output. '--listing-lhs-width2='number'' Sets the maximum width, in words, of any further lines of the hex byte dump for a given input source line. If this value is not specified, it defaults to being the same as the value specified for '--listing-lhs-width'. If neither switch is used the default is to one. '--listing-rhs-width='number'' Sets the maximum width, in characters, of the source line that is displayed alongside the hex dump. The default value for this parameter is 100. The source line is displayed on the right hand side of the listing output. '--listing-cont-lines='number'' Sets the maximum number of continuation lines of hex dump that will be displayed for a given single line of source input. The default value is 4.  File: as.info, Node: M, Next: MD, Prev: listing, Up: Invoking 2.9 Assemble in MRI Compatibility Mode: '-M' ============================================ The '-M' or '--mri' option selects MRI compatibility mode. This changes the syntax and pseudo-op handling of 'as' to make it compatible with the 'ASM68K' assembler from Microtec Research. The exact nature of the MRI syntax will not be documented here; see the MRI manuals for more information. Note in particular that the handling of macros and macro arguments is somewhat different. The purpose of this option is to permit assembling existing MRI assembler code using 'as'. The MRI compatibility is not complete. Certain operations of the MRI assembler depend upon its object file format, and can not be supported using other object file formats. Supporting these would require enhancing each object file format individually. These are: * global symbols in common section The m68k MRI assembler supports common sections which are merged by the linker. Other object file formats do not support this. 'as' handles common sections by treating them as a single common symbol. It permits local symbols to be defined within a common section, but it can not support global symbols, since it has no way to describe them. * complex relocations The MRI assemblers support relocations against a negated section address, and relocations which combine the start addresses of two or more sections. These are not support by other object file formats. * 'END' pseudo-op specifying start address The MRI 'END' pseudo-op permits the specification of a start address. This is not supported by other object file formats. The start address may instead be specified using the '-e' option to the linker, or in a linker script. * 'IDNT', '.ident' and 'NAME' pseudo-ops The MRI 'IDNT', '.ident' and 'NAME' pseudo-ops assign a module name to the output file. This is not supported by other object file formats. * 'ORG' pseudo-op The m68k MRI 'ORG' pseudo-op begins an absolute section at a given address. This differs from the usual 'as' '.org' pseudo-op, which changes the location within the current section. Absolute sections are not supported by other object file formats. The address of a section may be assigned within a linker script. There are some other features of the MRI assembler which are not supported by 'as', typically either because they are difficult or because they seem of little consequence. Some of these may be supported in future releases. * EBCDIC strings EBCDIC strings are not supported. * packed binary coded decimal Packed binary coded decimal is not supported. This means that the 'DC.P' and 'DCB.P' pseudo-ops are not supported. * 'FEQU' pseudo-op The m68k 'FEQU' pseudo-op is not supported. * 'NOOBJ' pseudo-op The m68k 'NOOBJ' pseudo-op is not supported. * 'OPT' branch control options The m68k 'OPT' branch control options--'B', 'BRS', 'BRB', 'BRL', and 'BRW'--are ignored. 'as' automatically relaxes all branches, whether forward or backward, to an appropriate size, so these options serve no purpose. * 'OPT' list control options The following m68k 'OPT' list control options are ignored: 'C', 'CEX', 'CL', 'CRE', 'E', 'G', 'I', 'M', 'MEX', 'MC', 'MD', 'X'. * other 'OPT' options The following m68k 'OPT' options are ignored: 'NEST', 'O', 'OLD', 'OP', 'P', 'PCO', 'PCR', 'PCS', 'R'. * 'OPT' 'D' option is default The m68k 'OPT' 'D' option is the default, unlike the MRI assembler. 'OPT NOD' may be used to turn it off. * 'XREF' pseudo-op. The m68k 'XREF' pseudo-op is ignored.  File: as.info, Node: MD, Next: no-pad-sections, Prev: M, Up: Invoking 2.10 Dependency Tracking: '--MD' ================================ 'as' can generate a dependency file for the file it creates. This file consists of a single rule suitable for 'make' describing the dependencies of the main source file. The rule is written to the file named in its argument. This feature is used in the automatic updating of makefiles.  File: as.info, Node: no-pad-sections, Next: o, Prev: MD, Up: Invoking 2.11 Output Section Padding =========================== Normally the assembler will pad the end of each output section up to its alignment boundary. But this can waste space, which can be significant on memory constrained targets. So the '--no-pad-sections' option will disable this behaviour.  File: as.info, Node: o, Next: R, Prev: no-pad-sections, Up: Invoking 2.12 Name the Object File: '-o' =============================== There is always one object file output when you run 'as'. By default it has the name 'a.out'. You use this option (which takes exactly one filename) to give the object file a different name. Whatever the object file is called, 'as' overwrites any existing file of the same name.  File: as.info, Node: R, Next: statistics, Prev: o, Up: Invoking 2.13 Join Data and Text Sections: '-R' ====================================== '-R' tells 'as' to write the object file as if all data-section data lives in the text section. This is only done at the very last moment: your binary data are the same, but data section parts are relocated differently. The data section part of your object file is zero bytes long because all its bytes are appended to the text section. (*Note Sections and Relocation: Sections.) When you specify '-R' it would be possible to generate shorter address displacements (because we do not have to cross between text and data section). We refrain from doing this simply for compatibility with older versions of 'as'. In future, '-R' may work this way. When 'as' is configured for COFF or ELF output, this option is only useful if you use sections named '.text' and '.data'. '-R' is not supported for any of the HPPA targets. Using '-R' generates a warning from 'as'.  File: as.info, Node: statistics, Next: traditional-format, Prev: R, Up: Invoking 2.14 Display Assembly Statistics: '--statistics' ================================================ Use '--statistics' to display two statistics about the resources used by 'as': the maximum amount of space allocated during the assembly (in bytes), and the total execution time taken for the assembly (in CPU seconds).  File: as.info, Node: traditional-format, Next: v, Prev: statistics, Up: Invoking 2.15 Compatible Output: '--traditional-format' ============================================== For some targets, the output of 'as' is different in some ways from the output of some existing assembler. This switch requests 'as' to use the traditional format instead. For example, it disables the exception frame optimizations which 'as' normally does by default on 'gcc' output.  File: as.info, Node: v, Next: W, Prev: traditional-format, Up: Invoking 2.16 Announce Version: '-v' =========================== You can find out what version of as is running by including the option '-v' (which you can also spell as '-version') on the command line.  File: as.info, Node: W, Next: Z, Prev: v, Up: Invoking 2.17 Control Warnings: '-W', '--warn', '--no-warn', '--fatal-warnings' ====================================================================== 'as' should never give a warning or error message when assembling compiler output. But programs written by people often cause 'as' to give a warning that a particular assumption was made. All such warnings are directed to the standard error file. If you use the '-W' and '--no-warn' options, no warnings are issued. This only affects the warning messages: it does not change any particular of how 'as' assembles your file. Errors, which stop the assembly, are still reported. If you use the '--fatal-warnings' option, 'as' considers files that generate warnings to be in error. You can switch these options off again by specifying '--warn', which causes warnings to be output as usual.  File: as.info, Node: Z, Prev: W, Up: Invoking 2.18 Generate Object File in Spite of Errors: '-Z' ================================================== After an error message, 'as' normally produces no output. If for some reason you are interested in object file output even after 'as' gives an error message on your program, use the '-Z' option. If there are any errors, 'as' continues anyways, and writes an object file after a final warning message of the form 'N errors, M warnings, generating bad object file.'  File: as.info, Node: Syntax, Next: Sections, Prev: Invoking, Up: Top 3 Syntax ******** This chapter describes the machine-independent syntax allowed in a source file. 'as' syntax is similar to what many other assemblers use; it is inspired by the BSD 4.2 assembler, except that 'as' does not assemble Vax bit-fields. * Menu: * Preprocessing:: Preprocessing * Whitespace:: Whitespace * Comments:: Comments * Symbol Intro:: Symbols * Statements:: Statements * Constants:: Constants  File: as.info, Node: Preprocessing, Next: Whitespace, Up: Syntax 3.1 Preprocessing ================= The 'as' internal preprocessor: * adjusts and removes extra whitespace. It leaves one space or tab before the keywords on a line, and turns any other whitespace on the line into a single space. * removes all comments, replacing them with a single space, or an appropriate number of newlines. * converts character constants into the appropriate numeric values. It does not do macro processing, include file handling, or anything else you may get from your C compiler's preprocessor. You can do include file processing with the '.include' directive (*note '.include': Include.). You can use the GNU C compiler driver to get other "CPP" style preprocessing by giving the input file a '.S' suffix. *Note Options Controlling the Kind of Output: (gcc info)Overall Options. Excess whitespace, comments, and character constants cannot be used in the portions of the input text that are not preprocessed. If the first line of an input file is '#NO_APP' or if you use the '-f' option, whitespace and comments are not removed from the input file. Within an input file, you can ask for whitespace and comment removal in specific portions of the by putting a line that says '#APP' before the text that may contain whitespace or comments, and putting a line that says '#NO_APP' after this text. This feature is mainly intend to support 'asm' statements in compilers whose output is otherwise free of comments and whitespace.  File: as.info, Node: Whitespace, Next: Comments, Prev: Preprocessing, Up: Syntax 3.2 Whitespace ============== "Whitespace" is one or more blanks or tabs, in any order. Whitespace is used to separate symbols, and to make programs neater for people to read. Unless within character constants (*note Character Constants: Characters.), any whitespace means the same as exactly one space.  File: as.info, Node: Comments, Next: Symbol Intro, Prev: Whitespace, Up: Syntax 3.3 Comments ============ There are two ways of rendering comments to 'as'. In both cases the comment is equivalent to one space. Anything from '/*' through the next '*/' is a comment. This means you may not nest these comments. /* The only way to include a newline ('\n') in a comment is to use this sort of comment. */ /* This sort of comment does not nest. */ Anything from a "line comment" character up to the next newline is considered a comment and is ignored. The line comment character is target specific, and some targets multiple comment characters. Some targets also have line comment characters that only work if they are the first character on a line. Some targets use a sequence of two characters to introduce a line comment. Some targets can also change their line comment characters depending upon command line options that have been used. For more details see the _Syntax_ section in the documentation for individual targets. If the line comment character is the hash sign ('#') then it still has the special ability to enable and disable preprocessing (*note Preprocessing::) and to specify logical line numbers: To be compatible with past assemblers, lines that begin with '#' have a special interpretation. Following the '#' should be an absolute expression (*note Expressions::): the logical line number of the _next_ line. Then a string (*note Strings: Strings.) is allowed: if present it is a new logical file name. The rest of the line, if any, should be whitespace. If the first non-whitespace characters on the line are not numeric, the line is ignored. (Just like a comment.) # This is an ordinary comment. # 42-6 "new_file_name" # New logical file name # This is logical line # 36. This feature is deprecated, and may disappear from future versions of 'as'.  File: as.info, Node: Symbol Intro, Next: Statements, Prev: Comments, Up: Syntax 3.4 Symbols =========== A "symbol" is one or more characters chosen from the set of all letters (both upper and lower case), digits and the three characters '_.$'. On most machines, you can also use '$' in symbol names; exceptions are noted in *note Machine Dependencies::. No symbol may begin with a digit. Case is significant. There is no length limit; all characters are significant. Multibyte characters are supported. Symbols are delimited by characters not in that set, or by the beginning of a file (since the source program must end with a newline, the end of a file is not a possible symbol delimiter). *Note Symbols::. Symbol names may also be enclosed in double quote '"' characters. In such cases any characters are allowed, except for the NUL character. If a double quote character is to be included in the symbol name it must be preceeded by a backslash '\' character.  File: as.info, Node: Statements, Next: Constants, Prev: Symbol Intro, Up: Syntax 3.5 Statements ============== A "statement" ends at a newline character ('\n') or a "line separator character". The line separator character is target specific and described in the _Syntax_ section of each target's documentation. Not all targets support a line separator character. The newline or line separator character is considered to be part of the preceding statement. Newlines and separators within character constants are an exception: they do not end statements. It is an error to end any statement with end-of-file: the last character of any input file should be a newline. An empty statement is allowed, and may include whitespace. It is ignored. A statement begins with zero or more labels, optionally followed by a key symbol which determines what kind of statement it is. The key symbol determines the syntax of the rest of the statement. If the symbol begins with a dot '.' then the statement is an assembler directive: typically valid for any computer. If the symbol begins with a letter the statement is an assembly language "instruction": it assembles into a machine language instruction. Different versions of 'as' for different computers recognize different instructions. In fact, the same symbol may represent a different instruction in a different computer's assembly language. A label is a symbol immediately followed by a colon (':'). Whitespace before a label or after a colon is permitted, but you may not have whitespace between a label's symbol and its colon. *Note Labels::. For HPPA targets, labels need not be immediately followed by a colon, but the definition of a label must begin in column zero. This also implies that only one label may be defined on each line. label: .directive followed by something another_label: # This is an empty statement. instruction operand_1, operand_2, ...  File: as.info, Node: Constants, Prev: Statements, Up: Syntax 3.6 Constants ============= A constant is a number, written so that its value is known by inspection, without knowing any context. Like this: .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value. .ascii "Ring the bell\7" # A string constant. .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum. .float 0f-314159265358979323846264338327\ 95028841971.693993751E-40 # - pi, a flonum. * Menu: * Characters:: Character Constants * Numbers:: Number Constants  File: as.info, Node: Characters, Next: Numbers, Up: Constants 3.6.1 Character Constants ------------------------- There are two kinds of character constants. A "character" stands for one character in one byte and its value may be used in numeric expressions. String constants (properly called string _literals_) are potentially many bytes and their values may not be used in arithmetic expressions. * Menu: * Strings:: Strings * Chars:: Characters  File: as.info, Node: Strings, Next: Chars, Up: Characters 3.6.1.1 Strings ............... A "string" is written between double-quotes. It may contain double-quotes or null characters. The way to get special characters into a string is to "escape" these characters: precede them with a backslash '\' character. For example '\\' represents one backslash: the first '\' is an escape which tells 'as' to interpret the second character literally as a backslash (which prevents 'as' from recognizing the second '\' as an escape character). The complete list of escapes follows. '\b' Mnemonic for backspace; for ASCII this is octal code 010. 'backslash-f' Mnemonic for FormFeed; for ASCII this is octal code 014. '\n' Mnemonic for newline; for ASCII this is octal code 012. '\r' Mnemonic for carriage-Return; for ASCII this is octal code 015. '\t' Mnemonic for horizontal Tab; for ASCII this is octal code 011. '\ DIGIT DIGIT DIGIT' An octal character code. The numeric code is 3 octal digits. For compatibility with other Unix systems, 8 and 9 are accepted as digits: for example, '\008' has the value 010, and '\009' the value 011. '\x HEX-DIGITS...' A hex character code. All trailing hex digits are combined. Either upper or lower case 'x' works. '\\' Represents one '\' character. '\"' Represents one '"' character. Needed in strings to represent this character, because an unescaped '"' would end the string. '\ ANYTHING-ELSE' Any other character when escaped by '\' gives a warning, but assembles as if the '\' was not present. The idea is that if you used an escape sequence you clearly didn't want the literal interpretation of the following character. However 'as' has no other interpretation, so 'as' knows it is giving you the wrong code and warns you of the fact. Which characters are escapable, and what those escapes represent, varies widely among assemblers. The current set is what we think the BSD 4.2 assembler recognizes, and is a subset of what most C compilers recognize. If you are in doubt, do not use an escape sequence.  File: as.info, Node: Chars, Prev: Strings, Up: Characters 3.6.1.2 Characters .................. A single character may be written as a single quote immediately followed by that character. Some backslash escapes apply to characters, '\b', '\f', '\n', '\r', '\t', and '\"' with the same meaning as for strings, plus '\'' for a single quote. So if you want to write the character backslash, you must write ''\\' where the first '\' escapes the second '\'. As you can see, the quote is an acute accent, not a grave accent. A newline immediately following an acute accent is taken as a literal character and does not count as the end of a statement. The value of a character constant in a numeric expression is the machine's byte-wide code for that character. 'as' assumes your character code is ASCII: ''A' means 65, ''B' means 66, and so on.  File: as.info, Node: Numbers, Prev: Characters, Up: Constants 3.6.2 Number Constants ---------------------- 'as' distinguishes three kinds of numbers according to how they are stored in the target machine. _Integers_ are numbers that would fit into an 'int' in the C language. _Bignums_ are integers, but they are stored in more than 32 bits. _Flonums_ are floating point numbers, described below. * Menu: * Integers:: Integers * Bignums:: Bignums * Flonums:: Flonums  File: as.info, Node: Integers, Next: Bignums, Up: Numbers 3.6.2.1 Integers ................ A binary integer is '0b' or '0B' followed by zero or more of the binary digits '01'. An octal integer is '0' followed by zero or more of the octal digits ('01234567'). A decimal integer starts with a non-zero digit followed by zero or more digits ('0123456789'). A hexadecimal integer is '0x' or '0X' followed by one or more hexadecimal digits chosen from '0123456789abcdefABCDEF'. Integers have the usual values. To denote a negative integer, use the prefix operator '-' discussed under expressions (*note Prefix Operators: Prefix Ops.).  File: as.info, Node: Bignums, Next: Flonums, Prev: Integers, Up: Numbers 3.6.2.2 Bignums ............... A "bignum" has the same syntax and semantics as an integer except that the number (or its negative) takes more than 32 bits to represent in binary. The distinction is made because in some places integers are permitted while bignums are not.  File: as.info, Node: Flonums, Prev: Bignums, Up: Numbers 3.6.2.3 Flonums ............... A "flonum" represents a floating point number. The translation is indirect: a decimal floating point number from the text is converted by 'as' to a generic binary floating point number of more than sufficient precision. This generic floating point number is converted to a particular computer's floating point format (or formats) by a portion of 'as' specialized to that computer. A flonum is written by writing (in order) * The digit '0'. ('0' is optional on the HPPA.) * A letter, to tell 'as' the rest of the number is a flonum. 'e' is recommended. Case is not important. On the H8/300 and Renesas / SuperH SH architectures, the letter must be one of the letters 'DFPRSX' (in upper or lower case). On the ARC, the letter must be one of the letters 'DFRS' (in upper or lower case). On the HPPA architecture, the letter must be 'E' (upper case only). * An optional sign: either '+' or '-'. * An optional "integer part": zero or more decimal digits. * An optional "fractional part": '.' followed by zero or more decimal digits. * An optional exponent, consisting of: * An 'E' or 'e'. * Optional sign: either '+' or '-'. * One or more decimal digits. At least one of the integer part or the fractional part must be present. The floating point number has the usual base-10 value. 'as' does all processing using integers. Flonums are computed independently of any floating point hardware in the computer running 'as'.  File: as.info, Node: Sections, Next: Symbols, Prev: Syntax, Up: Top 4 Sections and Relocation ************************* * Menu: * Secs Background:: Background * Ld Sections:: Linker Sections * As Sections:: Assembler Internal Sections * Sub-Sections:: Sub-Sections * bss:: bss Section  File: as.info, Node: Secs Background, Next: Ld Sections, Up: Sections 4.1 Background ============== Roughly, a section is a range of addresses, with no gaps; all data "in" those addresses is treated the same for some particular purpose. For example there may be a "read only" section. The linker 'ld' reads many object files (partial programs) and combines their contents to form a runnable program. When 'as' emits an object file, the partial program is assumed to start at address 0. 'ld' assigns the final addresses for the partial program, so that different partial programs do not overlap. This is actually an oversimplification, but it suffices to explain how 'as' uses sections. 'ld' moves blocks of bytes of your program to their run-time addresses. These blocks slide to their run-time addresses as rigid units; their length does not change and neither does the order of bytes within them. Such a rigid unit is called a _section_. Assigning run-time addresses to sections is called "relocation". It includes the task of adjusting mentions of object-file addresses so they refer to the proper run-time addresses. For the H8/300, and for the Renesas / SuperH SH, 'as' pads sections if needed to ensure they end on a word (sixteen bit) boundary. An object file written by 'as' has at least three sections, any of which may be empty. These are named "text", "data" and "bss" sections. When it generates COFF or ELF output, 'as' can also generate whatever other named sections you specify using the '.section' directive (*note '.section': Section.). If you do not use any directives that place output in the '.text' or '.data' sections, these sections still exist, but are empty. When 'as' generates SOM or ELF output for the HPPA, 'as' can also generate whatever other named sections you specify using the '.space' and '.subspace' directives. See 'HP9000 Series 800 Assembly Language Reference Manual' (HP 92432-90001) for details on the '.space' and '.subspace' assembler directives. Additionally, 'as' uses different names for the standard text, data, and bss sections when generating SOM output. Program text is placed into the '$CODE$' section, data into '$DATA$', and BSS into '$BSS$'. Within the object file, the text section starts at address '0', the data section follows, and the bss section follows the data section. When generating either SOM or ELF output files on the HPPA, the text section starts at address '0', the data section at address '0x4000000', and the bss section follows the data section. To let 'ld' know which data changes when the sections are relocated, and how to change that data, 'as' also writes to the object file details of the relocation needed. To perform relocation 'ld' must know, each time an address in the object file is mentioned: * Where in the object file is the beginning of this reference to an address? * How long (in bytes) is this reference? * Which section does the address refer to? What is the numeric value of (ADDRESS) - (START-ADDRESS OF SECTION)? * Is the reference to an address "Program-Counter relative"? In fact, every address 'as' ever uses is expressed as (SECTION) + (OFFSET INTO SECTION) Further, most expressions 'as' computes have this section-relative nature. (For some object formats, such as SOM for the HPPA, some expressions are symbol-relative instead.) In this manual we use the notation {SECNAME N} to mean "offset N into section SECNAME." Apart from text, data and bss sections you need to know about the "absolute" section. When 'ld' mixes partial programs, addresses in the absolute section remain unchanged. For example, address '{absolute 0}' is "relocated" to run-time address 0 by 'ld'. Although the linker never arranges two partial programs' data sections with overlapping addresses after linking, _by definition_ their absolute sections must overlap. Address '{absolute 239}' in one part of a program is always the same address when the program is running as address '{absolute 239}' in any other part of the program. The idea of sections is extended to the "undefined" section. Any address whose section is unknown at assembly time is by definition rendered {undefined U}--where U is filled in later. Since numbers are always defined, the only way to generate an undefined address is to mention an undefined symbol. A reference to a named common block would be such a symbol: its value is unknown at assembly time so it has section _undefined_. By analogy the word _section_ is used to describe groups of sections in the linked program. 'ld' puts all partial programs' text sections in contiguous addresses in the linked program. It is customary to refer to the _text section_ of a program, meaning all the addresses of all partial programs' text sections. Likewise for data and bss sections. Some sections are manipulated by 'ld'; others are invented for use of 'as' and have no meaning except during assembly.  File: as.info, Node: Ld Sections, Next: As Sections, Prev: Secs Background, Up: Sections 4.2 Linker Sections =================== 'ld' deals with just four kinds of sections, summarized below. *named sections* *text section* *data section* These sections hold your program. 'as' and 'ld' treat them as separate but equal sections. Anything you can say of one section is true of another. When the program is running, however, it is customary for the text section to be unalterable. The text section is often shared among processes: it contains instructions, constants and the like. The data section of a running program is usually alterable: for example, C variables would be stored in the data section. *bss section* This section contains zeroed bytes when your program begins running. It is used to hold uninitialized variables or common storage. The length of each partial program's bss section is important, but because it starts out containing zeroed bytes there is no need to store explicit zero bytes in the object file. The bss section was invented to eliminate those explicit zeros from object files. *absolute section* Address 0 of this section is always "relocated" to runtime address 0. This is useful if you want to refer to an address that 'ld' must not change when relocating. In this sense we speak of absolute addresses being "unrelocatable": they do not change during relocation. *undefined section* This "section" is a catch-all for address references to objects not in the preceding sections. An idealized example of three relocatable sections follows. The example uses the traditional section names '.text' and '.data'. Memory addresses are on the horizontal axis. +-----+----+--+ partial program # 1: |ttttt|dddd|00| +-----+----+--+ text data bss seg. seg. seg. +---+---+---+ partial program # 2: |TTT|DDD|000| +---+---+---+ +--+---+-----+--+----+---+-----+~~ linked program: | |TTT|ttttt| |dddd|DDD|00000| +--+---+-----+--+----+---+-----+~~ addresses: 0 ...  File: as.info, Node: As Sections, Next: Sub-Sections, Prev: Ld Sections, Up: Sections 4.3 Assembler Internal Sections =============================== These sections are meant only for the internal use of 'as'. They have no meaning at run-time. You do not really need to know about these sections for most purposes; but they can be mentioned in 'as' warning messages, so it might be helpful to have an idea of their meanings to 'as'. These sections are used to permit the value of every expression in your assembly language program to be a section-relative address. ASSEMBLER-INTERNAL-LOGIC-ERROR! An internal assembler logic error has been found. This means there is a bug in the assembler. expr section The assembler stores complex expression internally as combinations of symbols. When it needs to represent an expression as a symbol, it puts it in the expr section.  File: as.info, Node: Sub-Sections, Next: bss, Prev: As Sections, Up: Sections 4.4 Sub-Sections ================ Assembled bytes conventionally fall into two sections: text and data. You may have separate groups of data in named sections that you want to end up near to each other in the object file, even though they are not contiguous in the assembler source. 'as' allows you to use "subsections" for this purpose. Within each section, there can be numbered subsections with values from 0 to 8192. Objects assembled into the same subsection go into the object file together with other objects in the same subsection. For example, a compiler might want to store constants in the text section, but might not want to have them interspersed with the program being assembled. In this case, the compiler could issue a '.text 0' before each section of code being output, and a '.text 1' before each group of constants being output. Subsections are optional. If you do not use subsections, everything goes in subsection number zero. Each subsection is zero-padded up to a multiple of four bytes. (Subsections may be padded a different amount on different flavors of 'as'.) Subsections appear in your object file in numeric order, lowest numbered to highest. (All this to be compatible with other people's assemblers.) The object file contains no representation of subsections; 'ld' and other programs that manipulate object files see no trace of them. They just see all your text subsections as a text section, and all your data subsections as a data section. To specify which subsection you want subsequent statements assembled into, use a numeric argument to specify it, in a '.text EXPRESSION' or a '.data EXPRESSION' statement. When generating COFF output, you can also use an extra subsection argument with arbitrary named sections: '.section NAME, EXPRESSION'. When generating ELF output, you can also use the '.subsection' directive (*note SubSection::) to specify a subsection: '.subsection EXPRESSION'. EXPRESSION should be an absolute expression (*note Expressions::). If you just say '.text' then '.text 0' is assumed. Likewise '.data' means '.data 0'. Assembly begins in 'text 0'. For instance: .text 0 # The default subsection is text 0 anyway. .ascii "This lives in the first text subsection. *" .text 1 .ascii "But this lives in the second text subsection." .data 0 .ascii "This lives in the data section," .ascii "in the first data subsection." .text 0 .ascii "This lives in the first text section," .ascii "immediately following the asterisk (*)." Each section has a "location counter" incremented by one for every byte assembled into that section. Because subsections are merely a convenience restricted to 'as' there is no concept of a subsection location counter. There is no way to directly manipulate a location counter--but the '.align' directive changes it, and any label definition captures its current value. The location counter of the section where statements are being assembled is said to be the "active" location counter.  File: as.info, Node: bss, Prev: Sub-Sections, Up: Sections 4.5 bss Section =============== The bss section is used for local common variable storage. You may allocate address space in the bss section, but you may not dictate data to load into it before your program executes. When your program starts running, all the contents of the bss section are zeroed bytes. The '.lcomm' pseudo-op defines a symbol in the bss section; see *note '.lcomm': Lcomm. The '.comm' pseudo-op may be used to declare a common symbol, which is another form of uninitialized symbol; see *note '.comm': Comm. When assembling for a target which supports multiple sections, such as ELF or COFF, you may switch into the '.bss' section and define symbols as usual; see *note '.section': Section. You may only assemble zero values into the section. Typically the section will only contain symbol definitions and '.skip' directives (*note '.skip': Skip.).  File: as.info, Node: Symbols, Next: Expressions, Prev: Sections, Up: Top 5 Symbols ********* Symbols are a central concept: the programmer uses symbols to name things, the linker uses symbols to link, and the debugger uses symbols to debug. _Warning:_ 'as' does not place symbols in the object file in the same order they were declared. This may break some debuggers. * Menu: * Labels:: Labels * Setting Symbols:: Giving Symbols Other Values * Symbol Names:: Symbol Names * Dot:: The Special Dot Symbol * Symbol Attributes:: Symbol Attributes  File: as.info, Node: Labels, Next: Setting Symbols, Up: Symbols 5.1 Labels ========== A "label" is written as a symbol immediately followed by a colon ':'. The symbol then represents the current value of the active location counter, and is, for example, a suitable instruction operand. You are warned if you use the same symbol to represent two different locations: the first definition overrides any other definitions. On the HPPA, the usual form for a label need not be immediately followed by a colon, but instead must start in column zero. Only one label may be defined on a single line. To work around this, the HPPA version of 'as' also provides a special directive '.label' for defining labels more flexibly.  File: as.info, Node: Setting Symbols, Next: Symbol Names, Prev: Labels, Up: Symbols 5.2 Giving Symbols Other Values =============================== A symbol can be given an arbitrary value by writing a symbol, followed by an equals sign '=', followed by an expression (*note Expressions::). This is equivalent to using the '.set' directive. *Note '.set': Set. In the same way, using a double equals sign '=''=' here represents an equivalent of the '.eqv' directive. *Note '.eqv': Eqv. Blackfin does not support symbol assignment with '='.  File: as.info, Node: Symbol Names, Next: Dot, Prev: Setting Symbols, Up: Symbols 5.3 Symbol Names ================ Symbol names begin with a letter or with one of '._'. On most machines, you can also use '$' in symbol names; exceptions are noted in *note Machine Dependencies::. That character may be followed by any string of digits, letters, dollar signs (unless otherwise noted for a particular target machine), and underscores. Case of letters is significant: 'foo' is a different symbol name than 'Foo'. Symbol names do not start with a digit. An exception to this rule is made for Local Labels. See below. Multibyte characters are supported. To generate a symbol name containing multibyte characters enclose it within double quotes and use escape codes. cf *Note Strings::. Generating a multibyte symbol name from a label is not currently supported. Each symbol has exactly one name. Each name in an assembly language program refers to exactly one symbol. You may use that symbol name any number of times in a program. Local Symbol Names ------------------ A local symbol is any symbol beginning with certain local label prefixes. By default, the local label prefix is '.L' for ELF systems or 'L' for traditional a.out systems, but each target may have its own set of local label prefixes. On the HPPA local symbols begin with 'L$'. Local symbols are defined and used within the assembler, but they are normally not saved in object files. Thus, they are not visible when debugging. You may use the '-L' option (*note Include Local Symbols: L.) to retain the local symbols in the object files. Local Labels ------------ Local labels are different from local symbols. Local labels help compilers and programmers use names temporarily. They create symbols which are guaranteed to be unique over the entire scope of the input source code and which can be referred to by a simple notation. To define a local label, write a label of the form 'N:' (where N represents any non-negative integer). To refer to the most recent previous definition of that label write 'Nb', using the same number as when you defined the label. To refer to the next definition of a local label, write 'Nf'. The 'b' stands for "backwards" and the 'f' stands for "forwards". There is no restriction on how you can use these labels, and you can reuse them too. So that it is possible to repeatedly define the same local label (using the same number 'N'), although you can only refer to the most recently defined local label of that number (for a backwards reference) or the next definition of a specific local label for a forward reference. It is also worth noting that the first 10 local labels ('0:'...'9:') are implemented in a slightly more efficient manner than the others. Here is an example: 1: branch 1f 2: branch 1b 1: branch 2f 2: branch 1b Which is the equivalent of: label_1: branch label_3 label_2: branch label_1 label_3: branch label_4 label_4: branch label_3 Local label names are only a notational device. They are immediately transformed into more conventional symbol names before the assembler uses them. The symbol names are stored in the symbol table, appear in error messages, and are optionally emitted to the object file. The names are constructed using these parts: '_local label prefix_' All local symbols begin with the system-specific local label prefix. Normally both 'as' and 'ld' forget symbols that start with the local label prefix. These labels are used for symbols you are never intended to see. If you use the '-L' option then 'as' retains these symbols in the object file. If you also instruct 'ld' to retain these symbols, you may use them in debugging. 'NUMBER' This is the number that was used in the local label definition. So if the label is written '55:' then the number is '55'. 'C-B' This unusual character is included so you do not accidentally invent a symbol of the same name. The character has ASCII value of '\002' (control-B). '_ordinal number_' This is a serial number to keep the labels distinct. The first definition of '0:' gets the number '1'. The 15th definition of '0:' gets the number '15', and so on. Likewise the first definition of '1:' gets the number '1' and its 15th definition gets '15' as well. So for example, the first '1:' may be named '.L1C-B1', and the 44th '3:' may be named '.L3C-B44'. Dollar Local Labels ------------------- On some targets 'as' also supports an even more local form of local labels called dollar labels. These labels go out of scope (i.e., they become undefined) as soon as a non-local label is defined. Thus they remain valid for only a small region of the input source code. Normal local labels, by contrast, remain in scope for the entire file, or until they are redefined by another occurrence of the same local label. Dollar labels are defined in exactly the same way as ordinary local labels, except that they have a dollar sign suffix to their numeric value, e.g., '55$:'. They can also be distinguished from ordinary local labels by their transformed names which use ASCII character '\001' (control-A) as the magic character to distinguish them from ordinary labels. For example, the fifth definition of '6$' may be named '.L6'C-A'5'.  File: as.info, Node: Dot, Next: Symbol Attributes, Prev: Symbol Names, Up: Symbols 5.4 The Special Dot Symbol ========================== The special symbol '.' refers to the current address that 'as' is assembling into. Thus, the expression 'melvin: .long .' defines 'melvin' to contain its own address. Assigning a value to '.' is treated the same as a '.org' directive. Thus, the expression '.=.+4' is the same as saying '.space 4'.  File: as.info, Node: Symbol Attributes, Prev: Dot, Up: Symbols 5.5 Symbol Attributes ===================== Every symbol has, as well as its name, the attributes "Value" and "Type". Depending on output format, symbols can also have auxiliary attributes. If you use a symbol without defining it, 'as' assumes zero for all these attributes, and probably won't warn you. This makes the symbol an externally defined symbol, which is generally what you would want. * Menu: * Symbol Value:: Value * Symbol Type:: Type * a.out Symbols:: Symbol Attributes: 'a.out' * COFF Symbols:: Symbol Attributes for COFF * SOM Symbols:: Symbol Attributes for SOM  File: as.info, Node: Symbol Value, Next: Symbol Type, Up: Symbol Attributes 5.5.1 Value ----------- The value of a symbol is (usually) 32 bits. For a symbol which labels a location in the text, data, bss or absolute sections the value is the number of addresses from the start of that section to the label. Naturally for text, data and bss sections the value of a symbol changes as 'ld' changes section base addresses during linking. Absolute symbols' values do not change during linking: that is why they are called absolute. The value of an undefined symbol is treated in a special way. If it is 0 then the symbol is not defined in this assembler source file, and 'ld' tries to determine its value from other files linked into the same program. You make this kind of symbol simply by mentioning a symbol name without defining it. A non-zero value represents a '.comm' common declaration. The value is how much common storage to reserve, in bytes (addresses). The symbol refers to the first address of the allocated storage.  File: as.info, Node: Symbol Type, Next: a.out Symbols, Prev: Symbol Value, Up: Symbol Attributes 5.5.2 Type ---------- The type attribute of a symbol contains relocation (section) information, any flag settings indicating that a symbol is external, and (optionally), other information for linkers and debuggers. The exact format depends on the object-code output format in use.  File: as.info, Node: a.out Symbols, Next: COFF Symbols, Prev: Symbol Type, Up: Symbol Attributes 5.5.3 Symbol Attributes: 'a.out' -------------------------------- * Menu: * Symbol Desc:: Descriptor * Symbol Other:: Other  File: as.info, Node: Symbol Desc, Next: Symbol Other, Up: a.out Symbols 5.5.3.1 Descriptor .................. This is an arbitrary 16-bit value. You may establish a symbol's descriptor value by using a '.desc' statement (*note '.desc': Desc.). A descriptor value means nothing to 'as'.  File: as.info, Node: Symbol Other, Prev: Symbol Desc, Up: a.out Symbols 5.5.3.2 Other ............. This is an arbitrary 8-bit value. It means nothing to 'as'.  File: as.info, Node: COFF Symbols, Next: SOM Symbols, Prev: a.out Symbols, Up: Symbol Attributes 5.5.4 Symbol Attributes for COFF -------------------------------- The COFF format supports a multitude of auxiliary symbol attributes; like the primary symbol attributes, they are set between '.def' and '.endef' directives. 5.5.4.1 Primary Attributes .......................... The symbol name is set with '.def'; the value and type, respectively, with '.val' and '.type'. 5.5.4.2 Auxiliary Attributes ............................ The 'as' directives '.dim', '.line', '.scl', '.size', '.tag', and '.weak' can generate auxiliary symbol table information for COFF.  File: as.info, Node: SOM Symbols, Prev: COFF Symbols, Up: Symbol Attributes 5.5.5 Symbol Attributes for SOM ------------------------------- The SOM format for the HPPA supports a multitude of symbol attributes set with the '.EXPORT' and '.IMPORT' directives. The attributes are described in 'HP9000 Series 800 Assembly Language Reference Manual' (HP 92432-90001) under the 'IMPORT' and 'EXPORT' assembler directive documentation.  File: as.info, Node: Expressions, Next: Pseudo Ops, Prev: Symbols, Up: Top 6 Expressions ************* An "expression" specifies an address or numeric value. Whitespace may precede and/or follow an expression. The result of an expression must be an absolute number, or else an offset into a particular section. If an expression is not absolute, and there is not enough information when 'as' sees the expression to know its section, a second pass over the source program might be necessary to interpret the expression--but the second pass is currently not implemented. 'as' aborts with an error message in this situation. * Menu: * Empty Exprs:: Empty Expressions * Integer Exprs:: Integer Expressions  File: as.info, Node: Empty Exprs, Next: Integer Exprs, Up: Expressions 6.1 Empty Expressions ===================== An empty expression has no value: it is just whitespace or null. Wherever an absolute expression is required, you may omit the expression, and 'as' assumes a value of (absolute) 0. This is compatible with other assemblers.  File: as.info, Node: Integer Exprs, Prev: Empty Exprs, Up: Expressions 6.2 Integer Expressions ======================= An "integer expression" is one or more _arguments_ delimited by _operators_. * Menu: * Arguments:: Arguments * Operators:: Operators * Prefix Ops:: Prefix Operators * Infix Ops:: Infix Operators  File: as.info, Node: Arguments, Next: Operators, Up: Integer Exprs 6.2.1 Arguments --------------- "Arguments" are symbols, numbers or subexpressions. In other contexts arguments are sometimes called "arithmetic operands". In this manual, to avoid confusing them with the "instruction operands" of the machine language, we use the term "argument" to refer to parts of expressions only, reserving the word "operand" to refer only to machine instruction operands. Symbols are evaluated to yield {SECTION NNN} where SECTION is one of text, data, bss, absolute, or undefined. NNN is a signed, 2's complement 32 bit integer. Numbers are usually integers. A number can be a flonum or bignum. In this case, you are warned that only the low order 32 bits are used, and 'as' pretends these 32 bits are an integer. You may write integer-manipulating instructions that act on exotic constants, compatible with other assemblers. Subexpressions are a left parenthesis '(' followed by an integer expression, followed by a right parenthesis ')'; or a prefix operator followed by an argument.  File: as.info, Node: Operators, Next: Prefix Ops, Prev: Arguments, Up: Integer Exprs 6.2.2 Operators --------------- "Operators" are arithmetic functions, like '+' or '%'. Prefix operators are followed by an argument. Infix operators appear between their arguments. Operators may be preceded and/or followed by whitespace.  File: as.info, Node: Prefix Ops, Next: Infix Ops, Prev: Operators, Up: Integer Exprs 6.2.3 Prefix Operator --------------------- 'as' has the following "prefix operators". They each take one argument, which must be absolute. '-' "Negation". Two's complement negation. '~' "Complementation". Bitwise not.  File: as.info, Node: Infix Ops, Prev: Prefix Ops, Up: Integer Exprs 6.2.4 Infix Operators --------------------- "Infix operators" take two arguments, one on either side. Operators have precedence, but operations with equal precedence are performed left to right. Apart from '+' or '-', both arguments must be absolute, and the result is absolute. 1. Highest Precedence '*' "Multiplication". '/' "Division". Truncation is the same as the C operator '/' '%' "Remainder". '<<' "Shift Left". Same as the C operator '<<'. '>>' "Shift Right". Same as the C operator '>>'. 2. Intermediate precedence '|' "Bitwise Inclusive Or". '&' "Bitwise And". '^' "Bitwise Exclusive Or". '!' "Bitwise Or Not". 3. Low Precedence '+' "Addition". If either argument is absolute, the result has the section of the other argument. You may not add together arguments from different sections. '-' "Subtraction". If the right argument is absolute, the result has the section of the left argument. If both arguments are in the same section, the result is absolute. You may not subtract arguments from different sections. '==' "Is Equal To" '<>' '!=' "Is Not Equal To" '<' "Is Less Than" '>' "Is Greater Than" '>=' "Is Greater Than Or Equal To" '<=' "Is Less Than Or Equal To" The comparison operators can be used as infix operators. A true results has a value of -1 whereas a false result has a value of 0. Note, these operators perform signed comparisons. 4. Lowest Precedence '&&' "Logical And". '||' "Logical Or". These two logical operations can be used to combine the results of sub expressions. Note, unlike the comparison operators a true result returns a value of 1 but a false results does still return 0. Also note that the logical or operator has a slightly lower precedence than logical and. In short, it's only meaningful to add or subtract the _offsets_ in an address; you can only have a defined section in one of the two arguments.  File: as.info, Node: Pseudo Ops, Next: Object Attributes, Prev: Expressions, Up: Top 7 Assembler Directives ********************** All assembler directives have names that begin with a period ('.'). The names are case insensitive for most targets, and usually written in lower case. This chapter discusses directives that are available regardless of the target machine configuration for the GNU assembler. Some machine configurations provide additional directives. *Note Machine Dependencies::. * Menu: * Abort:: '.abort' * ABORT (COFF):: '.ABORT' * Align:: '.align ABS-EXPR , ABS-EXPR' * Altmacro:: '.altmacro' * Ascii:: '.ascii "STRING"'... * Asciz:: '.asciz "STRING"'... * Balign:: '.balign ABS-EXPR , ABS-EXPR' * Bundle directives:: '.bundle_align_mode ABS-EXPR', etc * Byte:: '.byte EXPRESSIONS' * CFI directives:: '.cfi_startproc [simple]', '.cfi_endproc', etc. * Comm:: '.comm SYMBOL , LENGTH ' * Data:: '.data SUBSECTION' * Dc:: '.dc[SIZE] EXPRESSIONS' * Dcb:: '.dcb[SIZE] NUMBER [,FILL]' * Ds:: '.ds[SIZE] NUMBER [,FILL]' * Def:: '.def NAME' * Desc:: '.desc SYMBOL, ABS-EXPRESSION' * Dim:: '.dim' * Double:: '.double FLONUMS' * Eject:: '.eject' * Else:: '.else' * Elseif:: '.elseif' * End:: '.end' * Endef:: '.endef' * Endfunc:: '.endfunc' * Endif:: '.endif' * Equ:: '.equ SYMBOL, EXPRESSION' * Equiv:: '.equiv SYMBOL, EXPRESSION' * Eqv:: '.eqv SYMBOL, EXPRESSION' * Err:: '.err' * Error:: '.error STRING' * Exitm:: '.exitm' * Extern:: '.extern' * Fail:: '.fail' * File:: '.file' * Fill:: '.fill REPEAT , SIZE , VALUE' * Float:: '.float FLONUMS' * Func:: '.func' * Global:: '.global SYMBOL', '.globl SYMBOL' * Gnu_attribute:: '.gnu_attribute TAG,VALUE' * Hidden:: '.hidden NAMES' * hword:: '.hword EXPRESSIONS' * Ident:: '.ident' * If:: '.if ABSOLUTE EXPRESSION' * Incbin:: '.incbin "FILE"[,SKIP[,COUNT]]' * Include:: '.include "FILE"' * Int:: '.int EXPRESSIONS' * Internal:: '.internal NAMES' * Irp:: '.irp SYMBOL,VALUES'... * Irpc:: '.irpc SYMBOL,VALUES'... * Lcomm:: '.lcomm SYMBOL , LENGTH' * Lflags:: '.lflags' * Line:: '.line LINE-NUMBER' * Linkonce:: '.linkonce [TYPE]' * List:: '.list' * Ln:: '.ln LINE-NUMBER' * Loc:: '.loc FILENO LINENO' * Loc_mark_labels:: '.loc_mark_labels ENABLE' * Local:: '.local NAMES' * Long:: '.long EXPRESSIONS' * Macro:: '.macro NAME ARGS'... * MRI:: '.mri VAL' * Noaltmacro:: '.noaltmacro' * Nolist:: '.nolist' * Nops:: '.nops SIZE[, CONTROL]' * Octa:: '.octa BIGNUMS' * Offset:: '.offset LOC' * Org:: '.org NEW-LC, FILL' * P2align:: '.p2align ABS-EXPR, ABS-EXPR, ABS-EXPR' * PopSection:: '.popsection' * Previous:: '.previous' * Print:: '.print STRING' * Protected:: '.protected NAMES' * Psize:: '.psize LINES, COLUMNS' * Purgem:: '.purgem NAME' * PushSection:: '.pushsection NAME' * Quad:: '.quad BIGNUMS' * Reloc:: '.reloc OFFSET, RELOC_NAME[, EXPRESSION]' * Rept:: '.rept COUNT' * Sbttl:: '.sbttl "SUBHEADING"' * Scl:: '.scl CLASS' * Section:: '.section NAME[, FLAGS]' * Set:: '.set SYMBOL, EXPRESSION' * Short:: '.short EXPRESSIONS' * Single:: '.single FLONUMS' * Size:: '.size [NAME , EXPRESSION]' * Skip:: '.skip SIZE [,FILL]' * Sleb128:: '.sleb128 EXPRESSIONS' * Space:: '.space SIZE [,FILL]' * Stab:: '.stabd, .stabn, .stabs' * String:: '.string "STR"', '.string8 "STR"', '.string16 "STR"', '.string32 "STR"', '.string64 "STR"' * Struct:: '.struct EXPRESSION' * SubSection:: '.subsection' * Symver:: '.symver NAME,NAME2@NODENAME' * Tag:: '.tag STRUCTNAME' * Text:: '.text SUBSECTION' * Title:: '.title "HEADING"' * Type:: '.type ' * Uleb128:: '.uleb128 EXPRESSIONS' * Val:: '.val ADDR' * Version:: '.version "STRING"' * VTableEntry:: '.vtable_entry TABLE, OFFSET' * VTableInherit:: '.vtable_inherit CHILD, PARENT' * Warning:: '.warning STRING' * Weak:: '.weak NAMES' * Weakref:: '.weakref ALIAS, SYMBOL' * Word:: '.word EXPRESSIONS' * Zero:: '.zero SIZE' * 2byte:: '.2byte EXPRESSIONS' * 4byte:: '.4byte EXPRESSIONS' * 8byte:: '.8byte BIGNUMS' * Deprecated:: Deprecated Directives  File: as.info, Node: Abort, Next: ABORT (COFF), Up: Pseudo Ops 7.1 '.abort' ============ This directive stops the assembly immediately. It is for compatibility with other assemblers. The original idea was that the assembly language source would be piped into the assembler. If the sender of the source quit, it could use this directive tells 'as' to quit also. One day '.abort' will not be supported.  File: as.info, Node: ABORT (COFF), Next: Align, Prev: Abort, Up: Pseudo Ops 7.2 '.ABORT' (COFF) =================== When producing COFF output, 'as' accepts this directive as a synonym for '.abort'.  File: as.info, Node: Align, Next: Altmacro, Prev: ABORT (COFF), Up: Pseudo Ops 7.3 '.align ABS-EXPR, ABS-EXPR, ABS-EXPR' ========================================= Pad the location counter (in the current subsection) to a particular storage boundary. The first expression (which must be absolute) is the alignment required, as described below. The second expression (also absolute) gives the fill value to be stored in the padding bytes. It (and the comma) may be omitted. If it is omitted, the padding bytes are normally zero. However, on most systems, if the section is marked as containing code and the fill value is omitted, the space is filled with no-op instructions. The third expression is also absolute, and is also optional. If it is present, it is the maximum number of bytes that should be skipped by this alignment directive. If doing the alignment would require skipping more bytes than the specified maximum, then the alignment is not done at all. You can omit the fill value (the second argument) entirely by simply using two commas after the required alignment; this can be useful if you want the alignment to be filled with no-op instructions when appropriate. The way the required alignment is specified varies from system to system. For the arc, hppa, i386 using ELF, iq2000, m68k, or1k, s390, sparc, tic4x, tic80 and xtensa, the first expression is the alignment request in bytes. For example '.align 8' advances the location counter until it is a multiple of 8. If the location counter is already a multiple of 8, no change is needed. For the tic54x, the first expression is the alignment request in words. For other systems, including ppc, i386 using a.out format, arm and strongarm, it is the number of low-order zero bits the location counter must have after advancement. For example '.align 3' advances the location counter until it a multiple of 8. If the location counter is already a multiple of 8, no change is needed. This inconsistency is due to the different behaviors of the various native assemblers for these systems which GAS must emulate. GAS also provides '.balign' and '.p2align' directives, described later, which have a consistent behavior across all architectures (but are specific to GAS).  File: as.info, Node: Altmacro, Next: Ascii, Prev: Align, Up: Pseudo Ops 7.4 '.altmacro' =============== Enable alternate macro mode, enabling: 'LOCAL NAME [ , ... ]' One additional directive, 'LOCAL', is available. It is used to generate a string replacement for each of the NAME arguments, and replace any instances of NAME in each macro expansion. The replacement string is unique in the assembly, and different for each separate macro expansion. 'LOCAL' allows you to write macros that define symbols, without fear of conflict between separate macro expansions. 'String delimiters' You can write strings delimited in these other ways besides '"STRING"': ''STRING'' You can delimit strings with single-quote characters. '' You can delimit strings with matching angle brackets. 'single-character string escape' To include any single character literally in a string (even if the character would otherwise have some special meaning), you can prefix the character with '!' (an exclamation mark). For example, you can write '<4.3 !> 5.4!!>' to get the literal text '4.3 > 5.4!'. 'Expression results as strings' You can write '%EXPR' to evaluate the expression EXPR and use the result as a string.  File: as.info, Node: Ascii, Next: Asciz, Prev: Altmacro, Up: Pseudo Ops 7.5 '.ascii "STRING"'... ======================== '.ascii' expects zero or more string literals (*note Strings::) separated by commas. It assembles each string (with no automatic trailing zero byte) into consecutive addresses.  File: as.info, Node: Asciz, Next: Balign, Prev: Ascii, Up: Pseudo Ops 7.6 '.asciz "STRING"'... ======================== '.asciz' is just like '.ascii', but each string is followed by a zero byte. The "z" in '.asciz' stands for "zero".  File: as.info, Node: Balign, Next: Bundle directives, Prev: Asciz, Up: Pseudo Ops 7.7 '.balign[wl] ABS-EXPR, ABS-EXPR, ABS-EXPR' ============================================== Pad the location counter (in the current subsection) to a particular storage boundary. The first expression (which must be absolute) is the alignment request in bytes. For example '.balign 8' advances the location counter until it is a multiple of 8. If the location counter is already a multiple of 8, no change is needed. The second expression (also absolute) gives the fill value to be stored in the padding bytes. It (and the comma) may be omitted. If it is omitted, the padding bytes are normally zero. However, on most systems, if the section is marked as containing code and the fill value is omitted, the space is filled with no-op instructions. The third expression is also absolute, and is also optional. If it is present, it is the maximum number of bytes that should be skipped by this alignment directive. If doing the alignment would require skipping more bytes than the specified maximum, then the alignment is not done at all. You can omit the fill value (the second argument) entirely by simply using two commas after the required alignment; this can be useful if you want the alignment to be filled with no-op instructions when appropriate. The '.balignw' and '.balignl' directives are variants of the '.balign' directive. The '.balignw' directive treats the fill pattern as a two byte word value. The '.balignl' directives treats the fill pattern as a four byte longword value. For example, '.balignw 4,0x368d' will align to a multiple of 4. If it skips two bytes, they will be filled in with the value 0x368d (the exact placement of the bytes depends upon the endianness of the processor). If it skips 1 or 3 bytes, the fill value is undefined.  File: as.info, Node: Bundle directives, Next: Byte, Prev: Balign, Up: Pseudo Ops 7.8 Bundle directives ===================== 7.8.1 '.bundle_align_mode ABS-EXPR' ----------------------------------- '.bundle_align_mode' enables or disables "aligned instruction bundle" mode. In this mode, sequences of adjacent instructions are grouped into fixed-sized "bundles". If the argument is zero, this mode is disabled (which is the default state). If the argument it not zero, it gives the size of an instruction bundle as a power of two (as for the '.p2align' directive, *note P2align::). For some targets, it's an ABI requirement that no instruction may span a certain aligned boundary. A "bundle" is simply a sequence of instructions that starts on an aligned boundary. For example, if ABS-EXPR is '5' then the bundle size is 32, so each aligned chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in effect, no single instruction may span a boundary between bundles. If an instruction would start too close to the end of a bundle for the length of that particular instruction to fit within the bundle, then the space at the end of that bundle is filled with no-op instructions so the instruction starts in the next bundle. As a corollary, it's an error if any single instruction's encoding is longer than the bundle size. 7.8.2 '.bundle_lock' and '.bundle_unlock' ----------------------------------------- The '.bundle_lock' and directive '.bundle_unlock' directives allow explicit control over instruction bundle padding. These directives are only valid when '.bundle_align_mode' has been used to enable aligned instruction bundle mode. It's an error if they appear when '.bundle_align_mode' has not been used at all, or when the last directive was '.bundle_align_mode 0'. For some targets, it's an ABI requirement that certain instructions may appear only as part of specified permissible sequences of multiple instructions, all within the same bundle. A pair of '.bundle_lock' and '.bundle_unlock' directives define a "bundle-locked" instruction sequence. For purposes of aligned instruction bundle mode, a sequence starting with '.bundle_lock' and ending with '.bundle_unlock' is treated as a single instruction. That is, the entire sequence must fit into a single bundle and may not span a bundle boundary. If necessary, no-op instructions will be inserted before the first instruction of the sequence so that the whole sequence starts on an aligned bundle boundary. It's an error if the sequence is longer than the bundle size. For convenience when using '.bundle_lock' and '.bundle_unlock' inside assembler macros (*note Macro::), bundle-locked sequences may be nested. That is, a second '.bundle_lock' directive before the next '.bundle_unlock' directive has no effect except that it must be matched by another closing '.bundle_unlock' so that there is the same number of '.bundle_lock' and '.bundle_unlock' directives.  File: as.info, Node: Byte, Next: CFI directives, Prev: Bundle directives, Up: Pseudo Ops 7.9 '.byte EXPRESSIONS' ======================= '.byte' expects zero or more expressions, separated by commas. Each expression is assembled into the next byte.  File: as.info, Node: CFI directives, Next: Comm, Prev: Byte, Up: Pseudo Ops 7.10 CFI directives =================== 7.10.1 '.cfi_sections SECTION_LIST' ----------------------------------- '.cfi_sections' may be used to specify whether CFI directives should emit '.eh_frame' section and/or '.debug_frame' section. If SECTION_LIST is '.eh_frame', '.eh_frame' is emitted, if SECTION_LIST is '.debug_frame', '.debug_frame' is emitted. To emit both use '.eh_frame, .debug_frame'. The default if this directive is not used is '.cfi_sections .eh_frame'. On targets that support compact unwinding tables these can be generated by specifying '.eh_frame_entry' instead of '.eh_frame'. Some targets may support an additional name, such as '.c6xabi.exidx' which is used by the target. The '.cfi_sections' directive can be repeated, with the same or different arguments, provided that CFI generation has not yet started. Once CFI generation has started however the section list is fixed and any attempts to redefine it will result in an error. 7.10.2 '.cfi_startproc [simple]' -------------------------------- '.cfi_startproc' is used at the beginning of each function that should have an entry in '.eh_frame'. It initializes some internal data structures. Don't forget to close the function by '.cfi_endproc'. Unless '.cfi_startproc' is used along with parameter 'simple' it also emits some architecture dependent initial CFI instructions. 7.10.3 '.cfi_endproc' --------------------- '.cfi_endproc' is used at the end of a function where it closes its unwind entry previously opened by '.cfi_startproc', and emits it to '.eh_frame'. 7.10.4 '.cfi_personality ENCODING [, EXP]' ------------------------------------------ '.cfi_personality' defines personality routine and its encoding. ENCODING must be a constant determining how the personality should be encoded. If it is 255 ('DW_EH_PE_omit'), second argument is not present, otherwise second argument should be a constant or a symbol name. When using indirect encodings, the symbol provided should be the location where personality can be loaded from, not the personality routine itself. The default after '.cfi_startproc' is '.cfi_personality 0xff', no personality routine. 7.10.5 '.cfi_personality_id ID' ------------------------------- 'cfi_personality_id' defines a personality routine by its index as defined in a compact unwinding format. Only valid when generating compact EH frames (i.e. with '.cfi_sections eh_frame_entry'. 7.10.6 '.cfi_fde_data [OPCODE1 [, ...]]' ---------------------------------------- 'cfi_fde_data' is used to describe the compact unwind opcodes to be used for the current function. These are emitted inline in the '.eh_frame_entry' section if small enough and there is no LSDA, or in the '.gnu.extab' section otherwise. Only valid when generating compact EH frames (i.e. with '.cfi_sections eh_frame_entry'. 7.10.7 '.cfi_lsda ENCODING [, EXP]' ----------------------------------- '.cfi_lsda' defines LSDA and its encoding. ENCODING must be a constant determining how the LSDA should be encoded. If it is 255 ('DW_EH_PE_omit'), the second argument is not present, otherwise the second argument should be a constant or a symbol name. The default after '.cfi_startproc' is '.cfi_lsda 0xff', meaning that no LSDA is present. 7.10.8 '.cfi_inline_lsda' [ALIGN] --------------------------------- '.cfi_inline_lsda' marks the start of a LSDA data section and switches to the corresponding '.gnu.extab' section. Must be preceded by a CFI block containing a '.cfi_lsda' directive. Only valid when generating compact EH frames (i.e. with '.cfi_sections eh_frame_entry'. The table header and unwinding opcodes will be generated at this point, so that they are immediately followed by the LSDA data. The symbol referenced by the '.cfi_lsda' directive should still be defined in case a fallback FDE based encoding is used. The LSDA data is terminated by a section directive. The optional ALIGN argument specifies the alignment required. The alignment is specified as a power of two, as with the '.p2align' directive. 7.10.9 '.cfi_def_cfa REGISTER, OFFSET' -------------------------------------- '.cfi_def_cfa' defines a rule for computing CFA as: take address from REGISTER and add OFFSET to it. 7.10.10 '.cfi_def_cfa_register REGISTER' ---------------------------------------- '.cfi_def_cfa_register' modifies a rule for computing CFA. From now on REGISTER will be used instead of the old one. Offset remains the same. 7.10.11 '.cfi_def_cfa_offset OFFSET' ------------------------------------ '.cfi_def_cfa_offset' modifies a rule for computing CFA. Register remains the same, but OFFSET is new. Note that it is the absolute offset that will be added to a defined register to compute CFA address. 7.10.12 '.cfi_adjust_cfa_offset OFFSET' --------------------------------------- Same as '.cfi_def_cfa_offset' but OFFSET is a relative value that is added/subtracted from the previous offset. 7.10.13 '.cfi_offset REGISTER, OFFSET' -------------------------------------- Previous value of REGISTER is saved at offset OFFSET from CFA. 7.10.14 '.cfi_val_offset REGISTER, OFFSET' ------------------------------------------ Previous value of REGISTER is CFA + OFFSET. 7.10.15 '.cfi_rel_offset REGISTER, OFFSET' ------------------------------------------ Previous value of REGISTER is saved at offset OFFSET from the current CFA register. This is transformed to '.cfi_offset' using the known displacement of the CFA register from the CFA. This is often easier to use, because the number will match the code it's annotating. 7.10.16 '.cfi_register REGISTER1, REGISTER2' -------------------------------------------- Previous value of REGISTER1 is saved in register REGISTER2. 7.10.17 '.cfi_restore REGISTER' ------------------------------- '.cfi_restore' says that the rule for REGISTER is now the same as it was at the beginning of the function, after all initial instruction added by '.cfi_startproc' were executed. 7.10.18 '.cfi_undefined REGISTER' --------------------------------- From now on the previous value of REGISTER can't be restored anymore. 7.10.19 '.cfi_same_value REGISTER' ---------------------------------- Current value of REGISTER is the same like in the previous frame, i.e. no restoration needed. 7.10.20 '.cfi_remember_state' and '.cfi_restore_state' ------------------------------------------------------ '.cfi_remember_state' pushes the set of rules for every register onto an implicit stack, while '.cfi_restore_state' pops them off the stack and places them in the current row. This is useful for situations where you have multiple '.cfi_*' directives that need to be undone due to the control flow of the program. For example, we could have something like this (assuming the CFA is the value of 'rbp'): je label popq %rbx .cfi_restore %rbx popq %r12 .cfi_restore %r12 popq %rbp .cfi_restore %rbp .cfi_def_cfa %rsp, 8 ret label: /* Do something else */ Here, we want the '.cfi' directives to affect only the rows corresponding to the instructions before 'label'. This means we'd have to add multiple '.cfi' directives after 'label' to recreate the original save locations of the registers, as well as setting the CFA back to the value of 'rbp'. This would be clumsy, and result in a larger binary size. Instead, we can write: je label popq %rbx .cfi_remember_state .cfi_restore %rbx popq %r12 .cfi_restore %r12 popq %rbp .cfi_restore %rbp .cfi_def_cfa %rsp, 8 ret label: .cfi_restore_state /* Do something else */ That way, the rules for the instructions after 'label' will be the same as before the first '.cfi_restore' without having to use multiple '.cfi' directives. 7.10.21 '.cfi_return_column REGISTER' ------------------------------------- Change return column REGISTER, i.e. the return address is either directly in REGISTER or can be accessed by rules for REGISTER. 7.10.22 '.cfi_signal_frame' --------------------------- Mark current function as signal trampoline. 7.10.23 '.cfi_window_save' -------------------------- SPARC register window has been saved. 7.10.24 '.cfi_escape' EXPRESSION[, ...] --------------------------------------- Allows the user to add arbitrary bytes to the unwind info. One might use this to add OS-specific CFI opcodes, or generic CFI opcodes that GAS does not yet support. 7.10.25 '.cfi_val_encoded_addr REGISTER, ENCODING, LABEL' --------------------------------------------------------- The current value of REGISTER is LABEL. The value of LABEL will be encoded in the output file according to ENCODING; see the description of '.cfi_personality' for details on this encoding. The usefulness of equating a register to a fixed label is probably limited to the return address register. Here, it can be useful to mark a code segment that has only one return address which is reached by a direct branch and no copy of the return address exists in memory or another register.  File: as.info, Node: Comm, Next: Data, Prev: CFI directives, Up: Pseudo Ops 7.11 '.comm SYMBOL , LENGTH ' ============================= '.comm' declares a common symbol named SYMBOL. When linking, a common symbol in one object file may be merged with a defined or common symbol of the same name in another object file. If 'ld' does not see a definition for the symbol-just one or more common symbols-then it will allocate LENGTH bytes of uninitialized memory. LENGTH must be an absolute expression. If 'ld' sees multiple common symbols with the same name, and they do not all have the same size, it will allocate space using the largest size. When using ELF or (as a GNU extension) PE, the '.comm' directive takes an optional third argument. This is the desired alignment of the symbol, specified for ELF as a byte boundary (for example, an alignment of 16 means that the least significant 4 bits of the address should be zero), and for PE as a power of two (for example, an alignment of 5 means aligned to a 32-byte boundary). The alignment must be an absolute expression, and it must be a power of two. If 'ld' allocates uninitialized memory for the common symbol, it will use the alignment when placing the symbol. If no alignment is specified, 'as' will set the alignment to the largest power of two less than or equal to the size of the symbol, up to a maximum of 16 on ELF, or the default section alignment of 4 on PE(1). The syntax for '.comm' differs slightly on the HPPA. The syntax is 'SYMBOL .comm, LENGTH'; SYMBOL is optional. ---------- Footnotes ---------- (1) This is not the same as the executable image file alignment controlled by 'ld''s '--section-alignment' option; image file sections in PE are aligned to multiples of 4096, which is far too large an alignment for ordinary variables. It is rather the default alignment for (non-debug) sections within object ('*.o') files, which are less strictly aligned.  File: as.info, Node: Data, Next: Dc, Prev: Comm, Up: Pseudo Ops 7.12 '.data SUBSECTION' ======================= '.data' tells 'as' to assemble the following statements onto the end of the data subsection numbered SUBSECTION (which is an absolute expression). If SUBSECTION is omitted, it defaults to zero.  File: as.info, Node: Dc, Next: Dcb, Prev: Data, Up: Pseudo Ops 7.13 '.dc[SIZE] EXPRESSIONS' ============================ The '.dc' directive expects zero or more EXPRESSIONS separated by commas. These expressions are evaluated and their values inserted into the current section. The size of the emitted value depends upon the suffix to the '.dc' directive: ''.a'' Emits N-bit values, where N is the size of an address on the target system. ''.b'' Emits 8-bit values. ''.d'' Emits double precision floating-point values. ''.l'' Emits 32-bit values. ''.s'' Emits single precision floating-point values. ''.w'' Emits 16-bit values. Note - this is true even on targets where the '.word' directive would emit 32-bit values. ''.x'' Emits long double precision floating-point values. If no suffix is used then '.w' is assumed. The byte ordering is target dependent, as is the size and format of floating point values.  File: as.info, Node: Dcb, Next: Ds, Prev: Dc, Up: Pseudo Ops 7.14 '.dcb[SIZE] NUMBER [,FILL]' ================================ This directive emits NUMBER copies of FILL, each of SIZE bytes. Both NUMBER and FILL are absolute expressions. If the comma and FILL are omitted, FILL is assumed to be zero. The SIZE suffix, if present, must be one of: ''.b'' Emits single byte values. ''.d'' Emits double-precision floating point values. ''.l'' Emits 4-byte values. ''.s'' Emits single-precision floating point values. ''.w'' Emits 2-byte values. ''.x'' Emits long double-precision floating point values. If the SIZE suffix is omitted then '.w' is assumed. The byte ordering is target dependent, as is the size and format of floating point values.  File: as.info, Node: Ds, Next: Def, Prev: Dcb, Up: Pseudo Ops 7.15 '.ds[SIZE] NUMBER [,FILL]' =============================== This directive emits NUMBER copies of FILL, each of SIZE bytes. Both NUMBER and FILL are absolute expressions. If the comma and FILL are omitted, FILL is assumed to be zero. The SIZE suffix, if present, must be one of: ''.b'' Emits single byte values. ''.d'' Emits 8-byte values. ''.l'' Emits 4-byte values. ''.p'' Emits 12-byte values. ''.s'' Emits 4-byte values. ''.w'' Emits 2-byte values. ''.x'' Emits 12-byte values. Note - unlike the '.dcb' directive the '.d', '.s' and '.x' suffixes do not indicate that floating-point values are to be inserted. If the SIZE suffix is omitted then '.w' is assumed. The byte ordering is target dependent.  File: as.info, Node: Def, Next: Desc, Prev: Ds, Up: Pseudo Ops 7.16 '.def NAME' ================ Begin defining debugging information for a symbol NAME; the definition extends until the '.endef' directive is encountered.  File: as.info, Node: Desc, Next: Dim, Prev: Def, Up: Pseudo Ops 7.17 '.desc SYMBOL, ABS-EXPRESSION' =================================== This directive sets the descriptor of the symbol (*note Symbol Attributes::) to the low 16 bits of an absolute expression. The '.desc' directive is not available when 'as' is configured for COFF output; it is only for 'a.out' or 'b.out' object format. For the sake of compatibility, 'as' accepts it, but produces no output, when configured for COFF.  File: as.info, Node: Dim, Next: Double, Prev: Desc, Up: Pseudo Ops 7.18 '.dim' =========== This directive is generated by compilers to include auxiliary debugging information in the symbol table. It is only permitted inside '.def'/'.endef' pairs.  File: as.info, Node: Double, Next: Eject, Prev: Dim, Up: Pseudo Ops 7.19 '.double FLONUMS' ====================== '.double' expects zero or more flonums, separated by commas. It assembles floating point numbers. The exact kind of floating point numbers emitted depends on how 'as' is configured. *Note Machine Dependencies::.  File: as.info, Node: Eject, Next: Else, Prev: Double, Up: Pseudo Ops 7.20 '.eject' ============= Force a page break at this point, when generating assembly listings.  File: as.info, Node: Else, Next: Elseif, Prev: Eject, Up: Pseudo Ops 7.21 '.else' ============ '.else' is part of the 'as' support for conditional assembly; see *note '.if': If. It marks the beginning of a section of code to be assembled if the condition for the preceding '.if' was false.  File: as.info, Node: Elseif, Next: End, Prev: Else, Up: Pseudo Ops 7.22 '.elseif' ============== '.elseif' is part of the 'as' support for conditional assembly; see *note '.if': If. It is shorthand for beginning a new '.if' block that would otherwise fill the entire '.else' section.  File: as.info, Node: End, Next: Endef, Prev: Elseif, Up: Pseudo Ops 7.23 '.end' =========== '.end' marks the end of the assembly file. 'as' does not process anything in the file past the '.end' directive.  File: as.info, Node: Endef, Next: Endfunc, Prev: End, Up: Pseudo Ops 7.24 '.endef' ============= This directive flags the end of a symbol definition begun with '.def'.  File: as.info, Node: Endfunc, Next: Endif, Prev: Endef, Up: Pseudo Ops 7.25 '.endfunc' =============== '.endfunc' marks the end of a function specified with '.func'.  File: as.info, Node: Endif, Next: Equ, Prev: Endfunc, Up: Pseudo Ops 7.26 '.endif' ============= '.endif' is part of the 'as' support for conditional assembly; it marks the end of a block of code that is only assembled conditionally. *Note '.if': If.  File: as.info, Node: Equ, Next: Equiv, Prev: Endif, Up: Pseudo Ops 7.27 '.equ SYMBOL, EXPRESSION' ============================== This directive sets the value of SYMBOL to EXPRESSION. It is synonymous with '.set'; see *note '.set': Set. The syntax for 'equ' on the HPPA is 'SYMBOL .equ EXPRESSION'. The syntax for 'equ' on the Z80 is 'SYMBOL equ EXPRESSION'. On the Z80 it is an error if SYMBOL is already defined, but the symbol is not protected from later redefinition. Compare *note Equiv::.  File: as.info, Node: Equiv, Next: Eqv, Prev: Equ, Up: Pseudo Ops 7.28 '.equiv SYMBOL, EXPRESSION' ================================ The '.equiv' directive is like '.equ' and '.set', except that the assembler will signal an error if SYMBOL is already defined. Note a symbol which has been referenced but not actually defined is considered to be undefined. Except for the contents of the error message, this is roughly equivalent to .ifdef SYM .err .endif .equ SYM,VAL plus it protects the symbol from later redefinition.  File: as.info, Node: Eqv, Next: Err, Prev: Equiv, Up: Pseudo Ops 7.29 '.eqv SYMBOL, EXPRESSION' ============================== The '.eqv' directive is like '.equiv', but no attempt is made to evaluate the expression or any part of it immediately. Instead each time the resulting symbol is used in an expression, a snapshot of its current value is taken.  File: as.info, Node: Err, Next: Error, Prev: Eqv, Up: Pseudo Ops 7.30 '.err' =========== If 'as' assembles a '.err' directive, it will print an error message and, unless the '-Z' option was used, it will not generate an object file. This can be used to signal an error in conditionally compiled code.  File: as.info, Node: Error, Next: Exitm, Prev: Err, Up: Pseudo Ops 7.31 '.error "STRING"' ====================== Similarly to '.err', this directive emits an error, but you can specify a string that will be emitted as the error message. If you don't specify the message, it defaults to '".error directive invoked in source file"'. *Note Error and Warning Messages: Errors. .error "This code has not been assembled and tested."  File: as.info, Node: Exitm, Next: Extern, Prev: Error, Up: Pseudo Ops 7.32 '.exitm' ============= Exit early from the current macro definition. *Note Macro::.  File: as.info, Node: Extern, Next: Fail, Prev: Exitm, Up: Pseudo Ops 7.33 '.extern' ============== '.extern' is accepted in the source program--for compatibility with other assemblers--but it is ignored. 'as' treats all undefined symbols as external.  File: as.info, Node: Fail, Next: File, Prev: Extern, Up: Pseudo Ops 7.34 '.fail EXPRESSION' ======================= Generates an error or a warning. If the value of the EXPRESSION is 500 or more, 'as' will print a warning message. If the value is less than 500, 'as' will print an error message. The message will include the value of EXPRESSION. This can occasionally be useful inside complex nested macros or conditional assembly.  File: as.info, Node: File, Next: Fill, Prev: Fail, Up: Pseudo Ops 7.35 '.file' ============ There are two different versions of the '.file' directive. Targets that support DWARF2 line number information use the DWARF2 version of '.file'. Other targets use the default version. Default Version --------------- This version of the '.file' directive tells 'as' that we are about to start a new logical file. The syntax is: .file STRING STRING is the new file name. In general, the filename is recognized whether or not it is surrounded by quotes '"'; but if you wish to specify an empty file name, you must give the quotes-'""'. This statement may go away in future: it is only recognized to be compatible with old 'as' programs. DWARF2 Version -------------- When emitting DWARF2 line number information, '.file' assigns filenames to the '.debug_line' file name table. The syntax is: .file FILENO FILENAME The FILENO operand should be a unique positive integer to use as the index of the entry in the table. The FILENAME operand is a C string literal. The detail of filename indices is exposed to the user because the filename table is shared with the '.debug_info' section of the DWARF2 debugging information, and thus the user must know the exact indices that table entries will have.  File: as.info, Node: Fill, Next: Float, Prev: File, Up: Pseudo Ops 7.36 '.fill REPEAT , SIZE , VALUE' ================================== REPEAT, SIZE and VALUE are absolute expressions. This emits REPEAT copies of SIZE bytes. REPEAT may be zero or more. SIZE may be zero or more, but if it is more than 8, then it is deemed to have the value 8, compatible with other people's assemblers. The contents of each REPEAT bytes is taken from an 8-byte number. The highest order 4 bytes are zero. The lowest order 4 bytes are VALUE rendered in the byte-order of an integer on the computer 'as' is assembling for. Each SIZE bytes in a repetition is taken from the lowest order SIZE bytes of this number. Again, this bizarre behavior is compatible with other people's assemblers. SIZE and VALUE are optional. If the second comma and VALUE are absent, VALUE is assumed zero. If the first comma and following tokens are absent, SIZE is assumed to be 1.  File: as.info, Node: Float, Next: Func, Prev: Fill, Up: Pseudo Ops 7.37 '.float FLONUMS' ===================== This directive assembles zero or more flonums, separated by commas. It has the same effect as '.single'. The exact kind of floating point numbers emitted depends on how 'as' is configured. *Note Machine Dependencies::.  File: as.info, Node: Func, Next: Global, Prev: Float, Up: Pseudo Ops 7.38 '.func NAME[,LABEL]' ========================= '.func' emits debugging information to denote function NAME, and is ignored unless the file is assembled with debugging enabled. Only '--gstabs[+]' is currently supported. LABEL is the entry point of the function and if omitted NAME prepended with the 'leading char' is used. 'leading char' is usually '_' or nothing, depending on the target. All functions are currently defined to have 'void' return type. The function must be terminated with '.endfunc'.  File: as.info, Node: Global, Next: Gnu_attribute, Prev: Func, Up: Pseudo Ops 7.39 '.global SYMBOL', '.globl SYMBOL' ====================================== '.global' makes the symbol visible to 'ld'. If you define SYMBOL in your partial program, its value is made available to other partial programs that are linked with it. Otherwise, SYMBOL takes its attributes from a symbol of the same name from another file linked into the same program. Both spellings ('.globl' and '.global') are accepted, for compatibility with other assemblers. On the HPPA, '.global' is not always enough to make it accessible to other partial programs. You may need the HPPA-only '.EXPORT' directive as well. *Note HPPA Assembler Directives: HPPA Directives.  File: as.info, Node: Gnu_attribute, Next: Hidden, Prev: Global, Up: Pseudo Ops 7.40 '.gnu_attribute TAG,VALUE' =============================== Record a GNU object attribute for this file. *Note Object Attributes::.  File: as.info, Node: Hidden, Next: hword, Prev: Gnu_attribute, Up: Pseudo Ops 7.41 '.hidden NAMES' ==================== This is one of the ELF visibility directives. The other two are '.internal' (*note '.internal': Internal.) and '.protected' (*note '.protected': Protected.). This directive overrides the named symbols default visibility (which is set by their binding: local, global or weak). The directive sets the visibility to 'hidden' which means that the symbols are not visible to other components. Such symbols are always considered to be 'protected' as well.  File: as.info, Node: hword, Next: Ident, Prev: Hidden, Up: Pseudo Ops 7.42 '.hword EXPRESSIONS' ========================= This expects zero or more EXPRESSIONS, and emits a 16 bit number for each. This directive is a synonym for '.short'; depending on the target architecture, it may also be a synonym for '.word'.  File: as.info, Node: Ident, Next: If, Prev: hword, Up: Pseudo Ops 7.43 '.ident' ============= This directive is used by some assemblers to place tags in object files. The behavior of this directive varies depending on the target. When using the a.out object file format, 'as' simply accepts the directive for source-file compatibility with existing assemblers, but does not emit anything for it. When using COFF, comments are emitted to the '.comment' or '.rdata' section, depending on the target. When using ELF, comments are emitted to the '.comment' section.  File: as.info, Node: If, Next: Incbin, Prev: Ident, Up: Pseudo Ops 7.44 '.if ABSOLUTE EXPRESSION' ============================== '.if' marks the beginning of a section of code which is only considered part of the source program being assembled if the argument (which must be an ABSOLUTE EXPRESSION) is non-zero. The end of the conditional section of code must be marked by '.endif' (*note '.endif': Endif.); optionally, you may include code for the alternative condition, flagged by '.else' (*note '.else': Else.). If you have several conditions to check, '.elseif' may be used to avoid nesting blocks if/else within each subsequent '.else' block. The following variants of '.if' are also supported: '.ifdef SYMBOL' Assembles the following section of code if the specified SYMBOL has been defined. Note a symbol which has been referenced but not yet defined is considered to be undefined. '.ifb TEXT' Assembles the following section of code if the operand is blank (empty). '.ifc STRING1,STRING2' Assembles the following section of code if the two strings are the same. The strings may be optionally quoted with single quotes. If they are not quoted, the first string stops at the first comma, and the second string stops at the end of the line. Strings which contain whitespace should be quoted. The string comparison is case sensitive. '.ifeq ABSOLUTE EXPRESSION' Assembles the following section of code if the argument is zero. '.ifeqs STRING1,STRING2' Another form of '.ifc'. The strings must be quoted using double quotes. '.ifge ABSOLUTE EXPRESSION' Assembles the following section of code if the argument is greater than or equal to zero. '.ifgt ABSOLUTE EXPRESSION' Assembles the following section of code if the argument is greater than zero. '.ifle ABSOLUTE EXPRESSION' Assembles the following section of code if the argument is less than or equal to zero. '.iflt ABSOLUTE EXPRESSION' Assembles the following section of code if the argument is less than zero. '.ifnb TEXT' Like '.ifb', but the sense of the test is reversed: this assembles the following section of code if the operand is non-blank (non-empty). '.ifnc STRING1,STRING2.' Like '.ifc', but the sense of the test is reversed: this assembles the following section of code if the two strings are not the same. '.ifndef SYMBOL' '.ifnotdef SYMBOL' Assembles the following section of code if the specified SYMBOL has not been defined. Both spelling variants are equivalent. Note a symbol which has been referenced but not yet defined is considered to be undefined. '.ifne ABSOLUTE EXPRESSION' Assembles the following section of code if the argument is not equal to zero (in other words, this is equivalent to '.if'). '.ifnes STRING1,STRING2' Like '.ifeqs', but the sense of the test is reversed: this assembles the following section of code if the two strings are not the same.  File: as.info, Node: Incbin, Next: Include, Prev: If, Up: Pseudo Ops 7.45 '.incbin "FILE"[,SKIP[,COUNT]]' ==================================== The 'incbin' directive includes FILE verbatim at the current location. You can control the search paths used with the '-I' command-line option (*note Command-Line Options: Invoking.). Quotation marks are required around FILE. The SKIP argument skips a number of bytes from the start of the FILE. The COUNT argument indicates the maximum number of bytes to read. Note that the data is not aligned in any way, so it is the user's responsibility to make sure that proper alignment is provided both before and after the 'incbin' directive.  File: as.info, Node: Include, Next: Int, Prev: Incbin, Up: Pseudo Ops 7.46 '.include "FILE"' ====================== This directive provides a way to include supporting files at specified points in your source program. The code from FILE is assembled as if it followed the point of the '.include'; when the end of the included file is reached, assembly of the original file continues. You can control the search paths used with the '-I' command-line option (*note Command-Line Options: Invoking.). Quotation marks are required around FILE.  File: as.info, Node: Int, Next: Internal, Prev: Include, Up: Pseudo Ops 7.47 '.int EXPRESSIONS' ======================= Expect zero or more EXPRESSIONS, of any section, separated by commas. For each expression, emit a number that, at run time, is the value of that expression. The byte order and bit size of the number depends on what kind of target the assembly is for.  File: as.info, Node: Internal, Next: Irp, Prev: Int, Up: Pseudo Ops 7.48 '.internal NAMES' ====================== This is one of the ELF visibility directives. The other two are '.hidden' (*note '.hidden': Hidden.) and '.protected' (*note '.protected': Protected.). This directive overrides the named symbols default visibility (which is set by their binding: local, global or weak). The directive sets the visibility to 'internal' which means that the symbols are considered to be 'hidden' (i.e., not visible to other components), and that some extra, processor specific processing must also be performed upon the symbols as well.  File: as.info, Node: Irp, Next: Irpc, Prev: Internal, Up: Pseudo Ops 7.49 '.irp SYMBOL,VALUES'... ============================ Evaluate a sequence of statements assigning different values to SYMBOL. The sequence of statements starts at the '.irp' directive, and is terminated by an '.endr' directive. For each VALUE, SYMBOL is set to VALUE, and the sequence of statements is assembled. If no VALUE is listed, the sequence of statements is assembled once, with SYMBOL set to the null string. To refer to SYMBOL within the sequence of statements, use \SYMBOL. For example, assembling .irp param,1,2,3 move d\param,sp@- .endr is equivalent to assembling move d1,sp@- move d2,sp@- move d3,sp@- For some caveats with the spelling of SYMBOL, see also *note Macro::.  File: as.info, Node: Irpc, Next: Lcomm, Prev: Irp, Up: Pseudo Ops 7.50 '.irpc SYMBOL,VALUES'... ============================= Evaluate a sequence of statements assigning different values to SYMBOL. The sequence of statements starts at the '.irpc' directive, and is terminated by an '.endr' directive. For each character in VALUE, SYMBOL is set to the character, and the sequence of statements is assembled. If no VALUE is listed, the sequence of statements is assembled once, with SYMBOL set to the null string. To refer to SYMBOL within the sequence of statements, use \SYMBOL. For example, assembling .irpc param,123 move d\param,sp@- .endr is equivalent to assembling move d1,sp@- move d2,sp@- move d3,sp@- For some caveats with the spelling of SYMBOL, see also the discussion at *Note Macro::.  File: as.info, Node: Lcomm, Next: Lflags, Prev: Irpc, Up: Pseudo Ops 7.51 '.lcomm SYMBOL , LENGTH' ============================= Reserve LENGTH (an absolute expression) bytes for a local common denoted by SYMBOL. The section and value of SYMBOL are those of the new local common. The addresses are allocated in the bss section, so that at run-time the bytes start off zeroed. SYMBOL is not declared global (*note '.global': Global.), so is normally not visible to 'ld'. Some targets permit a third argument to be used with '.lcomm'. This argument specifies the desired alignment of the symbol in the bss section. The syntax for '.lcomm' differs slightly on the HPPA. The syntax is 'SYMBOL .lcomm, LENGTH'; SYMBOL is optional.  File: as.info, Node: Lflags, Next: Line, Prev: Lcomm, Up: Pseudo Ops 7.52 '.lflags' ============== 'as' accepts this directive, for compatibility with other assemblers, but ignores it.  File: as.info, Node: Line, Next: Linkonce, Prev: Lflags, Up: Pseudo Ops 7.53 '.line LINE-NUMBER' ======================== Change the logical line number. LINE-NUMBER must be an absolute expression. The next line has that logical line number. Therefore any other statements on the current line (after a statement separator character) are reported as on logical line number LINE-NUMBER - 1. One day 'as' will no longer support this directive: it is recognized only for compatibility with existing assembler programs. Even though this is a directive associated with the 'a.out' or 'b.out' object-code formats, 'as' still recognizes it when producing COFF output, and treats '.line' as though it were the COFF '.ln' _if_ it is found outside a '.def'/'.endef' pair. Inside a '.def', '.line' is, instead, one of the directives used by compilers to generate auxiliary symbol information for debugging.  File: as.info, Node: Linkonce, Next: List, Prev: Line, Up: Pseudo Ops 7.54 '.linkonce [TYPE]' ======================= Mark the current section so that the linker only includes a single copy of it. This may be used to include the same section in several different object files, but ensure that the linker will only include it once in the final output file. The '.linkonce' pseudo-op must be used for each instance of the section. Duplicate sections are detected based on the section name, so it should be unique. This directive is only supported by a few object file formats; as of this writing, the only object file format which supports it is the Portable Executable format used on Windows NT. The TYPE argument is optional. If specified, it must be one of the following strings. For example: .linkonce same_size Not all types may be supported on all object file formats. 'discard' Silently discard duplicate sections. This is the default. 'one_only' Warn if there are duplicate sections, but still keep only one copy. 'same_size' Warn if any of the duplicates have different sizes. 'same_contents' Warn if any of the duplicates do not have exactly the same contents.  File: as.info, Node: List, Next: Ln, Prev: Linkonce, Up: Pseudo Ops 7.55 '.list' ============ Control (in conjunction with the '.nolist' directive) whether or not assembly listings are generated. These two directives maintain an internal counter (which is zero initially). '.list' increments the counter, and '.nolist' decrements it. Assembly listings are generated whenever the counter is greater than zero. By default, listings are disabled. When you enable them (with the '-a' command line option; *note Command-Line Options: Invoking.), the initial value of the listing counter is one.  File: as.info, Node: Ln, Next: Loc, Prev: List, Up: Pseudo Ops 7.56 '.ln LINE-NUMBER' ====================== '.ln' is a synonym for '.line'.  File: as.info, Node: Loc, Next: Loc_mark_labels, Prev: Ln, Up: Pseudo Ops 7.57 '.loc FILENO LINENO [COLUMN] [OPTIONS]' ============================================ When emitting DWARF2 line number information, the '.loc' directive will add a row to the '.debug_line' line number matrix corresponding to the immediately following assembly instruction. The FILENO, LINENO, and optional COLUMN arguments will be applied to the '.debug_line' state machine before the row is added. The OPTIONS are a sequence of the following tokens in any order: 'basic_block' This option will set the 'basic_block' register in the '.debug_line' state machine to 'true'. 'prologue_end' This option will set the 'prologue_end' register in the '.debug_line' state machine to 'true'. 'epilogue_begin' This option will set the 'epilogue_begin' register in the '.debug_line' state machine to 'true'. 'is_stmt VALUE' This option will set the 'is_stmt' register in the '.debug_line' state machine to 'value', which must be either 0 or 1. 'isa VALUE' This directive will set the 'isa' register in the '.debug_line' state machine to VALUE, which must be an unsigned integer. 'discriminator VALUE' This directive will set the 'discriminator' register in the '.debug_line' state machine to VALUE, which must be an unsigned integer. 'view VALUE' This option causes a row to be added to '.debug_line' in reference to the current address (which might not be the same as that of the following assembly instruction), and to associate VALUE with the 'view' register in the '.debug_line' state machine. If VALUE is a label, both the 'view' register and the label are set to the number of prior '.loc' directives at the same program location. If VALUE is the literal '0', the 'view' register is set to zero, and the assembler asserts that there aren't any prior '.loc' directives at the same program location. If VALUE is the literal '-0', the assembler arrange for the 'view' register to be reset in this row, even if there are prior '.loc' directives at the same program location.  File: as.info, Node: Loc_mark_labels, Next: Local, Prev: Loc, Up: Pseudo Ops 7.58 '.loc_mark_labels ENABLE' ============================== When emitting DWARF2 line number information, the '.loc_mark_labels' directive makes the assembler emit an entry to the '.debug_line' line number matrix with the 'basic_block' register in the state machine set whenever a code label is seen. The ENABLE argument should be either 1 or 0, to enable or disable this function respectively.  File: as.info, Node: Local, Next: Long, Prev: Loc_mark_labels, Up: Pseudo Ops 7.59 '.local NAMES' =================== This directive, which is available for ELF targets, marks each symbol in the comma-separated list of 'names' as a local symbol so that it will not be externally visible. If the symbols do not already exist, they will be created. For targets where the '.lcomm' directive (*note Lcomm::) does not accept an alignment argument, which is the case for most ELF targets, the '.local' directive can be used in combination with '.comm' (*note Comm::) to define aligned local common data.  File: as.info, Node: Long, Next: Macro, Prev: Local, Up: Pseudo Ops 7.60 '.long EXPRESSIONS' ======================== '.long' is the same as '.int'. *Note '.int': Int.  File: as.info, Node: Macro, Next: MRI, Prev: Long, Up: Pseudo Ops 7.61 '.macro' ============= The commands '.macro' and '.endm' allow you to define macros that generate assembly output. For example, this definition specifies a macro 'sum' that puts a sequence of numbers into memory: .macro sum from=0, to=5 .long \from .if \to-\from sum "(\from+1)",\to .endif .endm With that definition, 'SUM 0,5' is equivalent to this assembly input: .long 0 .long 1 .long 2 .long 3 .long 4 .long 5 '.macro MACNAME' '.macro MACNAME MACARGS ...' Begin the definition of a macro called MACNAME. If your macro definition requires arguments, specify their names after the macro name, separated by commas or spaces. You can qualify the macro argument to indicate whether all invocations must specify a non-blank value (through ':'req''), or whether it takes all of the remaining arguments (through ':'vararg''). You can supply a default value for any macro argument by following the name with '=DEFLT'. You cannot define two macros with the same MACNAME unless it has been subject to the '.purgem' directive (*note Purgem::) between the two definitions. For example, these are all valid '.macro' statements: '.macro comm' Begin the definition of a macro called 'comm', which takes no arguments. '.macro plus1 p, p1' '.macro plus1 p p1' Either statement begins the definition of a macro called 'plus1', which takes two arguments; within the macro definition, write '\p' or '\p1' to evaluate the arguments. '.macro reserve_str p1=0 p2' Begin the definition of a macro called 'reserve_str', with two arguments. The first argument has a default value, but not the second. After the definition is complete, you can call the macro either as 'reserve_str A,B' (with '\p1' evaluating to A and '\p2' evaluating to B), or as 'reserve_str ,B' (with '\p1' evaluating as the default, in this case '0', and '\p2' evaluating to B). '.macro m p1:req, p2=0, p3:vararg' Begin the definition of a macro called 'm', with at least three arguments. The first argument must always have a value specified, but not the second, which instead has a default value. The third formal will get assigned all remaining arguments specified at invocation time. When you call a macro, you can specify the argument values either by position, or by keyword. For example, 'sum 9,17' is equivalent to 'sum to=17, from=9'. Note that since each of the MACARGS can be an identifier exactly as any other one permitted by the target architecture, there may be occasional problems if the target hand-crafts special meanings to certain characters when they occur in a special position. For example, if the colon (':') is generally permitted to be part of a symbol name, but the architecture specific code special-cases it when occurring as the final character of a symbol (to denote a label), then the macro parameter replacement code will have no way of knowing that and consider the whole construct (including the colon) an identifier, and check only this identifier for being the subject to parameter substitution. So for example this macro definition: .macro label l \l: .endm might not work as expected. Invoking 'label foo' might not create a label called 'foo' but instead just insert the text '\l:' into the assembler source, probably generating an error about an unrecognised identifier. Similarly problems might occur with the period character ('.') which is often allowed inside opcode names (and hence identifier names). So for example constructing a macro to build an opcode from a base name and a length specifier like this: .macro opcode base length \base.\length .endm and invoking it as 'opcode store l' will not create a 'store.l' instruction but instead generate some kind of error as the assembler tries to interpret the text '\base.\length'. There are several possible ways around this problem: 'Insert white space' If it is possible to use white space characters then this is the simplest solution. eg: .macro label l \l : .endm 'Use '\()'' The string '\()' can be used to separate the end of a macro argument from the following text. eg: .macro opcode base length \base\().\length .endm 'Use the alternate macro syntax mode' In the alternative macro syntax mode the ampersand character ('&') can be used as a separator. eg: .altmacro .macro label l l&: .endm Note: this problem of correctly identifying string parameters to pseudo ops also applies to the identifiers used in '.irp' (*note Irp::) and '.irpc' (*note Irpc::) as well. '.endm' Mark the end of a macro definition. '.exitm' Exit early from the current macro definition. '\@' 'as' maintains a counter of how many macros it has executed in this pseudo-variable; you can copy that number to your output with '\@', but _only within a macro definition_. 'LOCAL NAME [ , ... ]' _Warning: 'LOCAL' is only available if you select "alternate macro syntax" with '--alternate' or '.altmacro'._ *Note '.altmacro': Altmacro.  File: as.info, Node: MRI, Next: Noaltmacro, Prev: Macro, Up: Pseudo Ops 7.62 '.mri VAL' =============== If VAL is non-zero, this tells 'as' to enter MRI mode. If VAL is zero, this tells 'as' to exit MRI mode. This change affects code assembled until the next '.mri' directive, or until the end of the file. *Note MRI mode: M.  File: as.info, Node: Noaltmacro, Next: Nolist, Prev: MRI, Up: Pseudo Ops 7.63 '.noaltmacro' ================== Disable alternate macro mode. *Note Altmacro::.  File: as.info, Node: Nolist, Next: Nops, Prev: Noaltmacro, Up: Pseudo Ops 7.64 '.nolist' ============== Control (in conjunction with the '.list' directive) whether or not assembly listings are generated. These two directives maintain an internal counter (which is zero initially). '.list' increments the counter, and '.nolist' decrements it. Assembly listings are generated whenever the counter is greater than zero.  File: as.info, Node: Nops, Next: Octa, Prev: Nolist, Up: Pseudo Ops 7.65 '.nops SIZE[, CONTROL]' ============================ This directive emits SIZE bytes filled with no-op instructions. SIZE is absolute expression, which must be a positve value. CONTROL controls how no-op instructions should be generated. If the comma and CONTROL are omitted, CONTROL is assumed to be zero. Note: For Intel 80386 and AMD x86-64 targets, CONTROL specifies the size limit of a no-op instruction. The valid values of CONTROL are between 0 and 4 in 16-bit mode, between 0 and 7 when tuning for older processors in 32-bit mode, between 0 and 11 in 64-bit mode or when tuning for newer processors in 32-bit mode. When 0 is used, the no-op instruction size limit is set to the maximum supported size.  File: as.info, Node: Octa, Next: Offset, Prev: Nops, Up: Pseudo Ops 7.66 '.octa BIGNUMS' ==================== This directive expects zero or more bignums, separated by commas. For each bignum, it emits a 16-byte integer. The term "octa" comes from contexts in which a "word" is two bytes; hence _octa_-word for 16 bytes.  File: as.info, Node: Offset, Next: Org, Prev: Octa, Up: Pseudo Ops 7.67 '.offset LOC' ================== Set the location counter to LOC in the absolute section. LOC must be an absolute expression. This directive may be useful for defining symbols with absolute values. Do not confuse it with the '.org' directive.  File: as.info, Node: Org, Next: P2align, Prev: Offset, Up: Pseudo Ops 7.68 '.org NEW-LC , FILL' ========================= Advance the location counter of the current section to NEW-LC. NEW-LC is either an absolute expression or an expression with the same section as the current subsection. That is, you can't use '.org' to cross sections: if NEW-LC has the wrong section, the '.org' directive is ignored. To be compatible with former assemblers, if the section of NEW-LC is absolute, 'as' issues a warning, then pretends the section of NEW-LC is the same as the current subsection. '.org' may only increase the location counter, or leave it unchanged; you cannot use '.org' to move the location counter backwards. Because 'as' tries to assemble programs in one pass, NEW-LC may not be undefined. If you really detest this restriction we eagerly await a chance to share your improved assembler. Beware that the origin is relative to the start of the section, not to the start of the subsection. This is compatible with other people's assemblers. When the location counter (of the current subsection) is advanced, the intervening bytes are filled with FILL which should be an absolute expression. If the comma and FILL are omitted, FILL defaults to zero.  File: as.info, Node: P2align, Next: PopSection, Prev: Org, Up: Pseudo Ops 7.69 '.p2align[wl] ABS-EXPR, ABS-EXPR, ABS-EXPR' ================================================ Pad the location counter (in the current subsection) to a particular storage boundary. The first expression (which must be absolute) is the number of low-order zero bits the location counter must have after advancement. For example '.p2align 3' advances the location counter until it a multiple of 8. If the location counter is already a multiple of 8, no change is needed. The second expression (also absolute) gives the fill value to be stored in the padding bytes. It (and the comma) may be omitted. If it is omitted, the padding bytes are normally zero. However, on most systems, if the section is marked as containing code and the fill value is omitted, the space is filled with no-op instructions. The third expression is also absolute, and is also optional. If it is present, it is the maximum number of bytes that should be skipped by this alignment directive. If doing the alignment would require skipping more bytes than the specified maximum, then the alignment is not done at all. You can omit the fill value (the second argument) entirely by simply using two commas after the required alignment; this can be useful if you want the alignment to be filled with no-op instructions when appropriate. The '.p2alignw' and '.p2alignl' directives are variants of the '.p2align' directive. The '.p2alignw' directive treats the fill pattern as a two byte word value. The '.p2alignl' directives treats the fill pattern as a four byte longword value. For example, '.p2alignw 2,0x368d' will align to a multiple of 4. If it skips two bytes, they will be filled in with the value 0x368d (the exact placement of the bytes depends upon the endianness of the processor). If it skips 1 or 3 bytes, the fill value is undefined.  File: as.info, Node: PopSection, Next: Previous, Prev: P2align, Up: Pseudo Ops 7.70 '.popsection' ================== This is one of the ELF section stack manipulation directives. The others are '.section' (*note Section::), '.subsection' (*note SubSection::), '.pushsection' (*note PushSection::), and '.previous' (*note Previous::). This directive replaces the current section (and subsection) with the top section (and subsection) on the section stack. This section is popped off the stack.  File: as.info, Node: Previous, Next: Print, Prev: PopSection, Up: Pseudo Ops 7.71 '.previous' ================ This is one of the ELF section stack manipulation directives. The others are '.section' (*note Section::), '.subsection' (*note SubSection::), '.pushsection' (*note PushSection::), and '.popsection' (*note PopSection::). This directive swaps the current section (and subsection) with most recently referenced section/subsection pair prior to this one. Multiple '.previous' directives in a row will flip between two sections (and their subsections). For example: .section A .subsection 1 .word 0x1234 .subsection 2 .word 0x5678 .previous .word 0x9abc Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of section A. Whilst: .section A .subsection 1 # Now in section A subsection 1 .word 0x1234 .section B .subsection 0 # Now in section B subsection 0 .word 0x5678 .subsection 1 # Now in section B subsection 1 .word 0x9abc .previous # Now in section B subsection 0 .word 0xdef0 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of section B and 0x9abc into subsection 1 of section B. In terms of the section stack, this directive swaps the current section with the top section on the section stack.  File: as.info, Node: Print, Next: Protected, Prev: Previous, Up: Pseudo Ops 7.72 '.print STRING' ==================== 'as' will print STRING on the standard output during assembly. You must put STRING in double quotes.  File: as.info, Node: Protected, Next: Psize, Prev: Print, Up: Pseudo Ops 7.73 '.protected NAMES' ======================= This is one of the ELF visibility directives. The other two are '.hidden' (*note Hidden::) and '.internal' (*note Internal::). This directive overrides the named symbols default visibility (which is set by their binding: local, global or weak). The directive sets the visibility to 'protected' which means that any references to the symbols from within the components that defines them must be resolved to the definition in that component, even if a definition in another component would normally preempt this.  File: as.info, Node: Psize, Next: Purgem, Prev: Protected, Up: Pseudo Ops 7.74 '.psize LINES , COLUMNS' ============================= Use this directive to declare the number of lines--and, optionally, the number of columns--to use for each page, when generating listings. If you do not use '.psize', listings use a default line-count of 60. You may omit the comma and COLUMNS specification; the default width is 200 columns. 'as' generates formfeeds whenever the specified number of lines is exceeded (or whenever you explicitly request one, using '.eject'). If you specify LINES as '0', no formfeeds are generated save those explicitly specified with '.eject'.  File: as.info, Node: Purgem, Next: PushSection, Prev: Psize, Up: Pseudo Ops 7.75 '.purgem NAME' =================== Undefine the macro NAME, so that later uses of the string will not be expanded. *Note Macro::.  File: as.info, Node: PushSection, Next: Quad, Prev: Purgem, Up: Pseudo Ops 7.76 '.pushsection NAME [, SUBSECTION] [, "FLAGS"[, @TYPE[,ARGUMENTS]]]' ======================================================================== This is one of the ELF section stack manipulation directives. The others are '.section' (*note Section::), '.subsection' (*note SubSection::), '.popsection' (*note PopSection::), and '.previous' (*note Previous::). This directive pushes the current section (and subsection) onto the top of the section stack, and then replaces the current section and subsection with 'name' and 'subsection'. The optional 'flags', 'type' and 'arguments' are treated the same as in the '.section' (*note Section::) directive.  File: as.info, Node: Quad, Next: Reloc, Prev: PushSection, Up: Pseudo Ops 7.77 '.quad BIGNUMS' ==================== '.quad' expects zero or more bignums, separated by commas. For each bignum, it emits an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a warning message; and just takes the lowest order 8 bytes of the bignum. The term "quad" comes from contexts in which a "word" is two bytes; hence _quad_-word for 8 bytes.  File: as.info, Node: Reloc, Next: Rept, Prev: Quad, Up: Pseudo Ops 7.78 '.reloc OFFSET, RELOC_NAME[, EXPRESSION]' ============================================== Generate a relocation at OFFSET of type RELOC_NAME with value EXPRESSION. If OFFSET is a number, the relocation is generated in the current section. If OFFSET is an expression that resolves to a symbol plus offset, the relocation is generated in the given symbol's section. EXPRESSION, if present, must resolve to a symbol plus addend or to an absolute value, but note that not all targets support an addend. e.g. ELF REL targets such as i386 store an addend in the section contents rather than in the relocation. This low level interface does not support addends stored in the section.  File: as.info, Node: Rept, Next: Sbttl, Prev: Reloc, Up: Pseudo Ops 7.79 '.rept COUNT' ================== Repeat the sequence of lines between the '.rept' directive and the next '.endr' directive COUNT times. For example, assembling .rept 3 .long 0 .endr is equivalent to assembling .long 0 .long 0 .long 0 A count of zero is allowed, but nothing is generated. Negative counts are not allowed and if encountered will be treated as if they were zero.  File: as.info, Node: Sbttl, Next: Scl, Prev: Rept, Up: Pseudo Ops 7.80 '.sbttl "SUBHEADING"' ========================== Use SUBHEADING as the title (third line, immediately after the title line) when generating assembly listings. This directive affects subsequent pages, as well as the current page if it appears within ten lines of the top of a page.  File: as.info, Node: Scl, Next: Section, Prev: Sbttl, Up: Pseudo Ops 7.81 '.scl CLASS' ================= Set the storage-class value for a symbol. This directive may only be used inside a '.def'/'.endef' pair. Storage class may flag whether a symbol is static or external, or it may record further symbolic debugging information.  File: as.info, Node: Section, Next: Set, Prev: Scl, Up: Pseudo Ops 7.82 '.section NAME' ==================== Use the '.section' directive to assemble the following code into a section named NAME. This directive is only supported for targets that actually support arbitrarily named sections; on 'a.out' targets, for example, it is not accepted, even with a standard 'a.out' section name. COFF Version ------------ For COFF targets, the '.section' directive is used in one of the following ways: .section NAME[, "FLAGS"] .section NAME[, SUBSECTION] If the optional argument is quoted, it is taken as flags to use for the section. Each flag is a single character. The following flags are recognized: 'b' bss section (uninitialized data) 'n' section is not loaded 'w' writable section 'd' data section 'e' exclude section from linking 'r' read-only section 'x' executable section 's' shared section (meaningful for PE targets) 'a' ignored. (For compatibility with the ELF version) 'y' section is not readable (meaningful for PE targets) '0-9' single-digit power-of-two section alignment (GNU extension) If no flags are specified, the default flags depend upon the section name. If the section name is not recognized, the default will be for the section to be loaded and writable. Note the 'n' and 'w' flags remove attributes from the section, rather than adding them, so if they are used on their own it will be as if no flags had been specified at all. If the optional argument to the '.section' directive is not quoted, it is taken as a subsection number (*note Sub-Sections::). ELF Version ----------- This is one of the ELF section stack manipulation directives. The others are '.subsection' (*note SubSection::), '.pushsection' (*note PushSection::), '.popsection' (*note PopSection::), and '.previous' (*note Previous::). For ELF targets, the '.section' directive is used like this: .section NAME [, "FLAGS"[, @TYPE[,FLAG_SPECIFIC_ARGUMENTS]]] If the '--sectname-subst' command-line option is provided, the NAME argument may contain a substitution sequence. Only '%S' is supported at the moment, and substitutes the current section name. For example: .macro exception_code .section %S.exception [exception code here] .previous .endm .text [code] exception_code [...] .section .init [init code] exception_code [...] The two 'exception_code' invocations above would create the '.text.exception' and '.init.exception' sections respectively. This is useful e.g. to discriminate between ancillary sections that are tied to setup code to be discarded after use from ancillary sections that need to stay resident without having to define multiple 'exception_code' macros just for that purpose. The optional FLAGS argument is a quoted string which may contain any combination of the following characters: 'a' section is allocatable 'd' section is a GNU_MBIND section 'e' section is excluded from executable and shared library. 'w' section is writable 'x' section is executable 'M' section is mergeable 'S' section contains zero terminated strings 'G' section is a member of a section group 'T' section is used for thread-local-storage '?' section is a member of the previously-current section's group, if any '' a numeric value indicating the bits to be set in the ELF section header's flags field. Note - if one or more of the alphabetic characters described above is also included in the flags field, their bit values will be ORed into the resulting value. '' some targets extend this list with their own flag characters Note - once a section's flags have been set they cannot be changed. There are a few exceptions to this rule however. Processor and application specific flags can be added to an already defined section. The '.interp', '.strtab' and '.symtab' sections can have the allocate flag ('a') set after they are initially defined, and the '.note-GNU-stack' section may have the executable ('x') flag added. The optional TYPE argument may contain one of the following constants: '@progbits' section contains data '@nobits' section does not contain data (i.e., section only occupies space) '@note' section contains data which is used by things other than the program '@init_array' section contains an array of pointers to init functions '@fini_array' section contains an array of pointers to finish functions '@preinit_array' section contains an array of pointers to pre-init functions '@' a numeric value to be set as the ELF section header's type field. '@' some targets extend this list with their own types Many targets only support the first three section types. The type may be enclosed in double quotes if necessary. Note on targets where the '@' character is the start of a comment (eg ARM) then another character is used instead. For example the ARM port uses the '%' character. Note - some sections, eg '.text' and '.data' are considered to be special and have fixed types. Any attempt to declare them with a different type will generate an error from the assembler. If FLAGS contains the 'M' symbol then the TYPE argument must be specified as well as an extra argument--ENTSIZE--like this: .section NAME , "FLAGS"M, @TYPE, ENTSIZE Sections with the 'M' flag but not 'S' flag must contain fixed size constants, each ENTSIZE octets long. Sections with both 'M' and 'S' must contain zero terminated strings where each character is ENTSIZE bytes long. The linker may remove duplicates within sections with the same name, same entity size and same flags. ENTSIZE must be an absolute expression. For sections with both 'M' and 'S', a string which is a suffix of a larger string is considered a duplicate. Thus '"def"' will be merged with '"abcdef"'; A reference to the first '"def"' will be changed to a reference to '"abcdef"+3'. If FLAGS contains the 'G' symbol then the TYPE argument must be present along with an additional field like this: .section NAME , "FLAGS"G, @TYPE, GROUPNAME[, LINKAGE] The GROUPNAME field specifies the name of the section group to which this particular section belongs. The optional linkage field can contain: 'comdat' indicates that only one copy of this section should be retained '.gnu.linkonce' an alias for comdat Note: if both the M and G flags are present then the fields for the Merge flag should come first, like this: .section NAME , "FLAGS"MG, @TYPE, ENTSIZE, GROUPNAME[, LINKAGE] If FLAGS contains the '?' symbol then it may not also contain the 'G' symbol and the GROUPNAME or LINKAGE fields should not be present. Instead, '?' says to consider the section that's current before this directive. If that section used 'G', then the new section will use 'G' with those same GROUPNAME and LINKAGE fields implicitly. If not, then the '?' symbol has no effect. If no flags are specified, the default flags depend upon the section name. If the section name is not recognized, the default will be for the section to have none of the above flags: it will not be allocated in memory, nor writable, nor executable. The section will contain data. For ELF targets, the assembler supports another type of '.section' directive for compatibility with the Solaris assembler: .section "NAME"[, FLAGS...] Note that the section name is quoted. There may be a sequence of comma separated flags: '#alloc' section is allocatable '#write' section is writable '#execinstr' section is executable '#exclude' section is excluded from executable and shared library. '#tls' section is used for thread local storage This directive replaces the current section and subsection. See the contents of the gas testsuite directory 'gas/testsuite/gas/elf' for some examples of how this directive and the other section stack directives work.  File: as.info, Node: Set, Next: Short, Prev: Section, Up: Pseudo Ops 7.83 '.set SYMBOL, EXPRESSION' ============================== Set the value of SYMBOL to EXPRESSION. This changes SYMBOL's value and type to conform to EXPRESSION. If SYMBOL was flagged as external, it remains flagged (*note Symbol Attributes::). You may '.set' a symbol many times in the same assembly provided that the values given to the symbol are constants. Values that are based on expressions involving other symbols are allowed, but some targets may restrict this to only being done once per assembly. This is because those targets do not set the addresses of symbols at assembly time, but rather delay the assignment until a final link is performed. This allows the linker a chance to change the code in the files, changing the location of, and the relative distance between, various different symbols. If you '.set' a global symbol, the value stored in the object file is the last value stored into it. On Z80 'set' is a real instruction, use 'SYMBOL defl EXPRESSION' instead.  File: as.info, Node: Short, Next: Single, Prev: Set, Up: Pseudo Ops 7.84 '.short EXPRESSIONS' ========================= '.short' is normally the same as '.word'. *Note '.word': Word. In some configurations, however, '.short' and '.word' generate numbers of different lengths. *Note Machine Dependencies::.  File: as.info, Node: Single, Next: Size, Prev: Short, Up: Pseudo Ops 7.85 '.single FLONUMS' ====================== This directive assembles zero or more flonums, separated by commas. It has the same effect as '.float'. The exact kind of floating point numbers emitted depends on how 'as' is configured. *Note Machine Dependencies::.  File: as.info, Node: Size, Next: Skip, Prev: Single, Up: Pseudo Ops 7.86 '.size' ============ This directive is used to set the size associated with a symbol. COFF Version ------------ For COFF targets, the '.size' directive is only permitted inside '.def'/'.endef' pairs. It is used like this: .size EXPRESSION ELF Version ----------- For ELF targets, the '.size' directive is used like this: .size NAME , EXPRESSION This directive sets the size associated with a symbol NAME. The size in bytes is computed from EXPRESSION which can make use of label arithmetic. This directive is typically used to set the size of function symbols.  File: as.info, Node: Skip, Next: Sleb128, Prev: Size, Up: Pseudo Ops 7.87 '.skip SIZE [,FILL]' ========================= This directive emits SIZE bytes, each of value FILL. Both SIZE and FILL are absolute expressions. If the comma and FILL are omitted, FILL is assumed to be zero. This is the same as '.space'.  File: as.info, Node: Sleb128, Next: Space, Prev: Skip, Up: Pseudo Ops 7.88 '.sleb128 EXPRESSIONS' =========================== SLEB128 stands for "signed little endian base 128." This is a compact, variable length representation of numbers used by the DWARF symbolic debugging format. *Note '.uleb128': Uleb128.  File: as.info, Node: Space, Next: Stab, Prev: Sleb128, Up: Pseudo Ops 7.89 '.space SIZE [,FILL]' ========================== This directive emits SIZE bytes, each of value FILL. Both SIZE and FILL are absolute expressions. If the comma and FILL are omitted, FILL is assumed to be zero. This is the same as '.skip'. _Warning:_ '.space' has a completely different meaning for HPPA targets; use '.block' as a substitute. See 'HP9000 Series 800 Assembly Language Reference Manual' (HP 92432-90001) for the meaning of the '.space' directive. *Note HPPA Assembler Directives: HPPA Directives, for a summary.  File: as.info, Node: Stab, Next: String, Prev: Space, Up: Pseudo Ops 7.90 '.stabd, .stabn, .stabs' ============================= There are three directives that begin '.stab'. All emit symbols (*note Symbols::), for use by symbolic debuggers. The symbols are not entered in the 'as' hash table: they cannot be referenced elsewhere in the source file. Up to five fields are required: STRING This is the symbol's name. It may contain any character except '\000', so is more general than ordinary symbol names. Some debuggers used to code arbitrarily complex structures into symbol names using this field. TYPE An absolute expression. The symbol's type is set to the low 8 bits of this expression. Any bit pattern is permitted, but 'ld' and debuggers choke on silly bit patterns. OTHER An absolute expression. The symbol's "other" attribute is set to the low 8 bits of this expression. DESC An absolute expression. The symbol's descriptor is set to the low 16 bits of this expression. VALUE An absolute expression which becomes the symbol's value. If a warning is detected while reading a '.stabd', '.stabn', or '.stabs' statement, the symbol has probably already been created; you get a half-formed symbol in your object file. This is compatible with earlier assemblers! '.stabd TYPE , OTHER , DESC' The "name" of the symbol generated is not even an empty string. It is a null pointer, for compatibility. Older assemblers used a null pointer so they didn't waste space in object files with empty strings. The symbol's value is set to the location counter, relocatably. When your program is linked, the value of this symbol is the address of the location counter when the '.stabd' was assembled. '.stabn TYPE , OTHER , DESC , VALUE' The name of the symbol is set to the empty string '""'. '.stabs STRING , TYPE , OTHER , DESC , VALUE' All five fields are specified.  File: as.info, Node: String, Next: Struct, Prev: Stab, Up: Pseudo Ops 7.91 '.string' "STR", '.string8' "STR", '.string16' =================================================== "STR", '.string32' "STR", '.string64' "STR" Copy the characters in STR to the object file. You may specify more than one string to copy, separated by commas. Unless otherwise specified for a particular machine, the assembler marks the end of each string with a 0 byte. You can use any of the escape sequences described in *note Strings: Strings. The variants 'string16', 'string32' and 'string64' differ from the 'string' pseudo opcode in that each 8-bit character from STR is copied and expanded to 16, 32 or 64 bits respectively. The expanded characters are stored in target endianness byte order. Example: .string32 "BYE" expands to: .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */ .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */  File: as.info, Node: Struct, Next: SubSection, Prev: String, Up: Pseudo Ops 7.92 '.struct EXPRESSION' ========================= Switch to the absolute section, and set the section offset to EXPRESSION, which must be an absolute expression. You might use this as follows: .struct 0 field1: .struct field1 + 4 field2: .struct field2 + 4 field3: This would define the symbol 'field1' to have the value 0, the symbol 'field2' to have the value 4, and the symbol 'field3' to have the value 8. Assembly would be left in the absolute section, and you would need to use a '.section' directive of some sort to change to some other section before further assembly.  File: as.info, Node: SubSection, Next: Symver, Prev: Struct, Up: Pseudo Ops 7.93 '.subsection NAME' ======================= This is one of the ELF section stack manipulation directives. The others are '.section' (*note Section::), '.pushsection' (*note PushSection::), '.popsection' (*note PopSection::), and '.previous' (*note Previous::). This directive replaces the current subsection with 'name'. The current section is not changed. The replaced subsection is put onto the section stack in place of the then current top of stack subsection.  File: as.info, Node: Symver, Next: Tag, Prev: SubSection, Up: Pseudo Ops 7.94 '.symver' ============== Use the '.symver' directive to bind symbols to specific version nodes within a source file. This is only supported on ELF platforms, and is typically used when assembling files to be linked into a shared library. There are cases where it may make sense to use this in objects to be bound into an application itself so as to override a versioned symbol from a shared library. For ELF targets, the '.symver' directive can be used like this: .symver NAME, NAME2@NODENAME If the symbol NAME is defined within the file being assembled, the '.symver' directive effectively creates a symbol alias with the name NAME2@NODENAME, and in fact the main reason that we just don't try and create a regular alias is that the @ character isn't permitted in symbol names. The NAME2 part of the name is the actual name of the symbol by which it will be externally referenced. The name NAME itself is merely a name of convenience that is used so that it is possible to have definitions for multiple versions of a function within a single source file, and so that the compiler can unambiguously know which version of a function is being mentioned. The NODENAME portion of the alias should be the name of a node specified in the version script supplied to the linker when building a shared library. If you are attempting to override a versioned symbol from a shared library, then NODENAME should correspond to the nodename of the symbol you are trying to override. If the symbol NAME is not defined within the file being assembled, all references to NAME will be changed to NAME2@NODENAME. If no reference to NAME is made, NAME2@NODENAME will be removed from the symbol table. Another usage of the '.symver' directive is: .symver NAME, NAME2@@NODENAME In this case, the symbol NAME must exist and be defined within the file being assembled. It is similar to NAME2@NODENAME. The difference is NAME2@@NODENAME will also be used to resolve references to NAME2 by the linker. The third usage of the '.symver' directive is: .symver NAME, NAME2@@@NODENAME When NAME is not defined within the file being assembled, it is treated as NAME2@NODENAME. When NAME is defined within the file being assembled, the symbol name, NAME, will be changed to NAME2@@NODENAME.  File: as.info, Node: Tag, Next: Text, Prev: Symver, Up: Pseudo Ops 7.95 '.tag STRUCTNAME' ====================== This directive is generated by compilers to include auxiliary debugging information in the symbol table. It is only permitted inside '.def'/'.endef' pairs. Tags are used to link structure definitions in the symbol table with instances of those structures.  File: as.info, Node: Text, Next: Title, Prev: Tag, Up: Pseudo Ops 7.96 '.text SUBSECTION' ======================= Tells 'as' to assemble the following statements onto the end of the text subsection numbered SUBSECTION, which is an absolute expression. If SUBSECTION is omitted, subsection number zero is used.  File: as.info, Node: Title, Next: Type, Prev: Text, Up: Pseudo Ops 7.97 '.title "HEADING"' ======================= Use HEADING as the title (second line, immediately after the source file name and pagenumber) when generating assembly listings. This directive affects subsequent pages, as well as the current page if it appears within ten lines of the top of a page.  File: as.info, Node: Type, Next: Uleb128, Prev: Title, Up: Pseudo Ops 7.98 '.type' ============ This directive is used to set the type of a symbol. COFF Version ------------ For COFF targets, this directive is permitted only within '.def'/'.endef' pairs. It is used like this: .type INT This records the integer INT as the type attribute of a symbol table entry. ELF Version ----------- For ELF targets, the '.type' directive is used like this: .type NAME , TYPE DESCRIPTION This sets the type of symbol NAME to be either a function symbol or an object symbol. There are five different syntaxes supported for the TYPE DESCRIPTION field, in order to provide compatibility with various other assemblers. Because some of the characters used in these syntaxes (such as '@' and '#') are comment characters for some architectures, some of the syntaxes below do not work on all architectures. The first variant will be accepted by the GNU assembler on all architectures so that variant should be used for maximum portability, if you do not need to assemble your code with other assemblers. The syntaxes supported are: .type STT_ .type ,# .type ,@ .type ,% .type ,"" The types supported are: 'STT_FUNC' 'function' Mark the symbol as being a function name. 'STT_GNU_IFUNC' 'gnu_indirect_function' Mark the symbol as an indirect function when evaluated during reloc processing. (This is only supported on assemblers targeting GNU systems). 'STT_OBJECT' 'object' Mark the symbol as being a data object. 'STT_TLS' 'tls_object' Mark the symbol as being a thread-local data object. 'STT_COMMON' 'common' Mark the symbol as being a common data object. 'STT_NOTYPE' 'notype' Does not mark the symbol in any way. It is supported just for completeness. 'gnu_unique_object' Marks the symbol as being a globally unique data object. The dynamic linker will make sure that in the entire process there is just one symbol with this name and type in use. (This is only supported on assemblers targeting GNU systems). Note: Some targets support extra types in addition to those listed above.  File: as.info, Node: Uleb128, Next: Val, Prev: Type, Up: Pseudo Ops 7.99 '.uleb128 EXPRESSIONS' =========================== ULEB128 stands for "unsigned little endian base 128." This is a compact, variable length representation of numbers used by the DWARF symbolic debugging format. *Note '.sleb128': Sleb128.  File: as.info, Node: Val, Next: Version, Prev: Uleb128, Up: Pseudo Ops 7.100 '.val ADDR' ================= This directive, permitted only within '.def'/'.endef' pairs, records the address ADDR as the value attribute of a symbol table entry.  File: as.info, Node: Version, Next: VTableEntry, Prev: Val, Up: Pseudo Ops 7.101 '.version "STRING"' ========================= This directive creates a '.note' section and places into it an ELF formatted note of type NT_VERSION. The note's name is set to 'string'.  File: as.info, Node: VTableEntry, Next: VTableInherit, Prev: Version, Up: Pseudo Ops 7.102 '.vtable_entry TABLE, OFFSET' =================================== This directive finds or creates a symbol 'table' and creates a 'VTABLE_ENTRY' relocation for it with an addend of 'offset'.  File: as.info, Node: VTableInherit, Next: Warning, Prev: VTableEntry, Up: Pseudo Ops 7.103 '.vtable_inherit CHILD, PARENT' ===================================== This directive finds the symbol 'child' and finds or creates the symbol 'parent' and then creates a 'VTABLE_INHERIT' relocation for the parent whose addend is the value of the child symbol. As a special case the parent name of '0' is treated as referring to the '*ABS*' section.  File: as.info, Node: Warning, Next: Weak, Prev: VTableInherit, Up: Pseudo Ops 7.104 '.warning "STRING"' ========================= Similar to the directive '.error' (*note '.error "STRING"': Error.), but just emits a warning.  File: as.info, Node: Weak, Next: Weakref, Prev: Warning, Up: Pseudo Ops 7.105 '.weak NAMES' =================== This directive sets the weak attribute on the comma separated list of symbol 'names'. If the symbols do not already exist, they will be created. On COFF targets other than PE, weak symbols are a GNU extension. This directive sets the weak attribute on the comma separated list of symbol 'names'. If the symbols do not already exist, they will be created. On the PE target, weak symbols are supported natively as weak aliases. When a weak symbol is created that is not an alias, GAS creates an alternate symbol to hold the default value.  File: as.info, Node: Weakref, Next: Word, Prev: Weak, Up: Pseudo Ops 7.106 '.weakref ALIAS, TARGET' ============================== This directive creates an alias to the target symbol that enables the symbol to be referenced with weak-symbol semantics, but without actually making it weak. If direct references or definitions of the symbol are present, then the symbol will not be weak, but if all references to it are through weak references, the symbol will be marked as weak in the symbol table. The effect is equivalent to moving all references to the alias to a separate assembly source file, renaming the alias to the symbol in it, declaring the symbol as weak there, and running a reloadable link to merge the object files resulting from the assembly of the new source file and the old source file that had the references to the alias removed. The alias itself never makes to the symbol table, and is entirely handled within the assembler.  File: as.info, Node: Word, Next: Zero, Prev: Weakref, Up: Pseudo Ops 7.107 '.word EXPRESSIONS' ========================= This directive expects zero or more EXPRESSIONS, of any section, separated by commas. The size of the number emitted, and its byte order, depend on what target computer the assembly is for. _Warning: Special Treatment to support Compilers_ Machines with a 32-bit address space, but that do less than 32-bit addressing, require the following special treatment. If the machine of interest to you does 32-bit addressing (or doesn't require it; *note Machine Dependencies::), you can ignore this issue. In order to assemble compiler output into something that works, 'as' occasionally does strange things to '.word' directives. Directives of the form '.word sym1-sym2' are often emitted by compilers as part of jump tables. Therefore, when 'as' assembles a directive of the form '.word sym1-sym2', and the difference between 'sym1' and 'sym2' does not fit in 16 bits, 'as' creates a "secondary jump table", immediately before the next label. This secondary jump table is preceded by a short-jump to the first byte after the secondary table. This short-jump prevents the flow of control from accidentally falling into the new table. Inside the table is a long-jump to 'sym2'. The original '.word' contains 'sym1' minus the address of the long-jump to 'sym2'. If there were several occurrences of '.word sym1-sym2' before the secondary jump table, all of them are adjusted. If there was a '.word sym3-sym4', that also did not fit in sixteen bits, a long-jump to 'sym4' is included in the secondary jump table, and the '.word' directives are adjusted to contain 'sym3' minus the address of the long-jump to 'sym4'; and so on, for as many entries in the original jump table as necessary.  File: as.info, Node: Zero, Next: 2byte, Prev: Word, Up: Pseudo Ops 7.108 '.zero SIZE' ================== This directive emits SIZE 0-valued bytes. SIZE must be an absolute expression. This directive is actually an alias for the '.skip' directive so in can take an optional second argument of the value to store in the bytes instead of zero. Using '.zero' in this way would be confusing however.  File: as.info, Node: 2byte, Next: 4byte, Prev: Zero, Up: Pseudo Ops 7.109 '.2byte EXPRESSION [, EXPRESSION]*' ========================================= This directive expects zero or more expressions, separated by commas. If there are no expressions then the directive does nothing. Otherwise each expression is evaluated in turn and placed in the next two bytes of the current output section, using the endian model of the target. If an expression will not fit in two bytes, a warning message is displayed and the least significant two bytes of the expression's value are used. If an expression cannot be evaluated at assembly time then relocations will be generated in order to compute the value at link time. This directive does not apply any alignment before or after inserting the values. As a result of this, if relocations are generated, they may be different from those used for inserting values with a guaranteed alignment. This directive is only available for ELF targets,  File: as.info, Node: 4byte, Next: 8byte, Prev: 2byte, Up: Pseudo Ops 7.110 '.4byte EXPRESSION [, EXPRESSION]*' ========================================= Like the '.2byte' directive, except that it inserts unaligned, four byte long values into the output.  File: as.info, Node: 8byte, Next: Deprecated, Prev: 4byte, Up: Pseudo Ops 7.111 '.8byte EXPRESSION [, EXPRESSION]*' ========================================= Like the '.2byte' directive, except that it inserts unaligned, eight byte long bignum values into the output.  File: as.info, Node: Deprecated, Prev: 8byte, Up: Pseudo Ops 7.112 Deprecated Directives =========================== One day these directives won't work. They are included for compatibility with older assemblers. .abort .line  File: as.info, Node: Object Attributes, Next: Machine Dependencies, Prev: Pseudo Ops, Up: Top 8 Object Attributes ******************* 'as' assembles source files written for a specific architecture into object files for that architecture. But not all object files are alike. Many architectures support incompatible variations. For instance, floating point arguments might be passed in floating point registers if the object file requires hardware floating point support--or floating point arguments might be passed in integer registers if the object file supports processors with no hardware floating point unit. Or, if two objects are built for different generations of the same architecture, the combination may require the newer generation at run-time. This information is useful during and after linking. At link time, 'ld' can warn about incompatible object files. After link time, tools like 'gdb' can use it to process the linked file correctly. Compatibility information is recorded as a series of object attributes. Each attribute has a "vendor", "tag", and "value". The vendor is a string, and indicates who sets the meaning of the tag. The tag is an integer, and indicates what property the attribute describes. The value may be a string or an integer, and indicates how the property affects this object. Missing attributes are the same as attributes with a zero value or empty string value. Object attributes were developed as part of the ABI for the ARM Architecture. The file format is documented in 'ELF for the ARM Architecture'. * Menu: * GNU Object Attributes:: GNU Object Attributes * Defining New Object Attributes:: Defining New Object Attributes  File: as.info, Node: GNU Object Attributes, Next: Defining New Object Attributes, Up: Object Attributes 8.1 GNU Object Attributes ========================= The '.gnu_attribute' directive records an object attribute with vendor 'gnu'. Except for 'Tag_compatibility', which has both an integer and a string for its value, GNU attributes have a string value if the tag number is odd and an integer value if the tag number is even. The second bit ('TAG & 2' is set for architecture-independent attributes and clear for architecture-dependent ones. 8.1.1 Common GNU attributes --------------------------- These attributes are valid on all architectures. Tag_compatibility (32) The compatibility attribute takes an integer flag value and a vendor name. If the flag value is 0, the file is compatible with other toolchains. If it is 1, then the file is only compatible with the named toolchain. If it is greater than 1, the file can only be processed by other toolchains under some private arrangement indicated by the flag value and the vendor name. 8.1.2 MIPS Attributes --------------------- Tag_GNU_MIPS_ABI_FP (4) The floating-point ABI used by this object file. The value will be: * 0 for files not affected by the floating-point ABI. * 1 for files using the hardware floating-point ABI with a standard double-precision FPU. * 2 for files using the hardware floating-point ABI with a single-precision FPU. * 3 for files using the software floating-point ABI. * 4 for files using the deprecated hardware floating-point ABI which used 64-bit floating-point registers, 32-bit general-purpose registers and increased the number of callee-saved floating-point registers. * 5 for files using the hardware floating-point ABI with a double-precision FPU with either 32-bit or 64-bit floating-point registers and 32-bit general-purpose registers. * 6 for files using the hardware floating-point ABI with 64-bit floating-point registers and 32-bit general-purpose registers. * 7 for files using the hardware floating-point ABI with 64-bit floating-point registers, 32-bit general-purpose registers and a rule that forbids the direct use of odd-numbered single-precision floating-point registers. 8.1.3 PowerPC Attributes ------------------------ Tag_GNU_Power_ABI_FP (4) The floating-point ABI used by this object file. The value will be: * 0 for files not affected by the floating-point ABI. * 1 for files using double-precision hardware floating-point ABI. * 2 for files using the software floating-point ABI. * 3 for files using single-precision hardware floating-point ABI. Tag_GNU_Power_ABI_Vector (8) The vector ABI used by this object file. The value will be: * 0 for files not affected by the vector ABI. * 1 for files using general purpose registers to pass vectors. * 2 for files using AltiVec registers to pass vectors. * 3 for files using SPE registers to pass vectors. 8.1.4 IBM z Systems Attributes ------------------------------ Tag_GNU_S390_ABI_Vector (8) The vector ABI used by this object file. The value will be: * 0 for files not affected by the vector ABI. * 1 for files using software vector ABI. * 2 for files using hardware vector ABI.  File: as.info, Node: Defining New Object Attributes, Prev: GNU Object Attributes, Up: Object Attributes 8.2 Defining New Object Attributes ================================== If you want to define a new GNU object attribute, here are the places you will need to modify. New attributes should be discussed on the 'binutils' mailing list. * This manual, which is the official register of attributes. * The header for your architecture 'include/elf', to define the tag. * The 'bfd' support file for your architecture, to merge the attribute and issue any appropriate link warnings. * Test cases in 'ld/testsuite' for merging and link warnings. * 'binutils/readelf.c' to display your attribute. * GCC, if you want the compiler to mark the attribute automatically.  File: as.info, Node: Machine Dependencies, Next: Reporting Bugs, Prev: Object Attributes, Up: Top 9 Machine Dependent Features **************************** The machine instruction sets are (almost by definition) different on each machine where 'as' runs. Floating point representations vary as well, and 'as' often supports a few additional directives or command-line options for compatibility with other assemblers on a particular platform. Finally, some versions of 'as' support special pseudo-instructions for branch optimization. This chapter discusses most of these differences, though it does not include details on any machine's instruction set. For details on that subject, see the hardware manufacturer's manual. * Menu: * AArch64-Dependent:: AArch64 Dependent Features * Alpha-Dependent:: Alpha Dependent Features * ARC-Dependent:: ARC Dependent Features * ARM-Dependent:: ARM Dependent Features * AVR-Dependent:: AVR Dependent Features * Blackfin-Dependent:: Blackfin Dependent Features * CR16-Dependent:: CR16 Dependent Features * CRIS-Dependent:: CRIS Dependent Features * D10V-Dependent:: D10V Dependent Features * D30V-Dependent:: D30V Dependent Features * Epiphany-Dependent:: EPIPHANY Dependent Features * H8/300-Dependent:: Renesas H8/300 Dependent Features * HPPA-Dependent:: HPPA Dependent Features * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features * IA-64-Dependent:: Intel IA-64 Dependent Features * IP2K-Dependent:: IP2K Dependent Features * LM32-Dependent:: LM32 Dependent Features * M32C-Dependent:: M32C Dependent Features * M32R-Dependent:: M32R Dependent Features * M68K-Dependent:: M680x0 Dependent Features * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features * S12Z-Dependent:: S12Z Dependent Features * Meta-Dependent :: Meta Dependent Features * MicroBlaze-Dependent:: MICROBLAZE Dependent Features * MIPS-Dependent:: MIPS Dependent Features * MMIX-Dependent:: MMIX Dependent Features * MSP430-Dependent:: MSP430 Dependent Features * NDS32-Dependent:: Andes NDS32 Dependent Features * NiosII-Dependent:: Altera Nios II Dependent Features * NS32K-Dependent:: NS32K Dependent Features * PDP-11-Dependent:: PDP-11 Dependent Features * PJ-Dependent:: picoJava Dependent Features * PPC-Dependent:: PowerPC Dependent Features * PRU-Dependent:: PRU Dependent Features * RISC-V-Dependent:: RISC-V Dependent Features * RL78-Dependent:: RL78 Dependent Features * RX-Dependent:: RX Dependent Features * S/390-Dependent:: IBM S/390 Dependent Features * SCORE-Dependent:: SCORE Dependent Features * SH-Dependent:: Renesas / SuperH SH Dependent Features * Sparc-Dependent:: SPARC Dependent Features * TIC54X-Dependent:: TI TMS320C54x Dependent Features * TIC6X-Dependent :: TI TMS320C6x Dependent Features * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features * TILEPro-Dependent :: Tilera TILEPro Dependent Features * V850-Dependent:: V850 Dependent Features * Vax-Dependent:: VAX Dependent Features * Visium-Dependent:: Visium Dependent Features * WebAssembly-Dependent:: WebAssembly Dependent Features * XGATE-Dependent:: XGATE Dependent Features * XSTORMY16-Dependent:: XStormy16 Dependent Features * Xtensa-Dependent:: Xtensa Dependent Features * Z80-Dependent:: Z80 Dependent Features * Z8000-Dependent:: Z8000 Dependent Features  File: as.info, Node: AArch64-Dependent, Next: Alpha-Dependent, Up: Machine Dependencies 9.1 AArch64 Dependent Features ============================== * Menu: * AArch64 Options:: Options * AArch64 Extensions:: Extensions * AArch64 Syntax:: Syntax * AArch64 Floating Point:: Floating Point * AArch64 Directives:: AArch64 Machine Directives * AArch64 Opcodes:: Opcodes * AArch64 Mapping Symbols:: Mapping Symbols  File: as.info, Node: AArch64 Options, Next: AArch64 Extensions, Up: AArch64-Dependent 9.1.1 Options ------------- '-EB' This option specifies that the output generated by the assembler should be marked as being encoded for a big-endian processor. '-EL' This option specifies that the output generated by the assembler should be marked as being encoded for a little-endian processor. '-mabi=ABI' Specify which ABI the source code uses. The recognized arguments are: 'ilp32' and 'lp64', which decides the generated object file in ELF32 and ELF64 format respectively. The default is 'lp64'. '-mcpu=PROCESSOR[+EXTENSION...]' This option specifies the target processor. The assembler will issue an error message if an attempt is made to assemble an instruction which will not execute on the target processor. The following processor names are recognized: 'cortex-a35', 'cortex-a53', 'cortex-a55', 'cortex-a57', 'cortex-a72', 'cortex-a73', 'cortex-a75', 'cortex-a76', 'exynos-m1', 'falkor', 'qdf24xx', 'saphira', 'thunderx', 'vulcan', 'xgene1' and 'xgene2'. The special name 'all' may be used to allow the assembler to accept instructions valid for any supported processor, including all optional extensions. In addition to the basic instruction set, the assembler can be told to accept, or restrict, various extension mnemonics that extend the processor. *Note AArch64 Extensions::. If some implementations of a particular processor can have an extension, then then those extensions are automatically enabled. Consequently, you will not normally have to specify any additional extensions. '-march=ARCHITECTURE[+EXTENSION...]' This option specifies the target architecture. The assembler will issue an error message if an attempt is made to assemble an instruction which will not execute on the target architecture. The following architecture names are recognized: 'armv8-a', 'armv8.1-a', 'armv8.2-a', 'armv8.3-a' and 'armv8.4-a'. If both '-mcpu' and '-march' are specified, the assembler will use the setting for '-mcpu'. If neither are specified, the assembler will default to '-mcpu=all'. The architecture option can be extended with the same instruction set extension options as the '-mcpu' option. Unlike '-mcpu', extensions are not always enabled by default, *Note AArch64 Extensions::. '-mverbose-error' This option enables verbose error messages for AArch64 gas. This option is enabled by default. '-mno-verbose-error' This option disables verbose error messages in AArch64 gas.  File: as.info, Node: AArch64 Extensions, Next: AArch64 Syntax, Prev: AArch64 Options, Up: AArch64-Dependent 9.1.2 Architecture Extensions ----------------------------- The table below lists the permitted architecture extensions that are supported by the assembler and the conditions under which they are automatically enabled. Multiple extensions may be specified, separated by a '+'. Extension mnemonics may also be removed from those the assembler accepts. This is done by prepending 'no' to the option that adds the extension. Extensions that are removed must be listed after all extensions that have been added. Enabling an extension that requires other extensions will automatically cause those extensions to be enabled. Similarly, disabling an extension that is required by other extensions will automatically cause those extensions to be disabled. Extension Minimum Enabled by Description Architecture default ---------------------------------------------------------------------------- 'compnum' ARMv8.2-A ARMv8.3-A Enable the complex number SIMD or later extensions. This implies 'fp16' and 'simd'. 'crc' ARMv8-A ARMv8.1-A Enable CRC instructions. or later 'crypto' ARMv8-A No Enable cryptographic extensions. This implies 'fp', 'simd', 'aes' and 'sha2'. 'aes' ARMv8-A No Enable the AES cryptographic extensions. This implies 'fp' and 'simd'. 'sha2' ARMv8-A No Enable the SHA2 cryptographic extensions. This implies 'fp' and 'simd'. 'sha3' ARMv8.2-A No Enable the ARMv8.2-A SHA2 and SHA3 cryptographic extensions. This implies 'fp', 'simd' and 'sha2'. 'sm4' ARMv8.2-A No Enable the ARMv8.2-A SM3 and SM4 cryptographic extensions. This implies 'fp' and 'simd'. 'fp' ARMv8-A ARMv8-A or Enable floating-point extensions. later 'fp16' ARMv8.2-A ARMv8.2-A Enable ARMv8.2 16-bit floating-point or later support. This implies 'fp'. 'lor' ARMv8-A ARMv8.1-A Enable Limited Ordering Regions or later extensions. 'lse' ARMv8-A ARMv8.1-A Enable Large System extensions. or later 'pan' ARMv8-A ARMv8.1-A Enable Privileged Access Never or later support. 'profile' ARMv8.2-A No Enable statistical profiling extensions. 'ras' ARMv8-A ARMv8.2-A Enable the Reliability, Availability or later and Serviceability extension. 'rcpc' ARMv8.2-A ARMv8.3-A Enable the weak release consistency or later extension. 'rdma' ARMv8-A ARMv8.1-A Enable ARMv8.1 Advanced SIMD or later extensions. This implies 'simd'. 'simd' ARMv8-A ARMv8-A or Enable Advanced SIMD extensions. later This implies 'fp'. 'sve' ARMv8.2-A No Enable the Scalable Vector Extensions. This implies 'fp16', 'simd' and 'compnum'. 'dotprod' ARMv8.2-A ARMv8.4-A Enable the Dot Product extension. or later This implies 'simd'. 'fp16fml' ARMv8.2-A ARMv8.4-A Enable ARMv8.2 16-bit floating-point or later multiplication variant support. This implies 'fp16'.  File: as.info, Node: AArch64 Syntax, Next: AArch64 Floating Point, Prev: AArch64 Extensions, Up: AArch64-Dependent 9.1.3 Syntax ------------ * Menu: * AArch64-Chars:: Special Characters * AArch64-Regs:: Register Names * AArch64-Relocations:: Relocations  File: as.info, Node: AArch64-Chars, Next: AArch64-Regs, Up: AArch64 Syntax 9.1.3.1 Special Characters .......................... The presence of a '//' on a line indicates the start of a comment that extends to the end of the current line. If a '#' appears as the first character of a line, the whole line is treated as a comment. The ';' character can be used instead of a newline to separate statements. The '#' can be optionally used to indicate immediate operands.  File: as.info, Node: AArch64-Regs, Next: AArch64-Relocations, Prev: AArch64-Chars, Up: AArch64 Syntax 9.1.3.2 Register Names ...................... Please refer to the section '4.4 Register Names' of 'ARMv8 Instruction Set Overview', which is available at .  File: as.info, Node: AArch64-Relocations, Prev: AArch64-Regs, Up: AArch64 Syntax 9.1.3.3 Relocations ................... Relocations for 'MOVZ' and 'MOVK' instructions can be generated by prefixing the label with '#:abs_g2:' etc. For example to load the 48-bit absolute address of FOO into x0: movz x0, #:abs_g2:foo // bits 32-47, overflow check movk x0, #:abs_g1_nc:foo // bits 16-31, no overflow check movk x0, #:abs_g0_nc:foo // bits 0-15, no overflow check Relocations for 'ADRP', and 'ADD', 'LDR' or 'STR' instructions can be generated by prefixing the label with ':pg_hi21:' and '#:lo12:' respectively. For example to use 33-bit (+/-4GB) pc-relative addressing to load the address of FOO into x0: adrp x0, :pg_hi21:foo add x0, x0, #:lo12:foo Or to load the value of FOO into x0: adrp x0, :pg_hi21:foo ldr x0, [x0, #:lo12:foo] Note that ':pg_hi21:' is optional. adrp x0, foo is equivalent to adrp x0, :pg_hi21:foo  File: as.info, Node: AArch64 Floating Point, Next: AArch64 Directives, Prev: AArch64 Syntax, Up: AArch64-Dependent 9.1.4 Floating Point -------------------- The AArch64 architecture uses IEEE floating-point numbers.  File: as.info, Node: AArch64 Directives, Next: AArch64 Opcodes, Prev: AArch64 Floating Point, Up: AArch64-Dependent 9.1.5 AArch64 Machine Directives -------------------------------- '.arch NAME' Select the target architecture. Valid values for NAME are the same as for the '-march' commandline option. Specifying '.arch' clears any previously selected architecture extensions. '.arch_extension NAME' Add or remove an architecture extension to the target architecture. Valid values for NAME are the same as those accepted as architectural extensions by the '-mcpu' commandline option. '.arch_extension' may be used multiple times to add or remove extensions incrementally to the architecture being compiled for. '.bss' This directive switches to the '.bss' section. '.cpu NAME' Set the target processor. Valid values for NAME are the same as those accepted by the '-mcpu=' command line option. '.dword EXPRESSIONS' The '.dword' directive produces 64 bit values. '.even' The '.even' directive aligns the output on the next even byte boundary. '.inst EXPRESSIONS' Inserts the expressions into the output as if they were instructions, rather than data. '.ltorg' This directive causes the current contents of the literal pool to be dumped into the current section (which is assumed to be the .text section) at the current location (aligned to a word boundary). GAS maintains a separate literal pool for each section and each sub-section. The '.ltorg' directive will only affect the literal pool of the current section and sub-section. At the end of assembly all remaining, un-empty literal pools will automatically be dumped. Note - older versions of GAS would dump the current literal pool any time a section change occurred. This is no longer done, since it prevents accurate control of the placement of literal pools. '.pool' This is a synonym for .ltorg. 'NAME .req REGISTER NAME' This creates an alias for REGISTER NAME called NAME. For example: foo .req w0 ip0, ip1, lr and fp are automatically defined to alias to X16, X17, X30 and X29 respectively. '.tlsdescadd' Emits a TLSDESC_ADD reloc on the next instruction. '.tlsdesccall' Emits a TLSDESC_CALL reloc on the next instruction. '.tlsdescldr' Emits a TLSDESC_LDR reloc on the next instruction. '.unreq ALIAS-NAME' This undefines a register alias which was previously defined using the 'req' directive. For example: foo .req w0 .unreq foo An error occurs if the name is undefined. Note - this pseudo op can be used to delete builtin in register name aliases (eg 'w0'). This should only be done if it is really necessary. '.xword EXPRESSIONS' The '.xword' directive produces 64 bit values. This is the same as the '.dword' directive.  File: as.info, Node: AArch64 Opcodes, Next: AArch64 Mapping Symbols, Prev: AArch64 Directives, Up: AArch64-Dependent 9.1.6 Opcodes ------------- GAS implements all the standard AArch64 opcodes. It also implements several pseudo opcodes, including several synthetic load instructions. 'LDR =' ldr , = The constant expression will be placed into the nearest literal pool (if it not already there) and a PC-relative LDR instruction will be generated. For more information on the AArch64 instruction set and assembly language notation, see 'ARMv8 Instruction Set Overview' available at .  File: as.info, Node: AArch64 Mapping Symbols, Prev: AArch64 Opcodes, Up: AArch64-Dependent 9.1.7 Mapping Symbols --------------------- The AArch64 ELF specification requires that special symbols be inserted into object files to mark certain features: '$x' At the start of a region of code containing AArch64 instructions. '$d' At the start of a region of data.  File: as.info, Node: Alpha-Dependent, Next: ARC-Dependent, Prev: AArch64-Dependent, Up: Machine Dependencies 9.2 Alpha Dependent Features ============================ * Menu: * Alpha Notes:: Notes * Alpha Options:: Options * Alpha Syntax:: Syntax * Alpha Floating Point:: Floating Point * Alpha Directives:: Alpha Machine Directives * Alpha Opcodes:: Opcodes  File: as.info, Node: Alpha Notes, Next: Alpha Options, Up: Alpha-Dependent 9.2.1 Notes ----------- The documentation here is primarily for the ELF object format. 'as' also supports the ECOFF and EVAX formats, but features specific to these formats are not yet documented.  File: as.info, Node: Alpha Options, Next: Alpha Syntax, Prev: Alpha Notes, Up: Alpha-Dependent 9.2.2 Options ------------- '-mCPU' This option specifies the target processor. If an attempt is made to assemble an instruction which will not execute on the target processor, the assembler may either expand the instruction as a macro or issue an error message. This option is equivalent to the '.arch' directive. The following processor names are recognized: '21064', '21064a', '21066', '21068', '21164', '21164a', '21164pc', '21264', '21264a', '21264b', 'ev4', 'ev5', 'lca45', 'ev5', 'ev56', 'pca56', 'ev6', 'ev67', 'ev68'. The special name 'all' may be used to allow the assembler to accept instructions valid for any Alpha processor. In order to support existing practice in OSF/1 with respect to '.arch', and existing practice within 'MILO' (the Linux ARC bootloader), the numbered processor names (e.g. 21064) enable the processor-specific PALcode instructions, while the "electro-vlasic" names (e.g. 'ev4') do not. '-mdebug' '-no-mdebug' Enables or disables the generation of '.mdebug' encapsulation for stabs directives and procedure descriptors. The default is to automatically enable '.mdebug' when the first stabs directive is seen. '-relax' This option forces all relocations to be put into the object file, instead of saving space and resolving some relocations at assembly time. Note that this option does not propagate all symbol arithmetic into the object file, because not all symbol arithmetic can be represented. However, the option can still be useful in specific applications. '-replace' '-noreplace' Enables or disables the optimization of procedure calls, both at assemblage and at link time. These options are only available for VMS targets and '-replace' is the default. See section 1.4.1 of the OpenVMS Linker Utility Manual. '-g' This option is used when the compiler generates debug information. When 'gcc' is using 'mips-tfile' to generate debug information for ECOFF, local labels must be passed through to the object file. Otherwise this option has no effect. '-GSIZE' A local common symbol larger than SIZE is placed in '.bss', while smaller symbols are placed in '.sbss'. '-F' '-32addr' These options are ignored for backward compatibility.  File: as.info, Node: Alpha Syntax, Next: Alpha Floating Point, Prev: Alpha Options, Up: Alpha-Dependent 9.2.3 Syntax ------------ The assembler syntax closely follow the Alpha Reference Manual; assembler directives and general syntax closely follow the OSF/1 and OpenVMS syntax, with a few differences for ELF. * Menu: * Alpha-Chars:: Special Characters * Alpha-Regs:: Register Names * Alpha-Relocs:: Relocations  File: as.info, Node: Alpha-Chars, Next: Alpha-Regs, Up: Alpha Syntax 9.2.3.1 Special Characters .......................... '#' is the line comment character. Note that if '#' is the first character on a line then it can also be a logical line number directive (*note Comments::) or a preprocessor control command (*note Preprocessing::). ';' can be used instead of a newline to separate statements.  File: as.info, Node: Alpha-Regs, Next: Alpha-Relocs, Prev: Alpha-Chars, Up: Alpha Syntax 9.2.3.2 Register Names ...................... The 32 integer registers are referred to as '$N' or '$rN'. In addition, registers 15, 28, 29, and 30 may be referred to by the symbols '$fp', '$at', '$gp', and '$sp' respectively. The 32 floating-point registers are referred to as '$fN'.  File: as.info, Node: Alpha-Relocs, Prev: Alpha-Regs, Up: Alpha Syntax 9.2.3.3 Relocations ................... Some of these relocations are available for ECOFF, but mostly only for ELF. They are modeled after the relocation format introduced in Digital Unix 4.0, but there are additions. The format is '!TAG' or '!TAG!NUMBER' where TAG is the name of the relocation. In some cases NUMBER is used to relate specific instructions. The relocation is placed at the end of the instruction like so: ldah $0,a($29) !gprelhigh lda $0,a($0) !gprellow ldq $1,b($29) !literal!100 ldl $2,0($1) !lituse_base!100 '!literal' '!literal!N' Used with an 'ldq' instruction to load the address of a symbol from the GOT. A sequence number N is optional, and if present is used to pair 'lituse' relocations with this 'literal' relocation. The 'lituse' relocations are used by the linker to optimize the code based on the final location of the symbol. Note that these optimizations are dependent on the data flow of the program. Therefore, if _any_ 'lituse' is paired with a 'literal' relocation, then _all_ uses of the register set by the 'literal' instruction must also be marked with 'lituse' relocations. This is because the original 'literal' instruction may be deleted or transformed into another instruction. Also note that there may be a one-to-many relationship between 'literal' and 'lituse', but not a many-to-one. That is, if there are two code paths that load up the same address and feed the value to a single use, then the use may not use a 'lituse' relocation. '!lituse_base!N' Used with any memory format instruction (e.g. 'ldl') to indicate that the literal is used for an address load. The offset field of the instruction must be zero. During relaxation, the code may be altered to use a gp-relative load. '!lituse_jsr!N' Used with a register branch format instruction (e.g. 'jsr') to indicate that the literal is used for a call. During relaxation, the code may be altered to use a direct branch (e.g. 'bsr'). '!lituse_jsrdirect!N' Similar to 'lituse_jsr', but also that this call cannot be vectored through a PLT entry. This is useful for functions with special calling conventions which do not allow the normal call-clobbered registers to be clobbered. '!lituse_bytoff!N' Used with a byte mask instruction (e.g. 'extbl') to indicate that only the low 3 bits of the address are relevant. During relaxation, the code may be altered to use an immediate instead of a register shift. '!lituse_addr!N' Used with any other instruction to indicate that the original address is in fact used, and the original 'ldq' instruction may not be altered or deleted. This is useful in conjunction with 'lituse_jsr' to test whether a weak symbol is defined. ldq $27,foo($29) !literal!1 beq $27,is_undef !lituse_addr!1 jsr $26,($27),foo !lituse_jsr!1 '!lituse_tlsgd!N' Used with a register branch format instruction to indicate that the literal is the call to '__tls_get_addr' used to compute the address of the thread-local storage variable whose descriptor was loaded with '!tlsgd!N'. '!lituse_tlsldm!N' Used with a register branch format instruction to indicate that the literal is the call to '__tls_get_addr' used to compute the address of the base of the thread-local storage block for the current module. The descriptor for the module must have been loaded with '!tlsldm!N'. '!gpdisp!N' Used with 'ldah' and 'lda' to load the GP from the current address, a-la the 'ldgp' macro. The source register for the 'ldah' instruction must contain the address of the 'ldah' instruction. There must be exactly one 'lda' instruction paired with the 'ldah' instruction, though it may appear anywhere in the instruction stream. The immediate operands must be zero. bsr $26,foo ldah $29,0($26) !gpdisp!1 lda $29,0($29) !gpdisp!1 '!gprelhigh' Used with an 'ldah' instruction to add the high 16 bits of a 32-bit displacement from the GP. '!gprellow' Used with any memory format instruction to add the low 16 bits of a 32-bit displacement from the GP. '!gprel' Used with any memory format instruction to add a 16-bit displacement from the GP. '!samegp' Used with any branch format instruction to skip the GP load at the target address. The referenced symbol must have the same GP as the source object file, and it must be declared to either not use '$27' or perform a standard GP load in the first two instructions via the '.prologue' directive. '!tlsgd' '!tlsgd!N' Used with an 'lda' instruction to load the address of a TLS descriptor for a symbol in the GOT. The sequence number N is optional, and if present it used to pair the descriptor load with both the 'literal' loading the address of the '__tls_get_addr' function and the 'lituse_tlsgd' marking the call to that function. For proper relaxation, both the 'tlsgd', 'literal' and 'lituse' relocations must be in the same extended basic block. That is, the relocation with the lowest address must be executed first at runtime. '!tlsldm' '!tlsldm!N' Used with an 'lda' instruction to load the address of a TLS descriptor for the current module in the GOT. Similar in other respects to 'tlsgd'. '!gotdtprel' Used with an 'ldq' instruction to load the offset of the TLS symbol within its module's thread-local storage block. Also known as the dynamic thread pointer offset or dtp-relative offset. '!dtprelhi' '!dtprello' '!dtprel' Like 'gprel' relocations except they compute dtp-relative offsets. '!gottprel' Used with an 'ldq' instruction to load the offset of the TLS symbol from the thread pointer. Also known as the tp-relative offset. '!tprelhi' '!tprello' '!tprel' Like 'gprel' relocations except they compute tp-relative offsets.  File: as.info, Node: Alpha Floating Point, Next: Alpha Directives, Prev: Alpha Syntax, Up: Alpha-Dependent 9.2.4 Floating Point -------------------- The Alpha family uses both IEEE and VAX floating-point numbers.  File: as.info, Node: Alpha Directives, Next: Alpha Opcodes, Prev: Alpha Floating Point, Up: Alpha-Dependent 9.2.5 Alpha Assembler Directives -------------------------------- 'as' for the Alpha supports many additional directives for compatibility with the native assembler. This section describes them only briefly. These are the additional directives in 'as' for the Alpha: '.arch CPU' Specifies the target processor. This is equivalent to the '-mCPU' command-line option. *Note Options: Alpha Options, for a list of values for CPU. '.ent FUNCTION[, N]' Mark the beginning of FUNCTION. An optional number may follow for compatibility with the OSF/1 assembler, but is ignored. When generating '.mdebug' information, this will create a procedure descriptor for the function. In ELF, it will mark the symbol as a function a-la the generic '.type' directive. '.end FUNCTION' Mark the end of FUNCTION. In ELF, it will set the size of the symbol a-la the generic '.size' directive. '.mask MASK, OFFSET' Indicate which of the integer registers are saved in the current function's stack frame. MASK is interpreted a bit mask in which bit N set indicates that register N is saved. The registers are saved in a block located OFFSET bytes from the "canonical frame address" (CFA) which is the value of the stack pointer on entry to the function. The registers are saved sequentially, except that the return address register (normally '$26') is saved first. This and the other directives that describe the stack frame are currently only used when generating '.mdebug' information. They may in the future be used to generate DWARF2 '.debug_frame' unwind information for hand written assembly. '.fmask MASK, OFFSET' Indicate which of the floating-point registers are saved in the current stack frame. The MASK and OFFSET parameters are interpreted as with '.mask'. '.frame FRAMEREG, FRAMEOFFSET, RETREG[, ARGOFFSET]' Describes the shape of the stack frame. The frame pointer in use is FRAMEREG; normally this is either '$fp' or '$sp'. The frame pointer is FRAMEOFFSET bytes below the CFA. The return address is initially located in RETREG until it is saved as indicated in '.mask'. For compatibility with OSF/1 an optional ARGOFFSET parameter is accepted and ignored. It is believed to indicate the offset from the CFA to the saved argument registers. '.prologue N' Indicate that the stack frame is set up and all registers have been spilled. The argument N indicates whether and how the function uses the incoming "procedure vector" (the address of the called function) in '$27'. 0 indicates that '$27' is not used; 1 indicates that the first two instructions of the function use '$27' to perform a load of the GP register; 2 indicates that '$27' is used in some non-standard way and so the linker cannot elide the load of the procedure vector during relaxation. '.usepv FUNCTION, WHICH' Used to indicate the use of the '$27' register, similar to '.prologue', but without the other semantics of needing to be inside an open '.ent'/'.end' block. The WHICH argument should be either 'no', indicating that '$27' is not used, or 'std', indicating that the first two instructions of the function perform a GP load. One might use this directive instead of '.prologue' if you are also using dwarf2 CFI directives. '.gprel32 EXPRESSION' Computes the difference between the address in EXPRESSION and the GP for the current object file, and stores it in 4 bytes. In addition to being smaller than a full 8 byte address, this also does not require a dynamic relocation when used in a shared library. '.t_floating EXPRESSION' Stores EXPRESSION as an IEEE double precision value. '.s_floating EXPRESSION' Stores EXPRESSION as an IEEE single precision value. '.f_floating EXPRESSION' Stores EXPRESSION as a VAX F format value. '.g_floating EXPRESSION' Stores EXPRESSION as a VAX G format value. '.d_floating EXPRESSION' Stores EXPRESSION as a VAX D format value. '.set FEATURE' Enables or disables various assembler features. Using the positive name of the feature enables while using 'noFEATURE' disables. 'at' Indicates that macro expansions may clobber the "assembler temporary" ('$at' or '$28') register. Some macros may not be expanded without this and will generate an error message if 'noat' is in effect. When 'at' is in effect, a warning will be generated if '$at' is used by the programmer. 'macro' Enables the expansion of macro instructions. Note that variants of real instructions, such as 'br label' vs 'br $31,label' are considered alternate forms and not macros. 'move' 'reorder' 'volatile' These control whether and how the assembler may re-order instructions. Accepted for compatibility with the OSF/1 assembler, but 'as' does not do instruction scheduling, so these features are ignored. The following directives are recognized for compatibility with the OSF/1 assembler but are ignored. .proc .aproc .reguse .livereg .option .aent .ugen .eflag .alias .noalias  File: as.info, Node: Alpha Opcodes, Prev: Alpha Directives, Up: Alpha-Dependent 9.2.6 Opcodes ------------- For detailed information on the Alpha machine instruction set, see the Alpha Architecture Handbook (ftp://ftp.digital.com/pub/Digital/info/semiconductor/literature/alphaahb.pdf).  File: as.info, Node: ARC-Dependent, Next: ARM-Dependent, Prev: Alpha-Dependent, Up: Machine Dependencies 9.3 ARC Dependent Features ========================== * Menu: * ARC Options:: Options * ARC Syntax:: Syntax * ARC Directives:: ARC Machine Directives * ARC Modifiers:: ARC Assembler Modifiers * ARC Symbols:: ARC Pre-defined Symbols * ARC Opcodes:: Opcodes  File: as.info, Node: ARC Options, Next: ARC Syntax, Up: ARC-Dependent 9.3.1 Options ------------- The following options control the type of CPU for which code is assembled, and generic constraints on the code generated: '-mcpu=CPU' Set architecture type and register usage for CPU. There are also shortcut alias options available for backward compatibility and convenience. Supported values for CPU are 'arc600' Assemble for ARC 600. Aliases: '-mA6', '-mARC600'. 'arc600_norm' Assemble for ARC 600 with norm instructions. 'arc600_mul64' Assemble for ARC 600 with mul64 instructions. 'arc600_mul32x16' Assemble for ARC 600 with mul32x16 instructions. 'arc601' Assemble for ARC 601. Alias: '-mARC601'. 'arc601_norm' Assemble for ARC 601 with norm instructions. 'arc601_mul64' Assemble for ARC 601 with mul64 instructions. 'arc601_mul32x16' Assemble for ARC 601 with mul32x16 instructions. 'arc700' Assemble for ARC 700. Aliases: '-mA7', '-mARC700'. 'arcem' Assemble for ARC EM. Aliases: '-mEM' 'em' Assemble for ARC EM, identical as arcem variant. 'em4' Assemble for ARC EM with code-density instructions. 'em4_dmips' Assemble for ARC EM with code-density instructions. 'em4_fpus' Assemble for ARC EM with code-density instructions. 'em4_fpuda' Assemble for ARC EM with code-density, and double-precision assist instructions. 'quarkse_em' Assemble for QuarkSE-EM cpu. 'archs' Assemble for ARC HS. Aliases: '-mHS', '-mav2hs'. 'hs' Assemble for ARC HS. 'hs34' Assemble for ARC HS34. 'hs38' Assemble for ARC HS38. 'hs38_linux' Assemble for ARC HS38 with floating point support on. 'nps400' Assemble for ARC 700 with NPS-400 extended instructions. Note: the '.cpu' directive (*note ARC Directives::) can to be used to select a core variant from within assembly code. '-EB' This option specifies that the output generated by the assembler should be marked as being encoded for a big-endian processor. '-EL' This option specifies that the output generated by the assembler should be marked as being encoded for a little-endian processor - this is the default. '-mcode-density' This option turns on Code Density instructions. Only valid for ARC EM processors. '-mrelax' Enable support for assembly-time relaxation. The assembler will replace a longer version of an instruction with a shorter one, whenever it is possible. '-mnps400' Enable support for NPS-400 extended instructions. '-mspfp' Enable support for single-precision floating point instructions. '-mdpfp' Enable support for double-precision floating point instructions. '-mfpuda' Enable support for double-precision assist floating point instructions. Only valid for ARC EM processors.  File: as.info, Node: ARC Syntax, Next: ARC Directives, Prev: ARC Options, Up: ARC-Dependent 9.3.2 Syntax ------------ * Menu: * ARC-Chars:: Special Characters * ARC-Regs:: Register Names  File: as.info, Node: ARC-Chars, Next: ARC-Regs, Up: ARC Syntax 9.3.2.1 Special Characters .......................... '%' A register name can optionally be prefixed by a '%' character. So register '%r0' is equivalent to 'r0' in the assembly code. '#' The presence of a '#' character within a line (but not at the start of a line) indicates the start of a comment that extends to the end of the current line. _Note:_ if a line starts with a '#' character then it can also be a logical line number directive (*note Comments::) or a preprocessor control command (*note Preprocessing::). '@' Prefixing an operand with an '@' specifies that the operand is a symbol and not a register. This is how the assembler disambiguates the use of an ARC register name as a symbol. So the instruction mov r0, @r0 moves the address of symbol 'r0' into register 'r0'. '`' The '`' (backtick) character is used to separate statements on a single line. '-' Used as a separator to obtain a sequence of commands from a C preprocessor macro.  File: as.info, Node: ARC-Regs, Prev: ARC-Chars, Up: ARC Syntax 9.3.2.2 Register Names ...................... The ARC assembler uses the following register names for its core registers: 'r0-r31' The core general registers. Registers 'r26' through 'r31' have special functions, and are usually referred to by those synonyms. 'gp' The global pointer and a synonym for 'r26'. 'fp' The frame pointer and a synonym for 'r27'. 'sp' The stack pointer and a synonym for 'r28'. 'ilink1' For ARC 600 and ARC 700, the level 1 interrupt link register and a synonym for 'r29'. Not supported for ARCv2. 'ilink' For ARCv2, the interrupt link register and a synonym for 'r29'. Not supported for ARC 600 and ARC 700. 'ilink2' For ARC 600 and ARC 700, the level 2 interrupt link register and a synonym for 'r30'. Not supported for ARC v2. 'blink' The link register and a synonym for 'r31'. 'r32-r59' The extension core registers. 'lp_count' The loop count register. 'pcl' The word aligned program counter. In addition the ARC processor has a large number of _auxiliary registers_. The precise set depends on the extensions being supported, but the following baseline set are always defined: 'identity' Processor Identification register. Auxiliary register address 0x4. 'pc' Program Counter. Auxiliary register address 0x6. 'status32' Status register. Auxiliary register address 0x0a. 'bta' Branch Target Address. Auxiliary register address 0x412. 'ecr' Exception Cause Register. Auxiliary register address 0x403. 'int_vector_base' Interrupt Vector Base address. Auxiliary register address 0x25. 'status32_p0' Stored STATUS32 register on entry to level P0 interrupts. Auxiliary register address 0xb. 'aux_user_sp' Saved User Stack Pointer. Auxiliary register address 0xd. 'eret' Exception Return Address. Auxiliary register address 0x400. 'erbta' BTA saved on exception entry. Auxiliary register address 0x401. 'erstatus' STATUS32 saved on exception. Auxiliary register address 0x402. 'bcr_ver' Build Configuration Registers Version. Auxiliary register address 0x60. 'bta_link_build' Build configuration for: BTA Registers. Auxiliary register address 0x63. 'vecbase_ac_build' Build configuration for: Interrupts. Auxiliary register address 0x68. 'rf_build' Build configuration for: Core Registers. Auxiliary register address 0x6e. 'dccm_build' DCCM RAM Configuration Register. Auxiliary register address 0xc1. Additional auxiliary register names are defined according to the processor architecture version and extensions selected by the options.  File: as.info, Node: ARC Directives, Next: ARC Modifiers, Prev: ARC Syntax, Up: ARC-Dependent 9.3.3 ARC Machine Directives ---------------------------- The ARC version of 'as' supports the following additional machine directives: '.lcomm SYMBOL, LENGTH[, ALIGNMENT]' Reserve LENGTH (an absolute expression) bytes for a local common denoted by SYMBOL. The section and value of SYMBOL are those of the new local common. The addresses are allocated in the bss section, so that at run-time the bytes start off zeroed. Since SYMBOL is not declared global, it is normally not visible to 'ld'. The optional third parameter, ALIGNMENT, specifies the desired alignment of the symbol in the bss section, specified as a byte boundary (for example, an alignment of 16 means that the least significant 4 bits of the address should be zero). The alignment must be an absolute expression, and it must be a power of two. If no alignment is specified, as will set the alignment to the largest power of two less than or equal to the size of the symbol, up to a maximum of 16. '.lcommon SYMBOL, LENGTH[, ALIGNMENT]' The same as 'lcomm' directive. '.cpu CPU' The '.cpu' directive must be followed by the desired core version. Permitted values for CPU are: 'ARC600' Assemble for the ARC600 instruction set. 'arc600_norm' Assemble for ARC 600 with norm instructions. 'arc600_mul64' Assemble for ARC 600 with mul64 instructions. 'arc600_mul32x16' Assemble for ARC 600 with mul32x16 instructions. 'arc601' Assemble for ARC 601 instruction set. 'arc601_norm' Assemble for ARC 601 with norm instructions. 'arc601_mul64' Assemble for ARC 601 with mul64 instructions. 'arc601_mul32x16' Assemble for ARC 601 with mul32x16 instructions. 'ARC700' Assemble for the ARC700 instruction set. 'NPS400' Assemble for the NPS400 instruction set. 'EM' Assemble for the ARC EM instruction set. 'arcem' Assemble for ARC EM instruction set 'em4' Assemble for ARC EM with code-density instructions. 'em4_dmips' Assemble for ARC EM with code-density instructions. 'em4_fpus' Assemble for ARC EM with code-density instructions. 'em4_fpuda' Assemble for ARC EM with code-density, and double-precision assist instructions. 'quarkse_em' Assemble for QuarkSE-EM instruction set. 'HS' Assemble for the ARC HS instruction set. 'archs' Assemble for ARC HS instruction set. 'hs' Assemble for ARC HS instruction set. 'hs34' Assemble for ARC HS34 instruction set. 'hs38' Assemble for ARC HS38 instruction set. 'hs38_linux' Assemble for ARC HS38 with floating point support on. Note: the '.cpu' directive overrides the command line option '-mcpu=CPU'; a warning is emitted when the version is not consistent between the two. '.extAuxRegister NAME, ADDR, MODE' Auxiliary registers can be defined in the assembler source code by using this directive. The first parameter, NAME, is the name of the new auxiliary register. The second parameter, ADDR, is address the of the auxiliary register. The third parameter, MODE, specifies whether the register is readable and/or writable and is one of: 'r' Read only; 'w' Write only; 'r|w' Read and write. For example: .extAuxRegister mulhi, 0x12, w specifies a write only extension auxiliary register, MULHI at address 0x12. '.extCondCode SUFFIX, VAL' ARC supports extensible condition codes. This directive defines a new condition code, to be known by the suffix, SUFFIX and will depend on the value, VAL in the condition code. For example: .extCondCode is_busy,0x14 add.is_busy r1,r2,r3 will only execute the 'add' instruction if the condition code value is 0x14. '.extCoreRegister NAME, REGNUM, MODE, SHORTCUT' Specifies an extension core register named NAME as a synonym for the register numbered REGNUM. The register number must be between 32 and 59. The third argument, MODE, indicates whether the register is readable and/or writable and is one of: 'r' Read only; 'w' Write only; 'r|w' Read and write. The final parameter, SHORTCUT indicates whether the register has a short cut in the pipeline. The valid values are: 'can_shortcut' The register has a short cut in the pipeline; 'cannot_shortcut' The register does not have a short cut in the pipeline. For example: .extCoreRegister mlo, 57, r , can_shortcut defines a read only extension core register, 'mlo', which is register 57, and can short cut the pipeline. '.extInstruction NAME, OPCODE, SUBOPCODE, SUFFIXCLASS, SYNTAXCLASS' ARC allows the user to specify extension instructions. These extension instructions are not macros; the assembler creates encodings for use of these instructions according to the specification by the user. The first argument, NAME, gives the name of the instruction. The second argument, OPCODE, is the opcode to be used (bits 31:27 in the encoding). The third argument, SUBOPCODE, is the sub-opcode to be used, but the correct value also depends on the fifth argument, SYNTAXCLASS The fourth argument, SUFFIXCLASS, determines the kinds of suffixes to be allowed. Valid values are: 'SUFFIX_NONE' No suffixes are permitted; 'SUFFIX_COND' Conditional suffixes are permitted; 'SUFFIX_FLAG' Flag setting suffixes are permitted. 'SUFFIX_COND|SUFFIX_FLAG' Both conditional and flag setting suffices are permitted. The fifth and final argument, SYNTAXCLASS, determines the syntax class for the instruction. It can have the following values: 'SYNTAX_2OP' Two Operand Instruction; 'SYNTAX_3OP' Three Operand Instruction. 'SYNTAX_1OP' One Operand Instruction. 'SYNTAX_NOP' No Operand Instruction. The syntax class may be followed by '|' and one of the following modifiers. 'OP1_MUST_BE_IMM' Modifies syntax class 'SYNTAX_3OP', specifying that the first operand of a three-operand instruction must be an immediate (i.e., the result is discarded). This is usually used to set the flags using specific instructions and not retain results. 'OP1_IMM_IMPLIED' Modifies syntax class 'SYNTAX_20P', specifying that there is an implied immediate destination operand which does not appear in the syntax. For example, if the source code contains an instruction like: inst r1,r2 the first argument is an implied immediate (that is, the result is discarded). This is the same as though the source code were: inst 0,r1,r2. For example, defining a 64-bit multiplier with immediate operands: .extInstruction mp64, 0x07, 0x2d, SUFFIX_COND|SUFFIX_FLAG, SYNTAX_3OP|OP1_MUST_BE_IMM which specifies an extension instruction named 'mp64' with 3 operands. It sets the flags and can be used with a condition code, for which the first operand is an immediate, i.e. equivalent to discarding the result of the operation. A two operands instruction variant would be: .extInstruction mul64, 0x07, 0x2d, SUFFIX_COND, SYNTAX_2OP|OP1_IMM_IMPLIED which describes a two operand instruction with an implicit first immediate operand. The result of this operation would be discarded. '.arc_attribute TAG, VALUE' Set the ARC object attribute TAG to VALUE. The TAG is either an attribute number, or one of the following: 'Tag_ARC_PCS_config', 'Tag_ARC_CPU_base', 'Tag_ARC_CPU_variation', 'Tag_ARC_CPU_name', 'Tag_ARC_ABI_rf16', 'Tag_ARC_ABI_osver', 'Tag_ARC_ABI_sda', 'Tag_ARC_ABI_pic', 'Tag_ARC_ABI_tls', 'Tag_ARC_ABI_enumsize', 'Tag_ARC_ABI_exceptions', 'Tag_ARC_ABI_double_size', 'Tag_ARC_ISA_config', 'Tag_ARC_ISA_apex', 'Tag_ARC_ISA_mpy_option' The VALUE is either a 'number', '"string"', or 'number, "string"' depending on the tag.  File: as.info, Node: ARC Modifiers, Next: ARC Symbols, Prev: ARC Directives, Up: ARC-Dependent 9.3.4 ARC Assembler Modifiers ----------------------------- The following additional assembler modifiers have been added for position-independent code. These modifiers are available only with the ARC 700 and above processors and generate relocation entries, which are interpreted by the linker as follows: '@pcl(SYMBOL)' Relative distance of SYMBOL's from the current program counter location. '@gotpc(SYMBOL)' Relative distance of SYMBOL's Global Offset Table entry from the current program counter location. '@gotoff(SYMBOL)' Distance of SYMBOL from the base of the Global Offset Table. '@plt(SYMBOL)' Distance of SYMBOL's Procedure Linkage Table entry from the current program counter. This is valid only with branch and link instructions and PC-relative calls. '@sda(SYMBOL)' Relative distance of SYMBOL from the base of the Small Data Pointer.  File: as.info, Node: ARC Symbols, Next: ARC Opcodes, Prev: ARC Modifiers, Up: ARC-Dependent 9.3.5 ARC Pre-defined Symbols ----------------------------- The following assembler symbols will prove useful when developing position-independent code. These symbols are available only with the ARC 700 and above processors. '__GLOBAL_OFFSET_TABLE__' Symbol referring to the base of the Global Offset Table. '__DYNAMIC__' An alias for the Global Offset Table 'Base__GLOBAL_OFFSET_TABLE__'. It can be used only with '@gotpc' modifiers.  File: as.info, Node: ARC Opcodes, Prev: ARC Symbols, Up: ARC-Dependent 9.3.6 Opcodes ------------- For information on the ARC instruction set, see 'ARC Programmers Reference Manual', available where you download the processor IP library.  File: as.info, Node: ARM-Dependent, Next: AVR-Dependent, Prev: ARC-Dependent, Up: Machine Dependencies 9.4 ARM Dependent Features ========================== * Menu: * ARM Options:: Options * ARM Syntax:: Syntax * ARM Floating Point:: Floating Point * ARM Directives:: ARM Machine Directives * ARM Opcodes:: Opcodes * ARM Mapping Symbols:: Mapping Symbols * ARM Unwinding Tutorial:: Unwinding  File: as.info, Node: ARM Options, Next: ARM Syntax, Up: ARM-Dependent 9.4.1 Options ------------- '-mcpu=PROCESSOR[+EXTENSION...]' This option specifies the target processor. The assembler will issue an error message if an attempt is made to assemble an instruction which will not execute on the target processor. The following processor names are recognized: 'arm1', 'arm2', 'arm250', 'arm3', 'arm6', 'arm60', 'arm600', 'arm610', 'arm620', 'arm7', 'arm7m', 'arm7d', 'arm7dm', 'arm7di', 'arm7dmi', 'arm70', 'arm700', 'arm700i', 'arm710', 'arm710t', 'arm720', 'arm720t', 'arm740t', 'arm710c', 'arm7100', 'arm7500', 'arm7500fe', 'arm7t', 'arm7tdmi', 'arm7tdmi-s', 'arm8', 'arm810', 'strongarm', 'strongarm1', 'strongarm110', 'strongarm1100', 'strongarm1110', 'arm9', 'arm920', 'arm920t', 'arm922t', 'arm940t', 'arm9tdmi', 'fa526' (Faraday FA526 processor), 'fa626' (Faraday FA626 processor), 'arm9e', 'arm926e', 'arm926ej-s', 'arm946e-r0', 'arm946e', 'arm946e-s', 'arm966e-r0', 'arm966e', 'arm966e-s', 'arm968e-s', 'arm10t', 'arm10tdmi', 'arm10e', 'arm1020', 'arm1020t', 'arm1020e', 'arm1022e', 'arm1026ej-s', 'fa606te' (Faraday FA606TE processor), 'fa616te' (Faraday FA616TE processor), 'fa626te' (Faraday FA626TE processor), 'fmp626' (Faraday FMP626 processor), 'fa726te' (Faraday FA726TE processor), 'arm1136j-s', 'arm1136jf-s', 'arm1156t2-s', 'arm1156t2f-s', 'arm1176jz-s', 'arm1176jzf-s', 'mpcore', 'mpcorenovfp', 'cortex-a5', 'cortex-a7', 'cortex-a8', 'cortex-a9', 'cortex-a15', 'cortex-a17', 'cortex-a32', 'cortex-a35', 'cortex-a53', 'cortex-a55', 'cortex-a57', 'cortex-a72', 'cortex-a73', 'cortex-a75', 'cortex-a76', 'cortex-r4', 'cortex-r4f', 'cortex-r5', 'cortex-r7', 'cortex-r8', 'cortex-r52', 'cortex-m33', 'cortex-m23', 'cortex-m7', 'cortex-m4', 'cortex-m3', 'cortex-m1', 'cortex-m0', 'cortex-m0plus', 'exynos-m1', 'marvell-pj4', 'marvell-whitney', 'xgene1', 'xgene2', 'ep9312' (ARM920 with Cirrus Maverick coprocessor), 'i80200' (Intel XScale processor) 'iwmmxt' (Intel(r) XScale processor with Wireless MMX(tm) technology coprocessor) and 'xscale'. The special name 'all' may be used to allow the assembler to accept instructions valid for any ARM processor. In addition to the basic instruction set, the assembler can be told to accept various extension mnemonics that extend the processor using the co-processor instruction space. For example, '-mcpu=arm920+maverick' is equivalent to specifying '-mcpu=ep9312'. Multiple extensions may be specified, separated by a '+'. The extensions should be specified in ascending alphabetical order. Some extensions may be restricted to particular architectures; this is documented in the list of extensions below. Extension mnemonics may also be removed from those the assembler accepts. This is done be prepending 'no' to the option that adds the extension. Extensions that are removed should be listed after all extensions which have been added, again in ascending alphabetical order. For example, '-mcpu=ep9312+nomaverick' is equivalent to specifying '-mcpu=arm920'. The following extensions are currently supported: 'crc' 'crypto' (Cryptography Extensions for v8-A architecture, implies 'fp+simd'), 'dotprod' (Dot Product Extensions for v8.2-A architecture, implies 'fp+simd'), 'fp' (Floating Point Extensions for v8-A architecture), 'fp16' (FP16 Extensions for v8.2-A architecture, implies 'fp'), 'fp16fml' (FP16 Floating Point Multiplication Variant Extensions for v8.2-A architecture, implies 'fp16'), 'idiv' (Integer Divide Extensions for v7-A and v7-R architectures), 'iwmmxt', 'iwmmxt2', 'xscale', 'maverick', 'mp' (Multiprocessing Extensions for v7-A and v7-R architectures), 'os' (Operating System for v6M architecture), 'sec' (Security Extensions for v6K and v7-A architectures), 'simd' (Advanced SIMD Extensions for v8-A architecture, implies 'fp'), 'virt' (Virtualization Extensions for v7-A architecture, implies 'idiv'), 'pan' (Privileged Access Never Extensions for v8-A architecture), 'ras' (Reliability, Availability and Serviceability extensions for v8-A architecture), 'rdma' (ARMv8.1 Advanced SIMD extensions for v8-A architecture, implies 'simd') and 'xscale'. '-march=ARCHITECTURE[+EXTENSION...]' This option specifies the target architecture. The assembler will issue an error message if an attempt is made to assemble an instruction which will not execute on the target architecture. The following architecture names are recognized: 'armv1', 'armv2', 'armv2a', 'armv2s', 'armv3', 'armv3m', 'armv4', 'armv4xm', 'armv4t', 'armv4txm', 'armv5', 'armv5t', 'armv5txm', 'armv5te', 'armv5texp', 'armv6', 'armv6j', 'armv6k', 'armv6z', 'armv6kz', 'armv6-m', 'armv6s-m', 'armv7', 'armv7-a', 'armv7ve', 'armv7-r', 'armv7-m', 'armv7e-m', 'armv8-a', 'armv8.1-a', 'armv8.2-a', 'armv8.3-a', 'armv8-r', 'armv8.4-a', 'iwmmxt' 'iwmmxt2' and 'xscale'. If both '-mcpu' and '-march' are specified, the assembler will use the setting for '-mcpu'. The architecture option can be extended with the same instruction set extension options as the '-mcpu' option. '-mfpu=FLOATING-POINT-FORMAT' This option specifies the floating point format to assemble for. The assembler will issue an error message if an attempt is made to assemble an instruction which will not execute on the target floating point unit. The following format options are recognized: 'softfpa', 'fpe', 'fpe2', 'fpe3', 'fpa', 'fpa10', 'fpa11', 'arm7500fe', 'softvfp', 'softvfp+vfp', 'vfp', 'vfp10', 'vfp10-r0', 'vfp9', 'vfpxd', 'vfpv2', 'vfpv3', 'vfpv3-fp16', 'vfpv3-d16', 'vfpv3-d16-fp16', 'vfpv3xd', 'vfpv3xd-d16', 'vfpv4', 'vfpv4-d16', 'fpv4-sp-d16', 'fpv5-sp-d16', 'fpv5-d16', 'fp-armv8', 'arm1020t', 'arm1020e', 'arm1136jf-s', 'maverick', 'neon', 'neon-vfpv3', 'neon-fp16', 'neon-vfpv4', 'neon-fp-armv8', 'crypto-neon-fp-armv8', 'neon-fp-armv8.1' and 'crypto-neon-fp-armv8.1'. In addition to determining which instructions are assembled, this option also affects the way in which the '.double' assembler directive behaves when assembling little-endian code. The default is dependent on the processor selected. For Architecture 5 or later, the default is to assemble for VFP instructions; for earlier architectures the default is to assemble for FPA instructions. '-mthumb' This option specifies that the assembler should start assembling Thumb instructions; that is, it should behave as though the file starts with a '.code 16' directive. '-mthumb-interwork' This option specifies that the output generated by the assembler should be marked as supporting interworking. It also affects the behaviour of the 'ADR' and 'ADRL' pseudo opcodes. '-mimplicit-it=never' '-mimplicit-it=always' '-mimplicit-it=arm' '-mimplicit-it=thumb' The '-mimplicit-it' option controls the behavior of the assembler when conditional instructions are not enclosed in IT blocks. There are four possible behaviors. If 'never' is specified, such constructs cause a warning in ARM code and an error in Thumb-2 code. If 'always' is specified, such constructs are accepted in both ARM and Thumb-2 code, where the IT instruction is added implicitly. If 'arm' is specified, such constructs are accepted in ARM code and cause an error in Thumb-2 code. If 'thumb' is specified, such constructs cause a warning in ARM code and are accepted in Thumb-2 code. If you omit this option, the behavior is equivalent to '-mimplicit-it=arm'. '-mapcs-26' '-mapcs-32' These options specify that the output generated by the assembler should be marked as supporting the indicated version of the Arm Procedure. Calling Standard. '-matpcs' This option specifies that the output generated by the assembler should be marked as supporting the Arm/Thumb Procedure Calling Standard. If enabled this option will cause the assembler to create an empty debugging section in the object file called .arm.atpcs. Debuggers can use this to determine the ABI being used by. '-mapcs-float' This indicates the floating point variant of the APCS should be used. In this variant floating point arguments are passed in FP registers rather than integer registers. '-mapcs-reentrant' This indicates that the reentrant variant of the APCS should be used. This variant supports position independent code. '-mfloat-abi=ABI' This option specifies that the output generated by the assembler should be marked as using specified floating point ABI. The following values are recognized: 'soft', 'softfp' and 'hard'. '-meabi=VER' This option specifies which EABI version the produced object files should conform to. The following values are recognized: 'gnu', '4' and '5'. '-EB' This option specifies that the output generated by the assembler should be marked as being encoded for a big-endian processor. Note: If a program is being built for a system with big-endian data and little-endian instructions then it should be assembled with the '-EB' option, (all of it, code and data) and then linked with the '--be8' option. This will reverse the endianness of the instructions back to little-endian, but leave the data as big-endian. '-EL' This option specifies that the output generated by the assembler should be marked as being encoded for a little-endian processor. '-k' This option specifies that the output of the assembler should be marked as position-independent code (PIC). '--fix-v4bx' Allow 'BX' instructions in ARMv4 code. This is intended for use with the linker option of the same name. '-mwarn-deprecated' '-mno-warn-deprecated' Enable or disable warnings about using deprecated options or features. The default is to warn. '-mccs' Turns on CodeComposer Studio assembly syntax compatibility mode. '-mwarn-syms' '-mno-warn-syms' Enable or disable warnings about symbols that match the names of ARM instructions. The default is to warn.  File: as.info, Node: ARM Syntax, Next: ARM Floating Point, Prev: ARM Options, Up: ARM-Dependent 9.4.2 Syntax ------------ * Menu: * ARM-Instruction-Set:: Instruction Set * ARM-Chars:: Special Characters * ARM-Regs:: Register Names * ARM-Relocations:: Relocations * ARM-Neon-Alignment:: NEON Alignment Specifiers  File: as.info, Node: ARM-Instruction-Set, Next: ARM-Chars, Up: ARM Syntax 9.4.2.1 Instruction Set Syntax .............................. Two slightly different syntaxes are support for ARM and THUMB instructions. The default, 'divided', uses the old style where ARM and THUMB instructions had their own, separate syntaxes. The new, 'unified' syntax, which can be selected via the '.syntax' directive, and has the following main features: * Immediate operands do not require a '#' prefix. * The 'IT' instruction may appear, and if it does it is validated against subsequent conditional affixes. In ARM mode it does not generate machine code, in THUMB mode it does. * For ARM instructions the conditional affixes always appear at the end of the instruction. For THUMB instructions conditional affixes can be used, but only inside the scope of an 'IT' instruction. * All of the instructions new to the V6T2 architecture (and later) are available. (Only a few such instructions can be written in the 'divided' syntax). * The '.N' and '.W' suffixes are recognized and honored. * All instructions set the flags if and only if they have an 's' affix.  File: as.info, Node: ARM-Chars, Next: ARM-Regs, Prev: ARM-Instruction-Set, Up: ARM Syntax 9.4.2.2 Special Characters .......................... The presence of a '@' anywhere on a line indicates the start of a comment that extends to the end of that line. If a '#' appears as the first character of a line then the whole line is treated as a comment, but in this case the line could also be a logical line number directive (*note Comments::) or a preprocessor control command (*note Preprocessing::). The ';' character can be used instead of a newline to separate statements. Either '#' or '$' can be used to indicate immediate operands. *TODO* Explain about /data modifier on symbols.  File: as.info, Node: ARM-Regs, Next: ARM-Relocations, Prev: ARM-Chars, Up: ARM Syntax 9.4.2.3 Register Names ...................... *TODO* Explain about ARM register naming, and the predefined names.  File: as.info, Node: ARM-Relocations, Next: ARM-Neon-Alignment, Prev: ARM-Regs, Up: ARM Syntax 9.4.2.4 ARM relocation generation ................................. Specific data relocations can be generated by putting the relocation name in parentheses after the symbol name. For example: .word foo(TARGET1) This will generate an 'R_ARM_TARGET1' relocation against the symbol FOO. The following relocations are supported: 'GOT', 'GOTOFF', 'TARGET1', 'TARGET2', 'SBREL', 'TLSGD', 'TLSLDM', 'TLSLDO', 'TLSDESC', 'TLSCALL', 'GOTTPOFF', 'GOT_PREL' and 'TPOFF'. For compatibility with older toolchains the assembler also accepts '(PLT)' after branch targets. On legacy targets this will generate the deprecated 'R_ARM_PLT32' relocation. On EABI targets it will encode either the 'R_ARM_CALL' or 'R_ARM_JUMP24' relocation, as appropriate. Relocations for 'MOVW' and 'MOVT' instructions can be generated by prefixing the value with '#:lower16:' and '#:upper16' respectively. For example to load the 32-bit address of foo into r0: MOVW r0, #:lower16:foo MOVT r0, #:upper16:foo Relocations 'R_ARM_THM_ALU_ABS_G0_NC', 'R_ARM_THM_ALU_ABS_G1_NC', 'R_ARM_THM_ALU_ABS_G2_NC' and 'R_ARM_THM_ALU_ABS_G3_NC' can be generated by prefixing the value with '#:lower0_7:#', '#:lower8_15:#', '#:upper0_7:#' and '#:upper8_15:#' respectively. For example to load the 32-bit address of foo into r0: MOVS r0, #:upper8_15:#foo LSLS r0, r0, #8 ADDS r0, #:upper0_7:#foo LSLS r0, r0, #8 ADDS r0, #:lower8_15:#foo LSLS r0, r0, #8 ADDS r0, #:lower0_7:#foo  File: as.info, Node: ARM-Neon-Alignment, Prev: ARM-Relocations, Up: ARM Syntax 9.4.2.5 NEON Alignment Specifiers ................................. Some NEON load/store instructions allow an optional address alignment qualifier. The ARM documentation specifies that this is indicated by '@ ALIGN'. However GAS already interprets the '@' character as a "line comment" start, so ': ALIGN' is used instead. For example: vld1.8 {q0}, [r0, :128]  File: as.info, Node: ARM Floating Point, Next: ARM Directives, Prev: ARM Syntax, Up: ARM-Dependent 9.4.3 Floating Point -------------------- The ARM family uses IEEE floating-point numbers.  File: as.info, Node: ARM Directives, Next: ARM Opcodes, Prev: ARM Floating Point, Up: ARM-Dependent 9.4.4 ARM Machine Directives ---------------------------- '.align EXPRESSION [, EXPRESSION]' This is the generic .ALIGN directive. For the ARM however if the first argument is zero (ie no alignment is needed) the assembler will behave as if the argument had been 2 (ie pad to the next four byte boundary). This is for compatibility with ARM's own assembler. '.arch NAME' Select the target architecture. Valid values for NAME are the same as for the '-march' commandline option. Specifying '.arch' clears any previously selected architecture extensions. '.arch_extension NAME' Add or remove an architecture extension to the target architecture. Valid values for NAME are the same as those accepted as architectural extensions by the '-mcpu' and '-march' commandline options. '.arch_extension' may be used multiple times to add or remove extensions incrementally to the architecture being compiled for. '.arm' This performs the same action as .CODE 32. '.bss' This directive switches to the '.bss' section. '.cantunwind' Prevents unwinding through the current function. No personality routine or exception table data is required or permitted. '.code [16|32]' This directive selects the instruction set being generated. The value 16 selects Thumb, with the value 32 selecting ARM. '.cpu NAME' Select the target processor. Valid values for NAME are the same as for the '-mcpu' commandline option. Specifying '.cpu' clears any previously selected architecture extensions. 'NAME .dn REGISTER NAME [.TYPE] [[INDEX]]' 'NAME .qn REGISTER NAME [.TYPE] [[INDEX]]' The 'dn' and 'qn' directives are used to create typed and/or indexed register aliases for use in Advanced SIMD Extension (Neon) instructions. The former should be used to create aliases of double-precision registers, and the latter to create aliases of quad-precision registers. If these directives are used to create typed aliases, those aliases can be used in Neon instructions instead of writing types after the mnemonic or after each operand. For example: x .dn d2.f32 y .dn d3.f32 z .dn d4.f32[1] vmul x,y,z This is equivalent to writing the following: vmul.f32 d2,d3,d4[1] Aliases created using 'dn' or 'qn' can be destroyed using 'unreq'. '.eabi_attribute TAG, VALUE' Set the EABI object attribute TAG to VALUE. The TAG is either an attribute number, or one of the following: 'Tag_CPU_raw_name', 'Tag_CPU_name', 'Tag_CPU_arch', 'Tag_CPU_arch_profile', 'Tag_ARM_ISA_use', 'Tag_THUMB_ISA_use', 'Tag_FP_arch', 'Tag_WMMX_arch', 'Tag_Advanced_SIMD_arch', 'Tag_PCS_config', 'Tag_ABI_PCS_R9_use', 'Tag_ABI_PCS_RW_data', 'Tag_ABI_PCS_RO_data', 'Tag_ABI_PCS_GOT_use', 'Tag_ABI_PCS_wchar_t', 'Tag_ABI_FP_rounding', 'Tag_ABI_FP_denormal', 'Tag_ABI_FP_exceptions', 'Tag_ABI_FP_user_exceptions', 'Tag_ABI_FP_number_model', 'Tag_ABI_align_needed', 'Tag_ABI_align_preserved', 'Tag_ABI_enum_size', 'Tag_ABI_HardFP_use', 'Tag_ABI_VFP_args', 'Tag_ABI_WMMX_args', 'Tag_ABI_optimization_goals', 'Tag_ABI_FP_optimization_goals', 'Tag_compatibility', 'Tag_CPU_unaligned_access', 'Tag_FP_HP_extension', 'Tag_ABI_FP_16bit_format', 'Tag_MPextension_use', 'Tag_DIV_use', 'Tag_nodefaults', 'Tag_also_compatible_with', 'Tag_conformance', 'Tag_T2EE_use', 'Tag_Virtualization_use' The VALUE is either a 'number', '"string"', or 'number, "string"' depending on the tag. Note - the following legacy values are also accepted by TAG: 'Tag_VFP_arch', 'Tag_ABI_align8_needed', 'Tag_ABI_align8_preserved', 'Tag_VFP_HP_extension', '.even' This directive aligns to an even-numbered address. '.extend EXPRESSION [, EXPRESSION]*' '.ldouble EXPRESSION [, EXPRESSION]*' These directives write 12byte long double floating-point values to the output section. These are not compatible with current ARM processors or ABIs. '.fnend' Marks the end of a function with an unwind table entry. The unwind index table entry is created when this directive is processed. If no personality routine has been specified then standard personality routine 0 or 1 will be used, depending on the number of unwind opcodes required. '.fnstart' Marks the start of a function with an unwind table entry. '.force_thumb' This directive forces the selection of Thumb instructions, even if the target processor does not support those instructions '.fpu NAME' Select the floating-point unit to assemble for. Valid values for NAME are the same as for the '-mfpu' commandline option. '.handlerdata' Marks the end of the current function, and the start of the exception table entry for that function. Anything between this directive and the '.fnend' directive will be added to the exception table entry. Must be preceded by a '.personality' or '.personalityindex' directive. '.inst OPCODE [ , ... ]' '.inst.n OPCODE [ , ... ]' '.inst.w OPCODE [ , ... ]' Generates the instruction corresponding to the numerical value OPCODE. '.inst.n' and '.inst.w' allow the Thumb instruction size to be specified explicitly, overriding the normal encoding rules. '.ldouble EXPRESSION [, EXPRESSION]*' See '.extend'. '.ltorg' This directive causes the current contents of the literal pool to be dumped into the current section (which is assumed to be the .text section) at the current location (aligned to a word boundary). 'GAS' maintains a separate literal pool for each section and each sub-section. The '.ltorg' directive will only affect the literal pool of the current section and sub-section. At the end of assembly all remaining, un-empty literal pools will automatically be dumped. Note - older versions of 'GAS' would dump the current literal pool any time a section change occurred. This is no longer done, since it prevents accurate control of the placement of literal pools. '.movsp REG [, #OFFSET]' Tell the unwinder that REG contains an offset from the current stack pointer. If OFFSET is not specified then it is assumed to be zero. '.object_arch NAME' Override the architecture recorded in the EABI object attribute section. Valid values for NAME are the same as for the '.arch' directive. Typically this is useful when code uses runtime detection of CPU features. '.packed EXPRESSION [, EXPRESSION]*' This directive writes 12-byte packed floating-point values to the output section. These are not compatible with current ARM processors or ABIs. '.pad #COUNT' Generate unwinder annotations for a stack adjustment of COUNT bytes. A positive value indicates the function prologue allocated stack space by decrementing the stack pointer. '.personality NAME' Sets the personality routine for the current function to NAME. '.personalityindex INDEX' Sets the personality routine for the current function to the EABI standard routine number INDEX '.pool' This is a synonym for .ltorg. 'NAME .req REGISTER NAME' This creates an alias for REGISTER NAME called NAME. For example: foo .req r0 '.save REGLIST' Generate unwinder annotations to restore the registers in REGLIST. The format of REGLIST is the same as the corresponding store-multiple instruction. _core registers_ .save {r4, r5, r6, lr} stmfd sp!, {r4, r5, r6, lr} _FPA registers_ .save f4, 2 sfmfd f4, 2, [sp]! _VFP registers_ .save {d8, d9, d10} fstmdx sp!, {d8, d9, d10} _iWMMXt registers_ .save {wr10, wr11} wstrd wr11, [sp, #-8]! wstrd wr10, [sp, #-8]! or .save wr11 wstrd wr11, [sp, #-8]! .save wr10 wstrd wr10, [sp, #-8]! '.setfp FPREG, SPREG [, #OFFSET]' Make all unwinder annotations relative to a frame pointer. Without this the unwinder will use offsets from the stack pointer. The syntax of this directive is the same as the 'add' or 'mov' instruction used to set the frame pointer. SPREG must be either 'sp' or mentioned in a previous '.movsp' directive. .movsp ip mov ip, sp ... .setfp fp, ip, #4 add fp, ip, #4 '.secrel32 EXPRESSION [, EXPRESSION]*' This directive emits relocations that evaluate to the section-relative offset of each expression's symbol. This directive is only supported for PE targets. '.syntax [unified | divided]' This directive sets the Instruction Set Syntax as described in the *note ARM-Instruction-Set:: section. '.thumb' This performs the same action as .CODE 16. '.thumb_func' This directive specifies that the following symbol is the name of a Thumb encoded function. This information is necessary in order to allow the assembler and linker to generate correct code for interworking between Arm and Thumb instructions and should be used even if interworking is not going to be performed. The presence of this directive also implies '.thumb' This directive is not necessary when generating EABI objects. On these targets the encoding is implicit when generating Thumb code. '.thumb_set' This performs the equivalent of a '.set' directive in that it creates a symbol which is an alias for another symbol (possibly not yet defined). This directive also has the added property in that it marks the aliased symbol as being a thumb function entry point, in the same way that the '.thumb_func' directive does. '.tlsdescseq TLS-VARIABLE' This directive is used to annotate parts of an inlined TLS descriptor trampoline. Normally the trampoline is provided by the linker, and this directive is not needed. '.unreq ALIAS-NAME' This undefines a register alias which was previously defined using the 'req', 'dn' or 'qn' directives. For example: foo .req r0 .unreq foo An error occurs if the name is undefined. Note - this pseudo op can be used to delete builtin in register name aliases (eg 'r0'). This should only be done if it is really necessary. '.unwind_raw OFFSET, BYTE1, ...' Insert one of more arbitrary unwind opcode bytes, which are known to adjust the stack pointer by OFFSET bytes. For example '.unwind_raw 4, 0xb1, 0x01' is equivalent to '.save {r0}' '.vsave VFP-REGLIST' Generate unwinder annotations to restore the VFP registers in VFP-REGLIST using FLDMD. Also works for VFPv3 registers that are to be restored using VLDM. The format of VFP-REGLIST is the same as the corresponding store-multiple instruction. _VFP registers_ .vsave {d8, d9, d10} fstmdd sp!, {d8, d9, d10} _VFPv3 registers_ .vsave {d15, d16, d17} vstm sp!, {d15, d16, d17} Since FLDMX and FSTMX are now deprecated, this directive should be used in favour of '.save' for saving VFP registers for ARMv6 and above.  File: as.info, Node: ARM Opcodes, Next: ARM Mapping Symbols, Prev: ARM Directives, Up: ARM-Dependent 9.4.5 Opcodes ------------- 'as' implements all the standard ARM opcodes. It also implements several pseudo opcodes, including several synthetic load instructions. 'NOP' nop This pseudo op will always evaluate to a legal ARM instruction that does nothing. Currently it will evaluate to MOV r0, r0. 'LDR' ldr , = If expression evaluates to a numeric constant then a MOV or MVN instruction will be used in place of the LDR instruction, if the constant can be generated by either of these instructions. Otherwise the constant will be placed into the nearest literal pool (if it not already there) and a PC relative LDR instruction will be generated. 'ADR' adr