1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2023 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2023 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2023 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]]
231 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
234 [@b{--debug-prefix-map} @var{old}=@var{new}]
235 [@b{--defsym} @var{sym}=@var{val}]
236 [@b{--elf-stt-common=[no|yes]}]
237 [@b{--emulation}=@var{name}]
239 [@b{-g}] [@b{--gstabs}] [@b{--gstabs+}]
240 [@b{--gdwarf-<N>}] [@b{--gdwarf-sections}]
241 [@b{--gdwarf-cie-version}=@var{VERSION}]
242 [@b{--generate-missing-build-notes=[no|yes]}]
244 [@b{--hash-size}=@var{N}]
245 [@b{--help}] [@b{--target-help}]
251 [@b{--listing-lhs-width}=@var{NUM}]
252 [@b{--listing-lhs-width2}=@var{NUM}]
253 [@b{--listing-rhs-width}=@var{NUM}]
254 [@b{--listing-cont-lines}=@var{NUM}]
255 [@b{--multibyte-handling=[allow|warn|warn-sym-only]}]
256 [@b{--no-pad-sections}]
257 [@b{-o} @var{objfile}] [@b{-R}]
258 [@b{--sectname-subst}]
259 [@b{--size-check=[error|warning]}]
261 [@b{-v}] [@b{-version}] [@b{--version}]
262 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
263 [@b{-Z}] [@b{@@@var{FILE}}]
264 [@var{target-options}]
265 [@b{--}|@var{files} @dots{}]
268 @c Target dependent options are listed below. Keep the list sorted.
269 @c Add an empty line for separation.
273 @emph{Target AArch64 options:}
275 [@b{-mabi}=@var{ABI}]
279 @emph{Target Alpha options:}
281 [@b{-mdebug} | @b{-no-mdebug}]
282 [@b{-replace} | @b{-noreplace}]
283 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
284 [@b{-F}] [@b{-32addr}]
288 @emph{Target ARC options:}
289 [@b{-mcpu=@var{cpu}}]
290 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
297 @emph{Target ARM options:}
298 @c Don't document the deprecated options
299 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
300 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
301 [@b{-mfpu}=@var{floating-point-format}]
302 [@b{-mfloat-abi}=@var{abi}]
303 [@b{-meabi}=@var{ver}]
306 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
307 @b{-mapcs-reentrant}]
308 [@b{-mthumb-interwork}] [@b{-k}]
312 @emph{Target Blackfin options:}
313 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
320 @emph{Target BPF options:}
325 @emph{Target CRIS options:}
326 [@b{--underscore} | @b{--no-underscore}]
328 [@b{--emulation=criself} | @b{--emulation=crisaout}]
329 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
330 @c Deprecated -- deliberately not documented.
335 @emph{Target C-SKY options:}
336 [@b{-march=@var{arch}}] [@b{-mcpu=@var{cpu}}]
337 [@b{-EL}] [@b{-mlittle-endian}] [@b{-EB}] [@b{-mbig-endian}]
338 [@b{-fpic}] [@b{-pic}]
339 [@b{-mljump}] [@b{-mno-ljump}]
340 [@b{-force2bsr}] [@b{-mforce2bsr}] [@b{-no-force2bsr}] [@b{-mno-force2bsr}]
341 [@b{-jsri2bsr}] [@b{-mjsri2bsr}] [@b{-no-jsri2bsr }] [@b{-mno-jsri2bsr}]
342 [@b{-mnolrw }] [@b{-mno-lrw}]
343 [@b{-melrw}] [@b{-mno-elrw}]
344 [@b{-mlaf }] [@b{-mliterals-after-func}]
345 [@b{-mno-laf}] [@b{-mno-literals-after-func}]
346 [@b{-mlabr}] [@b{-mliterals-after-br}]
347 [@b{-mno-labr}] [@b{-mnoliterals-after-br}]
348 [@b{-mistack}] [@b{-mno-istack}]
349 [@b{-mhard-float}] [@b{-mmp}] [@b{-mcp}] [@b{-mcache}]
350 [@b{-msecurity}] [@b{-mtrust}]
351 [@b{-mdsp}] [@b{-medsp}] [@b{-mvdsp}]
355 @emph{Target D10V options:}
360 @emph{Target D30V options:}
361 [@b{-O}|@b{-n}|@b{-N}]
365 @emph{Target EPIPHANY options:}
366 [@b{-mepiphany}|@b{-mepiphany16}]
370 @emph{Target H8/300 options:}
374 @c HPPA has no machine-dependent assembler options (yet).
378 @emph{Target i386 options:}
379 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
380 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
384 @emph{Target IA-64 options:}
385 [@b{-mconstant-gp}|@b{-mauto-pic}]
386 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
388 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
389 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
390 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
391 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
395 @emph{Target IP2K options:}
396 [@b{-mip2022}|@b{-mip2022ext}]
400 @emph{Target LOONGARCH options:}
401 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
405 @emph{Target M32C options:}
406 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
410 @emph{Target M32R options:}
411 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
416 @emph{Target M680X0 options:}
417 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
421 @emph{Target M68HC11 options:}
422 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
423 [@b{-mshort}|@b{-mlong}]
424 [@b{-mshort-double}|@b{-mlong-double}]
425 [@b{--force-long-branches}] [@b{--short-branches}]
426 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
427 [@b{--print-opcodes}] [@b{--generate-example}]
431 @emph{Target MCORE options:}
432 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
433 [@b{-mcpu=[210|340]}]
437 @emph{Target Meta options:}
438 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
441 @emph{Target MICROBLAZE options:}
442 @c MicroBlaze has no machine-dependent assembler options.
446 @emph{Target MIPS options:}
447 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
448 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
449 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
450 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
451 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
452 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
453 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
454 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
455 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
456 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
457 [@b{-construct-floats}] [@b{-no-construct-floats}]
458 [@b{-mignore-branch-isa}] [@b{-mno-ignore-branch-isa}]
459 [@b{-mnan=@var{encoding}}]
460 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
461 [@b{-mips16}] [@b{-no-mips16}]
462 [@b{-mmips16e2}] [@b{-mno-mips16e2}]
463 [@b{-mmicromips}] [@b{-mno-micromips}]
464 [@b{-msmartmips}] [@b{-mno-smartmips}]
465 [@b{-mips3d}] [@b{-no-mips3d}]
466 [@b{-mdmx}] [@b{-no-mdmx}]
467 [@b{-mdsp}] [@b{-mno-dsp}]
468 [@b{-mdspr2}] [@b{-mno-dspr2}]
469 [@b{-mdspr3}] [@b{-mno-dspr3}]
470 [@b{-mmsa}] [@b{-mno-msa}]
471 [@b{-mxpa}] [@b{-mno-xpa}]
472 [@b{-mmt}] [@b{-mno-mt}]
473 [@b{-mmcu}] [@b{-mno-mcu}]
474 [@b{-mcrc}] [@b{-mno-crc}]
475 [@b{-mginv}] [@b{-mno-ginv}]
476 [@b{-mloongson-mmi}] [@b{-mno-loongson-mmi}]
477 [@b{-mloongson-cam}] [@b{-mno-loongson-cam}]
478 [@b{-mloongson-ext}] [@b{-mno-loongson-ext}]
479 [@b{-mloongson-ext2}] [@b{-mno-loongson-ext2}]
480 [@b{-minsn32}] [@b{-mno-insn32}]
481 [@b{-mfix7000}] [@b{-mno-fix7000}]
482 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
483 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
484 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
485 [@b{-mfix-r5900}] [@b{-mno-fix-r5900}]
486 [@b{-mdebug}] [@b{-no-mdebug}]
487 [@b{-mpdr}] [@b{-mno-pdr}]
491 @emph{Target MMIX options:}
492 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
493 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
494 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
495 [@b{--linker-allocated-gregs}]
499 @emph{Target Nios II options:}
500 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
505 @emph{Target NDS32 options:}
506 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
507 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
508 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
509 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
510 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
511 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
512 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
516 @c OpenRISC has no machine-dependent assembler options.
520 @emph{Target PDP11 options:}
521 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
522 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
523 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
527 @emph{Target picoJava options:}
532 @emph{Target PowerPC options:}
534 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
535 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mgekko}|
536 @b{-mbroadway}|@b{-mppc64}|@b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|
537 @b{-me6500}|@b{-mppc64bridge}|@b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|
538 @b{-mpower6}|@b{-mpwr6}|@b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
539 @b{-mcell}|@b{-mspe}|@b{-mspe2}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
540 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
541 [@b{-mregnames}|@b{-mno-regnames}]
542 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
543 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
544 [@b{-msolaris}|@b{-mno-solaris}]
545 [@b{-nops=@var{count}}]
549 @emph{Target PRU options:}
552 [@b{-mno-warn-regname-label}]
556 @emph{Target RISC-V options:}
557 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
558 [@b{-march}=@var{ISA}]
559 [@b{-mabi}=@var{ABI}]
560 [@b{-mlittle-endian}|@b{-mbig-endian}]
564 @emph{Target RL78 options:}
566 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
570 @emph{Target RX options:}
571 [@b{-mlittle-endian}|@b{-mbig-endian}]
572 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
573 [@b{-muse-conventional-section-names}]
574 [@b{-msmall-data-limit}]
577 [@b{-mint-register=@var{number}}]
578 [@b{-mgcc-abi}|@b{-mrx-abi}]
582 @emph{Target s390 options:}
583 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
584 [@b{-mregnames}|@b{-mno-regnames}]
585 [@b{-mwarn-areg-zero}]
589 @emph{Target SCORE options:}
590 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
591 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
592 [@b{-march=score7}][@b{-march=score3}]
593 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
597 @emph{Target SPARC options:}
598 @c The order here is important. See c-sparc.texi.
599 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
600 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
601 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
602 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
603 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
604 @b{-Asparcvisr}|@b{-Asparc5}]
605 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
606 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
607 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
608 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
609 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
610 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
613 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
617 @emph{Target TIC54X options:}
618 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
619 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
623 @emph{Target TIC6X options:}
624 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
625 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
626 [@b{-mpic}|@b{-mno-pic}]
630 @emph{Target TILE-Gx options:}
631 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
634 @c TILEPro has no machine-dependent assembler options
638 @emph{Target Visium options:}
639 [@b{-mtune=@var{arch}}]
643 @emph{Target Xtensa options:}
644 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
645 [@b{--[no-]absolute-literals}]
646 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
647 [@b{--[no-]transform}]
648 [@b{--rename-section} @var{oldname}=@var{newname}]
649 [@b{--[no-]trampolines}]
650 [@b{--abi-windowed}|@b{--abi-call0}]
654 @emph{Target Z80 options:}
655 [@b{-march=@var{CPU}@var{[-EXT]}@var{[+EXT]}}]
656 [@b{-local-prefix=}@var{PREFIX}]
659 [@b{-fp-s=}@var{FORMAT}]
660 [@b{-fp-d=}@var{FORMAT}]
664 @c Z8000 has no machine-dependent assembler options
673 @include at-file.texi
676 Turn on listings, in any of a variety of ways:
680 omit false conditionals
683 omit debugging directives
686 include general information, like @value{AS} version and options passed
689 include high-level source
695 include macro expansions
698 omit forms processing
704 set the name of the listing file
707 You may combine these options; for example, use @samp{-aln} for assembly
708 listing without forms processing. The @samp{=file} option, if used, must be
709 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
712 Begin in alternate macro mode.
714 @xref{Altmacro,,@code{.altmacro}}.
717 @item --compress-debug-sections
718 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
719 ELF ABI. The resulting object file may not be compatible with older
720 linkers and object file utilities. Note if compression would make a
721 given section @emph{larger} then it is not compressed.
724 @cindex @samp{--compress-debug-sections=} option
725 @item --compress-debug-sections=none
726 @itemx --compress-debug-sections=zlib
727 @itemx --compress-debug-sections=zlib-gnu
728 @itemx --compress-debug-sections=zlib-gabi
729 @itemx --compress-debug-sections=zstd
730 These options control how DWARF debug sections are compressed.
731 @option{--compress-debug-sections=none} is equivalent to
732 @option{--nocompress-debug-sections}.
733 @option{--compress-debug-sections=zlib} and
734 @option{--compress-debug-sections=zlib-gabi} are equivalent to
735 @option{--compress-debug-sections}.
736 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug sections
737 using the obsoleted zlib-gnu format. The debug sections are renamed to begin
739 @option{--compress-debug-sections=zstd} compresses DWARF debug
740 sections using zstd. Note - if compression would actually make a section
741 @emph{larger}, then it is not compressed nor renamed.
745 @item --nocompress-debug-sections
746 Do not compress DWARF debug sections. This is usually the default for all
747 targets except the x86/x86_64, but a configure time option can be used to
751 Enable denugging in target specific backends, if supported. Otherwise ignored.
752 Even if ignored, this option is accepted for script compatibility with calls to
755 @item --debug-prefix-map @var{old}=@var{new}
756 When assembling files in directory @file{@var{old}}, record debugging
757 information describing them as in @file{@var{new}} instead.
759 @item --defsym @var{sym}=@var{value}
760 Define the symbol @var{sym} to be @var{value} before assembling the input file.
761 @var{value} must be an integer constant. As in C, a leading @samp{0x}
762 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
763 value. The value of the symbol can be overridden inside a source file via the
764 use of a @code{.set} pseudo-op.
767 Displays how the assembler is configured and then exits.
770 @item --elf-stt-common=no
771 @itemx --elf-stt-common=yes
772 These options control whether the ELF assembler should generate common
773 symbols with the @code{STT_COMMON} type. The default can be controlled
774 by a configure option @option{--enable-elf-stt-common}.
777 @item --emulation=@var{name}
778 If the assembler is configured to support multiple different target
779 configurations then this option can be used to select the desired form.
782 ``fast''---skip whitespace and comment preprocessing (assume source is
787 Generate debugging information for each assembler source line using whichever
788 debug format is preferred by the target. This currently means either STABS,
789 ECOFF or DWARF2. When the debug format is DWARF then a @code{.debug_info} and
790 @code{.debug_line} section is only emitted when the assembly file doesn't
794 Generate stabs debugging information for each assembler line. This
795 may help debugging assembler code, if the debugger can handle it.
798 Generate stabs debugging information for each assembler line, with GNU
799 extensions that probably only gdb can handle, and that could make other
800 debuggers crash or refuse to read your program. This
801 may help debugging assembler code. Currently the only GNU extension is
802 the location of the current working directory at assembling time.
805 Generate DWARF2 debugging information for each assembler line. This
806 may help debugging assembler code, if the debugger can handle it. Note---this
807 option is only supported by some targets, not all of them.
810 This option is the same as the @option{--gdwarf-2} option, except that it
811 allows for the possibility of the generation of extra debug information as per
812 version 3 of the DWARF specification. Note - enabling this option does not
813 guarantee the generation of any extra information, the choice to do so is on a
817 This option is the same as the @option{--gdwarf-2} option, except that it
818 allows for the possibility of the generation of extra debug information as per
819 version 4 of the DWARF specification. Note - enabling this option does not
820 guarantee the generation of any extra information, the choice to do so is on a
824 This option is the same as the @option{--gdwarf-2} option, except that it
825 allows for the possibility of the generation of extra debug information as per
826 version 5 of the DWARF specification. Note - enabling this option does not
827 guarantee the generation of any extra information, the choice to do so is on a
830 @item --gdwarf-sections
831 Instead of creating a .debug_line section, create a series of
832 .debug_line.@var{foo} sections where @var{foo} is the name of the
833 corresponding code section. For example a code section called @var{.text.func}
834 will have its dwarf line number information placed into a section called
835 @var{.debug_line.text.func}. If the code section is just called @var{.text}
836 then debug line section will still be called just @var{.debug_line} without any
839 @item --gdwarf-cie-version=@var{version}
840 Control which version of DWARF Common Information Entries (CIEs) are produced.
841 When this flag is not specificed the default is version 1, though some targets
842 can modify this default. Other possible values for @var{version} are 3 or 4.
845 @item --generate-missing-build-notes=yes
846 @itemx --generate-missing-build-notes=no
847 These options control whether the ELF assembler should generate GNU Build
848 attribute notes if none are present in the input sources.
849 The default can be controlled by the @option{--enable-generate-build-notes}
854 Create @var{.sframe} section from CFI directives.
858 @item --hash-size @var{N}
859 Ignored. Supported for command line compatibility with other assemblers.
862 Print a summary of the command-line options and exit.
865 Print a summary of all target specific options and exit.
868 Add directory @var{dir} to the search list for @code{.include} directives.
871 Don't warn about signed overflow.
874 @ifclear DIFF-TBL-KLUGE
875 This option is accepted but has no effect on the @value{TARGET} family.
877 @ifset DIFF-TBL-KLUGE
878 Issue warnings when difference tables altered for long displacements.
883 Keep (in the symbol table) local symbols. These symbols start with
884 system-specific local label prefixes, typically @samp{.L} for ELF systems
885 or @samp{L} for traditional a.out systems.
890 @item --listing-lhs-width=@var{number}
891 Set the maximum width, in words, of the output data column for an assembler
892 listing to @var{number}.
894 @item --listing-lhs-width2=@var{number}
895 Set the maximum width, in words, of the output data column for continuation
896 lines in an assembler listing to @var{number}.
898 @item --listing-rhs-width=@var{number}
899 Set the maximum width of an input source line, as displayed in a listing, to
902 @item --listing-cont-lines=@var{number}
903 Set the maximum number of lines printed in a listing for a single line of input
906 @item --multibyte-handling=allow
907 @itemx --multibyte-handling=warn
908 @itemx --multibyte-handling=warn-sym-only
909 @itemx --multibyte-handling=warn_sym_only
910 Controls how the assembler handles multibyte characters in the input. The
911 default (which can be restored by using the @option{allow} argument) is to
912 allow such characters without complaint. Using the @option{warn} argument will
913 make the assembler generate a warning message whenever any multibyte character
914 is encountered. Using the @option{warn-sym-only} argument will only cause a
915 warning to be generated when a symbol is defined with a name that contains
916 multibyte characters. (References to undefined symbols will not generate a
919 @item --no-pad-sections
920 Stop the assembler for padding the ends of output sections to the alignment
921 of that section. The default is to pad the sections, but this can waste space
922 which might be needed on targets which have tight memory constraints.
924 @item -o @var{objfile}
925 Name the object-file output from @command{@value{AS}} @var{objfile}.
928 Fold the data section into the text section.
930 @item --reduce-memory-overheads
931 Ignored. Supported for compatibility with tools that apss the same option to
932 both the assembler and the linker.
935 @item --sectname-subst
936 Honor substitution sequences in section names.
938 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
941 @item --size-check=error
942 @itemx --size-check=warning
943 Issue an error or warning for invalid ELF .size directive.
947 Print the maximum space (in bytes) and total time (in seconds) used by
950 @item --strip-local-absolute
951 Remove local absolute symbols from the outgoing symbol table.
955 Print the @command{as} version.
958 Print the @command{as} version and exit.
962 Suppress warning messages.
964 @item --fatal-warnings
965 Treat warnings as errors.
968 Don't suppress warning messages or treat them as errors.
977 Generate an object file even after errors.
979 @item -- | @var{files} @dots{}
980 Standard input, or source files to assemble.
988 @xref{AArch64 Options}, for the options available when @value{AS} is configured
989 for the 64-bit mode of the ARM Architecture (AArch64).
994 The following options are available when @value{AS} is configured for the
995 64-bit mode of the ARM Architecture (AArch64).
998 @include c-aarch64.texi
999 @c ended inside the included file
1007 @xref{Alpha Options}, for the options available when @value{AS} is configured
1008 for an Alpha processor.
1012 @c man begin OPTIONS
1013 The following options are available when @value{AS} is configured for an Alpha
1016 @c man begin INCLUDE
1017 @include c-alpha.texi
1018 @c ended inside the included file
1023 @c man begin OPTIONS
1025 The following options are available when @value{AS} is configured for an ARC
1029 @item -mcpu=@var{cpu}
1030 This option selects the core processor variant.
1032 Select either big-endian (-EB) or little-endian (-EL) output.
1033 @item -mcode-density
1034 Enable Code Density extension instructions.
1039 The following options are available when @value{AS} is configured for the ARM
1043 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
1044 Specify which ARM processor variant is the target.
1045 @item -march=@var{architecture}[+@var{extension}@dots{}]
1046 Specify which ARM architecture variant is used by the target.
1047 @item -mfpu=@var{floating-point-format}
1048 Select which Floating Point architecture is the target.
1049 @item -mfloat-abi=@var{abi}
1050 Select which floating point ABI is in use.
1052 Enable Thumb only instruction decoding.
1053 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
1054 Select which procedure calling convention is in use.
1056 Select either big-endian (-EB) or little-endian (-EL) output.
1057 @item -mthumb-interwork
1058 Specify that the code has been generated with interworking between Thumb and
1061 Turns on CodeComposer Studio assembly syntax compatibility mode.
1063 Specify that PIC code has been generated.
1071 @xref{Blackfin Options}, for the options available when @value{AS} is
1072 configured for the Blackfin processor family.
1076 @c man begin OPTIONS
1077 The following options are available when @value{AS} is configured for
1078 the Blackfin processor family.
1080 @c man begin INCLUDE
1081 @include c-bfin.texi
1082 @c ended inside the included file
1090 @xref{BPF Options}, for the options available when @value{AS} is
1091 configured for the Linux kernel BPF processor family.
1095 @c man begin OPTIONS
1096 The following options are available when @value{AS} is configured for
1097 the Linux kernel BPF processor family.
1099 @c man begin INCLUDE
1101 @c ended inside the included file
1106 @c man begin OPTIONS
1108 See the info pages for documentation of the CRIS-specific options.
1114 @xref{C-SKY Options}, for the options available when @value{AS} is
1115 configured for the C-SKY processor family.
1119 @c man begin OPTIONS
1120 The following options are available when @value{AS} is configured for
1121 the C-SKY processor family.
1123 @c man begin INCLUDE
1124 @include c-csky.texi
1125 @c ended inside the included file
1131 The following options are available when @value{AS} is configured for
1134 @cindex D10V optimization
1135 @cindex optimization, D10V
1137 Optimize output by parallelizing instructions.
1142 The following options are available when @value{AS} is configured for a D30V
1145 @cindex D30V optimization
1146 @cindex optimization, D30V
1148 Optimize output by parallelizing instructions.
1152 Warn when nops are generated.
1154 @cindex D30V nops after 32-bit multiply
1156 Warn when a nop after a 32-bit multiply instruction is generated.
1162 The following options are available when @value{AS} is configured for the
1163 Adapteva EPIPHANY series.
1166 @xref{Epiphany Options}, for the options available when @value{AS} is
1167 configured for an Epiphany processor.
1171 @c man begin OPTIONS
1172 The following options are available when @value{AS} is configured for
1173 an Epiphany processor.
1175 @c man begin INCLUDE
1176 @include c-epiphany.texi
1177 @c ended inside the included file
1185 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1186 for an H8/300 processor.
1190 @c man begin OPTIONS
1191 The following options are available when @value{AS} is configured for an H8/300
1194 @c man begin INCLUDE
1195 @include c-h8300.texi
1196 @c ended inside the included file
1204 @xref{i386-Options}, for the options available when @value{AS} is
1205 configured for an i386 processor.
1209 @c man begin OPTIONS
1210 The following options are available when @value{AS} is configured for
1213 @c man begin INCLUDE
1214 @include c-i386.texi
1215 @c ended inside the included file
1220 @c man begin OPTIONS
1222 The following options are available when @value{AS} is configured for the
1228 Specifies that the extended IP2022 instructions are allowed.
1231 Restores the default behaviour, which restricts the permitted instructions to
1232 just the basic IP2022 ones.
1238 The following options are available when @value{AS} is configured for the
1239 Renesas M32C and M16C processors.
1244 Assemble M32C instructions.
1247 Assemble M16C instructions (the default).
1250 Enable support for link-time relaxations.
1253 Support H'00 style hex constants in addition to 0x00 style.
1259 The following options are available when @value{AS} is configured for the
1260 Renesas M32R (formerly Mitsubishi M32R) series.
1265 Specify which processor in the M32R family is the target. The default
1266 is normally the M32R, but this option changes it to the M32RX.
1268 @item --warn-explicit-parallel-conflicts or --Wp
1269 Produce warning messages when questionable parallel constructs are
1272 @item --no-warn-explicit-parallel-conflicts or --Wnp
1273 Do not produce warning messages when questionable parallel constructs are
1280 The following options are available when @value{AS} is configured for the
1281 Motorola 68000 series.
1286 Shorten references to undefined symbols, to one word instead of two.
1288 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1289 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1290 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1291 Specify what processor in the 68000 family is the target. The default
1292 is normally the 68020, but this can be changed at configuration time.
1294 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1295 The target machine does (or does not) have a floating-point coprocessor.
1296 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1297 the basic 68000 is not compatible with the 68881, a combination of the
1298 two can be specified, since it's possible to do emulation of the
1299 coprocessor instructions with the main processor.
1301 @item -m68851 | -mno-68851
1302 The target machine does (or does not) have a memory-management
1303 unit coprocessor. The default is to assume an MMU for 68020 and up.
1311 @xref{Nios II Options}, for the options available when @value{AS} is configured
1312 for an Altera Nios II processor.
1316 @c man begin OPTIONS
1317 The following options are available when @value{AS} is configured for an
1318 Altera Nios II processor.
1320 @c man begin INCLUDE
1321 @include c-nios2.texi
1322 @c ended inside the included file
1328 For details about the PDP-11 machine dependent features options,
1329 see @ref{PDP-11-Options}.
1332 @item -mpic | -mno-pic
1333 Generate position-independent (or position-dependent) code. The
1334 default is @option{-mpic}.
1337 @itemx -mall-extensions
1338 Enable all instruction set extensions. This is the default.
1340 @item -mno-extensions
1341 Disable all instruction set extensions.
1343 @item -m@var{extension} | -mno-@var{extension}
1344 Enable (or disable) a particular instruction set extension.
1347 Enable the instruction set extensions supported by a particular CPU, and
1348 disable all other extensions.
1350 @item -m@var{machine}
1351 Enable the instruction set extensions supported by a particular machine
1352 model, and disable all other extensions.
1358 The following options are available when @value{AS} is configured for
1359 a picoJava processor.
1363 @cindex PJ endianness
1364 @cindex endianness, PJ
1365 @cindex big endian output, PJ
1367 Generate ``big endian'' format output.
1369 @cindex little endian output, PJ
1371 Generate ``little endian'' format output.
1379 @xref{PRU Options}, for the options available when @value{AS} is configured
1380 for a PRU processor.
1384 @c man begin OPTIONS
1385 The following options are available when @value{AS} is configured for a
1388 @c man begin INCLUDE
1390 @c ended inside the included file
1395 The following options are available when @value{AS} is configured for the
1396 Motorola 68HC11 or 68HC12 series.
1400 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1401 Specify what processor is the target. The default is
1402 defined by the configuration option when building the assembler.
1404 @item --xgate-ramoffset
1405 Instruct the linker to offset RAM addresses from S12X address space into
1406 XGATE address space.
1409 Specify to use the 16-bit integer ABI.
1412 Specify to use the 32-bit integer ABI.
1414 @item -mshort-double
1415 Specify to use the 32-bit double ABI.
1418 Specify to use the 64-bit double ABI.
1420 @item --force-long-branches
1421 Relative branches are turned into absolute ones. This concerns
1422 conditional branches, unconditional branches and branches to a
1425 @item -S | --short-branches
1426 Do not turn relative branches into absolute ones
1427 when the offset is out of range.
1429 @item --strict-direct-mode
1430 Do not turn the direct addressing mode into extended addressing mode
1431 when the instruction does not support direct addressing mode.
1433 @item --print-insn-syntax
1434 Print the syntax of instruction in case of error.
1436 @item --print-opcodes
1437 Print the list of instructions with syntax and then exit.
1439 @item --generate-example
1440 Print an example of instruction for each possible instruction and then exit.
1441 This option is only useful for testing @command{@value{AS}}.
1447 The following options are available when @command{@value{AS}} is configured
1448 for the SPARC architecture:
1451 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1452 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1453 Explicitly select a variant of the SPARC architecture.
1455 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1456 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1458 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1459 UltraSPARC extensions.
1461 @item -xarch=v8plus | -xarch=v8plusa
1462 For compatibility with the Solaris v9 assembler. These options are
1463 equivalent to -Av8plus and -Av8plusa, respectively.
1466 Warn when the assembler switches to another architecture.
1471 The following options are available when @value{AS} is configured for the 'c54x
1476 Enable extended addressing mode. All addresses and relocations will assume
1477 extended addressing (usually 23 bits).
1478 @item -mcpu=@var{CPU_VERSION}
1479 Sets the CPU version being compiled for.
1480 @item -merrors-to-file @var{FILENAME}
1481 Redirect error output to a file, for broken systems which don't support such
1482 behaviour in the shell.
1487 @c man begin OPTIONS
1488 The following options are available when @value{AS} is configured for
1493 This option sets the largest size of an object that can be referenced
1494 implicitly with the @code{gp} register. It is only accepted for targets that
1495 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1497 @cindex MIPS endianness
1498 @cindex endianness, MIPS
1499 @cindex big endian output, MIPS
1501 Generate ``big endian'' format output.
1503 @cindex little endian output, MIPS
1505 Generate ``little endian'' format output.
1523 Generate code for a particular MIPS Instruction Set Architecture level.
1524 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1525 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1526 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1527 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1528 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1529 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1530 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1531 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1532 MIPS64 Release 6 ISA processors, respectively.
1534 @item -march=@var{cpu}
1535 Generate code for a particular MIPS CPU.
1537 @item -mtune=@var{cpu}
1538 Schedule and tune for a particular MIPS CPU.
1542 Cause nops to be inserted if the read of the destination register
1543 of an mfhi or mflo instruction occurs in the following two instructions.
1546 @itemx -mno-fix-rm7000
1547 Cause nops to be inserted if a dmult or dmultu instruction is
1548 followed by a load instruction.
1551 @itemx -mno-fix-r5900
1552 Do not attempt to schedule the preceding instruction into the delay slot
1553 of a branch instruction placed at the end of a short loop of six
1554 instructions or fewer and always schedule a @code{nop} instruction there
1555 instead. The short loop bug under certain conditions causes loops to
1556 execute only once or twice, due to a hardware bug in the R5900 chip.
1560 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1561 section instead of the standard ELF .stabs sections.
1565 Control generation of @code{.pdr} sections.
1569 The register sizes are normally inferred from the ISA and ABI, but these
1570 flags force a certain group of registers to be treated as 32 bits wide at
1571 all times. @samp{-mgp32} controls the size of general-purpose registers
1572 and @samp{-mfp32} controls the size of floating-point registers.
1576 The register sizes are normally inferred from the ISA and ABI, but these
1577 flags force a certain group of registers to be treated as 64 bits wide at
1578 all times. @samp{-mgp64} controls the size of general-purpose registers
1579 and @samp{-mfp64} controls the size of floating-point registers.
1582 The register sizes are normally inferred from the ISA and ABI, but using
1583 this flag in combination with @samp{-mabi=32} enables an ABI variant
1584 which will operate correctly with floating-point registers which are
1588 @itemx -mno-odd-spreg
1589 Enable use of floating-point operations on odd-numbered single-precision
1590 registers when supported by the ISA. @samp{-mfpxx} implies
1591 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1595 Generate code for the MIPS 16 processor. This is equivalent to putting
1596 @code{.module mips16} at the start of the assembly file. @samp{-no-mips16}
1597 turns off this option.
1600 @itemx -mno-mips16e2
1601 Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent
1602 to putting @code{.module mips16e2} at the start of the assembly file.
1603 @samp{-mno-mips16e2} turns off this option.
1606 @itemx -mno-micromips
1607 Generate code for the microMIPS processor. This is equivalent to putting
1608 @code{.module micromips} at the start of the assembly file.
1609 @samp{-mno-micromips} turns off this option. This is equivalent to putting
1610 @code{.module nomicromips} at the start of the assembly file.
1613 @itemx -mno-smartmips
1614 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1615 equivalent to putting @code{.module smartmips} at the start of the assembly
1616 file. @samp{-mno-smartmips} turns off this option.
1620 Generate code for the MIPS-3D Application Specific Extension.
1621 This tells the assembler to accept MIPS-3D instructions.
1622 @samp{-no-mips3d} turns off this option.
1626 Generate code for the MDMX Application Specific Extension.
1627 This tells the assembler to accept MDMX instructions.
1628 @samp{-no-mdmx} turns off this option.
1632 Generate code for the DSP Release 1 Application Specific Extension.
1633 This tells the assembler to accept DSP Release 1 instructions.
1634 @samp{-mno-dsp} turns off this option.
1638 Generate code for the DSP Release 2 Application Specific Extension.
1639 This option implies @samp{-mdsp}.
1640 This tells the assembler to accept DSP Release 2 instructions.
1641 @samp{-mno-dspr2} turns off this option.
1645 Generate code for the DSP Release 3 Application Specific Extension.
1646 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1647 This tells the assembler to accept DSP Release 3 instructions.
1648 @samp{-mno-dspr3} turns off this option.
1652 Generate code for the MIPS SIMD Architecture Extension.
1653 This tells the assembler to accept MSA instructions.
1654 @samp{-mno-msa} turns off this option.
1658 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1659 This tells the assembler to accept XPA instructions.
1660 @samp{-mno-xpa} turns off this option.
1664 Generate code for the MT Application Specific Extension.
1665 This tells the assembler to accept MT instructions.
1666 @samp{-mno-mt} turns off this option.
1670 Generate code for the MCU Application Specific Extension.
1671 This tells the assembler to accept MCU instructions.
1672 @samp{-mno-mcu} turns off this option.
1676 Generate code for the MIPS cyclic redundancy check (CRC) Application
1677 Specific Extension. This tells the assembler to accept CRC instructions.
1678 @samp{-mno-crc} turns off this option.
1682 Generate code for the Global INValidate (GINV) Application Specific
1683 Extension. This tells the assembler to accept GINV instructions.
1684 @samp{-mno-ginv} turns off this option.
1686 @item -mloongson-mmi
1687 @itemx -mno-loongson-mmi
1688 Generate code for the Loongson MultiMedia extensions Instructions (MMI)
1689 Application Specific Extension. This tells the assembler to accept MMI
1691 @samp{-mno-loongson-mmi} turns off this option.
1693 @item -mloongson-cam
1694 @itemx -mno-loongson-cam
1695 Generate code for the Loongson Content Address Memory (CAM) instructions.
1696 This tells the assembler to accept Loongson CAM instructions.
1697 @samp{-mno-loongson-cam} turns off this option.
1699 @item -mloongson-ext
1700 @itemx -mno-loongson-ext
1701 Generate code for the Loongson EXTensions (EXT) instructions.
1702 This tells the assembler to accept Loongson EXT instructions.
1703 @samp{-mno-loongson-ext} turns off this option.
1705 @item -mloongson-ext2
1706 @itemx -mno-loongson-ext2
1707 Generate code for the Loongson EXTensions R2 (EXT2) instructions.
1708 This option implies @samp{-mloongson-ext}.
1709 This tells the assembler to accept Loongson EXT2 instructions.
1710 @samp{-mno-loongson-ext2} turns off this option.
1714 Only use 32-bit instruction encodings when generating code for the
1715 microMIPS processor. This option inhibits the use of any 16-bit
1716 instructions. This is equivalent to putting @code{.set insn32} at
1717 the start of the assembly file. @samp{-mno-insn32} turns off this
1718 option. This is equivalent to putting @code{.set noinsn32} at the
1719 start of the assembly file. By default @samp{-mno-insn32} is
1720 selected, allowing all instructions to be used.
1722 @item --construct-floats
1723 @itemx --no-construct-floats
1724 The @samp{--no-construct-floats} option disables the construction of
1725 double width floating point constants by loading the two halves of the
1726 value into the two single width floating point registers that make up
1727 the double width register. By default @samp{--construct-floats} is
1728 selected, allowing construction of these floating point constants.
1730 @item --relax-branch
1731 @itemx --no-relax-branch
1732 The @samp{--relax-branch} option enables the relaxation of out-of-range
1733 branches. By default @samp{--no-relax-branch} is selected, causing any
1734 out-of-range branches to produce an error.
1736 @item -mignore-branch-isa
1737 @itemx -mno-ignore-branch-isa
1738 Ignore branch checks for invalid transitions between ISA modes. The
1739 semantics of branches does not provide for an ISA mode switch, so in
1740 most cases the ISA mode a branch has been encoded for has to be the
1741 same as the ISA mode of the branch's target label. Therefore GAS has
1742 checks implemented that verify in branch assembly that the two ISA
1743 modes match. @samp{-mignore-branch-isa} disables these checks. By
1744 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1745 branch requiring a transition between ISA modes to produce an error.
1747 @item -mnan=@var{encoding}
1748 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1749 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1752 @item --emulation=@var{name}
1753 This option was formerly used to switch between ELF and ECOFF output
1754 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1755 removed in GAS 2.24, so the option now serves little purpose.
1756 It is retained for backwards compatibility.
1758 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1759 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1760 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1761 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1762 preferred options instead.
1765 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1772 Control how to deal with multiplication overflow and division by zero.
1773 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1774 (and only work for Instruction Set Architecture level 2 and higher);
1775 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1779 When this option is used, @command{@value{AS}} will issue a warning every
1780 time it generates a nop instruction from a macro.
1786 The following options are available when @value{AS} is configured for
1792 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1793 The command-line option @samp{-nojsri2bsr} can be used to disable it.
1797 Enable or disable the silicon filter behaviour. By default this is disabled.
1798 The default can be overridden by the @samp{-sifilter} command-line option.
1801 Alter jump instructions for long displacements.
1803 @item -mcpu=[210|340]
1804 Select the cpu type on the target hardware. This controls which instructions
1808 Assemble for a big endian target.
1811 Assemble for a little endian target.
1820 @xref{LoongArch-Options}, for the options available when @value{AS} is configured
1821 for a LoongArch processor.
1825 @c man begin OPTIONS
1826 The following options are available when @value{AS} is configured for a
1827 LoongArch processor.
1829 @c man begin INCLUDE
1830 @include c-loongarch.texi
1831 @c ended inside the included file
1839 @xref{Meta Options}, for the options available when @value{AS} is configured
1840 for a Meta processor.
1844 @c man begin OPTIONS
1845 The following options are available when @value{AS} is configured for a
1848 @c man begin INCLUDE
1849 @include c-metag.texi
1850 @c ended inside the included file
1855 @c man begin OPTIONS
1857 See the info pages for documentation of the MMIX-specific options.
1863 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1864 for a NDS32 processor.
1866 @c ended inside the included file
1870 @c man begin OPTIONS
1871 The following options are available when @value{AS} is configured for a
1874 @c man begin INCLUDE
1875 @include c-nds32.texi
1876 @c ended inside the included file
1883 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1884 for a PowerPC processor.
1888 @c man begin OPTIONS
1889 The following options are available when @value{AS} is configured for a
1892 @c man begin INCLUDE
1894 @c ended inside the included file
1902 @xref{RISC-V-Options}, for the options available when @value{AS} is configured
1903 for a RISC-V processor.
1907 @c man begin OPTIONS
1908 The following options are available when @value{AS} is configured for a
1911 @c man begin INCLUDE
1912 @include c-riscv.texi
1913 @c ended inside the included file
1918 @c man begin OPTIONS
1920 See the info pages for documentation of the RX-specific options.
1924 The following options are available when @value{AS} is configured for the s390
1930 Select the word size, either 31/32 bits or 64 bits.
1933 Select the architecture mode, either the Enterprise System
1934 Architecture (esa) or the z/Architecture mode (zarch).
1935 @item -march=@var{processor}
1936 Specify which s390 processor variant is the target, @samp{g5} (or
1937 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1938 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1939 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1940 @samp{z13} (or @samp{arch11}), @samp{z14} (or @samp{arch12}), @samp{z15}
1941 (or @samp{arch13}), or @samp{z16} (or @samp{arch14}).
1943 @itemx -mno-regnames
1944 Allow or disallow symbolic names for registers.
1945 @item -mwarn-areg-zero
1946 Warn whenever the operand for a base or index register has been specified
1947 but evaluates to zero.
1955 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1956 for a TMS320C6000 processor.
1960 @c man begin OPTIONS
1961 The following options are available when @value{AS} is configured for a
1962 TMS320C6000 processor.
1964 @c man begin INCLUDE
1965 @include c-tic6x.texi
1966 @c ended inside the included file
1974 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1975 for a TILE-Gx processor.
1979 @c man begin OPTIONS
1980 The following options are available when @value{AS} is configured for a TILE-Gx
1983 @c man begin INCLUDE
1984 @include c-tilegx.texi
1985 @c ended inside the included file
1993 @xref{Visium Options}, for the options available when @value{AS} is configured
1994 for a Visium processor.
1998 @c man begin OPTIONS
1999 The following option is available when @value{AS} is configured for a Visium
2002 @c man begin INCLUDE
2003 @include c-visium.texi
2004 @c ended inside the included file
2012 @xref{Xtensa Options}, for the options available when @value{AS} is configured
2013 for an Xtensa processor.
2017 @c man begin OPTIONS
2018 The following options are available when @value{AS} is configured for an
2021 @c man begin INCLUDE
2022 @include c-xtensa.texi
2023 @c ended inside the included file
2031 @xref{Z80 Options}, for the options available when @value{AS} is configured
2032 for an Z80 processor.
2036 @c man begin OPTIONS
2037 The following options are available when @value{AS} is configured for an
2040 @c man begin INCLUDE
2042 @c ended inside the included file
2048 * Manual:: Structure of this Manual
2049 * GNU Assembler:: The GNU Assembler
2050 * Object Formats:: Object File Formats
2051 * Command Line:: Command Line
2052 * Input Files:: Input Files
2053 * Object:: Output (Object) File
2054 * Errors:: Error and Warning Messages
2058 @section Structure of this Manual
2060 @cindex manual, structure and purpose
2061 This manual is intended to describe what you need to know to use
2062 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
2063 notation for symbols, constants, and expressions; the directives that
2064 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
2067 We also cover special features in the @value{TARGET}
2068 configuration of @command{@value{AS}}, including assembler directives.
2071 This manual also describes some of the machine-dependent features of
2072 various flavors of the assembler.
2075 @cindex machine instructions (not covered)
2076 On the other hand, this manual is @emph{not} intended as an introduction
2077 to programming in assembly language---let alone programming in general!
2078 In a similar vein, we make no attempt to introduce the machine
2079 architecture; we do @emph{not} describe the instruction set, standard
2080 mnemonics, registers or addressing modes that are standard to a
2081 particular architecture.
2083 You may want to consult the manufacturer's
2084 machine architecture manual for this information.
2088 For information on the H8/300 machine instruction set, see @cite{H8/300
2089 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
2090 Programming Manual} (Renesas).
2093 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
2094 see @cite{SH-Microcomputer User's Manual} (Renesas) or
2095 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
2096 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
2099 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
2103 @c I think this is premature---doc@cygnus.com, 17jan1991
2105 Throughout this manual, we assume that you are running @dfn{GNU},
2106 the portable operating system from the @dfn{Free Software
2107 Foundation, Inc.}. This restricts our attention to certain kinds of
2108 computer (in particular, the kinds of computers that @sc{gnu} can run on);
2109 once this assumption is granted examples and definitions need less
2112 @command{@value{AS}} is part of a team of programs that turn a high-level
2113 human-readable series of instructions into a low-level
2114 computer-readable series of instructions. Different versions of
2115 @command{@value{AS}} are used for different kinds of computer.
2118 @c There used to be a section "Terminology" here, which defined
2119 @c "contents", "byte", "word", and "long". Defining "word" to any
2120 @c particular size is confusing when the .word directive may generate 16
2121 @c bits on one machine and 32 bits on another; in general, for the user
2122 @c version of this manual, none of these terms seem essential to define.
2123 @c They were used very little even in the former draft of the manual;
2124 @c this draft makes an effort to avoid them (except in names of
2128 @section The GNU Assembler
2130 @c man begin DESCRIPTION
2132 @sc{gnu} @command{as} is really a family of assemblers.
2134 This manual describes @command{@value{AS}}, a member of that family which is
2135 configured for the @value{TARGET} architectures.
2137 If you use (or have used) the @sc{gnu} assembler on one architecture, you
2138 should find a fairly similar environment when you use it on another
2139 architecture. Each version has much in common with the others,
2140 including object file formats, most assembler directives (often called
2141 @dfn{pseudo-ops}) and assembler syntax.
2143 @cindex purpose of @sc{gnu} assembler
2144 @command{@value{AS}} is primarily intended to assemble the output of the
2145 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
2146 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
2147 assemble correctly everything that other assemblers for the same
2148 machine would assemble.
2150 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
2153 @c This remark should appear in generic version of manual; assumption
2154 @c here is that generic version sets M680x0.
2155 This doesn't mean @command{@value{AS}} always uses the same syntax as another
2156 assembler for the same architecture; for example, we know of several
2157 incompatible versions of 680x0 assembly language syntax.
2162 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
2163 program in one pass of the source file. This has a subtle impact on the
2164 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
2166 @node Object Formats
2167 @section Object File Formats
2169 @cindex object file format
2170 The @sc{gnu} assembler can be configured to produce several alternative
2171 object file formats. For the most part, this does not affect how you
2172 write assembly language programs; but directives for debugging symbols
2173 are typically different in different file formats. @xref{Symbol
2174 Attributes,,Symbol Attributes}.
2177 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
2178 @value{OBJ-NAME} format object files.
2180 @c The following should exhaust all configs that set MULTI-OBJ, ideally
2182 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
2183 SOM or ELF format object files.
2188 @section Command Line
2190 @cindex command line conventions
2192 After the program name @command{@value{AS}}, the command line may contain
2193 options and file names. Options may appear in any order, and may be
2194 before, after, or between file names. The order of file names is
2197 @cindex standard input, as input file
2199 @file{--} (two hyphens) by itself names the standard input file
2200 explicitly, as one of the files for @command{@value{AS}} to assemble.
2202 @cindex options, command line
2203 Except for @samp{--} any command-line argument that begins with a
2204 hyphen (@samp{-}) is an option. Each option changes the behavior of
2205 @command{@value{AS}}. No option changes the way another option works. An
2206 option is a @samp{-} followed by one or more letters; the case of
2207 the letter is important. All options are optional.
2209 Some options expect exactly one file name to follow them. The file
2210 name may either immediately follow the option's letter (compatible
2211 with older assemblers) or it may be the next command argument (@sc{gnu}
2212 standard). These two command lines are equivalent:
2215 @value{AS} -o my-object-file.o mumble.s
2216 @value{AS} -omy-object-file.o mumble.s
2220 @section Input Files
2223 @cindex source program
2224 @cindex files, input
2225 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2226 describe the program input to one run of @command{@value{AS}}. The program may
2227 be in one or more files; how the source is partitioned into files
2228 doesn't change the meaning of the source.
2230 @c I added "con" prefix to "catenation" just to prove I can overcome my
2231 @c APL training... doc@cygnus.com
2232 The source program is a concatenation of the text in all the files, in the
2235 @c man begin DESCRIPTION
2236 Each time you run @command{@value{AS}} it assembles exactly one source
2237 program. The source program is made up of one or more files.
2238 (The standard input is also a file.)
2240 You give @command{@value{AS}} a command line that has zero or more input file
2241 names. The input files are read (from left file name to right). A
2242 command-line argument (in any position) that has no special meaning
2243 is taken to be an input file name.
2245 If you give @command{@value{AS}} no file names it attempts to read one input file
2246 from the @command{@value{AS}} standard input, which is normally your terminal. You
2247 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2250 Use @samp{--} if you need to explicitly name the standard input file
2251 in your command line.
2253 If the source is empty, @command{@value{AS}} produces a small, empty object
2258 @subheading Filenames and Line-numbers
2260 @cindex input file linenumbers
2261 @cindex line numbers, in input files
2262 There are two ways of locating a line in the input file (or files) and
2263 either may be used in reporting error messages. One way refers to a line
2264 number in a physical file; the other refers to a line number in a
2265 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2267 @dfn{Physical files} are those files named in the command line given
2268 to @command{@value{AS}}.
2270 @dfn{Logical files} are simply names declared explicitly by assembler
2271 directives; they bear no relation to physical files. Logical file names help
2272 error messages reflect the original source file, when @command{@value{AS}} source
2273 is itself synthesized from other files. @command{@value{AS}} understands the
2274 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2275 @ref{File,,@code{.file}}.
2278 @section Output (Object) File
2284 Every time you run @command{@value{AS}} it produces an output file, which is
2285 your assembly language program translated into numbers. This file
2286 is the object file. Its default name is @code{a.out}.
2287 You can give it another name by using the @option{-o} option. Conventionally,
2288 object file names end with @file{.o}. The default name is used for historical
2289 reasons: older assemblers were capable of assembling self-contained programs
2290 directly into a runnable program. (For some formats, this isn't currently
2291 possible, but it can be done for the @code{a.out} format.)
2295 The object file is meant for input to the linker @code{@value{LD}}. It contains
2296 assembled program code, information to help @code{@value{LD}} integrate
2297 the assembled program into a runnable file, and (optionally) symbolic
2298 information for the debugger.
2300 @c link above to some info file(s) like the description of a.out.
2301 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2304 @section Error and Warning Messages
2306 @c man begin DESCRIPTION
2308 @cindex error messages
2309 @cindex warning messages
2310 @cindex messages from assembler
2311 @command{@value{AS}} may write warnings and error messages to the standard error
2312 file (usually your terminal). This should not happen when a compiler
2313 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2314 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2315 grave problem that stops the assembly.
2319 @cindex format of warning messages
2320 Warning messages have the format
2323 file_name:@b{NNN}:Warning Message Text
2327 @cindex file names and line numbers, in warnings/errors
2328 (where @b{NNN} is a line number). If both a logical file name
2329 (@pxref{File,,@code{.file}}) and a logical line number
2331 (@pxref{Line,,@code{.line}})
2333 have been given then they will be used, otherwise the file name and line number
2334 in the current assembler source file will be used. The message text is
2335 intended to be self explanatory (in the grand Unix tradition).
2337 Note the file name must be set via the logical version of the @code{.file}
2338 directive, not the DWARF2 version of the @code{.file} directive. For example:
2342 error_assembler_source
2348 produces this output:
2352 asm.s:2: Error: no such instruction: `error_assembler_source'
2353 foo.c:31: Error: no such instruction: `error_c_source'
2356 @cindex format of error messages
2357 Error messages have the format
2360 file_name:@b{NNN}:FATAL:Error Message Text
2363 The file name and line number are derived as for warning
2364 messages. The actual message text may be rather less explanatory
2365 because many of them aren't supposed to happen.
2368 @chapter Command-Line Options
2370 @cindex options, all versions of assembler
2371 This chapter describes command-line options available in @emph{all}
2372 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2373 for options specific
2375 to the @value{TARGET} target.
2378 to particular machine architectures.
2381 @c man begin DESCRIPTION
2383 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2384 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2385 The assembler arguments must be separated from each other (and the @samp{-Wa})
2386 by commas. For example:
2389 gcc -c -g -O -Wa,-alh,-L file.c
2393 This passes two options to the assembler: @samp{-alh} (emit a listing to
2394 standard output with high-level and assembly source) and @samp{-L} (retain
2395 local symbols in the symbol table).
2397 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2398 command-line options are automatically passed to the assembler by the compiler.
2399 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2400 precisely what options it passes to each compilation pass, including the
2406 * a:: -a[cdghlns] enable listings
2407 * alternate:: --alternate enable alternate macro syntax
2408 * D:: -D for compatibility and debugging
2409 * f:: -f to work faster
2410 * I:: -I for .include search path
2411 @ifclear DIFF-TBL-KLUGE
2412 * K:: -K for compatibility
2414 @ifset DIFF-TBL-KLUGE
2415 * K:: -K for difference tables
2418 * L:: -L to retain local symbols
2419 * listing:: --listing-XXX to configure listing output
2420 * M:: -M or --mri to assemble in MRI compatibility mode
2421 * MD:: --MD for dependency tracking
2422 * no-pad-sections:: --no-pad-sections to stop section padding
2423 * o:: -o to name the object file
2424 * R:: -R to join data and text sections
2425 * statistics:: --statistics to see statistics about assembly
2426 * traditional-format:: --traditional-format for compatible output
2427 * v:: -v to announce version
2428 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2429 * Z:: -Z to make object file even after errors
2433 @section Enable Listings: @option{-a[cdghlns]}
2443 @cindex listings, enabling
2444 @cindex assembly listings, enabling
2446 These options enable listing output from the assembler. By itself,
2447 @samp{-a} requests high-level, assembly, and symbols listing.
2448 You can use other letters to select specific options for the list:
2449 @samp{-ah} requests a high-level language listing,
2450 @samp{-al} requests an output-program assembly listing, and
2451 @samp{-as} requests a symbol table listing.
2452 High-level listings require that a compiler debugging option like
2453 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2456 Use the @samp{-ag} option to print a first section with general assembly
2457 information, like @value{AS} version, switches passed, or time stamp.
2459 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2460 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2461 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2462 omitted from the listing.
2464 Use the @samp{-ad} option to omit debugging directives from the
2467 Once you have specified one of these options, you can further control
2468 listing output and its appearance using the directives @code{.list},
2469 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2471 The @samp{-an} option turns off all forms processing.
2472 If you do not request listing output with one of the @samp{-a} options, the
2473 listing-control directives have no effect.
2475 The letters after @samp{-a} may be combined into one option,
2476 @emph{e.g.}, @samp{-aln}.
2478 Note if the assembler source is coming from the standard input (e.g.,
2480 is being created by @code{@value{GCC}} and the @samp{-pipe} command-line switch
2481 is being used) then the listing will not contain any comments or preprocessor
2482 directives. This is because the listing code buffers input source lines from
2483 stdin only after they have been preprocessed by the assembler. This reduces
2484 memory usage and makes the code more efficient.
2487 @section @option{--alternate}
2490 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2493 @section @option{-D}
2496 This option enables debugging, if it is supported by the assembler's
2497 configuration. Otherwise it does nothing as is ignored. This allows scripts
2498 designed to work with other assemblers to also work with GAS.
2499 @command{@value{AS}}.
2502 @section Work Faster: @option{-f}
2505 @cindex trusted compiler
2506 @cindex faster processing (@option{-f})
2507 @samp{-f} should only be used when assembling programs written by a
2508 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2509 and comment preprocessing on
2510 the input file(s) before assembling them. @xref{Preprocessing,
2514 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2515 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2520 @section @code{.include} Search Path: @option{-I} @var{path}
2522 @kindex -I @var{path}
2523 @cindex paths for @code{.include}
2524 @cindex search path for @code{.include}
2525 @cindex @code{include} directive search path
2526 Use this option to add a @var{path} to the list of directories
2527 @command{@value{AS}} searches for files specified in @code{.include}
2528 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2529 many times as necessary to include a variety of paths. The current
2530 working directory is always searched first; after that, @command{@value{AS}}
2531 searches any @samp{-I} directories in the same order as they were
2532 specified (left to right) on the command line.
2535 @section Difference Tables: @option{-K}
2538 @ifclear DIFF-TBL-KLUGE
2539 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2540 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2541 where it can be used to warn when the assembler alters the machine code
2542 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2543 family does not have the addressing limitations that sometimes lead to this
2544 alteration on other platforms.
2547 @ifset DIFF-TBL-KLUGE
2548 @cindex difference tables, warning
2549 @cindex warning for altered difference tables
2550 @command{@value{AS}} sometimes alters the code emitted for directives of the
2551 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2552 You can use the @samp{-K} option if you want a warning issued when this
2557 @section Include Local Symbols: @option{-L}
2560 @cindex local symbols, retaining in output
2561 Symbols beginning with system-specific local label prefixes, typically
2562 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2563 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2564 such symbols when debugging, because they are intended for the use of
2565 programs (like compilers) that compose assembler programs, not for your
2566 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2567 such symbols, so you do not normally debug with them.
2569 This option tells @command{@value{AS}} to retain those local symbols
2570 in the object file. Usually if you do this you also tell the linker
2571 @code{@value{LD}} to preserve those symbols.
2574 @section Configuring listing output: @option{--listing}
2576 The listing feature of the assembler can be enabled via the command-line switch
2577 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2578 hex dump of the corresponding locations in the output object file, and displays
2579 them as a listing file. The format of this listing can be controlled by
2580 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2581 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2582 @code{.psize} (@pxref{Psize}), and
2583 @code{.eject} (@pxref{Eject}) and also by the following switches:
2586 @item --listing-lhs-width=@samp{number}
2587 @kindex --listing-lhs-width
2588 @cindex Width of first line disassembly output
2589 Sets the maximum width, in words, of the first line of the hex byte dump. This
2590 dump appears on the left hand side of the listing output.
2592 @item --listing-lhs-width2=@samp{number}
2593 @kindex --listing-lhs-width2
2594 @cindex Width of continuation lines of disassembly output
2595 Sets the maximum width, in words, of any further lines of the hex byte dump for
2596 a given input source line. If this value is not specified, it defaults to being
2597 the same as the value specified for @samp{--listing-lhs-width}. If neither
2598 switch is used the default is to one.
2600 @item --listing-rhs-width=@samp{number}
2601 @kindex --listing-rhs-width
2602 @cindex Width of source line output
2603 Sets the maximum width, in characters, of the source line that is displayed
2604 alongside the hex dump. The default value for this parameter is 100. The
2605 source line is displayed on the right hand side of the listing output.
2607 @item --listing-cont-lines=@samp{number}
2608 @kindex --listing-cont-lines
2609 @cindex Maximum number of continuation lines
2610 Sets the maximum number of continuation lines of hex dump that will be
2611 displayed for a given single line of source input. The default value is 4.
2615 @section Assemble in MRI Compatibility Mode: @option{-M}
2618 @cindex MRI compatibility mode
2619 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2620 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2621 compatible with the @code{ASM68K} assembler from Microtec Research.
2622 The exact nature of the
2623 MRI syntax will not be documented here; see the MRI manuals for more
2624 information. Note in particular that the handling of macros and macro
2625 arguments is somewhat different. The purpose of this option is to permit
2626 assembling existing MRI assembler code using @command{@value{AS}}.
2628 The MRI compatibility is not complete. Certain operations of the MRI assembler
2629 depend upon its object file format, and can not be supported using other object
2630 file formats. Supporting these would require enhancing each object file format
2631 individually. These are:
2634 @item global symbols in common section
2636 The m68k MRI assembler supports common sections which are merged by the linker.
2637 Other object file formats do not support this. @command{@value{AS}} handles
2638 common sections by treating them as a single common symbol. It permits local
2639 symbols to be defined within a common section, but it can not support global
2640 symbols, since it has no way to describe them.
2642 @item complex relocations
2644 The MRI assemblers support relocations against a negated section address, and
2645 relocations which combine the start addresses of two or more sections. These
2646 are not support by other object file formats.
2648 @item @code{END} pseudo-op specifying start address
2650 The MRI @code{END} pseudo-op permits the specification of a start address.
2651 This is not supported by other object file formats. The start address may
2652 instead be specified using the @option{-e} option to the linker, or in a linker
2655 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2657 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2658 name to the output file. This is not supported by other object file formats.
2660 @item @code{ORG} pseudo-op
2662 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2663 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2664 which changes the location within the current section. Absolute sections are
2665 not supported by other object file formats. The address of a section may be
2666 assigned within a linker script.
2669 There are some other features of the MRI assembler which are not supported by
2670 @command{@value{AS}}, typically either because they are difficult or because they
2671 seem of little consequence. Some of these may be supported in future releases.
2675 @item EBCDIC strings
2677 EBCDIC strings are not supported.
2679 @item packed binary coded decimal
2681 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2682 and @code{DCB.P} pseudo-ops are not supported.
2684 @item @code{FEQU} pseudo-op
2686 The m68k @code{FEQU} pseudo-op is not supported.
2688 @item @code{NOOBJ} pseudo-op
2690 The m68k @code{NOOBJ} pseudo-op is not supported.
2692 @item @code{OPT} branch control options
2694 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2695 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2696 relaxes all branches, whether forward or backward, to an appropriate size, so
2697 these options serve no purpose.
2699 @item @code{OPT} list control options
2701 The following m68k @code{OPT} list control options are ignored: @code{C},
2702 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2703 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2705 @item other @code{OPT} options
2707 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2708 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2710 @item @code{OPT} @code{D} option is default
2712 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2713 @code{OPT NOD} may be used to turn it off.
2715 @item @code{XREF} pseudo-op.
2717 The m68k @code{XREF} pseudo-op is ignored.
2722 @section Dependency Tracking: @option{--MD}
2725 @cindex dependency tracking
2728 @command{@value{AS}} can generate a dependency file for the file it creates. This
2729 file consists of a single rule suitable for @code{make} describing the
2730 dependencies of the main source file.
2732 The rule is written to the file named in its argument.
2734 This feature is used in the automatic updating of makefiles.
2736 @node no-pad-sections
2737 @section Output Section Padding
2738 @kindex --no-pad-sections
2739 @cindex output section padding
2740 Normally the assembler will pad the end of each output section up to its
2741 alignment boundary. But this can waste space, which can be significant on
2742 memory constrained targets. So the @option{--no-pad-sections} option will
2743 disable this behaviour.
2746 @section Name the Object File: @option{-o}
2749 @cindex naming object file
2750 @cindex object file name
2751 There is always one object file output when you run @command{@value{AS}}. By
2752 default it has the name @file{a.out}.
2753 You use this option (which takes exactly one filename) to give the
2754 object file a different name.
2756 Whatever the object file is called, @command{@value{AS}} overwrites any
2757 existing file of the same name.
2760 @section Join Data and Text Sections: @option{-R}
2763 @cindex data and text sections, joining
2764 @cindex text and data sections, joining
2765 @cindex joining text and data sections
2766 @cindex merging text and data sections
2767 @option{-R} tells @command{@value{AS}} to write the object file as if all
2768 data-section data lives in the text section. This is only done at
2769 the very last moment: your binary data are the same, but data
2770 section parts are relocated differently. The data section part of
2771 your object file is zero bytes long because all its bytes are
2772 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2774 When you specify @option{-R} it would be possible to generate shorter
2775 address displacements (because we do not have to cross between text and
2776 data section). We refrain from doing this simply for compatibility with
2777 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2780 When @command{@value{AS}} is configured for COFF or ELF output,
2781 this option is only useful if you use sections named @samp{.text} and
2786 @option{-R} is not supported for any of the HPPA targets. Using
2787 @option{-R} generates a warning from @command{@value{AS}}.
2791 @section Display Assembly Statistics: @option{--statistics}
2793 @kindex --statistics
2794 @cindex statistics, about assembly
2795 @cindex time, total for assembly
2796 @cindex space used, maximum for assembly
2797 Use @samp{--statistics} to display two statistics about the resources used by
2798 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2799 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2802 @node traditional-format
2803 @section Compatible Output: @option{--traditional-format}
2805 @kindex --traditional-format
2806 For some targets, the output of @command{@value{AS}} is different in some ways
2807 from the output of some existing assembler. This switch requests
2808 @command{@value{AS}} to use the traditional format instead.
2810 For example, it disables the exception frame optimizations which
2811 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2814 @section Announce Version: @option{-v}
2818 @cindex assembler version
2819 @cindex version of assembler
2820 You can find out what version of as is running by including the
2821 option @samp{-v} (which you can also spell as @samp{-version}) on the
2825 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2827 @command{@value{AS}} should never give a warning or error message when
2828 assembling compiler output. But programs written by people often
2829 cause @command{@value{AS}} to give a warning that a particular assumption was
2830 made. All such warnings are directed to the standard error file.
2834 @cindex suppressing warnings
2835 @cindex warnings, suppressing
2836 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2837 This only affects the warning messages: it does not change any particular of
2838 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2841 @kindex --fatal-warnings
2842 @cindex errors, caused by warnings
2843 @cindex warnings, causing error
2844 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2845 files that generate warnings to be in error.
2848 @cindex warnings, switching on
2849 You can switch these options off again by specifying @option{--warn}, which
2850 causes warnings to be output as usual.
2853 @section Generate Object File in Spite of Errors: @option{-Z}
2854 @cindex object file, after errors
2855 @cindex errors, continuing after
2856 After an error message, @command{@value{AS}} normally produces no output. If for
2857 some reason you are interested in object file output even after
2858 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2859 option. If there are any errors, @command{@value{AS}} continues anyways, and
2860 writes an object file after a final warning message of the form @samp{@var{n}
2861 errors, @var{m} warnings, generating bad object file.}
2866 @cindex machine-independent syntax
2867 @cindex syntax, machine-independent
2868 This chapter describes the machine-independent syntax allowed in a
2869 source file. @command{@value{AS}} syntax is similar to what many other
2870 assemblers use; it is inspired by the BSD 4.2
2875 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2879 * Preprocessing:: Preprocessing
2880 * Whitespace:: Whitespace
2881 * Comments:: Comments
2882 * Symbol Intro:: Symbols
2883 * Statements:: Statements
2884 * Constants:: Constants
2888 @section Preprocessing
2890 @cindex preprocessing
2891 The @command{@value{AS}} internal preprocessor:
2893 @cindex whitespace, removed by preprocessor
2895 adjusts and removes extra whitespace. It leaves one space or tab before
2896 the keywords on a line, and turns any other whitespace on the line into
2899 @cindex comments, removed by preprocessor
2901 removes all comments, replacing them with a single space, or an
2902 appropriate number of newlines.
2904 @cindex constants, converted by preprocessor
2906 converts character constants into the appropriate numeric values.
2909 It does not do macro processing, include file handling, or
2910 anything else you may get from your C compiler's preprocessor. You can
2911 do include file processing with the @code{.include} directive
2912 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2913 to get other ``CPP'' style preprocessing by giving the input file a
2914 @samp{.S} suffix. @url{https://gcc.gnu.org/onlinedocs/gcc/Overall-Options.html#Overall-Options,
2915 See the 'Options Controlling the Kind of Output' section of the GCC manual for
2918 Excess whitespace, comments, and character constants
2919 cannot be used in the portions of the input text that are not
2922 @cindex turning preprocessing on and off
2923 @cindex preprocessing, turning on and off
2926 If the first line of an input file is @code{#NO_APP} or if you use the
2927 @samp{-f} option, whitespace and comments are not removed from the input file.
2928 Within an input file, you can ask for whitespace and comment removal in
2929 specific portions of the file by putting a line that says @code{#APP} before the
2930 text that may contain whitespace or comments, and putting a line that says
2931 @code{#NO_APP} after this text. This feature is mainly intended to support
2932 @code{asm} statements in compilers whose output is otherwise free of comments
2939 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2940 Whitespace is used to separate symbols, and to make programs neater for
2941 people to read. Unless within character constants
2942 (@pxref{Characters,,Character Constants}), any whitespace means the same
2943 as exactly one space.
2949 There are two ways of rendering comments to @command{@value{AS}}. In both
2950 cases the comment is equivalent to one space.
2952 Anything from @samp{/*} through the next @samp{*/} is a comment.
2953 This means you may not nest these comments.
2957 The only way to include a newline ('\n') in a comment
2958 is to use this sort of comment.
2961 /* This sort of comment does not nest. */
2964 @cindex line comment character
2965 Anything from a @dfn{line comment} character up to the next newline is
2966 considered a comment and is ignored. The line comment character is target
2967 specific, and some targets support multiple comment characters. Some targets
2968 also have line comment characters that only work if they are the first
2969 character on a line. Some targets use a sequence of two characters to
2970 introduce a line comment. Some targets can also change their line comment
2971 characters depending upon command-line options that have been used. For more
2972 details see the @emph{Syntax} section in the documentation for individual
2975 If the line comment character is the hash sign (@samp{#}) then it still has the
2976 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2977 to specify logical line numbers:
2980 @cindex lines starting with @code{#}
2981 @cindex logical line numbers
2982 To be compatible with past assemblers, lines that begin with @samp{#} have a
2983 special interpretation. Following the @samp{#} should be an absolute
2984 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2985 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2986 new logical file name. The rest of the line, if any, should be whitespace.
2988 If the first non-whitespace characters on the line are not numeric,
2989 the line is ignored. (Just like a comment.)
2992 # This is an ordinary comment.
2993 # 42-6 "new_file_name" # New logical file name
2994 # This is logical line # 36.
2996 This feature is deprecated, and may disappear from future versions
2997 of @command{@value{AS}}.
3002 @cindex characters used in symbols
3003 @ifclear SPECIAL-SYMS
3004 A @dfn{symbol} is one or more characters chosen from the set of all
3005 letters (both upper and lower case), digits and the three characters
3011 A @dfn{symbol} is one or more characters chosen from the set of all
3012 letters (both upper and lower case), digits and the three characters
3013 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
3019 On most machines, you can also use @code{$} in symbol names; exceptions
3020 are noted in @ref{Machine Dependencies}.
3022 No symbol may begin with a digit. Case is significant.
3023 There is no length limit; all characters are significant. Multibyte characters
3024 are supported, but note that the setting of the
3025 @option{--multibyte-handling} option might prevent their use. Symbols
3026 are delimited by characters not in that set, or by the beginning of a file
3027 (since the source program must end with a newline, the end of a file is not a
3028 possible symbol delimiter). @xref{Symbols}.
3030 Symbol names may also be enclosed in double quote @code{"} characters. In such
3031 cases any characters are allowed, except for the NUL character. If a double
3032 quote character is to be included in the symbol name it must be preceded by a
3033 backslash @code{\} character.
3034 @cindex length of symbols
3039 @cindex statements, structure of
3040 @cindex line separator character
3041 @cindex statement separator character
3043 A @dfn{statement} ends at a newline character (@samp{\n}) or a
3044 @dfn{line separator character}. The line separator character is target
3045 specific and described in the @emph{Syntax} section of each
3046 target's documentation. Not all targets support a line separator character.
3047 The newline or line separator character is considered to be part of the
3048 preceding statement. Newlines and separators within character constants are an
3049 exception: they do not end statements.
3051 @cindex newline, required at file end
3052 @cindex EOF, newline must precede
3053 It is an error to end any statement with end-of-file: the last
3054 character of any input file should be a newline.
3056 An empty statement is allowed, and may include whitespace. It is ignored.
3058 @cindex instructions and directives
3059 @cindex directives and instructions
3060 @c "key symbol" is not used elsewhere in the document; seems pedantic to
3061 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
3063 A statement begins with zero or more labels, optionally followed by a
3064 key symbol which determines what kind of statement it is. The key
3065 symbol determines the syntax of the rest of the statement. If the
3066 symbol begins with a dot @samp{.} then the statement is an assembler
3067 directive: typically valid for any computer. If the symbol begins with
3068 a letter the statement is an assembly language @dfn{instruction}: it
3069 assembles into a machine language instruction.
3071 Different versions of @command{@value{AS}} for different computers
3072 recognize different instructions. In fact, the same symbol may
3073 represent a different instruction in a different computer's assembly
3077 @cindex @code{:} (label)
3078 @cindex label (@code{:})
3079 A label is a symbol immediately followed by a colon (@code{:}).
3080 Whitespace before a label or after a colon is permitted, but you may not
3081 have whitespace between a label's symbol and its colon. @xref{Labels}.
3084 For HPPA targets, labels need not be immediately followed by a colon, but
3085 the definition of a label must begin in column zero. This also implies that
3086 only one label may be defined on each line.
3090 label: .directive followed by something
3091 another_label: # This is an empty statement.
3092 instruction operand_1, operand_2, @dots{}
3099 A constant is a number, written so that its value is known by
3100 inspection, without knowing any context. Like this:
3103 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
3104 .ascii "Ring the bell\7" # A string constant.
3105 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
3106 .float 0f-314159265358979323846264338327\
3107 95028841971.693993751E-40 # - pi, a flonum.
3112 * Characters:: Character Constants
3113 * Numbers:: Number Constants
3117 @subsection Character Constants
3119 @cindex character constants
3120 @cindex constants, character
3121 There are two kinds of character constants. A @dfn{character} stands
3122 for one character in one byte and its value may be used in
3123 numeric expressions. String constants (properly called string
3124 @emph{literals}) are potentially many bytes and their values may not be
3125 used in arithmetic expressions.
3129 * Chars:: Characters
3133 @subsubsection Strings
3135 @cindex string constants
3136 @cindex constants, string
3137 A @dfn{string} is written between double-quotes. It may contain
3138 double-quotes or null characters. The way to get special characters
3139 into a string is to @dfn{escape} these characters: precede them with
3140 a backslash @samp{\} character. For example @samp{\\} represents
3141 one backslash: the first @code{\} is an escape which tells
3142 @command{@value{AS}} to interpret the second character literally as a backslash
3143 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
3144 escape character). The complete list of escapes follows.
3146 @cindex escape codes, character
3147 @cindex character escape codes
3148 @c NOTE: Cindex entries must not start with a backlash character.
3149 @c NOTE: This confuses the pdf2texi script when it is creating the
3150 @c NOTE: index based upon the first character and so it generates:
3151 @c NOTE: \initial {\\}
3152 @c NOTE: which then results in the error message:
3153 @c NOTE: Argument of \\ has an extra }.
3154 @c NOTE: So in the index entries below a space character has been
3155 @c NOTE: prepended to avoid this problem.
3158 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3160 @cindex @code{ \b} (backspace character)
3161 @cindex backspace (@code{\b})
3163 Mnemonic for backspace; for ASCII this is octal code 010.
3166 @c Mnemonic for EOText; for ASCII this is octal code 004.
3168 @cindex @code{ \f} (formfeed character)
3169 @cindex formfeed (@code{\f})
3171 Mnemonic for FormFeed; for ASCII this is octal code 014.
3173 @cindex @code{ \n} (newline character)
3174 @cindex newline (@code{\n})
3176 Mnemonic for newline; for ASCII this is octal code 012.
3179 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3181 @cindex @code{ \r} (carriage return character)
3182 @cindex carriage return (@code{backslash-r})
3184 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3187 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3188 @c other assemblers.
3190 @cindex @code{ \t} (tab)
3191 @cindex tab (@code{\t})
3193 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3196 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3197 @c @item \x @var{digit} @var{digit} @var{digit}
3198 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3200 @cindex @code{ \@var{ddd}} (octal character code)
3201 @cindex octal character code (@code{\@var{ddd}})
3202 @item \ @var{digit} @var{digit} @var{digit}
3203 An octal character code. The numeric code is 3 octal digits.
3204 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3205 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3207 @cindex @code{ \@var{xd...}} (hex character code)
3208 @cindex hex character code (@code{\@var{xd...}})
3209 @item \@code{x} @var{hex-digits...}
3210 A hex character code. All trailing hex digits are combined. Either upper or
3211 lower case @code{x} works.
3213 @cindex @code{ \\} (@samp{\} character)
3214 @cindex backslash (@code{\\})
3216 Represents one @samp{\} character.
3219 @c Represents one @samp{'} (accent acute) character.
3220 @c This is needed in single character literals
3221 @c (@xref{Characters,,Character Constants}.) to represent
3224 @cindex @code{ \"} (doublequote character)
3225 @cindex doublequote (@code{\"})
3227 Represents one @samp{"} character. Needed in strings to represent
3228 this character, because an unescaped @samp{"} would end the string.
3230 @item \ @var{anything-else}
3231 Any other character when escaped by @kbd{\} gives a warning, but
3232 assembles as if the @samp{\} was not present. The idea is that if
3233 you used an escape sequence you clearly didn't want the literal
3234 interpretation of the following character. However @command{@value{AS}} has no
3235 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3236 code and warns you of the fact.
3239 Which characters are escapable, and what those escapes represent,
3240 varies widely among assemblers. The current set is what we think
3241 the BSD 4.2 assembler recognizes, and is a subset of what most C
3242 compilers recognize. If you are in doubt, do not use an escape
3246 @subsubsection Characters
3248 @cindex single character constant
3249 @cindex character, single
3250 @cindex constant, single character
3251 A single character may be written as a single quote immediately followed by
3252 that character. Some backslash escapes apply to characters, @code{\b},
3253 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3254 as for strings, plus @code{\'} for a single quote. So if you want to write the
3255 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3256 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3259 @ifclear abnormal-separator
3260 (or semicolon @samp{;})
3262 @ifset abnormal-separator
3264 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3269 immediately following an acute accent is taken as a literal character
3270 and does not count as the end of a statement. The value of a character
3271 constant in a numeric expression is the machine's byte-wide code for
3272 that character. @command{@value{AS}} assumes your character code is ASCII:
3273 @kbd{'A} means 65, @kbd{'B} means 66, and so on.
3276 @subsection Number Constants
3278 @cindex constants, number
3279 @cindex number constants
3280 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3281 are stored in the target machine. @emph{Integers} are numbers that
3282 would fit into an @code{int} in the C language. @emph{Bignums} are
3283 integers, but they are stored in more than 32 bits. @emph{Flonums}
3284 are floating point numbers, described below.
3287 * Integers:: Integers
3295 @subsubsection Integers
3297 @cindex constants, integer
3299 @cindex binary integers
3300 @cindex integers, binary
3301 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3302 the binary digits @samp{01}.
3304 @cindex octal integers
3305 @cindex integers, octal
3306 An octal integer is @samp{0} followed by zero or more of the octal
3307 digits (@samp{01234567}).
3309 @cindex decimal integers
3310 @cindex integers, decimal
3311 A decimal integer starts with a non-zero digit followed by zero or
3312 more digits (@samp{0123456789}).
3314 @cindex hexadecimal integers
3315 @cindex integers, hexadecimal
3316 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3317 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3319 Integers have the usual values. To denote a negative integer, use
3320 the prefix operator @samp{-} discussed under expressions
3321 (@pxref{Prefix Ops,,Prefix Operators}).
3324 @subsubsection Bignums
3327 @cindex constants, bignum
3328 A @dfn{bignum} has the same syntax and semantics as an integer
3329 except that the number (or its negative) takes more than 32 bits to
3330 represent in binary. The distinction is made because in some places
3331 integers are permitted while bignums are not.
3334 @subsubsection Flonums
3336 @cindex floating point numbers
3337 @cindex constants, floating point
3339 @cindex precision, floating point
3340 A @dfn{flonum} represents a floating point number. The translation is
3341 indirect: a decimal floating point number from the text is converted by
3342 @command{@value{AS}} to a generic binary floating point number of more than
3343 sufficient precision. This generic floating point number is converted
3344 to a particular computer's floating point format (or formats) by a
3345 portion of @command{@value{AS}} specialized to that computer.
3347 A flonum is written by writing (in order)
3352 (@samp{0} is optional on the HPPA.)
3356 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3358 @kbd{e} is recommended. Case is not important.
3360 @c FIXME: verify if flonum syntax really this vague for most cases
3361 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3362 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3365 On the H8/300 and Renesas / SuperH SH architectures, the letter must be
3366 one of the letters @samp{DFPRSX} (in upper or lower case).
3368 On the ARC, the letter must be one of the letters @samp{DFRS}
3369 (in upper or lower case).
3371 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3375 One of the letters @samp{DFRS} (in upper or lower case).
3378 One of the letters @samp{DFPRSX} (in upper or lower case).
3381 The letter @samp{E} (upper case only).
3386 An optional sign: either @samp{+} or @samp{-}.
3389 An optional @dfn{integer part}: zero or more decimal digits.
3392 An optional @dfn{fractional part}: @samp{.} followed by zero
3393 or more decimal digits.
3396 An optional exponent, consisting of:
3400 An @samp{E} or @samp{e}.
3401 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3402 @c principle this can perfectly well be different on different targets.
3404 Optional sign: either @samp{+} or @samp{-}.
3406 One or more decimal digits.
3411 At least one of the integer part or the fractional part must be
3412 present. The floating point number has the usual base-10 value.
3414 @command{@value{AS}} does all processing using integers. Flonums are computed
3415 independently of any floating point hardware in the computer running
3416 @command{@value{AS}}.
3419 @chapter Sections and Relocation
3424 * Secs Background:: Background
3425 * Ld Sections:: Linker Sections
3426 * As Sections:: Assembler Internal Sections
3427 * Sub-Sections:: Sub-Sections
3431 @node Secs Background
3434 Roughly, a section is a range of addresses, with no gaps; all data
3435 ``in'' those addresses is treated the same for some particular purpose.
3436 For example there may be a ``read only'' section.
3438 @cindex linker, and assembler
3439 @cindex assembler, and linker
3440 The linker @code{@value{LD}} reads many object files (partial programs) and
3441 combines their contents to form a runnable program. When @command{@value{AS}}
3442 emits an object file, the partial program is assumed to start at address 0.
3443 @code{@value{LD}} assigns the final addresses for the partial program, so that
3444 different partial programs do not overlap. This is actually an
3445 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3448 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3449 addresses. These blocks slide to their run-time addresses as rigid
3450 units; their length does not change and neither does the order of bytes
3451 within them. Such a rigid unit is called a @emph{section}. Assigning
3452 run-time addresses to sections is called @dfn{relocation}. It includes
3453 the task of adjusting mentions of object-file addresses so they refer to
3454 the proper run-time addresses.
3456 For the H8/300, and for the Renesas / SuperH SH,
3457 @command{@value{AS}} pads sections if needed to
3458 ensure they end on a word (sixteen bit) boundary.
3461 @cindex standard assembler sections
3462 An object file written by @command{@value{AS}} has at least three sections, any
3463 of which may be empty. These are named @dfn{text}, @dfn{data} and
3468 When it generates COFF or ELF output,
3470 @command{@value{AS}} can also generate whatever other named sections you specify
3471 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3472 If you do not use any directives that place output in the @samp{.text}
3473 or @samp{.data} sections, these sections still exist, but are empty.
3478 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3480 @command{@value{AS}} can also generate whatever other named sections you
3481 specify using the @samp{.space} and @samp{.subspace} directives. See
3482 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3483 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3484 assembler directives.
3487 Additionally, @command{@value{AS}} uses different names for the standard
3488 text, data, and bss sections when generating SOM output. Program text
3489 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3490 BSS into @samp{$BSS$}.
3494 Within the object file, the text section starts at address @code{0}, the
3495 data section follows, and the bss section follows the data section.
3498 When generating either SOM or ELF output files on the HPPA, the text
3499 section starts at address @code{0}, the data section at address
3500 @code{0x4000000}, and the bss section follows the data section.
3503 To let @code{@value{LD}} know which data changes when the sections are
3504 relocated, and how to change that data, @command{@value{AS}} also writes to the
3505 object file details of the relocation needed. To perform relocation
3506 @code{@value{LD}} must know, each time an address in the object
3510 Where in the object file is the beginning of this reference to
3513 How long (in bytes) is this reference?
3515 Which section does the address refer to? What is the numeric value of
3517 (@var{address}) @minus{} (@var{start-address of section})?
3520 Is the reference to an address ``Program-Counter relative''?
3523 @cindex addresses, format of
3524 @cindex section-relative addressing
3525 In fact, every address @command{@value{AS}} ever uses is expressed as
3527 (@var{section}) + (@var{offset into section})
3530 Further, most expressions @command{@value{AS}} computes have this section-relative
3533 (For some object formats, such as SOM for the HPPA, some expressions are
3534 symbol-relative instead.)
3537 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3538 @var{N} into section @var{secname}.''
3540 Apart from text, data and bss sections you need to know about the
3541 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3542 addresses in the absolute section remain unchanged. For example, address
3543 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3544 @code{@value{LD}}. Although the linker never arranges two partial programs'
3545 data sections with overlapping addresses after linking, @emph{by definition}
3546 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3547 part of a program is always the same address when the program is running as
3548 address @code{@{absolute@ 239@}} in any other part of the program.
3550 The idea of sections is extended to the @dfn{undefined} section. Any
3551 address whose section is unknown at assembly time is by definition
3552 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3553 Since numbers are always defined, the only way to generate an undefined
3554 address is to mention an undefined symbol. A reference to a named
3555 common block would be such a symbol: its value is unknown at assembly
3556 time so it has section @emph{undefined}.
3558 By analogy the word @emph{section} is used to describe groups of sections in
3559 the linked program. @code{@value{LD}} puts all partial programs' text
3560 sections in contiguous addresses in the linked program. It is
3561 customary to refer to the @emph{text section} of a program, meaning all
3562 the addresses of all partial programs' text sections. Likewise for
3563 data and bss sections.
3565 Some sections are manipulated by @code{@value{LD}}; others are invented for
3566 use of @command{@value{AS}} and have no meaning except during assembly.
3569 @section Linker Sections
3570 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3575 @cindex named sections
3576 @cindex sections, named
3577 @item named sections
3580 @cindex text section
3581 @cindex data section
3585 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3586 separate but equal sections. Anything you can say of one section is
3589 When the program is running, however, it is
3590 customary for the text section to be unalterable. The
3591 text section is often shared among processes: it contains
3592 instructions, constants and the like. The data section of a running
3593 program is usually alterable: for example, C variables would be stored
3594 in the data section.
3599 This section contains zeroed bytes when your program begins running. It
3600 is used to hold uninitialized variables or common storage. The length of
3601 each partial program's bss section is important, but because it starts
3602 out containing zeroed bytes there is no need to store explicit zero
3603 bytes in the object file. The bss section was invented to eliminate
3604 those explicit zeros from object files.
3606 @cindex absolute section
3607 @item absolute section
3608 Address 0 of this section is always ``relocated'' to runtime address 0.
3609 This is useful if you want to refer to an address that @code{@value{LD}} must
3610 not change when relocating. In this sense we speak of absolute
3611 addresses being ``unrelocatable'': they do not change during relocation.
3613 @cindex undefined section
3614 @item undefined section
3615 This ``section'' is a catch-all for address references to objects not in
3616 the preceding sections.
3617 @c FIXME: ref to some other doc on obj-file formats could go here.
3620 @cindex relocation example
3621 An idealized example of three relocatable sections follows.
3623 The example uses the traditional section names @samp{.text} and @samp{.data}.
3625 Memory addresses are on the horizontal axis.
3629 @c END TEXI2ROFF-KILL
3632 partial program # 1: |ttttt|dddd|00|
3639 partial program # 2: |TTT|DDD|000|
3642 +--+---+-----+--+----+---+-----+~~
3643 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3644 +--+---+-----+--+----+---+-----+~~
3646 addresses: 0 @dots{}
3653 \line{\it Partial program \#1: \hfil}
3654 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3655 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3657 \line{\it Partial program \#2: \hfil}
3658 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3659 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3661 \line{\it linked program: \hfil}
3662 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3663 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3664 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3665 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3667 \line{\it addresses: \hfil}
3671 @c END TEXI2ROFF-KILL
3674 @section Assembler Internal Sections
3676 @cindex internal assembler sections
3677 @cindex sections in messages, internal
3678 These sections are meant only for the internal use of @command{@value{AS}}. They
3679 have no meaning at run-time. You do not really need to know about these
3680 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3681 warning messages, so it might be helpful to have an idea of their
3682 meanings to @command{@value{AS}}. These sections are used to permit the
3683 value of every expression in your assembly language program to be a
3684 section-relative address.
3687 @cindex assembler internal logic error
3688 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3689 An internal assembler logic error has been found. This means there is a
3690 bug in the assembler.
3692 @cindex expr (internal section)
3694 The assembler stores complex expressions internally as combinations of
3695 symbols. When it needs to represent an expression as a symbol, it puts
3696 it in the expr section.
3698 @c FIXME item transfer[t] vector preload
3699 @c FIXME item transfer[t] vector postload
3700 @c FIXME item register
3704 @section Sub-Sections
3706 @cindex numbered subsections
3707 @cindex grouping data
3713 fall into two sections: text and data.
3715 You may have separate groups of
3717 data in named sections
3721 data in named sections
3727 that you want to end up near to each other in the object file, even though they
3728 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3729 use @dfn{subsections} for this purpose. Within each section, there can be
3730 numbered subsections with values from 0 to 8192. Objects assembled into the
3731 same subsection go into the object file together with other objects in the same
3732 subsection. For example, a compiler might want to store constants in the text
3733 section, but might not want to have them interspersed with the program being
3734 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3735 section of code being output, and a @samp{.text 1} before each group of
3736 constants being output.
3738 Subsections are optional. If you do not use subsections, everything
3739 goes in subsection number zero.
3742 Each subsection is zero-padded up to a multiple of four bytes.
3743 (Subsections may be padded a different amount on different flavors
3744 of @command{@value{AS}}.)
3748 On the H8/300 platform, each subsection is zero-padded to a word
3749 boundary (two bytes).
3750 The same is true on the Renesas SH.
3754 Subsections appear in your object file in numeric order, lowest numbered
3755 to highest. (All this to be compatible with other people's assemblers.)
3756 The object file contains no representation of subsections; @code{@value{LD}} and
3757 other programs that manipulate object files see no trace of them.
3758 They just see all your text subsections as a text section, and all your
3759 data subsections as a data section.
3761 To specify which subsection you want subsequent statements assembled
3762 into, use a numeric argument to specify it, in a @samp{.text
3763 @var{expression}} or a @samp{.data @var{expression}} statement.
3766 When generating COFF output, you
3771 can also use an extra subsection
3772 argument with arbitrary named sections: @samp{.section @var{name},
3777 When generating ELF output, you
3782 can also use the @code{.subsection} directive (@pxref{SubSection})
3783 to specify a subsection: @samp{.subsection @var{expression}}.
3785 @var{Expression} should be an absolute expression
3786 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3787 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3788 begins in @code{text 0}. For instance:
3790 .text 0 # The default subsection is text 0 anyway.
3791 .ascii "This lives in the first text subsection. *"
3793 .ascii "But this lives in the second text subsection."
3795 .ascii "This lives in the data section,"
3796 .ascii "in the first data subsection."
3798 .ascii "This lives in the first text section,"
3799 .ascii "immediately following the asterisk (*)."
3802 Each section has a @dfn{location counter} incremented by one for every byte
3803 assembled into that section. Because subsections are merely a convenience
3804 restricted to @command{@value{AS}} there is no concept of a subsection location
3805 counter. There is no way to directly manipulate a location counter---but the
3806 @code{.align} directive changes it, and any label definition captures its
3807 current value. The location counter of the section where statements are being
3808 assembled is said to be the @dfn{active} location counter.
3811 @section bss Section
3814 @cindex common variable storage
3815 The bss section is used for local common variable storage.
3816 You may allocate address space in the bss section, but you may
3817 not dictate data to load into it before your program executes. When
3818 your program starts running, all the contents of the bss
3819 section are zeroed bytes.
3821 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3822 @ref{Lcomm,,@code{.lcomm}}.
3824 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3825 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3828 When assembling for a target which supports multiple sections, such as ELF or
3829 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3830 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3831 section. Typically the section will only contain symbol definitions and
3832 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3839 Symbols are a central concept: the programmer uses symbols to name
3840 things, the linker uses symbols to link, and the debugger uses symbols
3844 @cindex debuggers, and symbol order
3845 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3846 the same order they were declared. This may break some debuggers.
3851 * Setting Symbols:: Giving Symbols Other Values
3852 * Symbol Names:: Symbol Names
3853 * Dot:: The Special Dot Symbol
3854 * Symbol Attributes:: Symbol Attributes
3861 A @dfn{label} is written as a symbol immediately followed by a colon
3862 @samp{:}. The symbol then represents the current value of the
3863 active location counter, and is, for example, a suitable instruction
3864 operand. You are warned if you use the same symbol to represent two
3865 different locations: the first definition overrides any other
3869 On the HPPA, the usual form for a label need not be immediately followed by a
3870 colon, but instead must start in column zero. Only one label may be defined on
3871 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3872 provides a special directive @code{.label} for defining labels more flexibly.
3875 @node Setting Symbols
3876 @section Giving Symbols Other Values
3878 @cindex assigning values to symbols
3879 @cindex symbol values, assigning
3880 A symbol can be given an arbitrary value by writing a symbol, followed
3881 by an equals sign @samp{=}, followed by an expression
3882 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3883 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3884 equals sign @samp{=}@samp{=} here represents an equivalent of the
3885 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3888 Blackfin does not support symbol assignment with @samp{=}.
3892 @section Symbol Names
3894 @cindex symbol names
3895 @cindex names, symbol
3896 @ifclear SPECIAL-SYMS
3897 Symbol names begin with a letter or with one of @samp{._}. On most
3898 machines, you can also use @code{$} in symbol names; exceptions are
3899 noted in @ref{Machine Dependencies}. That character may be followed by any
3900 string of digits, letters, dollar signs (unless otherwise noted for a
3901 particular target machine), and underscores. These restrictions do not
3902 apply when quoting symbol names by @samp{"}, which is permitted for most
3903 targets. Escaping characters in quoted symbol names with @samp{\} generally
3904 extends only to @samp{\} itself and @samp{"}, at the time of writing.
3908 Symbol names begin with a letter or with one of @samp{._}. On the
3909 Renesas SH you can also use @code{$} in symbol names. That
3910 character may be followed by any string of digits, letters, dollar signs (save
3911 on the H8/300), and underscores.
3915 Case of letters is significant: @code{foo} is a different symbol name
3918 Symbol names do not start with a digit. An exception to this rule is made for
3919 Local Labels. See below.
3921 Multibyte characters are supported, but note that the setting of the
3922 @option{multibyte-handling} option might prevent their use.
3923 To generate a symbol name containing
3924 multibyte characters enclose it within double quotes and use escape codes. cf
3925 @xref{Strings}. Generating a multibyte symbol name from a label is not
3926 currently supported.
3928 Since multibyte symbol names are unusual, and could possibly be used
3929 maliciously, @command{@value{AS}} provides a command line option
3930 (@option{--multibyte-handling=warn-sym-only}) which can be used to generate a
3931 warning message whenever a symbol name containing multibyte characters is defined.
3933 Each symbol has exactly one name. Each name in an assembly language program
3934 refers to exactly one symbol. You may use that symbol name any number of times
3937 @subheading Local Symbol Names
3939 @cindex local symbol names
3940 @cindex symbol names, local
3941 A local symbol is any symbol beginning with certain local label prefixes.
3942 By default, the local label prefix is @samp{.L} for ELF systems or
3943 @samp{L} for traditional a.out systems, but each target may have its own
3944 set of local label prefixes.
3946 On the HPPA local symbols begin with @samp{L$}.
3949 Local symbols are defined and used within the assembler, but they are
3950 normally not saved in object files. Thus, they are not visible when debugging.
3951 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3952 to retain the local symbols in the object files.
3954 @subheading Local Labels
3956 @cindex local labels
3957 @cindex temporary symbol names
3958 @cindex symbol names, temporary
3959 Local labels are different from local symbols. Local labels help compilers and
3960 programmers use names temporarily. They create symbols which are guaranteed to
3961 be unique over the entire scope of the input source code and which can be
3962 referred to by a simple notation. To define a local label, write a label of
3963 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3964 To refer to the most recent previous definition of that label write
3965 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3966 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3967 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3969 There is no restriction on how you can use these labels, and you can reuse them
3970 too. So that it is possible to repeatedly define the same local label (using
3971 the same number @samp{@b{N}}), although you can only refer to the most recently
3972 defined local label of that number (for a backwards reference) or the next
3973 definition of a specific local label for a forward reference. It is also worth
3974 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3975 implemented in a slightly more efficient manner than the others.
3986 Which is the equivalent of:
3989 label_1: branch label_3
3990 label_2: branch label_1
3991 label_3: branch label_4
3992 label_4: branch label_3
3995 Local label names are only a notational device. They are immediately
3996 transformed into more conventional symbol names before the assembler uses them.
3997 The symbol names are stored in the symbol table, appear in error messages, and
3998 are optionally emitted to the object file. The names are constructed using
4002 @item @emph{local label prefix}
4003 All local symbols begin with the system-specific local label prefix.
4004 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
4005 that start with the local label prefix. These labels are
4006 used for symbols you are never intended to see. If you use the
4007 @samp{-L} option then @command{@value{AS}} retains these symbols in the
4008 object file. If you also instruct @code{@value{LD}} to retain these symbols,
4009 you may use them in debugging.
4012 This is the number that was used in the local label definition. So if the
4013 label is written @samp{55:} then the number is @samp{55}.
4016 This unusual character is included so you do not accidentally invent a symbol
4017 of the same name. The character has ASCII value of @samp{\002} (control-B).
4019 @item @emph{ordinal number}
4020 This is a serial number to keep the labels distinct. The first definition of
4021 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
4022 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
4023 the number @samp{1} and its 15th definition gets @samp{15} as well.
4026 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
4027 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
4029 @subheading Dollar Local Labels
4030 @cindex dollar local symbols
4032 On some targets @code{@value{AS}} also supports an even more local form of
4033 local labels called dollar labels. These labels go out of scope (i.e., they
4034 become undefined) as soon as a non-local label is defined. Thus they remain
4035 valid for only a small region of the input source code. Normal local labels,
4036 by contrast, remain in scope for the entire file, or until they are redefined
4037 by another occurrence of the same local label.
4039 Dollar labels are defined in exactly the same way as ordinary local labels,
4040 except that they have a dollar sign suffix to their numeric value, e.g.,
4043 They can also be distinguished from ordinary local labels by their transformed
4044 names which use ASCII character @samp{\001} (control-A) as the magic character
4045 to distinguish them from ordinary labels. For example, the fifth definition of
4046 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
4049 @section The Special Dot Symbol
4051 @cindex dot (symbol)
4052 @cindex @code{.} (symbol)
4053 @cindex current address
4054 @cindex location counter
4055 The special symbol @samp{.} refers to the current address that
4056 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
4057 .long .} defines @code{melvin} to contain its own address.
4058 Assigning a value to @code{.} is treated the same as a @code{.org}
4060 @ifclear no-space-dir
4061 Thus, the expression @samp{.=.+4} is the same as saying
4065 @node Symbol Attributes
4066 @section Symbol Attributes
4068 @cindex symbol attributes
4069 @cindex attributes, symbol
4070 Every symbol has, as well as its name, the attributes ``Value'' and
4071 ``Type''. Depending on output format, symbols can also have auxiliary
4074 The detailed definitions are in @file{a.out.h}.
4077 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
4078 all these attributes, and probably won't warn you. This makes the
4079 symbol an externally defined symbol, which is generally what you
4083 * Symbol Value:: Value
4084 * Symbol Type:: Type
4086 * a.out Symbols:: Symbol Attributes: @code{a.out}
4089 * COFF Symbols:: Symbol Attributes for COFF
4092 * SOM Symbols:: Symbol Attributes for SOM
4099 @cindex value of a symbol
4100 @cindex symbol value
4101 The value of a symbol is (usually) 32 bits. For a symbol which labels a
4102 location in the text, data, bss or absolute sections the value is the
4103 number of addresses from the start of that section to the label.
4104 Naturally for text, data and bss sections the value of a symbol changes
4105 as @code{@value{LD}} changes section base addresses during linking. Absolute
4106 symbols' values do not change during linking: that is why they are
4109 The value of an undefined symbol is treated in a special way. If it is
4110 0 then the symbol is not defined in this assembler source file, and
4111 @code{@value{LD}} tries to determine its value from other files linked into the
4112 same program. You make this kind of symbol simply by mentioning a symbol
4113 name without defining it. A non-zero value represents a @code{.comm}
4114 common declaration. The value is how much common storage to reserve, in
4115 bytes (addresses). The symbol refers to the first address of the
4121 @cindex type of a symbol
4123 The type attribute of a symbol contains relocation (section)
4124 information, any flag settings indicating that a symbol is external, and
4125 (optionally), other information for linkers and debuggers. The exact
4126 format depends on the object-code output format in use.
4130 @subsection Symbol Attributes: @code{a.out}
4132 @cindex @code{a.out} symbol attributes
4133 @cindex symbol attributes, @code{a.out}
4136 * Symbol Desc:: Descriptor
4137 * Symbol Other:: Other
4141 @subsubsection Descriptor
4143 @cindex descriptor, of @code{a.out} symbol
4144 This is an arbitrary 16-bit value. You may establish a symbol's
4145 descriptor value by using a @code{.desc} statement
4146 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4147 @command{@value{AS}}.
4150 @subsubsection Other
4152 @cindex other attribute, of @code{a.out} symbol
4153 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4158 @subsection Symbol Attributes for COFF
4160 @cindex COFF symbol attributes
4161 @cindex symbol attributes, COFF
4163 The COFF format supports a multitude of auxiliary symbol attributes;
4164 like the primary symbol attributes, they are set between @code{.def} and
4165 @code{.endef} directives.
4167 @subsubsection Primary Attributes
4169 @cindex primary attributes, COFF symbols
4170 The symbol name is set with @code{.def}; the value and type,
4171 respectively, with @code{.val} and @code{.type}.
4173 @subsubsection Auxiliary Attributes
4175 @cindex auxiliary attributes, COFF symbols
4176 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4177 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4178 table information for COFF.
4183 @subsection Symbol Attributes for SOM
4185 @cindex SOM symbol attributes
4186 @cindex symbol attributes, SOM
4188 The SOM format for the HPPA supports a multitude of symbol attributes set with
4189 the @code{.EXPORT} and @code{.IMPORT} directives.
4191 The attributes are described in @cite{HP9000 Series 800 Assembly
4192 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4193 @code{EXPORT} assembler directive documentation.
4197 @chapter Expressions
4201 @cindex numeric values
4202 An @dfn{expression} specifies an address or numeric value.
4203 Whitespace may precede and/or follow an expression.
4205 The result of an expression must be an absolute number, or else an offset into
4206 a particular section. If an expression is not absolute, and there is not
4207 enough information when @command{@value{AS}} sees the expression to know its
4208 section, a second pass over the source program might be necessary to interpret
4209 the expression---but the second pass is currently not implemented.
4210 @command{@value{AS}} aborts with an error message in this situation.
4213 * Empty Exprs:: Empty Expressions
4214 * Integer Exprs:: Integer Expressions
4218 @section Empty Expressions
4220 @cindex empty expressions
4221 @cindex expressions, empty
4222 An empty expression has no value: it is just whitespace or null.
4223 Wherever an absolute expression is required, you may omit the
4224 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4225 is compatible with other assemblers.
4228 @section Integer Expressions
4230 @cindex integer expressions
4231 @cindex expressions, integer
4232 An @dfn{integer expression} is one or more @emph{arguments} delimited
4233 by @emph{operators}.
4236 * Arguments:: Arguments
4237 * Operators:: Operators
4238 * Prefix Ops:: Prefix Operators
4239 * Infix Ops:: Infix Operators
4243 @subsection Arguments
4245 @cindex expression arguments
4246 @cindex arguments in expressions
4247 @cindex operands in expressions
4248 @cindex arithmetic operands
4249 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4250 contexts arguments are sometimes called ``arithmetic operands''. In
4251 this manual, to avoid confusing them with the ``instruction operands'' of
4252 the machine language, we use the term ``argument'' to refer to parts of
4253 expressions only, reserving the word ``operand'' to refer only to machine
4254 instruction operands.
4256 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4257 @var{section} is one of text, data, bss, absolute,
4258 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4261 Numbers are usually integers.
4263 A number can be a flonum or bignum. In this case, you are warned
4264 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4265 these 32 bits are an integer. You may write integer-manipulating
4266 instructions that act on exotic constants, compatible with other
4269 @cindex subexpressions
4270 Subexpressions are a left parenthesis @samp{(} followed by an integer
4271 expression, followed by a right parenthesis @samp{)}; or a prefix
4272 operator followed by an argument.
4275 @subsection Operators
4277 @cindex operators, in expressions
4278 @cindex arithmetic functions
4279 @cindex functions, in expressions
4280 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4281 operators are followed by an argument. Infix operators appear
4282 between their arguments. Operators may be preceded and/or followed by
4286 @subsection Prefix Operator
4288 @cindex prefix operators
4289 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4290 one argument, which must be absolute.
4292 @c the tex/end tex stuff surrounding this small table is meant to make
4293 @c it align, on the printed page, with the similar table in the next
4294 @c section (which is inside an enumerate).
4296 \global\advance\leftskip by \itemindent
4301 @dfn{Negation}. Two's complement negation.
4303 @dfn{Complementation}. Bitwise not.
4307 \global\advance\leftskip by -\itemindent
4311 @subsection Infix Operators
4313 @cindex infix operators
4314 @cindex operators, permitted arguments
4315 @dfn{Infix operators} take two arguments, one on either side. Operators
4316 have precedence, but operations with equal precedence are performed left
4317 to right. Apart from @code{+} or @option{-}, both arguments must be
4318 absolute, and the result is absolute.
4321 @cindex operator precedence
4322 @cindex precedence of operators
4329 @dfn{Multiplication}.
4332 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4338 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4341 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4345 Intermediate precedence
4350 @dfn{Bitwise Inclusive Or}.
4356 @dfn{Bitwise Exclusive Or}.
4359 @dfn{Bitwise Or Not}.
4366 @cindex addition, permitted arguments
4367 @cindex plus, permitted arguments
4368 @cindex arguments for addition
4370 @dfn{Addition}. If either argument is absolute, the result has the section of
4371 the other argument. You may not add together arguments from different
4374 @cindex subtraction, permitted arguments
4375 @cindex minus, permitted arguments
4376 @cindex arguments for subtraction
4378 @dfn{Subtraction}. If the right argument is absolute, the
4379 result has the section of the left argument.
4380 If both arguments are in the same section, the result is absolute.
4381 You may not subtract arguments from different sections.
4382 @c FIXME is there still something useful to say about undefined - undefined ?
4384 @cindex comparison expressions
4385 @cindex expressions, comparison
4390 @dfn{Is Not Equal To}
4394 @dfn{Is Greater Than}
4396 @dfn{Is Greater Than Or Equal To}
4398 @dfn{Is Less Than Or Equal To}
4400 The comparison operators can be used as infix operators. A true result has a
4401 value of -1 whereas a false result has a value of 0. Note, these operators
4402 perform signed comparisons.
4405 @item Lowest Precedence
4414 These two logical operations can be used to combine the results of sub
4415 expressions. Note, unlike the comparison operators a true result returns a
4416 value of 1 but a false result does still return 0. Also note that the logical
4417 or operator has a slightly lower precedence than logical and.
4422 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4423 address; you can only have a defined section in one of the two arguments.
4426 @chapter Assembler Directives
4428 @cindex directives, machine independent
4429 @cindex pseudo-ops, machine independent
4430 @cindex machine independent directives
4431 All assembler directives have names that begin with a period (@samp{.}).
4432 The names are case insensitive for most targets, and usually written
4435 This chapter discusses directives that are available regardless of the
4436 target machine configuration for the @sc{gnu} assembler.
4438 Some machine configurations provide additional directives.
4439 @xref{Machine Dependencies}.
4442 @ifset machine-directives
4443 @xref{Machine Dependencies}, for additional directives.
4448 * Abort:: @code{.abort}
4450 * ABORT (COFF):: @code{.ABORT}
4453 * Align:: @code{.align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4454 * Altmacro:: @code{.altmacro}
4455 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4456 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4457 * Attach_to_group:: @code{.attach_to_group @var{name}}
4458 * Balign:: @code{.balign [@var{abs-expr}[, @var{abs-expr}]]}
4459 * Bss:: @code{.bss @var{subsection}}
4460 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4461 * Byte:: @code{.byte @var{expressions}}
4462 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4463 * Comm:: @code{.comm @var{symbol} , @var{length} }
4464 * Data:: @code{.data @var{subsection}}
4465 * Dc:: @code{.dc[@var{size}] @var{expressions}}
4466 * Dcb:: @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
4467 * Ds:: @code{.ds[@var{size}] @var{number} [,@var{fill}]}
4469 * Def:: @code{.def @var{name}}
4472 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4478 * Double:: @code{.double @var{flonums}}
4479 * Eject:: @code{.eject}
4480 * Else:: @code{.else}
4481 * Elseif:: @code{.elseif}
4484 * Endef:: @code{.endef}
4487 * Endfunc:: @code{.endfunc}
4488 * Endif:: @code{.endif}
4489 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4490 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4491 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4493 * Error:: @code{.error @var{string}}
4494 * Exitm:: @code{.exitm}
4495 * Extern:: @code{.extern}
4496 * Fail:: @code{.fail}
4497 * File:: @code{.file}
4498 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4499 * Float:: @code{.float @var{flonums}}
4500 * Func:: @code{.func}
4501 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4503 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4504 * Hidden:: @code{.hidden @var{names}}
4507 * hword:: @code{.hword @var{expressions}}
4508 * Ident:: @code{.ident}
4509 * If:: @code{.if @var{absolute expression}}
4510 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4511 * Include:: @code{.include "@var{file}"}
4512 * Int:: @code{.int @var{expressions}}
4514 * Internal:: @code{.internal @var{names}}
4517 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4518 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4519 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4520 * Lflags:: @code{.lflags}
4521 @ifclear no-line-dir
4522 * Line:: @code{.line @var{line-number}}
4525 * Linkonce:: @code{.linkonce [@var{type}]}
4526 * List:: @code{.list}
4527 * Ln:: @code{.ln @var{line-number}}
4528 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4529 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4531 * Local:: @code{.local @var{names}}
4534 * Long:: @code{.long @var{expressions}}
4536 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4539 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4540 * MRI:: @code{.mri @var{val}}
4541 * Noaltmacro:: @code{.noaltmacro}
4542 * Nolist:: @code{.nolist}
4544 * Nops:: @code{.nops @var{size}[, @var{control}]}
4545 * Octa:: @code{.octa @var{bignums}}
4546 * Offset:: @code{.offset @var{loc}}
4547 * Org:: @code{.org @var{new-lc}, @var{fill}}
4548 * P2align:: @code{.p2align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4550 * PopSection:: @code{.popsection}
4551 * Previous:: @code{.previous}
4554 * Print:: @code{.print @var{string}}
4556 * Protected:: @code{.protected @var{names}}
4559 * Psize:: @code{.psize @var{lines}, @var{columns}}
4560 * Purgem:: @code{.purgem @var{name}}
4562 * PushSection:: @code{.pushsection @var{name}}
4565 * Quad:: @code{.quad @var{bignums}}
4566 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4567 * Rept:: @code{.rept @var{count}}
4568 * Sbttl:: @code{.sbttl "@var{subheading}"}
4570 * Scl:: @code{.scl @var{class}}
4573 * Section:: @code{.section @var{name}[, @var{flags}]}
4576 * Set:: @code{.set @var{symbol}, @var{expression}}
4577 * Short:: @code{.short @var{expressions}}
4578 * Single:: @code{.single @var{flonums}}
4580 * Size:: @code{.size [@var{name} , @var{expression}]}
4582 @ifclear no-space-dir
4583 * Skip:: @code{.skip @var{size} [,@var{fill}]}
4586 * Sleb128:: @code{.sleb128 @var{expressions}}
4587 @ifclear no-space-dir
4588 * Space:: @code{.space @var{size} [,@var{fill}]}
4591 * Stab:: @code{.stabd, .stabn, .stabs}
4594 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4595 * Struct:: @code{.struct @var{expression}}
4597 * SubSection:: @code{.subsection}
4598 * Symver:: @code{.symver @var{name},@var{name2@@nodename}[,@var{visibility}]}
4602 * Tag:: @code{.tag @var{structname}}
4605 * Text:: @code{.text @var{subsection}}
4606 * Title:: @code{.title "@var{heading}"}
4608 * Tls_common:: @code{.tls_common @var{symbol}, @var{length}[, @var{alignment}]}
4611 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4614 * Uleb128:: @code{.uleb128 @var{expressions}}
4616 * Val:: @code{.val @var{addr}}
4620 * Version:: @code{.version "@var{string}"}
4621 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4622 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4625 * Warning:: @code{.warning @var{string}}
4626 * Weak:: @code{.weak @var{names}}
4627 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4628 * Word:: @code{.word @var{expressions}}
4629 @ifclear no-space-dir
4630 * Zero:: @code{.zero @var{size}}
4632 * 2byte:: @code{.2byte @var{expressions}}
4633 * 4byte:: @code{.4byte @var{expressions}}
4634 * 8byte:: @code{.8byte @var{bignums}}
4635 * Deprecated:: Deprecated Directives
4639 @section @code{.abort}
4641 @cindex @code{abort} directive
4642 @cindex stopping the assembly
4643 This directive stops the assembly immediately. It is for
4644 compatibility with other assemblers. The original idea was that the
4645 assembly language source would be piped into the assembler. If the sender
4646 of the source quit, it could use this directive tells @command{@value{AS}} to
4647 quit also. One day @code{.abort} will not be supported.
4651 @section @code{.ABORT} (COFF)
4653 @cindex @code{ABORT} directive
4654 When producing COFF output, @command{@value{AS}} accepts this directive as a
4655 synonym for @samp{.abort}.
4660 @section @code{.align [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4662 @cindex padding the location counter
4663 @cindex @code{align} directive
4664 Pad the location counter (in the current subsection) to a particular storage
4665 boundary. The first expression (which must be absolute) is the alignment
4666 required, as described below. If this expression is omitted then a default
4667 value of 0 is used, effectively disabling alignment requirements.
4669 The second expression (also absolute) gives the fill value to be stored in the
4670 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4671 padding bytes are normally zero. However, on most systems, if the section is
4672 marked as containing code and the fill value is omitted, the space is filled
4673 with no-op instructions.
4675 The third expression is also absolute, and is also optional. If it is present,
4676 it is the maximum number of bytes that should be skipped by this alignment
4677 directive. If doing the alignment would require skipping more bytes than the
4678 specified maximum, then the alignment is not done at all. You can omit the
4679 fill value (the second argument) entirely by simply using two commas after the
4680 required alignment; this can be useful if you want the alignment to be filled
4681 with no-op instructions when appropriate.
4683 The way the required alignment is specified varies from system to system.
4684 For the arc, hppa, i386 using ELF, iq2000, m68k, or1k,
4685 s390, sparc, tic4x and xtensa, the first expression is the
4686 alignment request in bytes. For example @samp{.align 8} advances
4687 the location counter until it is a multiple of 8. If the location counter
4688 is already a multiple of 8, no change is needed. For the tic54x, the
4689 first expression is the alignment request in words.
4691 For other systems, including ppc, i386 using a.out format, arm and
4692 strongarm, it is the
4693 number of low-order zero bits the location counter must have after
4694 advancement. For example @samp{.align 3} advances the location
4695 counter until it is a multiple of 8. If the location counter is already a
4696 multiple of 8, no change is needed.
4698 This inconsistency is due to the different behaviors of the various
4699 native assemblers for these systems which GAS must emulate.
4700 GAS also provides @code{.balign} and @code{.p2align} directives,
4701 described later, which have a consistent behavior across all
4702 architectures (but are specific to GAS).
4705 @section @code{.altmacro}
4706 Enable alternate macro mode, enabling:
4709 @item LOCAL @var{name} [ , @dots{} ]
4710 One additional directive, @code{LOCAL}, is available. It is used to
4711 generate a string replacement for each of the @var{name} arguments, and
4712 replace any instances of @var{name} in each macro expansion. The
4713 replacement string is unique in the assembly, and different for each
4714 separate macro expansion. @code{LOCAL} allows you to write macros that
4715 define symbols, without fear of conflict between separate macro expansions.
4717 @item String delimiters
4718 You can write strings delimited in these other ways besides
4719 @code{"@var{string}"}:
4722 @item '@var{string}'
4723 You can delimit strings with single-quote characters.
4725 @item <@var{string}>
4726 You can delimit strings with matching angle brackets.
4729 @item single-character string escape
4730 To include any single character literally in a string (even if the
4731 character would otherwise have some special meaning), you can prefix the
4732 character with @samp{!} (an exclamation mark). For example, you can
4733 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4735 @item Expression results as strings
4736 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4737 and use the result as a string.
4741 @section @code{.ascii "@var{string}"}@dots{}
4743 @cindex @code{ascii} directive
4744 @cindex string literals
4745 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4746 separated by commas. It assembles each string (with no automatic
4747 trailing zero byte) into consecutive addresses.
4750 @section @code{.asciz "@var{string}"}@dots{}
4752 @cindex @code{asciz} directive
4753 @cindex zero-terminated strings
4754 @cindex null-terminated strings
4755 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4756 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''. Note that
4757 multiple string arguments not separated by commas will be concatenated
4758 together and only one final zero byte will be stored.
4760 @node Attach_to_group
4761 @section @code{.attach_to_group @var{name}}
4762 Attaches the current section to the named group. This is like declaring
4763 the section with the @code{G} attribute, but can be done after the section
4764 has been created. Note if the group section does not exist at the point that
4765 this directive is used then it will be created.
4768 @section @code{.balign[wl] [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
4770 @cindex padding the location counter given number of bytes
4771 @cindex @code{balign} directive
4772 Pad the location counter (in the current subsection) to a particular
4773 storage boundary. The first expression (which must be absolute) is the
4774 alignment request in bytes. For example @samp{.balign 8} advances
4775 the location counter until it is a multiple of 8. If the location counter
4776 is already a multiple of 8, no change is needed. If the expression is omitted
4777 then a default value of 0 is used, effectively disabling alignment requirements.
4779 The second expression (also absolute) gives the fill value to be stored in the
4780 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4781 padding bytes are normally zero. However, on most systems, if the section is
4782 marked as containing code and the fill value is omitted, the space is filled
4783 with no-op instructions.
4785 The third expression is also absolute, and is also optional. If it is present,
4786 it is the maximum number of bytes that should be skipped by this alignment
4787 directive. If doing the alignment would require skipping more bytes than the
4788 specified maximum, then the alignment is not done at all. You can omit the
4789 fill value (the second argument) entirely by simply using two commas after the
4790 required alignment; this can be useful if you want the alignment to be filled
4791 with no-op instructions when appropriate.
4793 @cindex @code{balignw} directive
4794 @cindex @code{balignl} directive
4795 The @code{.balignw} and @code{.balignl} directives are variants of the
4796 @code{.balign} directive. The @code{.balignw} directive treats the fill
4797 pattern as a two byte word value. The @code{.balignl} directives treats the
4798 fill pattern as a four byte longword value. For example, @code{.balignw
4799 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4800 filled in with the value 0x368d (the exact placement of the bytes depends upon
4801 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4805 @section @code{.bss @var{subsection}}
4806 @cindex @code{bss} directive
4808 @code{.bss} tells @command{@value{AS}} to assemble the following statements
4809 onto the end of the bss section.
4811 For ELF based targets an optional @var{subsection} expression (which must
4812 evaluate to a positive integer) can be provided. In this case the statements
4813 are appended to the end of the indicated bss subsection.
4816 @node Bundle directives
4817 @section Bundle directives
4818 @subsection @code{.bundle_align_mode @var{abs-expr}}
4819 @cindex @code{bundle_align_mode} directive
4821 @cindex instruction bundle
4822 @cindex aligned instruction bundle
4823 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4824 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4825 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4826 disabled (which is the default state). If the argument it not zero, it
4827 gives the size of an instruction bundle as a power of two (as for the
4828 @code{.p2align} directive, @pxref{P2align}).
4830 For some targets, it's an ABI requirement that no instruction may span a
4831 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4832 instructions that starts on an aligned boundary. For example, if
4833 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4834 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4835 effect, no single instruction may span a boundary between bundles. If an
4836 instruction would start too close to the end of a bundle for the length of
4837 that particular instruction to fit within the bundle, then the space at the
4838 end of that bundle is filled with no-op instructions so the instruction
4839 starts in the next bundle. As a corollary, it's an error if any single
4840 instruction's encoding is longer than the bundle size.
4842 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4843 @cindex @code{bundle_lock} directive
4844 @cindex @code{bundle_unlock} directive
4845 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4846 allow explicit control over instruction bundle padding. These directives
4847 are only valid when @code{.bundle_align_mode} has been used to enable
4848 aligned instruction bundle mode. It's an error if they appear when
4849 @code{.bundle_align_mode} has not been used at all, or when the last
4850 directive was @w{@code{.bundle_align_mode 0}}.
4852 @cindex bundle-locked
4853 For some targets, it's an ABI requirement that certain instructions may
4854 appear only as part of specified permissible sequences of multiple
4855 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4856 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4857 instruction sequence. For purposes of aligned instruction bundle mode, a
4858 sequence starting with @code{.bundle_lock} and ending with
4859 @code{.bundle_unlock} is treated as a single instruction. That is, the
4860 entire sequence must fit into a single bundle and may not span a bundle
4861 boundary. If necessary, no-op instructions will be inserted before the
4862 first instruction of the sequence so that the whole sequence starts on an
4863 aligned bundle boundary. It's an error if the sequence is longer than the
4866 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4867 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4868 nested. That is, a second @code{.bundle_lock} directive before the next
4869 @code{.bundle_unlock} directive has no effect except that it must be
4870 matched by another closing @code{.bundle_unlock} so that there is the
4871 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4874 @section @code{.byte @var{expressions}}
4876 @cindex @code{byte} directive
4877 @cindex integers, one byte
4878 @code{.byte} expects zero or more expressions, separated by commas.
4879 Each expression is assembled into the next byte.
4881 Note - this directive is not intended for encoding instructions, and it will
4882 not trigger effects like DWARF line number generation. Instead some targets
4883 support special directives for encoding arbitrary binary sequences as
4884 instructions such as @code{.insn} or @code{.inst}.
4886 @node CFI directives
4887 @section CFI directives
4888 @subsection @code{.cfi_sections @var{section_list}}
4889 @cindex @code{cfi_sections} directive
4890 @code{.cfi_sections} may be used to specify whether CFI directives
4891 should emit @code{.eh_frame} section, @code{.debug_frame} section and/or
4892 @code{.sframe} section. If @var{section_list} contains @code{.eh_frame},
4893 @code{.eh_frame} is emitted, if @var{section_list} contains
4894 @code{.debug_frame}, @code{.debug_frame} is emitted, and finally, if
4895 @var{section_list} contains @code{.sframe}, @code{.sframe} is emitted.
4896 To emit multiple sections, specify them together in a list. For example, to
4897 emit both @code{.eh_frame} and @code{.debug_frame}, use
4898 @code{.eh_frame, .debug_frame}. The default if this directive is not used
4899 is @code{.cfi_sections .eh_frame}.
4901 On targets that support compact unwinding tables these can be generated
4902 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4904 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4905 which is used by the @value{TIC6X} target.
4907 The @code{.cfi_sections} directive can be repeated, with the same or different
4908 arguments, provided that CFI generation has not yet started. Once CFI
4909 generation has started however the section list is fixed and any attempts to
4910 redefine it will result in an error.
4912 @subsection @code{.cfi_startproc [simple]}
4913 @cindex @code{cfi_startproc} directive
4914 @code{.cfi_startproc} is used at the beginning of each function that
4915 should have an entry in @code{.eh_frame}. It initializes some internal
4916 data structures. Don't forget to close the function by
4917 @code{.cfi_endproc}.
4919 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4920 it also emits some architecture dependent initial CFI instructions.
4922 @subsection @code{.cfi_endproc}
4923 @cindex @code{cfi_endproc} directive
4924 @code{.cfi_endproc} is used at the end of a function where it closes its
4925 unwind entry previously opened by
4926 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4928 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4929 @cindex @code{cfi_personality} directive
4930 @code{.cfi_personality} defines personality routine and its encoding.
4931 @var{encoding} must be a constant determining how the personality
4932 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4933 argument is not present, otherwise second argument should be
4934 a constant or a symbol name. When using indirect encodings,
4935 the symbol provided should be the location where personality
4936 can be loaded from, not the personality routine itself.
4937 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4938 no personality routine.
4940 @subsection @code{.cfi_personality_id @var{id}}
4941 @cindex @code{cfi_personality_id} directive
4942 @code{cfi_personality_id} defines a personality routine by its index as
4943 defined in a compact unwinding format.
4944 Only valid when generating compact EH frames (i.e.
4945 with @code{.cfi_sections eh_frame_entry}.
4947 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4948 @cindex @code{cfi_fde_data} directive
4949 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4950 used for the current function. These are emitted inline in the
4951 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4952 in the @code{.gnu.extab} section otherwise.
4953 Only valid when generating compact EH frames (i.e.
4954 with @code{.cfi_sections eh_frame_entry}.
4956 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4957 @code{.cfi_lsda} defines LSDA and its encoding.
4958 @var{encoding} must be a constant determining how the LSDA
4959 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4960 argument is not present, otherwise the second argument should be a constant
4961 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4962 meaning that no LSDA is present.
4964 @subsection @code{.cfi_inline_lsda} [@var{align}]
4965 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4966 switches to the corresponding @code{.gnu.extab} section.
4967 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4968 Only valid when generating compact EH frames (i.e.
4969 with @code{.cfi_sections eh_frame_entry}.
4971 The table header and unwinding opcodes will be generated at this point,
4972 so that they are immediately followed by the LSDA data. The symbol
4973 referenced by the @code{.cfi_lsda} directive should still be defined
4974 in case a fallback FDE based encoding is used. The LSDA data is terminated
4975 by a section directive.
4977 The optional @var{align} argument specifies the alignment required.
4978 The alignment is specified as a power of two, as with the
4979 @code{.p2align} directive.
4981 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4982 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4983 address from @var{register} and add @var{offset} to it}.
4985 @subsection @code{.cfi_def_cfa_register @var{register}}
4986 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4987 now on @var{register} will be used instead of the old one. Offset
4990 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4991 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4992 remains the same, but @var{offset} is new. Note that it is the
4993 absolute offset that will be added to a defined register to compute
4996 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4997 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4998 value that is added/subtracted from the previous offset.
5000 @subsection @code{.cfi_offset @var{register}, @var{offset}}
5001 Previous value of @var{register} is saved at offset @var{offset} from
5004 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
5005 Previous value of @var{register} is CFA + @var{offset}.
5007 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
5008 Previous value of @var{register} is saved at offset @var{offset} from
5009 the current CFA register. This is transformed to @code{.cfi_offset}
5010 using the known displacement of the CFA register from the CFA.
5011 This is often easier to use, because the number will match the
5012 code it's annotating.
5014 @subsection @code{.cfi_register @var{register1}, @var{register2}}
5015 Previous value of @var{register1} is saved in register @var{register2}.
5017 @subsection @code{.cfi_restore @var{register}}
5018 @code{.cfi_restore} says that the rule for @var{register} is now the
5019 same as it was at the beginning of the function, after all initial
5020 instruction added by @code{.cfi_startproc} were executed.
5022 @subsection @code{.cfi_undefined @var{register}}
5023 From now on the previous value of @var{register} can't be restored anymore.
5025 @subsection @code{.cfi_same_value @var{register}}
5026 Current value of @var{register} is the same like in the previous frame,
5027 i.e. no restoration needed.
5029 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
5030 @code{.cfi_remember_state} pushes the set of rules for every register onto an
5031 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
5032 places them in the current row. This is useful for situations where you have
5033 multiple @code{.cfi_*} directives that need to be undone due to the control
5034 flow of the program. For example, we could have something like this (assuming
5035 the CFA is the value of @code{rbp}):
5045 .cfi_def_cfa %rsp, 8
5048 /* Do something else */
5051 Here, we want the @code{.cfi} directives to affect only the rows corresponding
5052 to the instructions before @code{label}. This means we'd have to add multiple
5053 @code{.cfi} directives after @code{label} to recreate the original save
5054 locations of the registers, as well as setting the CFA back to the value of
5055 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
5067 .cfi_def_cfa %rsp, 8
5071 /* Do something else */
5074 That way, the rules for the instructions after @code{label} will be the same
5075 as before the first @code{.cfi_restore} without having to use multiple
5076 @code{.cfi} directives.
5078 @subsection @code{.cfi_return_column @var{register}}
5079 Change return column @var{register}, i.e. the return address is either
5080 directly in @var{register} or can be accessed by rules for @var{register}.
5082 @subsection @code{.cfi_signal_frame}
5083 Mark current function as signal trampoline.
5085 @subsection @code{.cfi_window_save}
5086 SPARC register window has been saved.
5088 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
5089 Allows the user to add arbitrary bytes to the unwind info. One
5090 might use this to add OS-specific CFI opcodes, or generic CFI
5091 opcodes that GAS does not yet support.
5093 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
5094 The current value of @var{register} is @var{label}. The value of @var{label}
5095 will be encoded in the output file according to @var{encoding}; see the
5096 description of @code{.cfi_personality} for details on this encoding.
5098 The usefulness of equating a register to a fixed label is probably
5099 limited to the return address register. Here, it can be useful to
5100 mark a code segment that has only one return address which is reached
5101 by a direct branch and no copy of the return address exists in memory
5102 or another register.
5105 @section @code{.comm @var{symbol} , @var{length} }
5107 @cindex @code{comm} directive
5108 @cindex symbol, common
5109 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
5110 common symbol in one object file may be merged with a defined or common symbol
5111 of the same name in another object file. If @code{@value{LD}} does not see a
5112 definition for the symbol--just one or more common symbols--then it will
5113 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
5114 absolute expression. If @code{@value{LD}} sees multiple common symbols with
5115 the same name, and they do not all have the same size, it will allocate space
5116 using the largest size.
5119 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
5120 an optional third argument. This is the desired alignment of the symbol,
5121 specified for ELF as a byte boundary (for example, an alignment of 16 means
5122 that the least significant 4 bits of the address should be zero), and for PE
5123 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
5124 boundary). The alignment must be an absolute expression, and it must be a
5125 power of two. If @code{@value{LD}} allocates uninitialized memory for the
5126 common symbol, it will use the alignment when placing the symbol. If no
5127 alignment is specified, @command{@value{AS}} will set the alignment to the
5128 largest power of two less than or equal to the size of the symbol, up to a
5129 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
5130 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
5131 @samp{--section-alignment} option; image file sections in PE are aligned to
5132 multiples of 4096, which is far too large an alignment for ordinary variables.
5133 It is rather the default alignment for (non-debug) sections within object
5134 (@samp{*.o}) files, which are less strictly aligned.}.
5138 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
5139 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
5143 @section @code{.data @var{subsection}}
5144 @cindex @code{data} directive
5146 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5147 end of the data subsection numbered @var{subsection} (which is an
5148 absolute expression). If @var{subsection} is omitted, it defaults
5152 @section @code{.dc[@var{size}] @var{expressions}}
5153 @cindex @code{dc} directive
5155 The @code{.dc} directive expects zero or more @var{expressions} separated by
5156 commas. These expressions are evaluated and their values inserted into the
5157 current section. The size of the emitted value depends upon the suffix to the
5158 @code{.dc} directive:
5162 Emits N-bit values, where N is the size of an address on the target system.
5166 Emits double precision floating-point values.
5168 Emits 32-bit values.
5170 Emits single precision floating-point values.
5172 Emits 16-bit values.
5173 Note - this is true even on targets where the @code{.word} directive would emit
5176 Emits long double precision floating-point values.
5179 If no suffix is used then @samp{.w} is assumed.
5181 The byte ordering is target dependent, as is the size and format of floating
5184 Note - these directives are not intended for encoding instructions, and they
5185 will not trigger effects like DWARF line number generation. Instead some
5186 targets support special directives for encoding arbitrary binary sequences as
5187 instructions such as @code{.insn} or @code{.inst}.
5190 @section @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
5191 @cindex @code{dcb} directive
5192 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5193 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5194 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5195 @var{size} suffix, if present, must be one of:
5199 Emits single byte values.
5201 Emits double-precision floating point values.
5203 Emits 4-byte values.
5205 Emits single-precision floating point values.
5207 Emits 2-byte values.
5209 Emits long double-precision floating point values.
5212 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5214 The byte ordering is target dependent, as is the size and format of floating
5218 @section @code{.ds[@var{size}] @var{number} [,@var{fill}]}
5219 @cindex @code{ds} directive
5220 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5221 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5222 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5223 @var{size} suffix, if present, must be one of:
5227 Emits single byte values.
5229 Emits 8-byte values.
5231 Emits 4-byte values.
5233 Emits values with size matching packed-decimal floating-point ones.
5235 Emits 4-byte values.
5237 Emits 2-byte values.
5239 Emits values with size matching long double precision floating-point ones.
5242 Note - unlike the @code{.dcb} directive the @samp{.d}, @samp{.s} and @samp{.x}
5243 suffixes do not indicate that floating-point values are to be inserted.
5245 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5247 The byte ordering is target dependent.
5251 @section @code{.def @var{name}}
5253 @cindex @code{def} directive
5254 @cindex COFF symbols, debugging
5255 @cindex debugging COFF symbols
5256 Begin defining debugging information for a symbol @var{name}; the
5257 definition extends until the @code{.endef} directive is encountered.
5262 @section @code{.desc @var{symbol}, @var{abs-expression}}
5264 @cindex @code{desc} directive
5265 @cindex COFF symbol descriptor
5266 @cindex symbol descriptor, COFF
5267 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5268 to the low 16 bits of an absolute expression.
5271 The @samp{.desc} directive is not available when @command{@value{AS}} is
5272 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5273 object format. For the sake of compatibility, @command{@value{AS}} accepts
5274 it, but produces no output, when configured for COFF.
5280 @section @code{.dim}
5282 @cindex @code{dim} directive
5283 @cindex COFF auxiliary symbol information
5284 @cindex auxiliary symbol information, COFF
5285 This directive is generated by compilers to include auxiliary debugging
5286 information in the symbol table. It is only permitted inside
5287 @code{.def}/@code{.endef} pairs.
5291 @section @code{.double @var{flonums}}
5293 @cindex @code{double} directive
5294 @cindex floating point numbers (double)
5295 @code{.double} expects zero or more flonums, separated by commas. It
5296 assembles floating point numbers.
5298 The exact kind of floating point numbers emitted depends on how
5299 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5303 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5304 in @sc{ieee} format.
5309 @section @code{.eject}
5311 @cindex @code{eject} directive
5312 @cindex new page, in listings
5313 @cindex page, in listings
5314 @cindex listing control: new page
5315 Force a page break at this point, when generating assembly listings.
5318 @section @code{.else}
5320 @cindex @code{else} directive
5321 @code{.else} is part of the @command{@value{AS}} support for conditional
5322 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5323 of code to be assembled if the condition for the preceding @code{.if}
5327 @section @code{.elseif}
5329 @cindex @code{elseif} directive
5330 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5331 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5332 @code{.if} block that would otherwise fill the entire @code{.else} section.
5335 @section @code{.end}
5337 @cindex @code{end} directive
5338 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5339 process anything in the file past the @code{.end} directive.
5343 @section @code{.endef}
5345 @cindex @code{endef} directive
5346 This directive flags the end of a symbol definition begun with
5351 @section @code{.endfunc}
5352 @cindex @code{endfunc} directive
5353 @code{.endfunc} marks the end of a function specified with @code{.func}.
5356 @section @code{.endif}
5358 @cindex @code{endif} directive
5359 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5360 it marks the end of a block of code that is only assembled
5361 conditionally. @xref{If,,@code{.if}}.
5364 @section @code{.equ @var{symbol}, @var{expression}}
5366 @cindex @code{equ} directive
5367 @cindex assigning values to symbols
5368 @cindex symbols, assigning values to
5369 This directive sets the value of @var{symbol} to @var{expression}.
5370 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5373 The syntax for @code{equ} on the HPPA is
5374 @samp{@var{symbol} .equ @var{expression}}.
5378 The syntax for @code{equ} on the Z80 is
5379 @samp{@var{symbol} equ @var{expression}}.
5380 On the Z80 it is an error if @var{symbol} is already defined,
5381 but the symbol is not protected from later redefinition.
5382 Compare @ref{Equiv}.
5386 @section @code{.equiv @var{symbol}, @var{expression}}
5387 @cindex @code{equiv} directive
5388 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5389 the assembler will signal an error if @var{symbol} is already defined. Note a
5390 symbol which has been referenced but not actually defined is considered to be
5393 Except for the contents of the error message, this is roughly equivalent to
5400 plus it protects the symbol from later redefinition.
5403 @section @code{.eqv @var{symbol}, @var{expression}}
5404 @cindex @code{eqv} directive
5405 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5406 evaluate the expression or any part of it immediately. Instead each time
5407 the resulting symbol is used in an expression, a snapshot of its current
5411 @section @code{.err}
5412 @cindex @code{err} directive
5413 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5414 message and, unless the @option{-Z} option was used, it will not generate an
5415 object file. This can be used to signal an error in conditionally compiled code.
5418 @section @code{.error "@var{string}"}
5419 @cindex error directive
5421 Similarly to @code{.err}, this directive emits an error, but you can specify a
5422 string that will be emitted as the error message. If you don't specify the
5423 message, it defaults to @code{".error directive invoked in source file"}.
5424 @xref{Errors, ,Error and Warning Messages}.
5427 .error "This code has not been assembled and tested."
5431 @section @code{.exitm}
5432 Exit early from the current macro definition. @xref{Macro}.
5435 @section @code{.extern}
5437 @cindex @code{extern} directive
5438 @code{.extern} is accepted in the source program---for compatibility
5439 with other assemblers---but it is ignored. @command{@value{AS}} treats
5440 all undefined symbols as external.
5443 @section @code{.fail @var{expression}}
5445 @cindex @code{fail} directive
5446 Generates an error or a warning. If the value of the @var{expression} is 500
5447 or more, @command{@value{AS}} will print a warning message. If the value is less
5448 than 500, @command{@value{AS}} will print an error message. The message will
5449 include the value of @var{expression}. This can occasionally be useful inside
5450 complex nested macros or conditional assembly.
5453 @section @code{.file}
5454 @cindex @code{file} directive
5456 @ifclear no-file-dir
5457 There are two different versions of the @code{.file} directive. Targets
5458 that support DWARF2 line number information use the DWARF2 version of
5459 @code{.file}. Other targets use the default version.
5461 @subheading Default Version
5463 @cindex logical file name
5464 @cindex file name, logical
5465 This version of the @code{.file} directive tells @command{@value{AS}} that we
5466 are about to start a new logical file. The syntax is:
5472 @var{string} is the new file name. In general, the filename is
5473 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5474 to specify an empty file name, you must give the quotes--@code{""}. This
5475 statement may go away in future: it is only recognized to be compatible with
5476 old @command{@value{AS}} programs.
5478 @subheading DWARF2 Version
5481 When emitting DWARF2 line number information, @code{.file} assigns filenames
5482 to the @code{.debug_line} file name table. The syntax is:
5485 .file @var{fileno} @var{filename}
5488 The @var{fileno} operand should be a unique positive integer to use as the
5489 index of the entry in the table. The @var{filename} operand is a C string
5490 literal enclosed in double quotes. The @var{filename} can include directory
5491 elements. If it does, then the directory will be added to the directory table
5492 and the basename will be added to the file table.
5494 The detail of filename indices is exposed to the user because the filename
5495 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5496 information, and thus the user must know the exact indices that table
5499 If DWARF5 support has been enabled via the @option{-gdwarf-5} option then
5500 an extended version of @code{.file} is also allowed:
5503 .file @var{fileno} [@var{dirname}] @var{filename} [md5 @var{value}]
5506 With this version a separate directory name is allowed, although if this is
5507 used then @var{filename} should not contain any directory component, except
5508 for @var{fileno} equal to 0: in this case, @var{dirname} is expected to be
5509 the current directory and @var{filename} the currently processed file, and
5510 the latter need not be located in the former. In addtion an MD5 hash value
5511 of the contents of @var{filename} can be provided. This will be stored in
5512 the the file table as well, and can be used by tools reading the debug
5513 information to verify that the contents of the source file match the
5514 contents of the compiled file.
5517 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5519 @cindex @code{fill} directive
5520 @cindex writing patterns in memory
5521 @cindex patterns, writing in memory
5522 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5523 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5524 may be zero or more. @var{Size} may be zero or more, but if it is
5525 more than 8, then it is deemed to have the value 8, compatible with
5526 other people's assemblers. The contents of each @var{repeat} bytes
5527 is taken from an 8-byte number. The highest order 4 bytes are
5528 zero. The lowest order 4 bytes are @var{value} rendered in the
5529 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5530 Each @var{size} bytes in a repetition is taken from the lowest order
5531 @var{size} bytes of this number. Again, this bizarre behavior is
5532 compatible with other people's assemblers.
5534 @var{size} and @var{value} are optional.
5535 If the second comma and @var{value} are absent, @var{value} is
5536 assumed zero. If the first comma and following tokens are absent,
5537 @var{size} is assumed to be 1.
5540 @section @code{.float @var{flonums}}
5542 @cindex floating point numbers (single)
5543 @cindex @code{float} directive
5544 This directive assembles zero or more flonums, separated by commas. It
5545 has the same effect as @code{.single}.
5547 The exact kind of floating point numbers emitted depends on how
5548 @command{@value{AS}} is configured.
5549 @xref{Machine Dependencies}.
5553 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5554 in @sc{ieee} format.
5559 @section @code{.func @var{name}[,@var{label}]}
5560 @cindex @code{func} directive
5561 @code{.func} emits debugging information to denote function @var{name}, and
5562 is ignored unless the file is assembled with debugging enabled.
5563 Only @samp{--gstabs[+]} is currently supported.
5564 @var{label} is the entry point of the function and if omitted @var{name}
5565 prepended with the @samp{leading char} is used.
5566 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5567 All functions are currently defined to have @code{void} return type.
5568 The function must be terminated with @code{.endfunc}.
5571 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5573 @cindex @code{global} directive
5574 @cindex symbol, making visible to linker
5575 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5576 @var{symbol} in your partial program, its value is made available to
5577 other partial programs that are linked with it. Otherwise,
5578 @var{symbol} takes its attributes from a symbol of the same name
5579 from another file linked into the same program.
5581 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5582 compatibility with other assemblers.
5585 On the HPPA, @code{.global} is not always enough to make it accessible to other
5586 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5587 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5592 @section @code{.gnu_attribute @var{tag},@var{value}}
5593 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5596 @section @code{.hidden @var{names}}
5598 @cindex @code{hidden} directive
5600 This is one of the ELF visibility directives. The other two are
5601 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5602 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5604 This directive overrides the named symbols default visibility (which is set by
5605 their binding: local, global or weak). The directive sets the visibility to
5606 @code{hidden} which means that the symbols are not visible to other components.
5607 Such symbols are always considered to be @code{protected} as well.
5611 @section @code{.hword @var{expressions}}
5613 @cindex @code{hword} directive
5614 @cindex integers, 16-bit
5615 @cindex numbers, 16-bit
5616 @cindex sixteen bit integers
5617 This expects zero or more @var{expressions}, and emits
5618 a 16 bit number for each.
5621 This directive is a synonym for @samp{.short}; depending on the target
5622 architecture, it may also be a synonym for @samp{.word}.
5626 This directive is a synonym for @samp{.short}.
5629 This directive is a synonym for both @samp{.short} and @samp{.word}.
5634 @section @code{.ident}
5636 @cindex @code{ident} directive
5638 This directive is used by some assemblers to place tags in object files. The
5639 behavior of this directive varies depending on the target. When using the
5640 a.out object file format, @command{@value{AS}} simply accepts the directive for
5641 source-file compatibility with existing assemblers, but does not emit anything
5642 for it. When using COFF, comments are emitted to the @code{.comment} or
5643 @code{.rdata} section, depending on the target. When using ELF, comments are
5644 emitted to the @code{.comment} section.
5647 @section @code{.if @var{absolute expression}}
5649 @cindex conditional assembly
5650 @cindex @code{if} directive
5651 @code{.if} marks the beginning of a section of code which is only
5652 considered part of the source program being assembled if the argument
5653 (which must be an @var{absolute expression}) is non-zero. The end of
5654 the conditional section of code must be marked by @code{.endif}
5655 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5656 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5657 If you have several conditions to check, @code{.elseif} may be used to avoid
5658 nesting blocks if/else within each subsequent @code{.else} block.
5660 The following variants of @code{.if} are also supported:
5662 @cindex @code{ifdef} directive
5663 @item .ifdef @var{symbol}
5664 Assembles the following section of code if the specified @var{symbol}
5665 has been defined. Note a symbol which has been referenced but not yet defined
5666 is considered to be undefined.
5668 @cindex @code{ifb} directive
5669 @item .ifb @var{text}
5670 Assembles the following section of code if the operand is blank (empty).
5672 @cindex @code{ifc} directive
5673 @item .ifc @var{string1},@var{string2}
5674 Assembles the following section of code if the two strings are the same. The
5675 strings may be optionally quoted with single quotes. If they are not quoted,
5676 the first string stops at the first comma, and the second string stops at the
5677 end of the line. Strings which contain whitespace should be quoted. The
5678 string comparison is case sensitive.
5680 @cindex @code{ifeq} directive
5681 @item .ifeq @var{absolute expression}
5682 Assembles the following section of code if the argument is zero.
5684 @cindex @code{ifeqs} directive
5685 @item .ifeqs @var{string1},@var{string2}
5686 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5688 @cindex @code{ifge} directive
5689 @item .ifge @var{absolute expression}
5690 Assembles the following section of code if the argument is greater than or
5693 @cindex @code{ifgt} directive
5694 @item .ifgt @var{absolute expression}
5695 Assembles the following section of code if the argument is greater than zero.
5697 @cindex @code{ifle} directive
5698 @item .ifle @var{absolute expression}
5699 Assembles the following section of code if the argument is less than or equal
5702 @cindex @code{iflt} directive
5703 @item .iflt @var{absolute expression}
5704 Assembles the following section of code if the argument is less than zero.
5706 @cindex @code{ifnb} directive
5707 @item .ifnb @var{text}
5708 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5709 following section of code if the operand is non-blank (non-empty).
5711 @cindex @code{ifnc} directive
5712 @item .ifnc @var{string1},@var{string2}.
5713 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5714 following section of code if the two strings are not the same.
5716 @cindex @code{ifndef} directive
5717 @cindex @code{ifnotdef} directive
5718 @item .ifndef @var{symbol}
5719 @itemx .ifnotdef @var{symbol}
5720 Assembles the following section of code if the specified @var{symbol}
5721 has not been defined. Both spelling variants are equivalent. Note a symbol
5722 which has been referenced but not yet defined is considered to be undefined.
5724 @cindex @code{ifne} directive
5725 @item .ifne @var{absolute expression}
5726 Assembles the following section of code if the argument is not equal to zero
5727 (in other words, this is equivalent to @code{.if}).
5729 @cindex @code{ifnes} directive
5730 @item .ifnes @var{string1},@var{string2}
5731 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5732 following section of code if the two strings are not the same.
5736 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5738 @cindex @code{incbin} directive
5739 @cindex binary files, including
5740 The @code{incbin} directive includes @var{file} verbatim at the current
5741 location. You can control the search paths used with the @samp{-I} command-line
5742 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5745 The @var{skip} argument skips a number of bytes from the start of the
5746 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5747 read. Note that the data is not aligned in any way, so it is the user's
5748 responsibility to make sure that proper alignment is provided both before and
5749 after the @code{incbin} directive.
5752 @section @code{.include "@var{file}"}
5754 @cindex @code{include} directive
5755 @cindex supporting files, including
5756 @cindex files, including
5757 This directive provides a way to include supporting files at specified
5758 points in your source program. The code from @var{file} is assembled as
5759 if it followed the point of the @code{.include}; when the end of the
5760 included file is reached, assembly of the original file continues. You
5761 can control the search paths used with the @samp{-I} command-line option
5762 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5766 @section @code{.int @var{expressions}}
5768 @cindex @code{int} directive
5769 @cindex integers, 32-bit
5770 Expect zero or more @var{expressions}, of any section, separated by commas.
5771 For each expression, emit a number that, at run time, is the value of that
5772 expression. The byte order and bit size of the number depends on what kind
5773 of target the assembly is for.
5777 On most forms of the H8/300, @code{.int} emits 16-bit
5778 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5783 Note - this directive is not intended for encoding instructions, and it will
5784 not trigger effects like DWARF line number generation. Instead some targets
5785 support special directives for encoding arbitrary binary sequences as
5786 instructions such as eg @code{.insn} or @code{.inst}.
5790 @section @code{.internal @var{names}}
5792 @cindex @code{internal} directive
5794 This is one of the ELF visibility directives. The other two are
5795 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5796 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5798 This directive overrides the named symbols default visibility (which is set by
5799 their binding: local, global or weak). The directive sets the visibility to
5800 @code{internal} which means that the symbols are considered to be @code{hidden}
5801 (i.e., not visible to other components), and that some extra, processor specific
5802 processing must also be performed upon the symbols as well.
5806 @section @code{.irp @var{symbol},@var{values}}@dots{}
5808 @cindex @code{irp} directive
5809 Evaluate a sequence of statements assigning different values to @var{symbol}.
5810 The sequence of statements starts at the @code{.irp} directive, and is
5811 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5812 set to @var{value}, and the sequence of statements is assembled. If no
5813 @var{value} is listed, the sequence of statements is assembled once, with
5814 @var{symbol} set to the null string. To refer to @var{symbol} within the
5815 sequence of statements, use @var{\symbol}.
5817 For example, assembling
5825 is equivalent to assembling
5833 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5836 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5838 @cindex @code{irpc} directive
5839 Evaluate a sequence of statements assigning different values to @var{symbol}.
5840 The sequence of statements starts at the @code{.irpc} directive, and is
5841 terminated by an @code{.endr} directive. For each character in @var{value},
5842 @var{symbol} is set to the character, and the sequence of statements is
5843 assembled. If no @var{value} is listed, the sequence of statements is
5844 assembled once, with @var{symbol} set to the null string. To refer to
5845 @var{symbol} within the sequence of statements, use @var{\symbol}.
5847 For example, assembling
5855 is equivalent to assembling
5863 For some caveats with the spelling of @var{symbol}, see also the discussion
5867 @section @code{.lcomm @var{symbol} , @var{length}}
5869 @cindex @code{lcomm} directive
5870 @cindex local common symbols
5871 @cindex symbols, local common
5872 Reserve @var{length} (an absolute expression) bytes for a local common
5873 denoted by @var{symbol}. The section and value of @var{symbol} are
5874 those of the new local common. The addresses are allocated in the bss
5875 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5876 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5877 not visible to @code{@value{LD}}.
5880 Some targets permit a third argument to be used with @code{.lcomm}. This
5881 argument specifies the desired alignment of the symbol in the bss section.
5885 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5886 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5890 @section @code{.lflags}
5892 @cindex @code{lflags} directive (ignored)
5893 @command{@value{AS}} accepts this directive, for compatibility with other
5894 assemblers, but ignores it.
5896 @ifclear no-line-dir
5898 @section @code{.line @var{line-number}}
5900 @cindex @code{line} directive
5901 @cindex logical line number
5903 Change the logical line number. @var{line-number} must be an absolute
5904 expression. The next line has that logical line number. Therefore any other
5905 statements on the current line (after a statement separator character) are
5906 reported as on logical line number @var{line-number} @minus{} 1. One day
5907 @command{@value{AS}} will no longer support this directive: it is recognized only
5908 for compatibility with existing assembler programs.
5911 Even though this is a directive associated with the @code{a.out} or
5912 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5913 when producing COFF output, and treats @samp{.line} as though it
5914 were the COFF @samp{.ln} @emph{if} it is found outside a
5915 @code{.def}/@code{.endef} pair.
5917 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5918 used by compilers to generate auxiliary symbol information for
5923 @section @code{.linkonce [@var{type}]}
5925 @cindex @code{linkonce} directive
5926 @cindex common sections
5927 Mark the current section so that the linker only includes a single copy of it.
5928 This may be used to include the same section in several different object files,
5929 but ensure that the linker will only include it once in the final output file.
5930 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5931 Duplicate sections are detected based on the section name, so it should be
5934 This directive is only supported by a few object file formats; as of this
5935 writing, the only object file format which supports it is the Portable
5936 Executable format used on Windows NT.
5938 The @var{type} argument is optional. If specified, it must be one of the
5939 following strings. For example:
5943 Not all types may be supported on all object file formats.
5947 Silently discard duplicate sections. This is the default.
5950 Warn if there are duplicate sections, but still keep only one copy.
5953 Warn if any of the duplicates have different sizes.
5956 Warn if any of the duplicates do not have exactly the same contents.
5960 @section @code{.list}
5962 @cindex @code{list} directive
5963 @cindex listing control, turning on
5964 Control (in conjunction with the @code{.nolist} directive) whether or
5965 not assembly listings are generated. These two directives maintain an
5966 internal counter (which is zero initially). @code{.list} increments the
5967 counter, and @code{.nolist} decrements it. Assembly listings are
5968 generated whenever the counter is greater than zero.
5970 By default, listings are disabled. When you enable them (with the
5971 @samp{-a} command-line option; @pxref{Invoking,,Command-Line Options}),
5972 the initial value of the listing counter is one.
5975 @section @code{.ln @var{line-number}}
5977 @cindex @code{ln} directive
5978 @ifclear no-line-dir
5979 @samp{.ln} is a synonym for @samp{.line}.
5982 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5983 must be an absolute expression. The next line has that logical
5984 line number, so any other statements on the current line (after a
5985 statement separator character @code{;}) are reported as on logical
5986 line number @var{line-number} @minus{} 1.
5990 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5991 @cindex @code{loc} directive
5992 When emitting DWARF2 line number information,
5993 the @code{.loc} directive will add a row to the @code{.debug_line} line
5994 number matrix corresponding to the immediately following assembly
5995 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5996 arguments will be applied to the @code{.debug_line} state machine before
5997 the row is added. It is an error for the input assembly file to generate
5998 a non-empty @code{.debug_line} and also use @code{loc} directives.
6000 The @var{options} are a sequence of the following tokens in any order:
6004 This option will set the @code{basic_block} register in the
6005 @code{.debug_line} state machine to @code{true}.
6008 This option will set the @code{prologue_end} register in the
6009 @code{.debug_line} state machine to @code{true}.
6011 @item epilogue_begin
6012 This option will set the @code{epilogue_begin} register in the
6013 @code{.debug_line} state machine to @code{true}.
6015 @item is_stmt @var{value}
6016 This option will set the @code{is_stmt} register in the
6017 @code{.debug_line} state machine to @code{value}, which must be
6020 @item isa @var{value}
6021 This directive will set the @code{isa} register in the @code{.debug_line}
6022 state machine to @var{value}, which must be an unsigned integer.
6024 @item discriminator @var{value}
6025 This directive will set the @code{discriminator} register in the @code{.debug_line}
6026 state machine to @var{value}, which must be an unsigned integer.
6028 @item view @var{value}
6029 This option causes a row to be added to @code{.debug_line} in reference to the
6030 current address (which might not be the same as that of the following assembly
6031 instruction), and to associate @var{value} with the @code{view} register in the
6032 @code{.debug_line} state machine. If @var{value} is a label, both the
6033 @code{view} register and the label are set to the number of prior @code{.loc}
6034 directives at the same program location. If @var{value} is the literal
6035 @code{0}, the @code{view} register is set to zero, and the assembler asserts
6036 that there aren't any prior @code{.loc} directives at the same program
6037 location. If @var{value} is the literal @code{-0}, the assembler arrange for
6038 the @code{view} register to be reset in this row, even if there are prior
6039 @code{.loc} directives at the same program location.
6043 @node Loc_mark_labels
6044 @section @code{.loc_mark_labels @var{enable}}
6045 @cindex @code{loc_mark_labels} directive
6046 When emitting DWARF2 line number information,
6047 the @code{.loc_mark_labels} directive makes the assembler emit an entry
6048 to the @code{.debug_line} line number matrix with the @code{basic_block}
6049 register in the state machine set whenever a code label is seen.
6050 The @var{enable} argument should be either 1 or 0, to enable or disable
6051 this function respectively.
6055 @section @code{.local @var{names}}
6057 @cindex @code{local} directive
6058 This directive, which is available for ELF targets, marks each symbol in
6059 the comma-separated list of @code{names} as a local symbol so that it
6060 will not be externally visible. If the symbols do not already exist,
6061 they will be created.
6063 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
6064 accept an alignment argument, which is the case for most ELF targets,
6065 the @code{.local} directive can be used in combination with @code{.comm}
6066 (@pxref{Comm}) to define aligned local common data.
6070 @section @code{.long @var{expressions}}
6072 @cindex @code{long} directive
6073 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
6076 @c no one seems to know what this is for or whether this description is
6077 @c what it really ought to do
6079 @section @code{.lsym @var{symbol}, @var{expression}}
6081 @cindex @code{lsym} directive
6082 @cindex symbol, not referenced in assembly
6083 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
6084 the hash table, ensuring it cannot be referenced by name during the
6085 rest of the assembly. This sets the attributes of the symbol to be
6086 the same as the expression value:
6088 @var{other} = @var{descriptor} = 0
6089 @var{type} = @r{(section of @var{expression})}
6090 @var{value} = @var{expression}
6093 The new symbol is not flagged as external.
6097 @section @code{.macro}
6100 The commands @code{.macro} and @code{.endm} allow you to define macros that
6101 generate assembly output. For example, this definition specifies a macro
6102 @code{sum} that puts a sequence of numbers into memory:
6105 .macro sum from=0, to=5
6114 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
6126 @item .macro @var{macname}
6127 @itemx .macro @var{macname} @var{macargs} @dots{}
6128 @cindex @code{macro} directive
6129 Begin the definition of a macro called @var{macname}. If your macro
6130 definition requires arguments, specify their names after the macro name,
6131 separated by commas or spaces. You can qualify the macro argument to
6132 indicate whether all invocations must specify a non-blank value (through
6133 @samp{:@code{req}}), or whether it takes all of the remaining arguments
6134 (through @samp{:@code{vararg}}). You can supply a default value for any
6135 macro argument by following the name with @samp{=@var{deflt}}. You
6136 cannot define two macros with the same @var{macname} unless it has been
6137 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
6138 definitions. For example, these are all valid @code{.macro} statements:
6142 Begin the definition of a macro called @code{comm}, which takes no
6145 @item .macro plus1 p, p1
6146 @itemx .macro plus1 p p1
6147 Either statement begins the definition of a macro called @code{plus1},
6148 which takes two arguments; within the macro definition, write
6149 @samp{\p} or @samp{\p1} to evaluate the arguments.
6151 @item .macro reserve_str p1=0 p2
6152 Begin the definition of a macro called @code{reserve_str}, with two
6153 arguments. The first argument has a default value, but not the second.
6154 After the definition is complete, you can call the macro either as
6155 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
6156 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
6157 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
6158 @samp{0}, and @samp{\p2} evaluating to @var{b}).
6160 @item .macro m p1:req, p2=0, p3:vararg
6161 Begin the definition of a macro called @code{m}, with at least three
6162 arguments. The first argument must always have a value specified, but
6163 not the second, which instead has a default value. The third formal
6164 will get assigned all remaining arguments specified at invocation time.
6166 When you call a macro, you can specify the argument values either by
6167 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
6168 @samp{sum to=17, from=9}.
6172 Note that since each of the @var{macargs} can be an identifier exactly
6173 as any other one permitted by the target architecture, there may be
6174 occasional problems if the target hand-crafts special meanings to certain
6175 characters when they occur in a special position. For example, if the colon
6176 (@code{:}) is generally permitted to be part of a symbol name, but the
6177 architecture specific code special-cases it when occurring as the final
6178 character of a symbol (to denote a label), then the macro parameter
6179 replacement code will have no way of knowing that and consider the whole
6180 construct (including the colon) an identifier, and check only this
6181 identifier for being the subject to parameter substitution. So for example
6182 this macro definition:
6190 might not work as expected. Invoking @samp{label foo} might not create a label
6191 called @samp{foo} but instead just insert the text @samp{\l:} into the
6192 assembler source, probably generating an error about an unrecognised
6195 Similarly problems might occur with the period character (@samp{.})
6196 which is often allowed inside opcode names (and hence identifier names). So
6197 for example constructing a macro to build an opcode from a base name and a
6198 length specifier like this:
6201 .macro opcode base length
6206 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
6207 instruction but instead generate some kind of error as the assembler tries to
6208 interpret the text @samp{\base.\length}.
6210 There are several possible ways around this problem:
6213 @item Insert white space
6214 If it is possible to use white space characters then this is the simplest
6223 @item Use @samp{\()}
6224 The string @samp{\()} can be used to separate the end of a macro argument from
6225 the following text. eg:
6228 .macro opcode base length
6233 @item Use the alternate macro syntax mode
6234 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6235 used as a separator. eg:
6245 Note: this problem of correctly identifying string parameters to pseudo ops
6246 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6247 and @code{.irpc} (@pxref{Irpc}) as well.
6249 Another issue can occur with the actual arguments passed during macro
6250 invocation: Multiple arguments can be separated by blanks or commas. To have
6251 arguments actually contain blanks or commas (or potentially other non-alpha-
6252 numeric characters), individual arguments will need to be enclosed in either
6253 parentheses @code{()}, square brackets @code{[]}, or double quote @code{"}
6254 characters. The latter may be the only viable option in certain situations,
6255 as only double quotes are actually stripped while establishing arguments. It
6256 may be important to be aware of two escaping models used when processing such
6257 quoted argument strings: For one two adjacent double quotes represent a single
6258 double quote in the resulting argument, going along the lines of the stripping
6259 of the enclosing quotes. But then double quotes can also be escaped by a
6260 backslash @code{\}, but this backslash will not be retained in the resulting
6261 actual argument as then seen / used while expanding the macro.
6263 As a consequence to the first of these escaping mechanisms two string literals
6264 intended to be representing separate macro arguments need to be separated by
6265 white space (or, better yet, by a comma). To state it differently, such
6266 adjacent string literals - even if separated only by a blank - will not be
6267 concatenated when determining macro arguments, even if they're only separated
6268 by white space. This is unlike certain other pseudo ops, e.g. @code{.ascii}.
6271 @cindex @code{endm} directive
6272 Mark the end of a macro definition.
6275 @cindex @code{exitm} directive
6276 Exit early from the current macro definition.
6278 @cindex number of macros executed
6279 @cindex macros, count executed
6281 @command{@value{AS}} maintains a counter of how many macros it has
6282 executed in this pseudo-variable; you can copy that number to your
6283 output with @samp{\@@}, but @emph{only within a macro definition}.
6285 @item LOCAL @var{name} [ , @dots{} ]
6286 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6287 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6288 @xref{Altmacro,,@code{.altmacro}}.
6292 @section @code{.mri @var{val}}
6294 @cindex @code{mri} directive
6295 @cindex MRI mode, temporarily
6296 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6297 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6298 affects code assembled until the next @code{.mri} directive, or until the end
6299 of the file. @xref{M, MRI mode, MRI mode}.
6302 @section @code{.noaltmacro}
6303 Disable alternate macro mode. @xref{Altmacro}.
6306 @section @code{.nolist}
6308 @cindex @code{nolist} directive
6309 @cindex listing control, turning off
6310 Control (in conjunction with the @code{.list} directive) whether or
6311 not assembly listings are generated. These two directives maintain an
6312 internal counter (which is zero initially). @code{.list} increments the
6313 counter, and @code{.nolist} decrements it. Assembly listings are
6314 generated whenever the counter is greater than zero.
6317 @section @code{.nop [@var{size}]}
6319 @cindex @code{nop} directive
6320 @cindex filling memory with no-op instructions
6321 This directive emits no-op instructions. It is provided on all architectures,
6322 allowing the creation of architecture neutral tests involving actual code. The
6323 size of the generated instruction is target specific, but if the optional
6324 @var{size} argument is given and resolves to an absolute positive value at that
6325 point in assembly (no forward expressions allowed) then the fewest no-op
6326 instructions are emitted that equal or exceed a total @var{size} in bytes.
6327 @code{.nop} does affect the generation of DWARF debug line information.
6328 Some targets do not support using @code{.nop} with @var{size}.
6331 @section @code{.nops @var{size}[, @var{control}]}
6333 @cindex @code{nops} directive
6334 @cindex filling memory with no-op instructions
6335 This directive emits no-op instructions. It is specific to the Intel 80386 and
6336 AMD x86-64 targets. It takes a @var{size} argument and generates @var{size}
6337 bytes of no-op instructions. @var{size} must be absolute and positive. These
6338 bytes do not affect the generation of DWARF debug line information.
6340 The optional @var{control} argument specifies a size limit for a single no-op
6341 instruction. If not provided then a value of 0 is assumed. The valid values
6342 of @var{control} are between 0 and 4 in 16-bit mode, between 0 and 7 when
6343 tuning for older processors in 32-bit mode, between 0 and 11 in 64-bit mode or
6344 when tuning for newer processors in 32-bit mode. When 0 is used, the no-op
6345 instruction size limit is set to the maximum supported size.
6348 @section @code{.octa @var{bignums}}
6350 @c FIXME: double size emitted for "octa" on some? Or warn?
6351 @cindex @code{octa} directive
6352 @cindex integer, 16-byte
6353 @cindex sixteen byte integer
6354 This directive expects zero or more bignums, separated by commas. For each
6355 bignum, it emits a 16-byte integer.
6357 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6358 hence @emph{octa}-word for 16 bytes.
6361 @section @code{.offset @var{loc}}
6363 @cindex @code{offset} directive
6364 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6365 be an absolute expression. This directive may be useful for defining
6366 symbols with absolute values. Do not confuse it with the @code{.org}
6370 @section @code{.org @var{new-lc} , @var{fill}}
6372 @cindex @code{org} directive
6373 @cindex location counter, advancing
6374 @cindex advancing location counter
6375 @cindex current address, advancing
6376 Advance the location counter of the current section to
6377 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6378 expression with the same section as the current subsection. That is,
6379 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6380 wrong section, the @code{.org} directive is ignored. To be compatible
6381 with former assemblers, if the section of @var{new-lc} is absolute,
6382 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6383 is the same as the current subsection.
6385 @code{.org} may only increase the location counter, or leave it
6386 unchanged; you cannot use @code{.org} to move the location counter
6389 @c double negative used below "not undefined" because this is a specific
6390 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6391 @c section. doc@cygnus.com 18feb91
6392 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6393 may not be undefined. If you really detest this restriction we eagerly await
6394 a chance to share your improved assembler.
6396 Beware that the origin is relative to the start of the section, not
6397 to the start of the subsection. This is compatible with other
6398 people's assemblers.
6400 When the location counter (of the current subsection) is advanced, the
6401 intervening bytes are filled with @var{fill} which should be an
6402 absolute expression. If the comma and @var{fill} are omitted,
6403 @var{fill} defaults to zero.
6406 @section @code{.p2align[wl] [@var{abs-expr}[, @var{abs-expr}[, @var{abs-expr}]]]}
6408 @cindex padding the location counter given a power of two
6409 @cindex @code{p2align} directive
6410 Pad the location counter (in the current subsection) to a particular
6411 storage boundary. The first expression (which must be absolute) is the
6412 number of low-order zero bits the location counter must have after
6413 advancement. For example @samp{.p2align 3} advances the location
6414 counter until it is a multiple of 8. If the location counter is already a
6415 multiple of 8, no change is needed. If the expression is omitted then a
6416 default value of 0 is used, effectively disabling alignment requirements.
6418 The second expression (also absolute) gives the fill value to be stored in the
6419 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6420 padding bytes are normally zero. However, on most systems, if the section is
6421 marked as containing code and the fill value is omitted, the space is filled
6422 with no-op instructions.
6424 The third expression is also absolute, and is also optional. If it is present,
6425 it is the maximum number of bytes that should be skipped by this alignment
6426 directive. If doing the alignment would require skipping more bytes than the
6427 specified maximum, then the alignment is not done at all. You can omit the
6428 fill value (the second argument) entirely by simply using two commas after the
6429 required alignment; this can be useful if you want the alignment to be filled
6430 with no-op instructions when appropriate.
6432 @cindex @code{p2alignw} directive
6433 @cindex @code{p2alignl} directive
6434 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6435 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6436 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6437 fill pattern as a four byte longword value. For example, @code{.p2alignw
6438 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6439 filled in with the value 0x368d (the exact placement of the bytes depends upon
6440 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6445 @section @code{.popsection}
6447 @cindex @code{popsection} directive
6448 @cindex Section Stack
6449 This is one of the ELF section stack manipulation directives. The others are
6450 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6451 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6454 This directive replaces the current section (and subsection) with the top
6455 section (and subsection) on the section stack. This section is popped off the
6461 @section @code{.previous}
6463 @cindex @code{previous} directive
6464 @cindex Section Stack
6465 This is one of the ELF section stack manipulation directives. The others are
6466 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6467 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6468 (@pxref{PopSection}).
6470 This directive swaps the current section (and subsection) with most recently
6471 referenced section/subsection pair prior to this one. Multiple
6472 @code{.previous} directives in a row will flip between two sections (and their
6473 subsections). For example:
6485 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6491 # Now in section A subsection 1
6495 # Now in section B subsection 0
6498 # Now in section B subsection 1
6501 # Now in section B subsection 0
6505 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6506 section B and 0x9abc into subsection 1 of section B.
6508 In terms of the section stack, this directive swaps the current section with
6509 the top section on the section stack.
6513 @section @code{.print @var{string}}
6515 @cindex @code{print} directive
6516 @command{@value{AS}} will print @var{string} on the standard output during
6517 assembly. You must put @var{string} in double quotes.
6521 @section @code{.protected @var{names}}
6523 @cindex @code{protected} directive
6525 This is one of the ELF visibility directives. The other two are
6526 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6528 This directive overrides the named symbols default visibility (which is set by
6529 their binding: local, global or weak). The directive sets the visibility to
6530 @code{protected} which means that any references to the symbols from within the
6531 components that defines them must be resolved to the definition in that
6532 component, even if a definition in another component would normally preempt
6537 @section @code{.psize @var{lines} , @var{columns}}
6539 @cindex @code{psize} directive
6540 @cindex listing control: paper size
6541 @cindex paper size, for listings
6542 Use this directive to declare the number of lines---and, optionally, the
6543 number of columns---to use for each page, when generating listings.
6545 If you do not use @code{.psize}, listings use a default line-count
6546 of 60. You may omit the comma and @var{columns} specification; the
6547 default width is 200 columns.
6549 @command{@value{AS}} generates formfeeds whenever the specified number of
6550 lines is exceeded (or whenever you explicitly request one, using
6553 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6554 those explicitly specified with @code{.eject}.
6557 @section @code{.purgem @var{name}}
6559 @cindex @code{purgem} directive
6560 Undefine the macro @var{name}, so that later uses of the string will not be
6561 expanded. @xref{Macro}.
6565 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6567 @cindex @code{pushsection} directive
6568 @cindex Section Stack
6569 This is one of the ELF section stack manipulation directives. The others are
6570 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6571 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6574 This directive pushes the current section (and subsection) onto the
6575 top of the section stack, and then replaces the current section and
6576 subsection with @code{name} and @code{subsection}. The optional
6577 @code{flags}, @code{type} and @code{arguments} are treated the same
6578 as in the @code{.section} (@pxref{Section}) directive.
6582 @section @code{.quad @var{bignums}}
6584 @cindex @code{quad} directive
6585 @code{.quad} expects zero or more bignums, separated by commas. For
6586 each bignum, it emits
6588 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6589 warning message; and just takes the lowest order 8 bytes of the bignum.
6590 @cindex eight-byte integer
6591 @cindex integer, 8-byte
6593 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6594 hence @emph{quad}-word for 8 bytes.
6597 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6598 warning message; and just takes the lowest order 16 bytes of the bignum.
6599 @cindex sixteen-byte integer
6600 @cindex integer, 16-byte
6603 Note - this directive is not intended for encoding instructions, and it will
6604 not trigger effects like DWARF line number generation. Instead some targets
6605 support special directives for encoding arbitrary binary sequences as
6606 instructions such as @code{.insn} or @code{.inst}.
6609 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6611 @cindex @code{reloc} directive
6612 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6613 @var{expression}. If @var{offset} is a number, the relocation is generated in
6614 the current section. If @var{offset} is an expression that resolves to a
6615 symbol plus offset, the relocation is generated in the given symbol's section.
6616 @var{expression}, if present, must resolve to a symbol plus addend or to an
6617 absolute value, but note that not all targets support an addend. e.g. ELF REL
6618 targets such as i386 store an addend in the section contents rather than in the
6619 relocation. This low level interface does not support addends stored in the
6623 @section @code{.rept @var{count}}
6625 @cindex @code{rept} directive
6626 Repeat the sequence of lines between the @code{.rept} directive and the next
6627 @code{.endr} directive @var{count} times.
6629 For example, assembling
6637 is equivalent to assembling
6645 A count of zero is allowed, but nothing is generated. Negative counts are not
6646 allowed and if encountered will be treated as if they were zero.
6649 @section @code{.sbttl "@var{subheading}"}
6651 @cindex @code{sbttl} directive
6652 @cindex subtitles for listings
6653 @cindex listing control: subtitle
6654 Use @var{subheading} as the title (third line, immediately after the
6655 title line) when generating assembly listings.
6657 This directive affects subsequent pages, as well as the current page if
6658 it appears within ten lines of the top of a page.
6662 @section @code{.scl @var{class}}
6664 @cindex @code{scl} directive
6665 @cindex symbol storage class (COFF)
6666 @cindex COFF symbol storage class
6667 Set the storage-class value for a symbol. This directive may only be
6668 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6669 whether a symbol is static or external, or it may record further
6670 symbolic debugging information.
6675 @section @code{.section @var{name}}
6677 @cindex named section
6678 Use the @code{.section} directive to assemble the following code into a section
6681 This directive is only supported for targets that actually support arbitrarily
6682 named sections; on @code{a.out} targets, for example, it is not accepted, even
6683 with a standard @code{a.out} section name.
6687 @c only print the extra heading if both COFF and ELF are set
6688 @subheading COFF Version
6691 @cindex @code{section} directive (COFF version)
6692 For COFF targets, the @code{.section} directive is used in one of the following
6696 .section @var{name}[, "@var{flags}"]
6697 .section @var{name}[, @var{subsection}]
6700 If the optional argument is quoted, it is taken as flags to use for the
6701 section. Each flag is a single character. The following flags are recognized:
6705 bss section (uninitialized data)
6707 section is not loaded
6713 exclude section from linking
6719 shared section (meaningful for PE targets)
6721 ignored. (For compatibility with the ELF version)
6723 section is not readable (meaningful for PE targets)
6725 single-digit power-of-two section alignment (GNU extension)
6728 If no flags are specified, the default flags depend upon the section name. If
6729 the section name is not recognized, the default will be for the section to be
6730 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6731 from the section, rather than adding them, so if they are used on their own it
6732 will be as if no flags had been specified at all.
6734 If the optional argument to the @code{.section} directive is not quoted, it is
6735 taken as a subsection number (@pxref{Sub-Sections}).
6740 @c only print the extra heading if both COFF and ELF are set
6741 @subheading ELF Version
6744 @cindex Section Stack
6745 This is one of the ELF section stack manipulation directives. The others are
6746 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6747 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6748 @code{.previous} (@pxref{Previous}).
6750 @cindex @code{section} directive (ELF version)
6751 For ELF targets, the @code{.section} directive is used like this:
6754 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6757 @anchor{Section Name Substitutions}
6758 @kindex --sectname-subst
6759 @cindex section name substitution
6760 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6761 argument may contain a substitution sequence. Only @code{%S} is supported
6762 at the moment, and substitutes the current section name. For example:
6765 .macro exception_code
6766 .section %S.exception
6767 [exception code here]
6782 The two @code{exception_code} invocations above would create the
6783 @code{.text.exception} and @code{.init.exception} sections respectively.
6784 This is useful e.g. to discriminate between ancillary sections that are
6785 tied to setup code to be discarded after use from ancillary sections that
6786 need to stay resident without having to define multiple @code{exception_code}
6787 macros just for that purpose.
6789 The optional @var{flags} argument is a quoted string which may contain any
6790 combination of the following characters:
6794 section is allocatable
6796 section is a GNU_MBIND section
6798 section is excluded from executable and shared library.
6800 section references a symbol defined in another section (the linked-to
6801 section) in the same file.
6805 section is executable
6807 section is mergeable
6809 section contains zero terminated strings
6811 section is a member of a section group
6813 section is used for thread-local-storage
6815 section is a member of the previously-current section's group, if any
6817 retained section (apply SHF_GNU_RETAIN to prevent linker garbage
6818 collection, GNU ELF extension)
6819 @item @code{<number>}
6820 a numeric value indicating the bits to be set in the ELF section header's flags
6821 field. Note - if one or more of the alphabetic characters described above is
6822 also included in the flags field, their bit values will be ORed into the
6824 @item @code{<target specific>}
6825 some targets extend this list with their own flag characters
6828 Note - once a section's flags have been set they cannot be changed. There are
6829 a few exceptions to this rule however. Processor and application specific
6830 flags can be added to an already defined section. The @code{.interp},
6831 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6832 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6833 section may have the executable (@code{x}) flag added. Also note that the
6834 @code{.attach_to_group} directive can be used to add a section to a group even
6835 if the section was not originally declared to be part of that group.
6837 The optional @var{type} argument may contain one of the following constants:
6841 section contains data
6843 section does not contain data (i.e., section only occupies space)
6845 section contains data which is used by things other than the program
6847 section contains an array of pointers to init functions
6849 section contains an array of pointers to finish functions
6850 @item @@preinit_array
6851 section contains an array of pointers to pre-init functions
6852 @item @@@code{<number>}
6853 a numeric value to be set as the ELF section header's type field.
6854 @item @@@code{<target specific>}
6855 some targets extend this list with their own types
6858 Many targets only support the first three section types. The type may be
6859 enclosed in double quotes if necessary.
6861 Note on targets where the @code{@@} character is the start of a comment (eg
6862 ARM) then another character is used instead. For example the ARM port uses the
6865 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6866 special and have fixed types. Any attempt to declare them with a different
6867 type will generate an error from the assembler.
6869 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6870 be specified as well as an extra argument---@var{entsize}---like this:
6873 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6876 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6877 constants, each @var{entsize} octets long. Sections with both @code{M} and
6878 @code{S} must contain zero terminated strings where each character is
6879 @var{entsize} bytes long. The linker may remove duplicates within sections with
6880 the same name, same entity size and same flags. @var{entsize} must be an
6881 absolute expression. For sections with both @code{M} and @code{S}, a string
6882 which is a suffix of a larger string is considered a duplicate. Thus
6883 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6884 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6886 If @var{flags} contains the @code{o} flag, then the @var{type} argument
6887 must be present along with an additional field like this:
6890 .section @var{name},"@var{flags}"o,@@@var{type},@var{SymbolName}|@var{SectionIndex}
6893 The @var{SymbolName} field specifies the symbol name which the section
6894 references. Alternatively a numeric @var{SectionIndex} can be provided. This
6895 is not generally a good idea as section indicies are rarely known at assembly
6896 time, but the facility is provided for testing purposes. An index of zero is
6897 allowed. It indicates that the linked-to section has already been discarded.
6899 Note: If both the @var{M} and @var{o} flags are present, then the fields
6900 for the Merge flag should come first, like this:
6903 .section @var{name},"@var{flags}"Mo,@@@var{type},@var{entsize},@var{SymbolName}
6906 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6907 be present along with an additional field like this:
6910 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6913 The @var{GroupName} field specifies the name of the section group to which this
6914 particular section belongs. The optional linkage field can contain:
6918 indicates that only one copy of this section should be retained
6923 Note: if both the @var{M} and @var{G} flags are present then the fields for
6924 the Merge flag should come first, like this:
6927 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6930 If both @code{o} flag and @code{G} flag are present, then the
6931 @var{SymbolName} field for @code{o} comes first, like this:
6934 .section @var{name},"@var{flags}"oG,@@@var{type},@var{SymbolName},@var{GroupName}[,@var{linkage}]
6937 If @var{flags} contains the @code{?} symbol then it may not also contain the
6938 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6939 present. Instead, @code{?} says to consider the section that's current before
6940 this directive. If that section used @code{G}, then the new section will use
6941 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6942 If not, then the @code{?} symbol has no effect.
6944 The optional @var{unique,@code{<number>}} argument must come last. It
6945 assigns @var{@code{<number>}} as a unique section ID to distinguish
6946 different sections with the same section name like these:
6949 .section @var{name},"@var{flags}",@@@var{type},@var{unique,@code{<number>}}
6950 .section @var{name},"@var{flags}"G,@@@var{type},@var{GroupName},[@var{linkage}],@var{unique,@code{<number>}}
6951 .section @var{name},"@var{flags}"MG,@@@var{type},@var{entsize},@var{GroupName}[,@var{linkage}],@var{unique,@code{<number>}}
6954 The valid values of @var{@code{<number>}} are between 0 and 4294967295.
6956 If no flags are specified, the default flags depend upon the section name. If
6957 the section name is not recognized, the default will be for the section to have
6958 none of the above flags: it will not be allocated in memory, nor writable, nor
6959 executable. The section will contain data.
6961 For ELF targets, the assembler supports another type of @code{.section}
6962 directive for compatibility with the Solaris assembler:
6965 .section "@var{name}"[, @var{flags}...]
6968 Note that the section name is quoted. There may be a sequence of comma
6973 section is allocatable
6977 section is executable
6979 section is excluded from executable and shared library.
6981 section is used for thread local storage
6984 This directive replaces the current section and subsection. See the
6985 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6986 some examples of how this directive and the other section stack directives
6992 @section @code{.set @var{symbol}, @var{expression}}
6994 @cindex @code{set} directive
6995 @cindex symbol value, setting
6996 Set the value of @var{symbol} to @var{expression}. This
6997 changes @var{symbol}'s value and type to conform to
6998 @var{expression}. If @var{symbol} was flagged as external, it remains
6999 flagged (@pxref{Symbol Attributes}).
7001 You may @code{.set} a symbol many times in the same assembly provided that the
7002 values given to the symbol are constants. Values that are based on expressions
7003 involving other symbols are allowed, but some targets may restrict this to only
7004 being done once per assembly. This is because those targets do not set the
7005 addresses of symbols at assembly time, but rather delay the assignment until a
7006 final link is performed. This allows the linker a chance to change the code in
7007 the files, changing the location of, and the relative distance between, various
7010 If you @code{.set} a global symbol, the value stored in the object
7011 file is the last value stored into it.
7014 On Z80 @code{set} is a real instruction, use @code{.set} or
7015 @samp{@var{symbol} defl @var{expression}} instead.
7019 @section @code{.short @var{expressions}}
7021 @cindex @code{short} directive
7023 @code{.short} is normally the same as @samp{.word}.
7024 @xref{Word,,@code{.word}}.
7026 In some configurations, however, @code{.short} and @code{.word} generate
7027 numbers of different lengths. @xref{Machine Dependencies}.
7031 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
7034 This expects zero or more @var{expressions}, and emits
7035 a 16 bit number for each.
7039 Note - this directive is not intended for encoding instructions, and it will
7040 not trigger effects like DWARF line number generation. Instead some targets
7041 support special directives for encoding arbitrary binary sequences as
7042 instructions such as @code{.insn} or @code{.inst}.
7045 @section @code{.single @var{flonums}}
7047 @cindex @code{single} directive
7048 @cindex floating point numbers (single)
7049 This directive assembles zero or more flonums, separated by commas. It
7050 has the same effect as @code{.float}.
7052 The exact kind of floating point numbers emitted depends on how
7053 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
7057 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
7058 numbers in @sc{ieee} format.
7064 @section @code{.size}
7066 This directive is used to set the size associated with a symbol.
7070 @c only print the extra heading if both COFF and ELF are set
7071 @subheading COFF Version
7074 @cindex @code{size} directive (COFF version)
7075 For COFF targets, the @code{.size} directive is only permitted inside
7076 @code{.def}/@code{.endef} pairs. It is used like this:
7079 .size @var{expression}
7086 @c only print the extra heading if both COFF and ELF are set
7087 @subheading ELF Version
7090 @cindex @code{size} directive (ELF version)
7091 For ELF targets, the @code{.size} directive is used like this:
7094 .size @var{name} , @var{expression}
7097 This directive sets the size associated with a symbol @var{name}.
7098 The size in bytes is computed from @var{expression} which can make use of label
7099 arithmetic. This directive is typically used to set the size of function
7104 @ifclear no-space-dir
7106 @section @code{.skip @var{size} [,@var{fill}]}
7108 @cindex @code{skip} directive
7109 @cindex filling memory
7110 This directive emits @var{size} bytes, each of value @var{fill}. Both
7111 @var{size} and @var{fill} are absolute expressions. If the comma and
7112 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
7117 @section @code{.sleb128 @var{expressions}}
7119 @cindex @code{sleb128} directive
7120 @var{sleb128} stands for ``signed little endian base 128.'' This is a
7121 compact, variable length representation of numbers used by the DWARF
7122 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
7124 @ifclear no-space-dir
7126 @section @code{.space @var{size} [,@var{fill}]}
7128 @cindex @code{space} directive
7129 @cindex filling memory
7130 This directive emits @var{size} bytes, each of value @var{fill}. Both
7131 @var{size} and @var{fill} are absolute expressions. If the comma
7132 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
7137 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
7138 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
7139 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
7140 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
7148 @section @code{.stabd, .stabn, .stabs}
7150 @cindex symbolic debuggers, information for
7151 @cindex @code{stab@var{x}} directives
7152 There are three directives that begin @samp{.stab}.
7153 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
7154 The symbols are not entered in the @command{@value{AS}} hash table: they
7155 cannot be referenced elsewhere in the source file.
7156 Up to five fields are required:
7160 This is the symbol's name. It may contain any character except
7161 @samp{\000}, so is more general than ordinary symbol names. Some
7162 debuggers used to code arbitrarily complex structures into symbol names
7166 An absolute expression. The symbol's type is set to the low 8 bits of
7167 this expression. Any bit pattern is permitted, but @code{@value{LD}}
7168 and debuggers choke on silly bit patterns.
7171 An absolute expression. The symbol's ``other'' attribute is set to the
7172 low 8 bits of this expression.
7175 An absolute expression. The symbol's descriptor is set to the low 16
7176 bits of this expression.
7179 An absolute expression which becomes the symbol's value.
7182 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
7183 or @code{.stabs} statement, the symbol has probably already been created;
7184 you get a half-formed symbol in your object file. This is
7185 compatible with earlier assemblers!
7188 @cindex @code{stabd} directive
7189 @item .stabd @var{type} , @var{other} , @var{desc}
7191 The ``name'' of the symbol generated is not even an empty string.
7192 It is a null pointer, for compatibility. Older assemblers used a
7193 null pointer so they didn't waste space in object files with empty
7196 The symbol's value is set to the location counter,
7197 relocatably. When your program is linked, the value of this symbol
7198 is the address of the location counter when the @code{.stabd} was
7201 @cindex @code{stabn} directive
7202 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
7203 The name of the symbol is set to the empty string @code{""}.
7205 @cindex @code{stabs} directive
7206 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
7207 All five fields are specified.
7213 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
7214 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
7216 @cindex string, copying to object file
7217 @cindex string8, copying to object file
7218 @cindex string16, copying to object file
7219 @cindex string32, copying to object file
7220 @cindex string64, copying to object file
7221 @cindex @code{string} directive
7222 @cindex @code{string8} directive
7223 @cindex @code{string16} directive
7224 @cindex @code{string32} directive
7225 @cindex @code{string64} directive
7227 Copy the characters in @var{str} to the object file. You may specify more than
7228 one string to copy, separated by commas. Unless otherwise specified for a
7229 particular machine, the assembler marks the end of each string with a 0 byte.
7230 You can use any of the escape sequences described in @ref{Strings,,Strings}.
7232 The variants @code{string16}, @code{string32} and @code{string64} differ from
7233 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
7234 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
7235 are stored in target endianness byte order.
7241 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
7242 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
7247 @section @code{.struct @var{expression}}
7249 @cindex @code{struct} directive
7250 Switch to the absolute section, and set the section offset to @var{expression},
7251 which must be an absolute expression. You might use this as follows:
7260 This would define the symbol @code{field1} to have the value 0, the symbol
7261 @code{field2} to have the value 4, and the symbol @code{field3} to have the
7262 value 8. Assembly would be left in the absolute section, and you would need to
7263 use a @code{.section} directive of some sort to change to some other section
7264 before further assembly.
7268 @section @code{.subsection @var{name}}
7270 @cindex @code{subsection} directive
7271 @cindex Section Stack
7272 This is one of the ELF section stack manipulation directives. The others are
7273 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
7274 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
7277 This directive replaces the current subsection with @code{name}. The current
7278 section is not changed. The replaced subsection is put onto the section stack
7279 in place of the then current top of stack subsection.
7284 @section @code{.symver}
7285 @cindex @code{symver} directive
7286 @cindex symbol versioning
7287 @cindex versions of symbols
7288 Use the @code{.symver} directive to bind symbols to specific version nodes
7289 within a source file. This is only supported on ELF platforms, and is
7290 typically used when assembling files to be linked into a shared library.
7291 There are cases where it may make sense to use this in objects to be bound
7292 into an application itself so as to override a versioned symbol from a
7295 For ELF targets, the @code{.symver} directive can be used like this:
7297 .symver @var{name}, @var{name2@@nodename}[ ,@var{visibility}]
7299 If the original symbol @var{name} is defined within the file
7300 being assembled, the @code{.symver} directive effectively creates a symbol
7301 alias with the name @var{name2@@nodename}, and in fact the main reason that we
7302 just don't try and create a regular alias is that the @var{@@} character isn't
7303 permitted in symbol names. The @var{name2} part of the name is the actual name
7304 of the symbol by which it will be externally referenced. The name @var{name}
7305 itself is merely a name of convenience that is used so that it is possible to
7306 have definitions for multiple versions of a function within a single source
7307 file, and so that the compiler can unambiguously know which version of a
7308 function is being mentioned. The @var{nodename} portion of the alias should be
7309 the name of a node specified in the version script supplied to the linker when
7310 building a shared library. If you are attempting to override a versioned
7311 symbol from a shared library, then @var{nodename} should correspond to the
7312 nodename of the symbol you are trying to override. The optional argument
7313 @var{visibility} updates the visibility of the original symbol. The valid
7314 visibilities are @code{local}, @code{hidden}, and @code{remove}. The
7315 @code{local} visibility makes the original symbol a local symbol
7316 (@pxref{Local}). The @code{hidden} visibility sets the visibility of the
7317 original symbol to @code{hidden} (@pxref{Hidden}). The @code{remove}
7318 visibility removes the original symbol from the symbol table. If visibility
7319 isn't specified, the original symbol is unchanged.
7321 If the symbol @var{name} is not defined within the file being assembled, all
7322 references to @var{name} will be changed to @var{name2@@nodename}. If no
7323 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
7326 Another usage of the @code{.symver} directive is:
7328 .symver @var{name}, @var{name2@@@@nodename}
7330 In this case, the symbol @var{name} must exist and be defined within
7331 the file being assembled. It is similar to @var{name2@@nodename}. The
7332 difference is @var{name2@@@@nodename} will also be used to resolve
7333 references to @var{name2} by the linker.
7335 The third usage of the @code{.symver} directive is:
7337 .symver @var{name}, @var{name2@@@@@@nodename}
7339 When @var{name} is not defined within the
7340 file being assembled, it is treated as @var{name2@@nodename}. When
7341 @var{name} is defined within the file being assembled, the symbol
7342 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7347 @section @code{.tag @var{structname}}
7349 @cindex COFF structure debugging
7350 @cindex structure debugging, COFF
7351 @cindex @code{tag} directive
7352 This directive is generated by compilers to include auxiliary debugging
7353 information in the symbol table. It is only permitted inside
7354 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7355 definitions in the symbol table with instances of those structures.
7359 @section @code{.text @var{subsection}}
7361 @cindex @code{text} directive
7362 Tells @command{@value{AS}} to assemble the following statements onto the end of
7363 the text subsection numbered @var{subsection}, which is an absolute
7364 expression. If @var{subsection} is omitted, subsection number zero
7368 @section @code{.title "@var{heading}"}
7370 @cindex @code{title} directive
7371 @cindex listing control: title line
7372 Use @var{heading} as the title (second line, immediately after the
7373 source file name and pagenumber) when generating assembly listings.
7375 This directive affects subsequent pages, as well as the current page if
7376 it appears within ten lines of the top of a page.
7380 @section @code{.tls_common @var{symbol}, @var{length}[, @var{alignment}]}
7382 @cindex @code{tls_common} directive
7383 This directive behaves in the same way as the @code{.comm} directive
7384 (@pxref{Comm}) except that @var{symbol} has type of STT_TLS instead of
7390 @section @code{.type}
7392 This directive is used to set the type of a symbol.
7396 @c only print the extra heading if both COFF and ELF are set
7397 @subheading COFF Version
7400 @cindex COFF symbol type
7401 @cindex symbol type, COFF
7402 @cindex @code{type} directive (COFF version)
7403 For COFF targets, this directive is permitted only within
7404 @code{.def}/@code{.endef} pairs. It is used like this:
7410 This records the integer @var{int} as the type attribute of a symbol table
7417 @c only print the extra heading if both COFF and ELF are set
7418 @subheading ELF Version
7421 @cindex ELF symbol type
7422 @cindex symbol type, ELF
7423 @cindex @code{type} directive (ELF version)
7424 For ELF targets, the @code{.type} directive is used like this:
7427 .type @var{name} , @var{type description}
7430 This sets the type of symbol @var{name} to be either a
7431 function symbol or an object symbol. There are five different syntaxes
7432 supported for the @var{type description} field, in order to provide
7433 compatibility with various other assemblers.
7435 Because some of the characters used in these syntaxes (such as @samp{@@} and
7436 @samp{#}) are comment characters for some architectures, some of the syntaxes
7437 below do not work on all architectures. The first variant will be accepted by
7438 the GNU assembler on all architectures so that variant should be used for
7439 maximum portability, if you do not need to assemble your code with other
7442 The syntaxes supported are:
7445 .type <name> STT_<TYPE_IN_UPPER_CASE>
7446 .type <name>,#<type>
7447 .type <name>,@@<type>
7448 .type <name>,%<type>
7449 .type <name>,"<type>"
7452 The types supported are:
7457 Mark the symbol as being a function name.
7460 @itemx gnu_indirect_function
7461 Mark the symbol as an indirect function when evaluated during reloc
7462 processing. (This is only supported on assemblers targeting GNU systems).
7466 Mark the symbol as being a data object.
7470 Mark the symbol as being a thread-local data object.
7474 Mark the symbol as being a common data object.
7478 Does not mark the symbol in any way. It is supported just for completeness.
7480 @item gnu_unique_object
7481 Marks the symbol as being a globally unique data object. The dynamic linker
7482 will make sure that in the entire process there is just one symbol with this
7483 name and type in use. (This is only supported on assemblers targeting GNU
7488 Changing between incompatible types other than from/to STT_NOTYPE will
7489 result in a diagnostic. An intermediate change to STT_NOTYPE will silence
7492 Note: Some targets support extra types in addition to those listed above.
7498 @section @code{.uleb128 @var{expressions}}
7500 @cindex @code{uleb128} directive
7501 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7502 compact, variable length representation of numbers used by the DWARF
7503 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7507 @section @code{.val @var{addr}}
7509 @cindex @code{val} directive
7510 @cindex COFF value attribute
7511 @cindex value attribute, COFF
7512 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7513 records the address @var{addr} as the value attribute of a symbol table
7519 @section @code{.version "@var{string}"}
7521 @cindex @code{version} directive
7522 This directive creates a @code{.note} section and places into it an ELF
7523 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7528 @section @code{.vtable_entry @var{table}, @var{offset}}
7530 @cindex @code{vtable_entry} directive
7531 This directive finds or creates a symbol @code{table} and creates a
7532 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7535 @section @code{.vtable_inherit @var{child}, @var{parent}}
7537 @cindex @code{vtable_inherit} directive
7538 This directive finds the symbol @code{child} and finds or creates the symbol
7539 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7540 parent whose addend is the value of the child symbol. As a special case the
7541 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7545 @section @code{.warning "@var{string}"}
7546 @cindex warning directive
7547 Similar to the directive @code{.error}
7548 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7551 @section @code{.weak @var{names}}
7553 @cindex @code{weak} directive
7554 This directive sets the weak attribute on the comma separated list of symbol
7555 @code{names}. If the symbols do not already exist, they will be created.
7557 On COFF targets other than PE, weak symbols are a GNU extension. This
7558 directive sets the weak attribute on the comma separated list of symbol
7559 @code{names}. If the symbols do not already exist, they will be created.
7561 On the PE target, weak symbols are supported natively as weak aliases.
7562 When a weak symbol is created that is not an alias, GAS creates an
7563 alternate symbol to hold the default value.
7566 @section @code{.weakref @var{alias}, @var{target}}
7568 @cindex @code{weakref} directive
7569 This directive creates an alias to the target symbol that enables the symbol to
7570 be referenced with weak-symbol semantics, but without actually making it weak.
7571 If direct references or definitions of the symbol are present, then the symbol
7572 will not be weak, but if all references to it are through weak references, the
7573 symbol will be marked as weak in the symbol table.
7575 The effect is equivalent to moving all references to the alias to a separate
7576 assembly source file, renaming the alias to the symbol in it, declaring the
7577 symbol as weak there, and running a reloadable link to merge the object files
7578 resulting from the assembly of the new source file and the old source file that
7579 had the references to the alias removed.
7581 The alias itself never makes to the symbol table, and is entirely handled
7582 within the assembler.
7585 @section @code{.word @var{expressions}}
7587 @cindex @code{word} directive
7588 This directive expects zero or more @var{expressions}, of any section,
7589 separated by commas.
7592 For each expression, @command{@value{AS}} emits a 32-bit number.
7595 For each expression, @command{@value{AS}} emits a 16-bit number.
7600 The size of the number emitted, and its byte order,
7601 depend on what target computer the assembly is for.
7604 @c on sparc the "special treatment to support compilers" doesn't
7605 @c happen---32-bit addressability, period; no long/short jumps.
7606 @ifset DIFF-TBL-KLUGE
7607 @cindex difference tables altered
7608 @cindex altered difference tables
7610 @emph{Warning: Special Treatment to support Compilers}
7614 Machines with a 32-bit address space, but that do less than 32-bit
7615 addressing, require the following special treatment. If the machine of
7616 interest to you does 32-bit addressing (or doesn't require it;
7617 @pxref{Machine Dependencies}), you can ignore this issue.
7620 In order to assemble compiler output into something that works,
7621 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7622 Directives of the form @samp{.word sym1-sym2} are often emitted by
7623 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7624 directive of the form @samp{.word sym1-sym2}, and the difference between
7625 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7626 creates a @dfn{secondary jump table}, immediately before the next label.
7627 This secondary jump table is preceded by a short-jump to the
7628 first byte after the secondary table. This short-jump prevents the flow
7629 of control from accidentally falling into the new table. Inside the
7630 table is a long-jump to @code{sym2}. The original @samp{.word}
7631 contains @code{sym1} minus the address of the long-jump to
7634 If there were several occurrences of @samp{.word sym1-sym2} before the
7635 secondary jump table, all of them are adjusted. If there was a
7636 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7637 long-jump to @code{sym4} is included in the secondary jump table,
7638 and the @code{.word} directives are adjusted to contain @code{sym3}
7639 minus the address of the long-jump to @code{sym4}; and so on, for as many
7640 entries in the original jump table as necessary.
7643 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7644 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7645 assembly language programmers.
7648 @c end DIFF-TBL-KLUGE
7650 @ifclear no-space-dir
7652 @section @code{.zero @var{size}}
7654 @cindex @code{zero} directive
7655 @cindex filling memory with zero bytes
7656 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7657 expression. This directive is actually an alias for the @samp{.skip} directive
7658 so it can take an optional second argument of the value to store in the bytes
7659 instead of zero. Using @samp{.zero} in this way would be confusing however.
7663 @section @code{.2byte @var{expression} [, @var{expression}]*}
7664 @cindex @code{2byte} directive
7665 @cindex two-byte integer
7666 @cindex integer, 2-byte
7668 This directive expects zero or more expressions, separated by commas. If there
7669 are no expressions then the directive does nothing. Otherwise each expression
7670 is evaluated in turn and placed in the next two bytes of the current output
7671 section, using the endian model of the target. If an expression will not fit
7672 in two bytes, a warning message is displayed and the least significant two
7673 bytes of the expression's value are used. If an expression cannot be evaluated
7674 at assembly time then relocations will be generated in order to compute the
7677 This directive does not apply any alignment before or after inserting the
7678 values. As a result of this, if relocations are generated, they may be
7679 different from those used for inserting values with a guaranteed alignment.
7682 @section @code{.4byte @var{expression} [, @var{expression}]*}
7683 @cindex @code{4byte} directive
7684 @cindex four-byte integer
7685 @cindex integer, 4-byte
7687 Like the @option{.2byte} directive, except that it inserts unaligned, four byte
7688 long values into the output.
7691 @section @code{.8byte @var{expression} [, @var{expression}]*}
7692 @cindex @code{8byte} directive
7693 @cindex eight-byte integer
7694 @cindex integer, 8-byte
7696 Like the @option{.2byte} directive, except that it inserts unaligned, eight
7697 byte long bignum values into the output.
7700 @section Deprecated Directives
7702 @cindex deprecated directives
7703 @cindex obsolescent directives
7704 One day these directives won't work.
7705 They are included for compatibility with older assemblers.
7712 @node Object Attributes
7713 @chapter Object Attributes
7714 @cindex object attributes
7716 @command{@value{AS}} assembles source files written for a specific architecture
7717 into object files for that architecture. But not all object files are alike.
7718 Many architectures support incompatible variations. For instance, floating
7719 point arguments might be passed in floating point registers if the object file
7720 requires hardware floating point support---or floating point arguments might be
7721 passed in integer registers if the object file supports processors with no
7722 hardware floating point unit. Or, if two objects are built for different
7723 generations of the same architecture, the combination may require the
7724 newer generation at run-time.
7726 This information is useful during and after linking. At link time,
7727 @command{@value{LD}} can warn about incompatible object files. After link
7728 time, tools like @command{gdb} can use it to process the linked file
7731 Compatibility information is recorded as a series of object attributes. Each
7732 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7733 string, and indicates who sets the meaning of the tag. The tag is an integer,
7734 and indicates what property the attribute describes. The value may be a string
7735 or an integer, and indicates how the property affects this object. Missing
7736 attributes are the same as attributes with a zero value or empty string value.
7738 Object attributes were developed as part of the ABI for the ARM Architecture.
7739 The file format is documented in @cite{ELF for the ARM Architecture}.
7742 * GNU Object Attributes:: @sc{gnu} Object Attributes
7743 * Defining New Object Attributes:: Defining New Object Attributes
7746 @node GNU Object Attributes
7747 @section @sc{gnu} Object Attributes
7749 The @code{.gnu_attribute} directive records an object attribute
7750 with vendor @samp{gnu}.
7752 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7753 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7754 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7755 2} is set for architecture-independent attributes and clear for
7756 architecture-dependent ones.
7758 @subsection Common @sc{gnu} attributes
7760 These attributes are valid on all architectures.
7763 @item Tag_compatibility (32)
7764 The compatibility attribute takes an integer flag value and a vendor name. If
7765 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7766 then the file is only compatible with the named toolchain. If it is greater
7767 than 1, the file can only be processed by other toolchains under some private
7768 arrangement indicated by the flag value and the vendor name.
7771 @subsection M680x0 Attributes
7774 @item Tag_GNU_M68K_ABI_FP (4)
7775 The floating-point ABI used by this object file. The value will be:
7779 0 for files not affected by the floating-point ABI.
7781 1 for files using double-precision hardware floating-point ABI.
7783 2 for files using the software floating-point ABI.
7787 @subsection MIPS Attributes
7790 @item Tag_GNU_MIPS_ABI_FP (4)
7791 The floating-point ABI used by this object file. The value will be:
7795 0 for files not affected by the floating-point ABI.
7797 1 for files using the hardware floating-point ABI with a standard
7798 double-precision FPU.
7800 2 for files using the hardware floating-point ABI with a single-precision FPU.
7802 3 for files using the software floating-point ABI.
7804 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7805 floating-point registers, 32-bit general-purpose registers and increased the
7806 number of callee-saved floating-point registers.
7808 5 for files using the hardware floating-point ABI with a double-precision FPU
7809 with either 32-bit or 64-bit floating-point registers and 32-bit
7810 general-purpose registers.
7812 6 for files using the hardware floating-point ABI with 64-bit floating-point
7813 registers and 32-bit general-purpose registers.
7815 7 for files using the hardware floating-point ABI with 64-bit floating-point
7816 registers, 32-bit general-purpose registers and a rule that forbids the
7817 direct use of odd-numbered single-precision floating-point registers.
7821 @subsection PowerPC Attributes
7824 @item Tag_GNU_Power_ABI_FP (4)
7825 The floating-point ABI used by this object file. The value will be:
7829 0 for files not affected by the floating-point ABI.
7831 1 for files using double-precision hardware floating-point ABI.
7833 2 for files using the software floating-point ABI.
7835 3 for files using single-precision hardware floating-point ABI.
7838 @item Tag_GNU_Power_ABI_Vector (8)
7839 The vector ABI used by this object file. The value will be:
7843 0 for files not affected by the vector ABI.
7845 1 for files using general purpose registers to pass vectors.
7847 2 for files using AltiVec registers to pass vectors.
7849 3 for files using SPE registers to pass vectors.
7853 @subsection IBM z Systems Attributes
7856 @item Tag_GNU_S390_ABI_Vector (8)
7857 The vector ABI used by this object file. The value will be:
7861 0 for files not affected by the vector ABI.
7863 1 for files using software vector ABI.
7865 2 for files using hardware vector ABI.
7869 @subsection MSP430 Attributes
7872 @item Tag_GNU_MSP430_Data_Region (4)
7873 The data region used by this object file. The value will be:
7877 0 for files not using the large memory model.
7879 1 for files which have been compiled with the condition that all
7880 data is in the lower memory region, i.e. below address 0x10000.
7882 2 for files which allow data to be placed in the full 20-bit memory range.
7886 @node Defining New Object Attributes
7887 @section Defining New Object Attributes
7889 If you want to define a new @sc{gnu} object attribute, here are the places you
7890 will need to modify. New attributes should be discussed on the @samp{binutils}
7895 This manual, which is the official register of attributes.
7897 The header for your architecture @file{include/elf}, to define the tag.
7899 The @file{bfd} support file for your architecture, to merge the attribute
7900 and issue any appropriate link warnings.
7902 Test cases in @file{ld/testsuite} for merging and link warnings.
7904 @file{binutils/readelf.c} to display your attribute.
7906 GCC, if you want the compiler to mark the attribute automatically.
7912 @node Machine Dependencies
7913 @chapter Machine Dependent Features
7915 @cindex machine dependencies
7916 The machine instruction sets are (almost by definition) different on
7917 each machine where @command{@value{AS}} runs. Floating point representations
7918 vary as well, and @command{@value{AS}} often supports a few additional
7919 directives or command-line options for compatibility with other
7920 assemblers on a particular platform. Finally, some versions of
7921 @command{@value{AS}} support special pseudo-instructions for branch
7924 This chapter discusses most of these differences, though it does not
7925 include details on any machine's instruction set. For details on that
7926 subject, see the hardware manufacturer's manual.
7930 * AArch64-Dependent:: AArch64 Dependent Features
7933 * Alpha-Dependent:: Alpha Dependent Features
7936 * ARC-Dependent:: ARC Dependent Features
7939 * ARM-Dependent:: ARM Dependent Features
7942 * AVR-Dependent:: AVR Dependent Features
7945 * Blackfin-Dependent:: Blackfin Dependent Features
7948 * BPF-Dependent:: BPF Dependent Features
7951 * CR16-Dependent:: CR16 Dependent Features
7954 * CRIS-Dependent:: CRIS Dependent Features
7957 * C-SKY-Dependent:: C-SKY Dependent Features
7960 * D10V-Dependent:: D10V Dependent Features
7963 * D30V-Dependent:: D30V Dependent Features
7966 * Epiphany-Dependent:: EPIPHANY Dependent Features
7969 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7972 * HPPA-Dependent:: HPPA Dependent Features
7975 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7978 * IA-64-Dependent:: Intel IA-64 Dependent Features
7981 * IP2K-Dependent:: IP2K Dependent Features
7984 * LoongArch-Dependent:: LoongArch Dependent Features
7987 * LM32-Dependent:: LM32 Dependent Features
7990 * M32C-Dependent:: M32C Dependent Features
7993 * M32R-Dependent:: M32R Dependent Features
7996 * M68K-Dependent:: M680x0 Dependent Features
7999 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
8002 * S12Z-Dependent:: S12Z Dependent Features
8005 * Meta-Dependent :: Meta Dependent Features
8008 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
8011 * MIPS-Dependent:: MIPS Dependent Features
8014 * MMIX-Dependent:: MMIX Dependent Features
8017 * MSP430-Dependent:: MSP430 Dependent Features
8020 * NDS32-Dependent:: Andes NDS32 Dependent Features
8023 * NiosII-Dependent:: Altera Nios II Dependent Features
8026 * NS32K-Dependent:: NS32K Dependent Features
8029 * OpenRISC-Dependent:: OpenRISC 1000 Features
8032 * PDP-11-Dependent:: PDP-11 Dependent Features
8035 * PJ-Dependent:: picoJava Dependent Features
8038 * PPC-Dependent:: PowerPC Dependent Features
8041 * PRU-Dependent:: PRU Dependent Features
8044 * RISC-V-Dependent:: RISC-V Dependent Features
8047 * RL78-Dependent:: RL78 Dependent Features
8050 * RX-Dependent:: RX Dependent Features
8053 * S/390-Dependent:: IBM S/390 Dependent Features
8056 * SCORE-Dependent:: SCORE Dependent Features
8059 * SH-Dependent:: Renesas / SuperH SH Dependent Features
8062 * Sparc-Dependent:: SPARC Dependent Features
8065 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
8068 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
8071 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
8074 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
8077 * V850-Dependent:: V850 Dependent Features
8080 * Vax-Dependent:: VAX Dependent Features
8083 * Visium-Dependent:: Visium Dependent Features
8086 * WebAssembly-Dependent:: WebAssembly Dependent Features
8089 * XGATE-Dependent:: XGATE Dependent Features
8092 * XSTORMY16-Dependent:: XStormy16 Dependent Features
8095 * Xtensa-Dependent:: Xtensa Dependent Features
8098 * Z80-Dependent:: Z80 Dependent Features
8101 * Z8000-Dependent:: Z8000 Dependent Features
8108 @c The following major nodes are *sections* in the GENERIC version, *chapters*
8109 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
8110 @c peculiarity: to preserve cross-references, there must be a node called
8111 @c "Machine Dependencies". Hence the conditional nodenames in each
8112 @c major node below. Node defaulting in makeinfo requires adjacency of
8113 @c node and sectioning commands; hence the repetition of @chapter BLAH
8114 @c in both conditional blocks.
8117 @include c-aarch64.texi
8121 @include c-alpha.texi
8137 @include c-bfin.texi
8145 @include c-cr16.texi
8149 @include c-cris.texi
8153 @include c-csky.texi
8158 @node Machine Dependencies
8159 @chapter Machine Dependent Features
8161 The machine instruction sets are different on each Renesas chip family,
8162 and there are also some syntax differences among the families. This
8163 chapter describes the specific @command{@value{AS}} features for each
8167 * H8/300-Dependent:: Renesas H8/300 Dependent Features
8168 * SH-Dependent:: Renesas SH Dependent Features
8175 @include c-d10v.texi
8179 @include c-d30v.texi
8183 @include c-epiphany.texi
8187 @include c-h8300.texi
8191 @include c-hppa.texi
8195 @include c-i386.texi
8199 @include c-ia64.texi
8203 @include c-ip2k.texi
8207 @include c-lm32.texi
8211 @include c-loongarch.texi
8215 @include c-m32c.texi
8219 @include c-m32r.texi
8223 @include c-m68k.texi
8227 @include c-m68hc11.texi
8231 @include c-s12z.texi
8235 @include c-metag.texi
8239 @include c-microblaze.texi
8243 @include c-mips.texi
8247 @include c-mmix.texi
8251 @include c-msp430.texi
8255 @include c-nds32.texi
8259 @include c-nios2.texi
8263 @include c-ns32k.texi
8267 @include c-or1k.texi
8271 @include c-pdp11.texi
8287 @include c-riscv.texi
8291 @include c-rl78.texi
8299 @include c-s390.texi
8303 @include c-score.texi
8311 @include c-sparc.texi
8315 @include c-tic54x.texi
8319 @include c-tic6x.texi
8323 @include c-tilegx.texi
8327 @include c-tilepro.texi
8331 @include c-v850.texi
8339 @include c-visium.texi
8343 @include c-wasm32.texi
8347 @include c-xgate.texi
8351 @include c-xstormy16.texi
8355 @include c-xtensa.texi
8367 @c reverse effect of @down at top of generic Machine-Dep chapter
8371 @node Reporting Bugs
8372 @chapter Reporting Bugs
8373 @cindex bugs in assembler
8374 @cindex reporting bugs in assembler
8376 Your bug reports play an essential role in making @command{@value{AS}} reliable.
8378 Reporting a bug may help you by bringing a solution to your problem, or it may
8379 not. But in any case the principal function of a bug report is to help the
8380 entire community by making the next version of @command{@value{AS}} work better.
8381 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
8383 In order for a bug report to serve its purpose, you must include the
8384 information that enables us to fix the bug.
8387 * Bug Criteria:: Have you found a bug?
8388 * Bug Reporting:: How to report bugs
8392 @section Have You Found a Bug?
8393 @cindex bug criteria
8395 If you are not sure whether you have found a bug, here are some guidelines:
8398 @cindex fatal signal
8399 @cindex assembler crash
8400 @cindex crash of assembler
8402 If the assembler gets a fatal signal, for any input whatever, that is a
8403 @command{@value{AS}} bug. Reliable assemblers never crash.
8405 @cindex error on valid input
8407 If @command{@value{AS}} produces an error message for valid input, that is a bug.
8409 @cindex invalid input
8411 If @command{@value{AS}} does not produce an error message for invalid input, that
8412 is a bug. However, you should note that your idea of ``invalid input'' might
8413 be our idea of ``an extension'' or ``support for traditional practice''.
8416 If you are an experienced user of assemblers, your suggestions for improvement
8417 of @command{@value{AS}} are welcome in any case.
8421 @section How to Report Bugs
8423 @cindex assembler bugs, reporting
8425 A number of companies and individuals offer support for @sc{gnu} products. If
8426 you obtained @command{@value{AS}} from a support organization, we recommend you
8427 contact that organization first.
8429 You can find contact information for many support companies and
8430 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8434 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8438 The fundamental principle of reporting bugs usefully is this:
8439 @strong{report all the facts}. If you are not sure whether to state a
8440 fact or leave it out, state it!
8442 Often people omit facts because they think they know what causes the problem
8443 and assume that some details do not matter. Thus, you might assume that the
8444 name of a symbol you use in an example does not matter. Well, probably it does
8445 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8446 happens to fetch from the location where that name is stored in memory;
8447 perhaps, if the name were different, the contents of that location would fool
8448 the assembler into doing the right thing despite the bug. Play it safe and
8449 give a specific, complete example. That is the easiest thing for you to do,
8450 and the most helpful.
8452 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8453 it is new to us. Therefore, always write your bug reports on the assumption
8454 that the bug has not been reported previously.
8456 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8457 bell?'' This cannot help us fix a bug, so it is basically useless. We
8458 respond by asking for enough details to enable us to investigate.
8459 You might as well expedite matters by sending them to begin with.
8461 To enable us to fix the bug, you should include all these things:
8465 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8466 it with the @samp{--version} argument.
8468 Without this, we will not know whether there is any point in looking for
8469 the bug in the current version of @command{@value{AS}}.
8472 Any patches you may have applied to the @command{@value{AS}} source.
8475 The type of machine you are using, and the operating system name and
8479 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8483 The command arguments you gave the assembler to assemble your example and
8484 observe the bug. To guarantee you will not omit something important, list them
8485 all. A copy of the Makefile (or the output from make) is sufficient.
8487 If we were to try to guess the arguments, we would probably guess wrong
8488 and then we might not encounter the bug.
8491 A complete input file that will reproduce the bug. If the bug is observed when
8492 the assembler is invoked via a compiler, send the assembler source, not the
8493 high level language source. Most compilers will produce the assembler source
8494 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8495 the options @samp{-v --save-temps}; this will save the assembler source in a
8496 file with an extension of @file{.s}, and also show you exactly how
8497 @command{@value{AS}} is being run.
8500 A description of what behavior you observe that you believe is
8501 incorrect. For example, ``It gets a fatal signal.''
8503 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8504 will certainly notice it. But if the bug is incorrect output, we might not
8505 notice unless it is glaringly wrong. You might as well not give us a chance to
8508 Even if the problem you experience is a fatal signal, you should still say so
8509 explicitly. Suppose something strange is going on, such as, your copy of
8510 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8511 library on your system. (This has happened!) Your copy might crash and ours
8512 would not. If you told us to expect a crash, then when ours fails to crash, we
8513 would know that the bug was not happening for us. If you had not told us to
8514 expect a crash, then we would not be able to draw any conclusion from our
8518 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8519 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8520 option. Always send diffs from the old file to the new file. If you even
8521 discuss something in the @command{@value{AS}} source, refer to it by context, not
8524 The line numbers in our development sources will not match those in your
8525 sources. Your line numbers would convey no useful information to us.
8528 Here are some things that are not necessary:
8532 A description of the envelope of the bug.
8534 Often people who encounter a bug spend a lot of time investigating
8535 which changes to the input file will make the bug go away and which
8536 changes will not affect it.
8538 This is often time consuming and not very useful, because the way we
8539 will find the bug is by running a single example under the debugger
8540 with breakpoints, not by pure deduction from a series of examples.
8541 We recommend that you save your time for something else.
8543 Of course, if you can find a simpler example to report @emph{instead}
8544 of the original one, that is a convenience for us. Errors in the
8545 output will be easier to spot, running under the debugger will take
8546 less time, and so on.
8548 However, simplification is not vital; if you do not want to do this,
8549 report the bug anyway and send us the entire test case you used.
8552 A patch for the bug.
8554 A patch for the bug does help us if it is a good one. But do not omit
8555 the necessary information, such as the test case, on the assumption that
8556 a patch is all we need. We might see problems with your patch and decide
8557 to fix the problem another way, or we might not understand it at all.
8559 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8560 construct an example that will make the program follow a certain path through
8561 the code. If you do not send us the example, we will not be able to construct
8562 one, so we will not be able to verify that the bug is fixed.
8564 And if we cannot understand what bug you are trying to fix, or why your
8565 patch should be an improvement, we will not install it. A test case will
8566 help us to understand.
8569 A guess about what the bug is or what it depends on.
8571 Such guesses are usually wrong. Even we cannot guess right about such
8572 things without first using the debugger to find the facts.
8575 @node Acknowledgements
8576 @chapter Acknowledgements
8578 If you have contributed to GAS and your name isn't listed here,
8579 it is not meant as a slight. We just don't know about it. Send mail to the
8580 maintainer, and we'll correct the situation. Currently
8582 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8584 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8587 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8588 information and the 68k series machines, most of the preprocessing pass, and
8589 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8591 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8592 many bug fixes, including merging support for several processors, breaking GAS
8593 up to handle multiple object file format back ends (including heavy rewrite,
8594 testing, an integration of the coff and b.out back ends), adding configuration
8595 including heavy testing and verification of cross assemblers and file splits
8596 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8597 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8598 port (including considerable amounts of reverse engineering), a SPARC opcode
8599 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8600 assertions and made them work, much other reorganization, cleanup, and lint.
8602 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8603 in format-specific I/O modules.
8605 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8606 has done much work with it since.
8608 The Intel 80386 machine description was written by Eliot Dresselhaus.
8610 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8612 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8613 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8615 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8616 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8617 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8618 support a.out format.
8620 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8621 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8622 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8623 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8626 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8627 simplified the configuration of which versions accept which directives. He
8628 updated the 68k machine description so that Motorola's opcodes always produced
8629 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8630 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8631 cross-compilation support, and one bug in relaxation that took a week and
8632 required the proverbial one-bit fix.
8634 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8635 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8636 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8637 PowerPC assembler, and made a few other minor patches.
8639 Steve Chamberlain made GAS able to generate listings.
8641 Hewlett-Packard contributed support for the HP9000/300.
8643 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8644 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8645 formats). This work was supported by both the Center for Software Science at
8646 the University of Utah and Cygnus Support.
8648 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8649 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8650 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8651 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8652 and some initial 64-bit support).
8654 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8656 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8657 support for openVMS/Alpha.
8659 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8662 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8663 Inc.@: added support for Xtensa processors.
8665 Several engineers at Cygnus Support have also provided many small bug fixes and
8666 configuration enhancements.
8668 Jon Beniston added support for the Lattice Mico32 architecture.
8670 Many others have contributed large or small bugfixes and enhancements. If
8671 you have contributed significant work and are not mentioned on this list, and
8672 want to be, let us know. Some of the history has been lost; we are not
8673 intentionally leaving anyone out.
8675 @node GNU Free Documentation License
8676 @appendix GNU Free Documentation License
8680 @unnumbered AS Index