1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2018 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
50 @set abnormal-separator
54 @settitle Using @value{AS}
57 @settitle Using @value{AS} (@value{TARGET})
59 @setchapternewpage odd
64 @c WARE! Some of the machine-dependent sections contain tables of machine
65 @c instructions. Except in multi-column format, these tables look silly.
66 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
67 @c the multi-col format is faked within @example sections.
69 @c Again unfortunately, the natural size that fits on a page, for these tables,
70 @c is different depending on whether or not smallbook is turned on.
71 @c This matters, because of order: text flow switches columns at each page
74 @c The format faked in this source works reasonably well for smallbook,
75 @c not well for the default large-page format. This manual expects that if you
76 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
77 @c tables in question. You can turn on one without the other at your
78 @c discretion, of course.
81 @c the insn tables look just as silly in info files regardless of smallbook,
82 @c might as well show 'em anyways.
86 @dircategory Software development
88 * As: (as). The GNU assembler.
89 * Gas: (as). The GNU assembler.
97 This file documents the GNU Assembler "@value{AS}".
99 @c man begin COPYRIGHT
100 Copyright @copyright{} 1991-2018 Free Software Foundation, Inc.
102 Permission is granted to copy, distribute and/or modify this document
103 under the terms of the GNU Free Documentation License, Version 1.3
104 or any later version published by the Free Software Foundation;
105 with no Invariant Sections, with no Front-Cover Texts, and with no
106 Back-Cover Texts. A copy of the license is included in the
107 section entitled ``GNU Free Documentation License''.
113 @title Using @value{AS}
114 @subtitle The @sc{gnu} Assembler
116 @subtitle for the @value{TARGET} family
118 @ifset VERSION_PACKAGE
120 @subtitle @value{VERSION_PACKAGE}
123 @subtitle Version @value{VERSION}
126 The Free Software Foundation Inc.@: thanks The Nice Computer
127 Company of Australia for loaning Dean Elsner to write the
128 first (Vax) version of @command{as} for Project @sc{gnu}.
129 The proprietors, management and staff of TNCCA thank FSF for
130 distracting the boss while they got some work
133 @author Dean Elsner, Jay Fenlason & friends
137 \hfill {\it Using {\tt @value{AS}}}\par
138 \hfill Edited by Cygnus Support\par
140 %"boxit" macro for figures:
141 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
142 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
143 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
144 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
145 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
148 @vskip 0pt plus 1filll
149 Copyright @copyright{} 1991-2018 Free Software Foundation, Inc.
151 Permission is granted to copy, distribute and/or modify this document
152 under the terms of the GNU Free Documentation License, Version 1.3
153 or any later version published by the Free Software Foundation;
154 with no Invariant Sections, with no Front-Cover Texts, and with no
155 Back-Cover Texts. A copy of the license is included in the
156 section entitled ``GNU Free Documentation License''.
163 @top Using @value{AS}
165 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
166 @ifset VERSION_PACKAGE
167 @value{VERSION_PACKAGE}
169 version @value{VERSION}.
171 This version of the file describes @command{@value{AS}} configured to generate
172 code for @value{TARGET} architectures.
175 This document is distributed under the terms of the GNU Free
176 Documentation License. A copy of the license is included in the
177 section entitled ``GNU Free Documentation License''.
180 * Overview:: Overview
181 * Invoking:: Command-Line Options
183 * Sections:: Sections and Relocation
185 * Expressions:: Expressions
186 * Pseudo Ops:: Assembler Directives
188 * Object Attributes:: Object Attributes
190 * Machine Dependencies:: Machine Dependent Features
191 * Reporting Bugs:: Reporting Bugs
192 * Acknowledgements:: Who Did What
193 * GNU Free Documentation License:: GNU Free Documentation License
194 * AS Index:: AS Index
201 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
203 This version of the manual describes @command{@value{AS}} configured to generate
204 code for @value{TARGET} architectures.
208 @cindex invocation summary
209 @cindex option summary
210 @cindex summary of options
211 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
212 see @ref{Invoking,,Command-Line Options}.
214 @c man title AS the portable GNU assembler.
218 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
222 @c We don't use deffn and friends for the following because they seem
223 @c to be limited to one line for the header.
225 @c man begin SYNOPSIS
226 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
227 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
228 [@b{--debug-prefix-map} @var{old}=@var{new}]
229 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
230 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
231 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
232 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
233 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
234 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
235 [@b{--no-pad-sections}]
236 [@b{-o} @var{objfile}] [@b{-R}]
237 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
239 [@b{-v}] [@b{-version}] [@b{--version}]
240 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
241 [@b{-Z}] [@b{@@@var{FILE}}]
242 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
243 [@b{--elf-stt-common=[no|yes]}]
244 [@b{--generate-missing-build-notes=[no|yes]}]
245 [@b{--target-help}] [@var{target-options}]
246 [@b{--}|@var{files} @dots{}]
249 @c Target dependent options are listed below. Keep the list sorted.
250 @c Add an empty line for separation.
254 @emph{Target AArch64 options:}
256 [@b{-mabi}=@var{ABI}]
260 @emph{Target Alpha options:}
262 [@b{-mdebug} | @b{-no-mdebug}]
263 [@b{-replace} | @b{-noreplace}]
264 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
265 [@b{-F}] [@b{-32addr}]
269 @emph{Target ARC options:}
270 [@b{-mcpu=@var{cpu}}]
271 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
278 @emph{Target ARM options:}
279 @c Don't document the deprecated options
280 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
281 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
282 [@b{-mfpu}=@var{floating-point-format}]
283 [@b{-mfloat-abi}=@var{abi}]
284 [@b{-meabi}=@var{ver}]
287 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
288 @b{-mapcs-reentrant}]
289 [@b{-mthumb-interwork}] [@b{-k}]
293 @emph{Target Blackfin options:}
294 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
301 @emph{Target CRIS options:}
302 [@b{--underscore} | @b{--no-underscore}]
304 [@b{--emulation=criself} | @b{--emulation=crisaout}]
305 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
306 @c Deprecated -- deliberately not documented.
311 @emph{Target C-SKY options:}
312 [@b{-march=@var{arch}}] [@b{-mcpu=@var{cpu}}]
313 [@b{-EL}] [@b{-mlittle-endian}] [@b{-EB}] [@b{-mbig-endian}]
314 [@b{-fpic}] [@b{-pic}]
315 [@b{-mljump}] [@b{-mno-ljump}]
316 [@b{-force2bsr}] [@b{-mforce2bsr}] [@b{-no-force2bsr}] [@b{-mno-force2bsr}]
317 [@b{-jsri2bsr}] [@b{-mjsri2bsr}] [@b{-no-jsri2bsr }] [@b{-mno-jsri2bsr}]
318 [@b{-mnolrw }] [@b{-mno-lrw}]
319 [@b{-melrw}] [@b{-mno-elrw}]
320 [@b{-mlaf }] [@b{-mliterals-after-func}]
321 [@b{-mno-laf}] [@b{-mno-literals-after-func}]
322 [@b{-mlabr}] [@b{-mliterals-after-br}]
323 [@b{-mno-labr}] [@b{-mnoliterals-after-br}]
324 [@b{-mistack}] [@b{-mno-istack}]
325 [@b{-mhard-float}] [@b{-mmp}] [@b{-mcp}] [@b{-mcache}]
326 [@b{-msecurity}] [@b{-mtrust}]
327 [@b{-mdsp}] [@b{-medsp}] [@b{-mvdsp}]
331 @emph{Target D10V options:}
336 @emph{Target D30V options:}
337 [@b{-O}|@b{-n}|@b{-N}]
341 @emph{Target EPIPHANY options:}
342 [@b{-mepiphany}|@b{-mepiphany16}]
346 @emph{Target H8/300 options:}
350 @c HPPA has no machine-dependent assembler options (yet).
354 @emph{Target i386 options:}
355 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
356 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
360 @emph{Target IA-64 options:}
361 [@b{-mconstant-gp}|@b{-mauto-pic}]
362 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
364 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
365 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
366 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
367 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
371 @emph{Target IP2K options:}
372 [@b{-mip2022}|@b{-mip2022ext}]
376 @emph{Target M32C options:}
377 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
381 @emph{Target M32R options:}
382 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
387 @emph{Target M680X0 options:}
388 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
392 @emph{Target M68HC11 options:}
393 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
394 [@b{-mshort}|@b{-mlong}]
395 [@b{-mshort-double}|@b{-mlong-double}]
396 [@b{--force-long-branches}] [@b{--short-branches}]
397 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
398 [@b{--print-opcodes}] [@b{--generate-example}]
402 @emph{Target MCORE options:}
403 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
404 [@b{-mcpu=[210|340]}]
408 @emph{Target Meta options:}
409 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
412 @emph{Target MICROBLAZE options:}
413 @c MicroBlaze has no machine-dependent assembler options.
417 @emph{Target MIPS options:}
418 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
419 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
420 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
421 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
422 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
423 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
424 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
425 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
426 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
427 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
428 [@b{-construct-floats}] [@b{-no-construct-floats}]
429 [@b{-mignore-branch-isa}] [@b{-mno-ignore-branch-isa}]
430 [@b{-mnan=@var{encoding}}]
431 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
432 [@b{-mips16}] [@b{-no-mips16}]
433 [@b{-mmips16e2}] [@b{-mno-mips16e2}]
434 [@b{-mmicromips}] [@b{-mno-micromips}]
435 [@b{-msmartmips}] [@b{-mno-smartmips}]
436 [@b{-mips3d}] [@b{-no-mips3d}]
437 [@b{-mdmx}] [@b{-no-mdmx}]
438 [@b{-mdsp}] [@b{-mno-dsp}]
439 [@b{-mdspr2}] [@b{-mno-dspr2}]
440 [@b{-mdspr3}] [@b{-mno-dspr3}]
441 [@b{-mmsa}] [@b{-mno-msa}]
442 [@b{-mxpa}] [@b{-mno-xpa}]
443 [@b{-mmt}] [@b{-mno-mt}]
444 [@b{-mmcu}] [@b{-mno-mcu}]
445 [@b{-mcrc}] [@b{-mno-crc}]
446 [@b{-mginv}] [@b{-mno-ginv}]
447 [@b{-mloongson-mmi}] [@b{-mno-loongson-mmi}]
448 [@b{-mloongson-cam}] [@b{-mno-loongson-cam}]
449 [@b{-mloongson-ext}] [@b{-mno-loongson-ext}]
450 [@b{-mloongson-ext2}] [@b{-mno-loongson-ext2}]
451 [@b{-minsn32}] [@b{-mno-insn32}]
452 [@b{-mfix7000}] [@b{-mno-fix7000}]
453 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
454 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
455 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
456 [@b{-mdebug}] [@b{-no-mdebug}]
457 [@b{-mpdr}] [@b{-mno-pdr}]
461 @emph{Target MMIX options:}
462 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
463 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
464 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
465 [@b{--linker-allocated-gregs}]
469 @emph{Target Nios II options:}
470 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
475 @emph{Target NDS32 options:}
476 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
477 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
478 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
479 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
480 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
481 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
482 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
487 @emph{Target PDP11 options:}
488 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
489 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
490 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
494 @emph{Target picoJava options:}
499 @emph{Target PowerPC options:}
501 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
502 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mgekko}|
503 @b{-mbroadway}|@b{-mppc64}|@b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|
504 @b{-me6500}|@b{-mppc64bridge}|@b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|
505 @b{-mpower6}|@b{-mpwr6}|@b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
506 @b{-mcell}|@b{-mspe}|@b{-mspe2}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
507 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
508 [@b{-mregnames}|@b{-mno-regnames}]
509 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
510 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
511 [@b{-msolaris}|@b{-mno-solaris}]
512 [@b{-nops=@var{count}}]
516 @emph{Target PRU options:}
519 [@b{-mno-warn-regname-label}]
523 @emph{Target RISC-V options:}
524 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
525 [@b{-march}=@var{ISA}]
526 [@b{-mabi}=@var{ABI}]
530 @emph{Target RL78 options:}
532 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
536 @emph{Target RX options:}
537 [@b{-mlittle-endian}|@b{-mbig-endian}]
538 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
539 [@b{-muse-conventional-section-names}]
540 [@b{-msmall-data-limit}]
543 [@b{-mint-register=@var{number}}]
544 [@b{-mgcc-abi}|@b{-mrx-abi}]
548 @emph{Target s390 options:}
549 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
550 [@b{-mregnames}|@b{-mno-regnames}]
551 [@b{-mwarn-areg-zero}]
555 @emph{Target SCORE options:}
556 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
557 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
558 [@b{-march=score7}][@b{-march=score3}]
559 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
563 @emph{Target SPARC options:}
564 @c The order here is important. See c-sparc.texi.
565 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
566 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
567 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
568 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
569 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
570 @b{-Asparcvisr}|@b{-Asparc5}]
571 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
572 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
573 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
574 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
575 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
576 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
579 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
583 @emph{Target TIC54X options:}
584 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
585 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
589 @emph{Target TIC6X options:}
590 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
591 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
592 [@b{-mpic}|@b{-mno-pic}]
596 @emph{Target TILE-Gx options:}
597 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
600 @c TILEPro has no machine-dependent assembler options
604 @emph{Target Visium options:}
605 [@b{-mtune=@var{arch}}]
609 @emph{Target Xtensa options:}
610 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
611 [@b{--[no-]absolute-literals}]
612 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
613 [@b{--[no-]transform}]
614 [@b{--rename-section} @var{oldname}=@var{newname}]
615 [@b{--[no-]trampolines}]
619 @emph{Target Z80 options:}
620 [@b{-z80}] [@b{-r800}]
621 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
622 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
623 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
624 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
625 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
626 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
630 @c Z8000 has no machine-dependent assembler options
639 @include at-file.texi
642 Turn on listings, in any of a variety of ways:
646 omit false conditionals
649 omit debugging directives
652 include general information, like @value{AS} version and options passed
655 include high-level source
661 include macro expansions
664 omit forms processing
670 set the name of the listing file
673 You may combine these options; for example, use @samp{-aln} for assembly
674 listing without forms processing. The @samp{=file} option, if used, must be
675 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
678 Begin in alternate macro mode.
680 @xref{Altmacro,,@code{.altmacro}}.
683 @item --compress-debug-sections
684 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
685 ELF ABI. The resulting object file may not be compatible with older
686 linkers and object file utilities. Note if compression would make a
687 given section @emph{larger} then it is not compressed.
690 @cindex @samp{--compress-debug-sections=} option
691 @item --compress-debug-sections=none
692 @itemx --compress-debug-sections=zlib
693 @itemx --compress-debug-sections=zlib-gnu
694 @itemx --compress-debug-sections=zlib-gabi
695 These options control how DWARF debug sections are compressed.
696 @option{--compress-debug-sections=none} is equivalent to
697 @option{--nocompress-debug-sections}.
698 @option{--compress-debug-sections=zlib} and
699 @option{--compress-debug-sections=zlib-gabi} are equivalent to
700 @option{--compress-debug-sections}.
701 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
702 sections using zlib. The debug sections are renamed to begin with
703 @samp{.zdebug}. Note if compression would make a given section
704 @emph{larger} then it is not compressed nor renamed.
708 @item --nocompress-debug-sections
709 Do not compress DWARF debug sections. This is usually the default for all
710 targets except the x86/x86_64, but a configure time option can be used to
714 Ignored. This option is accepted for script compatibility with calls to
717 @item --debug-prefix-map @var{old}=@var{new}
718 When assembling files in directory @file{@var{old}}, record debugging
719 information describing them as in @file{@var{new}} instead.
721 @item --defsym @var{sym}=@var{value}
722 Define the symbol @var{sym} to be @var{value} before assembling the input file.
723 @var{value} must be an integer constant. As in C, a leading @samp{0x}
724 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
725 value. The value of the symbol can be overridden inside a source file via the
726 use of a @code{.set} pseudo-op.
729 ``fast''---skip whitespace and comment preprocessing (assume source is
734 Generate debugging information for each assembler source line using whichever
735 debug format is preferred by the target. This currently means either STABS,
739 Generate stabs debugging information for each assembler line. This
740 may help debugging assembler code, if the debugger can handle it.
743 Generate stabs debugging information for each assembler line, with GNU
744 extensions that probably only gdb can handle, and that could make other
745 debuggers crash or refuse to read your program. This
746 may help debugging assembler code. Currently the only GNU extension is
747 the location of the current working directory at assembling time.
750 Generate DWARF2 debugging information for each assembler line. This
751 may help debugging assembler code, if the debugger can handle it. Note---this
752 option is only supported by some targets, not all of them.
754 @item --gdwarf-sections
755 Instead of creating a .debug_line section, create a series of
756 .debug_line.@var{foo} sections where @var{foo} is the name of the
757 corresponding code section. For example a code section called @var{.text.func}
758 will have its dwarf line number information placed into a section called
759 @var{.debug_line.text.func}. If the code section is just called @var{.text}
760 then debug line section will still be called just @var{.debug_line} without any
764 @item --size-check=error
765 @itemx --size-check=warning
766 Issue an error or warning for invalid ELF .size directive.
768 @item --elf-stt-common=no
769 @itemx --elf-stt-common=yes
770 These options control whether the ELF assembler should generate common
771 symbols with the @code{STT_COMMON} type. The default can be controlled
772 by a configure option @option{--enable-elf-stt-common}.
774 @item --generate-missing-build-notes=yes
775 @itemx --generate-missing-build-notes=no
776 These options control whether the ELF assembler should generate GNU Build
777 attribute notes if none are present in the input sources.
778 The default can be controlled by the @option{--enable-generate-build-notes}
784 Print a summary of the command-line options and exit.
787 Print a summary of all target specific options and exit.
790 Add directory @var{dir} to the search list for @code{.include} directives.
793 Don't warn about signed overflow.
796 @ifclear DIFF-TBL-KLUGE
797 This option is accepted but has no effect on the @value{TARGET} family.
799 @ifset DIFF-TBL-KLUGE
800 Issue warnings when difference tables altered for long displacements.
805 Keep (in the symbol table) local symbols. These symbols start with
806 system-specific local label prefixes, typically @samp{.L} for ELF systems
807 or @samp{L} for traditional a.out systems.
812 @item --listing-lhs-width=@var{number}
813 Set the maximum width, in words, of the output data column for an assembler
814 listing to @var{number}.
816 @item --listing-lhs-width2=@var{number}
817 Set the maximum width, in words, of the output data column for continuation
818 lines in an assembler listing to @var{number}.
820 @item --listing-rhs-width=@var{number}
821 Set the maximum width of an input source line, as displayed in a listing, to
824 @item --listing-cont-lines=@var{number}
825 Set the maximum number of lines printed in a listing for a single line of input
828 @item --no-pad-sections
829 Stop the assembler for padding the ends of output sections to the alignment
830 of that section. The default is to pad the sections, but this can waste space
831 which might be needed on targets which have tight memory constraints.
833 @item -o @var{objfile}
834 Name the object-file output from @command{@value{AS}} @var{objfile}.
837 Fold the data section into the text section.
839 @item --hash-size=@var{number}
840 Set the default size of GAS's hash tables to a prime number close to
841 @var{number}. Increasing this value can reduce the length of time it takes the
842 assembler to perform its tasks, at the expense of increasing the assembler's
843 memory requirements. Similarly reducing this value can reduce the memory
844 requirements at the expense of speed.
846 @item --reduce-memory-overheads
847 This option reduces GAS's memory requirements, at the expense of making the
848 assembly processes slower. Currently this switch is a synonym for
849 @samp{--hash-size=4051}, but in the future it may have other effects as well.
852 @item --sectname-subst
853 Honor substitution sequences in section names.
855 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
860 Print the maximum space (in bytes) and total time (in seconds) used by
863 @item --strip-local-absolute
864 Remove local absolute symbols from the outgoing symbol table.
868 Print the @command{as} version.
871 Print the @command{as} version and exit.
875 Suppress warning messages.
877 @item --fatal-warnings
878 Treat warnings as errors.
881 Don't suppress warning messages or treat them as errors.
890 Generate an object file even after errors.
892 @item -- | @var{files} @dots{}
893 Standard input, or source files to assemble.
901 @xref{AArch64 Options}, for the options available when @value{AS} is configured
902 for the 64-bit mode of the ARM Architecture (AArch64).
907 The following options are available when @value{AS} is configured for the
908 64-bit mode of the ARM Architecture (AArch64).
911 @include c-aarch64.texi
912 @c ended inside the included file
920 @xref{Alpha Options}, for the options available when @value{AS} is configured
921 for an Alpha processor.
926 The following options are available when @value{AS} is configured for an Alpha
930 @include c-alpha.texi
931 @c ended inside the included file
938 The following options are available when @value{AS} is configured for an ARC
942 @item -mcpu=@var{cpu}
943 This option selects the core processor variant.
945 Select either big-endian (-EB) or little-endian (-EL) output.
947 Enable Code Density extenssion instructions.
952 The following options are available when @value{AS} is configured for the ARM
956 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
957 Specify which ARM processor variant is the target.
958 @item -march=@var{architecture}[+@var{extension}@dots{}]
959 Specify which ARM architecture variant is used by the target.
960 @item -mfpu=@var{floating-point-format}
961 Select which Floating Point architecture is the target.
962 @item -mfloat-abi=@var{abi}
963 Select which floating point ABI is in use.
965 Enable Thumb only instruction decoding.
966 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
967 Select which procedure calling convention is in use.
969 Select either big-endian (-EB) or little-endian (-EL) output.
970 @item -mthumb-interwork
971 Specify that the code has been generated with interworking between Thumb and
974 Turns on CodeComposer Studio assembly syntax compatibility mode.
976 Specify that PIC code has been generated.
984 @xref{Blackfin Options}, for the options available when @value{AS} is
985 configured for the Blackfin processor family.
990 The following options are available when @value{AS} is configured for
991 the Blackfin processor family.
995 @c ended inside the included file
1000 @c man begin OPTIONS
1002 See the info pages for documentation of the CRIS-specific options.
1008 @xref{C-SKY Options}, for the options available when @value{AS} is
1009 configured for the C-SKY processor family.
1013 @c man begin OPTIONS
1014 The following options are available when @value{AS} is configured for
1015 the C-SKY processor family.
1017 @c man begin INCLUDE
1018 @include c-csky.texi
1019 @c ended inside the included file
1025 The following options are available when @value{AS} is configured for
1028 @cindex D10V optimization
1029 @cindex optimization, D10V
1031 Optimize output by parallelizing instructions.
1036 The following options are available when @value{AS} is configured for a D30V
1039 @cindex D30V optimization
1040 @cindex optimization, D30V
1042 Optimize output by parallelizing instructions.
1046 Warn when nops are generated.
1048 @cindex D30V nops after 32-bit multiply
1050 Warn when a nop after a 32-bit multiply instruction is generated.
1056 The following options are available when @value{AS} is configured for the
1057 Adapteva EPIPHANY series.
1060 @xref{Epiphany Options}, for the options available when @value{AS} is
1061 configured for an Epiphany processor.
1065 @c man begin OPTIONS
1066 The following options are available when @value{AS} is configured for
1067 an Epiphany processor.
1069 @c man begin INCLUDE
1070 @include c-epiphany.texi
1071 @c ended inside the included file
1079 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1080 for an H8/300 processor.
1084 @c man begin OPTIONS
1085 The following options are available when @value{AS} is configured for an H8/300
1088 @c man begin INCLUDE
1089 @include c-h8300.texi
1090 @c ended inside the included file
1098 @xref{i386-Options}, for the options available when @value{AS} is
1099 configured for an i386 processor.
1103 @c man begin OPTIONS
1104 The following options are available when @value{AS} is configured for
1107 @c man begin INCLUDE
1108 @include c-i386.texi
1109 @c ended inside the included file
1114 @c man begin OPTIONS
1116 The following options are available when @value{AS} is configured for the
1122 Specifies that the extended IP2022 instructions are allowed.
1125 Restores the default behaviour, which restricts the permitted instructions to
1126 just the basic IP2022 ones.
1132 The following options are available when @value{AS} is configured for the
1133 Renesas M32C and M16C processors.
1138 Assemble M32C instructions.
1141 Assemble M16C instructions (the default).
1144 Enable support for link-time relaxations.
1147 Support H'00 style hex constants in addition to 0x00 style.
1153 The following options are available when @value{AS} is configured for the
1154 Renesas M32R (formerly Mitsubishi M32R) series.
1159 Specify which processor in the M32R family is the target. The default
1160 is normally the M32R, but this option changes it to the M32RX.
1162 @item --warn-explicit-parallel-conflicts or --Wp
1163 Produce warning messages when questionable parallel constructs are
1166 @item --no-warn-explicit-parallel-conflicts or --Wnp
1167 Do not produce warning messages when questionable parallel constructs are
1174 The following options are available when @value{AS} is configured for the
1175 Motorola 68000 series.
1180 Shorten references to undefined symbols, to one word instead of two.
1182 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1183 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1184 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1185 Specify what processor in the 68000 family is the target. The default
1186 is normally the 68020, but this can be changed at configuration time.
1188 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1189 The target machine does (or does not) have a floating-point coprocessor.
1190 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1191 the basic 68000 is not compatible with the 68881, a combination of the
1192 two can be specified, since it's possible to do emulation of the
1193 coprocessor instructions with the main processor.
1195 @item -m68851 | -mno-68851
1196 The target machine does (or does not) have a memory-management
1197 unit coprocessor. The default is to assume an MMU for 68020 and up.
1205 @xref{Nios II Options}, for the options available when @value{AS} is configured
1206 for an Altera Nios II processor.
1210 @c man begin OPTIONS
1211 The following options are available when @value{AS} is configured for an
1212 Altera Nios II processor.
1214 @c man begin INCLUDE
1215 @include c-nios2.texi
1216 @c ended inside the included file
1222 For details about the PDP-11 machine dependent features options,
1223 see @ref{PDP-11-Options}.
1226 @item -mpic | -mno-pic
1227 Generate position-independent (or position-dependent) code. The
1228 default is @option{-mpic}.
1231 @itemx -mall-extensions
1232 Enable all instruction set extensions. This is the default.
1234 @item -mno-extensions
1235 Disable all instruction set extensions.
1237 @item -m@var{extension} | -mno-@var{extension}
1238 Enable (or disable) a particular instruction set extension.
1241 Enable the instruction set extensions supported by a particular CPU, and
1242 disable all other extensions.
1244 @item -m@var{machine}
1245 Enable the instruction set extensions supported by a particular machine
1246 model, and disable all other extensions.
1252 The following options are available when @value{AS} is configured for
1253 a picoJava processor.
1257 @cindex PJ endianness
1258 @cindex endianness, PJ
1259 @cindex big endian output, PJ
1261 Generate ``big endian'' format output.
1263 @cindex little endian output, PJ
1265 Generate ``little endian'' format output.
1273 @xref{PRU Options}, for the options available when @value{AS} is configured
1274 for a PRU processor.
1278 @c man begin OPTIONS
1279 The following options are available when @value{AS} is configured for a
1282 @c man begin INCLUDE
1284 @c ended inside the included file
1289 The following options are available when @value{AS} is configured for the
1290 Motorola 68HC11 or 68HC12 series.
1294 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1295 Specify what processor is the target. The default is
1296 defined by the configuration option when building the assembler.
1298 @item --xgate-ramoffset
1299 Instruct the linker to offset RAM addresses from S12X address space into
1300 XGATE address space.
1303 Specify to use the 16-bit integer ABI.
1306 Specify to use the 32-bit integer ABI.
1308 @item -mshort-double
1309 Specify to use the 32-bit double ABI.
1312 Specify to use the 64-bit double ABI.
1314 @item --force-long-branches
1315 Relative branches are turned into absolute ones. This concerns
1316 conditional branches, unconditional branches and branches to a
1319 @item -S | --short-branches
1320 Do not turn relative branches into absolute ones
1321 when the offset is out of range.
1323 @item --strict-direct-mode
1324 Do not turn the direct addressing mode into extended addressing mode
1325 when the instruction does not support direct addressing mode.
1327 @item --print-insn-syntax
1328 Print the syntax of instruction in case of error.
1330 @item --print-opcodes
1331 Print the list of instructions with syntax and then exit.
1333 @item --generate-example
1334 Print an example of instruction for each possible instruction and then exit.
1335 This option is only useful for testing @command{@value{AS}}.
1341 The following options are available when @command{@value{AS}} is configured
1342 for the SPARC architecture:
1345 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1346 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1347 Explicitly select a variant of the SPARC architecture.
1349 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1350 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1352 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1353 UltraSPARC extensions.
1355 @item -xarch=v8plus | -xarch=v8plusa
1356 For compatibility with the Solaris v9 assembler. These options are
1357 equivalent to -Av8plus and -Av8plusa, respectively.
1360 Warn when the assembler switches to another architecture.
1365 The following options are available when @value{AS} is configured for the 'c54x
1370 Enable extended addressing mode. All addresses and relocations will assume
1371 extended addressing (usually 23 bits).
1372 @item -mcpu=@var{CPU_VERSION}
1373 Sets the CPU version being compiled for.
1374 @item -merrors-to-file @var{FILENAME}
1375 Redirect error output to a file, for broken systems which don't support such
1376 behaviour in the shell.
1381 @c man begin OPTIONS
1382 The following options are available when @value{AS} is configured for
1387 This option sets the largest size of an object that can be referenced
1388 implicitly with the @code{gp} register. It is only accepted for targets that
1389 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1391 @cindex MIPS endianness
1392 @cindex endianness, MIPS
1393 @cindex big endian output, MIPS
1395 Generate ``big endian'' format output.
1397 @cindex little endian output, MIPS
1399 Generate ``little endian'' format output.
1417 Generate code for a particular MIPS Instruction Set Architecture level.
1418 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1419 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1420 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1421 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1422 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1423 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1424 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1425 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1426 MIPS64 Release 6 ISA processors, respectively.
1428 @item -march=@var{cpu}
1429 Generate code for a particular MIPS CPU.
1431 @item -mtune=@var{cpu}
1432 Schedule and tune for a particular MIPS CPU.
1436 Cause nops to be inserted if the read of the destination register
1437 of an mfhi or mflo instruction occurs in the following two instructions.
1440 @itemx -mno-fix-rm7000
1441 Cause nops to be inserted if a dmult or dmultu instruction is
1442 followed by a load instruction.
1446 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1447 section instead of the standard ELF .stabs sections.
1451 Control generation of @code{.pdr} sections.
1455 The register sizes are normally inferred from the ISA and ABI, but these
1456 flags force a certain group of registers to be treated as 32 bits wide at
1457 all times. @samp{-mgp32} controls the size of general-purpose registers
1458 and @samp{-mfp32} controls the size of floating-point registers.
1462 The register sizes are normally inferred from the ISA and ABI, but these
1463 flags force a certain group of registers to be treated as 64 bits wide at
1464 all times. @samp{-mgp64} controls the size of general-purpose registers
1465 and @samp{-mfp64} controls the size of floating-point registers.
1468 The register sizes are normally inferred from the ISA and ABI, but using
1469 this flag in combination with @samp{-mabi=32} enables an ABI variant
1470 which will operate correctly with floating-point registers which are
1474 @itemx -mno-odd-spreg
1475 Enable use of floating-point operations on odd-numbered single-precision
1476 registers when supported by the ISA. @samp{-mfpxx} implies
1477 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1481 Generate code for the MIPS 16 processor. This is equivalent to putting
1482 @code{.module mips16} at the start of the assembly file. @samp{-no-mips16}
1483 turns off this option.
1486 @itemx -mno-mips16e2
1487 Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent
1488 to putting @code{.module mips16e2} at the start of the assembly file.
1489 @samp{-mno-mips16e2} turns off this option.
1492 @itemx -mno-micromips
1493 Generate code for the microMIPS processor. This is equivalent to putting
1494 @code{.module micromips} at the start of the assembly file.
1495 @samp{-mno-micromips} turns off this option. This is equivalent to putting
1496 @code{.module nomicromips} at the start of the assembly file.
1499 @itemx -mno-smartmips
1500 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1501 equivalent to putting @code{.module smartmips} at the start of the assembly
1502 file. @samp{-mno-smartmips} turns off this option.
1506 Generate code for the MIPS-3D Application Specific Extension.
1507 This tells the assembler to accept MIPS-3D instructions.
1508 @samp{-no-mips3d} turns off this option.
1512 Generate code for the MDMX Application Specific Extension.
1513 This tells the assembler to accept MDMX instructions.
1514 @samp{-no-mdmx} turns off this option.
1518 Generate code for the DSP Release 1 Application Specific Extension.
1519 This tells the assembler to accept DSP Release 1 instructions.
1520 @samp{-mno-dsp} turns off this option.
1524 Generate code for the DSP Release 2 Application Specific Extension.
1525 This option implies @samp{-mdsp}.
1526 This tells the assembler to accept DSP Release 2 instructions.
1527 @samp{-mno-dspr2} turns off this option.
1531 Generate code for the DSP Release 3 Application Specific Extension.
1532 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1533 This tells the assembler to accept DSP Release 3 instructions.
1534 @samp{-mno-dspr3} turns off this option.
1538 Generate code for the MIPS SIMD Architecture Extension.
1539 This tells the assembler to accept MSA instructions.
1540 @samp{-mno-msa} turns off this option.
1544 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1545 This tells the assembler to accept XPA instructions.
1546 @samp{-mno-xpa} turns off this option.
1550 Generate code for the MT Application Specific Extension.
1551 This tells the assembler to accept MT instructions.
1552 @samp{-mno-mt} turns off this option.
1556 Generate code for the MCU Application Specific Extension.
1557 This tells the assembler to accept MCU instructions.
1558 @samp{-mno-mcu} turns off this option.
1562 Generate code for the MIPS cyclic redundancy check (CRC) Application
1563 Specific Extension. This tells the assembler to accept CRC instructions.
1564 @samp{-mno-crc} turns off this option.
1568 Generate code for the Global INValidate (GINV) Application Specific
1569 Extension. This tells the assembler to accept GINV instructions.
1570 @samp{-mno-ginv} turns off this option.
1572 @item -mloongson-mmi
1573 @itemx -mno-loongson-mmi
1574 Generate code for the Loongson MultiMedia extensions Instructions (MMI)
1575 Application Specific Extension. This tells the assembler to accept MMI
1577 @samp{-mno-loongson-mmi} turns off this option.
1579 @item -mloongson-cam
1580 @itemx -mno-loongson-cam
1581 Generate code for the Loongson Content Address Memory (CAM) instructions.
1582 This tells the assembler to accept Loongson CAM instructions.
1583 @samp{-mno-loongson-cam} turns off this option.
1585 @item -mloongson-ext
1586 @itemx -mno-loongson-ext
1587 Generate code for the Loongson EXTensions (EXT) instructions.
1588 This tells the assembler to accept Loongson EXT instructions.
1589 @samp{-mno-loongson-ext} turns off this option.
1591 @item -mloongson-ext2
1592 @itemx -mno-loongson-ext2
1593 Generate code for the Loongson EXTensions R2 (EXT2) instructions.
1594 This option implies @samp{-mloongson-ext}.
1595 This tells the assembler to accept Loongson EXT2 instructions.
1596 @samp{-mno-loongson-ext2} turns off this option.
1600 Only use 32-bit instruction encodings when generating code for the
1601 microMIPS processor. This option inhibits the use of any 16-bit
1602 instructions. This is equivalent to putting @code{.set insn32} at
1603 the start of the assembly file. @samp{-mno-insn32} turns off this
1604 option. This is equivalent to putting @code{.set noinsn32} at the
1605 start of the assembly file. By default @samp{-mno-insn32} is
1606 selected, allowing all instructions to be used.
1608 @item --construct-floats
1609 @itemx --no-construct-floats
1610 The @samp{--no-construct-floats} option disables the construction of
1611 double width floating point constants by loading the two halves of the
1612 value into the two single width floating point registers that make up
1613 the double width register. By default @samp{--construct-floats} is
1614 selected, allowing construction of these floating point constants.
1616 @item --relax-branch
1617 @itemx --no-relax-branch
1618 The @samp{--relax-branch} option enables the relaxation of out-of-range
1619 branches. By default @samp{--no-relax-branch} is selected, causing any
1620 out-of-range branches to produce an error.
1622 @item -mignore-branch-isa
1623 @itemx -mno-ignore-branch-isa
1624 Ignore branch checks for invalid transitions between ISA modes. The
1625 semantics of branches does not provide for an ISA mode switch, so in
1626 most cases the ISA mode a branch has been encoded for has to be the
1627 same as the ISA mode of the branch's target label. Therefore GAS has
1628 checks implemented that verify in branch assembly that the two ISA
1629 modes match. @samp{-mignore-branch-isa} disables these checks. By
1630 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1631 branch requiring a transition between ISA modes to produce an error.
1633 @item -mnan=@var{encoding}
1634 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1635 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1638 @item --emulation=@var{name}
1639 This option was formerly used to switch between ELF and ECOFF output
1640 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1641 removed in GAS 2.24, so the option now serves little purpose.
1642 It is retained for backwards compatibility.
1644 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1645 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1646 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1647 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1648 preferred options instead.
1651 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1658 Control how to deal with multiplication overflow and division by zero.
1659 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1660 (and only work for Instruction Set Architecture level 2 and higher);
1661 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1665 When this option is used, @command{@value{AS}} will issue a warning every
1666 time it generates a nop instruction from a macro.
1672 The following options are available when @value{AS} is configured for
1678 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1679 The command-line option @samp{-nojsri2bsr} can be used to disable it.
1683 Enable or disable the silicon filter behaviour. By default this is disabled.
1684 The default can be overridden by the @samp{-sifilter} command-line option.
1687 Alter jump instructions for long displacements.
1689 @item -mcpu=[210|340]
1690 Select the cpu type on the target hardware. This controls which instructions
1694 Assemble for a big endian target.
1697 Assemble for a little endian target.
1706 @xref{Meta Options}, for the options available when @value{AS} is configured
1707 for a Meta processor.
1711 @c man begin OPTIONS
1712 The following options are available when @value{AS} is configured for a
1715 @c man begin INCLUDE
1716 @include c-metag.texi
1717 @c ended inside the included file
1722 @c man begin OPTIONS
1724 See the info pages for documentation of the MMIX-specific options.
1730 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1731 for a NDS32 processor.
1733 @c ended inside the included file
1737 @c man begin OPTIONS
1738 The following options are available when @value{AS} is configured for a
1741 @c man begin INCLUDE
1742 @include c-nds32.texi
1743 @c ended inside the included file
1750 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1751 for a PowerPC processor.
1755 @c man begin OPTIONS
1756 The following options are available when @value{AS} is configured for a
1759 @c man begin INCLUDE
1761 @c ended inside the included file
1769 @xref{RISC-V-Options}, for the options available when @value{AS} is configured
1770 for a RISC-V processor.
1774 @c man begin OPTIONS
1775 The following options are available when @value{AS} is configured for a
1778 @c man begin INCLUDE
1779 @include c-riscv.texi
1780 @c ended inside the included file
1785 @c man begin OPTIONS
1787 See the info pages for documentation of the RX-specific options.
1791 The following options are available when @value{AS} is configured for the s390
1797 Select the word size, either 31/32 bits or 64 bits.
1800 Select the architecture mode, either the Enterprise System
1801 Architecture (esa) or the z/Architecture mode (zarch).
1802 @item -march=@var{processor}
1803 Specify which s390 processor variant is the target, @samp{g5} (or
1804 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1805 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1806 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1807 @samp{z13} (or @samp{arch11}), or @samp{z14} (or @samp{arch12}).
1809 @itemx -mno-regnames
1810 Allow or disallow symbolic names for registers.
1811 @item -mwarn-areg-zero
1812 Warn whenever the operand for a base or index register has been specified
1813 but evaluates to zero.
1821 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1822 for a TMS320C6000 processor.
1826 @c man begin OPTIONS
1827 The following options are available when @value{AS} is configured for a
1828 TMS320C6000 processor.
1830 @c man begin INCLUDE
1831 @include c-tic6x.texi
1832 @c ended inside the included file
1840 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1841 for a TILE-Gx processor.
1845 @c man begin OPTIONS
1846 The following options are available when @value{AS} is configured for a TILE-Gx
1849 @c man begin INCLUDE
1850 @include c-tilegx.texi
1851 @c ended inside the included file
1859 @xref{Visium Options}, for the options available when @value{AS} is configured
1860 for a Visium processor.
1864 @c man begin OPTIONS
1865 The following option is available when @value{AS} is configured for a Visium
1868 @c man begin INCLUDE
1869 @include c-visium.texi
1870 @c ended inside the included file
1878 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1879 for an Xtensa processor.
1883 @c man begin OPTIONS
1884 The following options are available when @value{AS} is configured for an
1887 @c man begin INCLUDE
1888 @include c-xtensa.texi
1889 @c ended inside the included file
1894 @c man begin OPTIONS
1897 The following options are available when @value{AS} is configured for
1898 a Z80 family processor.
1901 Assemble for Z80 processor.
1903 Assemble for R800 processor.
1904 @item -ignore-undocumented-instructions
1906 Assemble undocumented Z80 instructions that also work on R800 without warning.
1907 @item -ignore-unportable-instructions
1909 Assemble all undocumented Z80 instructions without warning.
1910 @item -warn-undocumented-instructions
1912 Issue a warning for undocumented Z80 instructions that also work on R800.
1913 @item -warn-unportable-instructions
1915 Issue a warning for undocumented Z80 instructions that do not work on R800.
1916 @item -forbid-undocumented-instructions
1918 Treat all undocumented instructions as errors.
1919 @item -forbid-unportable-instructions
1921 Treat undocumented Z80 instructions that do not work on R800 as errors.
1928 * Manual:: Structure of this Manual
1929 * GNU Assembler:: The GNU Assembler
1930 * Object Formats:: Object File Formats
1931 * Command Line:: Command Line
1932 * Input Files:: Input Files
1933 * Object:: Output (Object) File
1934 * Errors:: Error and Warning Messages
1938 @section Structure of this Manual
1940 @cindex manual, structure and purpose
1941 This manual is intended to describe what you need to know to use
1942 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1943 notation for symbols, constants, and expressions; the directives that
1944 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1947 We also cover special features in the @value{TARGET}
1948 configuration of @command{@value{AS}}, including assembler directives.
1951 This manual also describes some of the machine-dependent features of
1952 various flavors of the assembler.
1955 @cindex machine instructions (not covered)
1956 On the other hand, this manual is @emph{not} intended as an introduction
1957 to programming in assembly language---let alone programming in general!
1958 In a similar vein, we make no attempt to introduce the machine
1959 architecture; we do @emph{not} describe the instruction set, standard
1960 mnemonics, registers or addressing modes that are standard to a
1961 particular architecture.
1963 You may want to consult the manufacturer's
1964 machine architecture manual for this information.
1968 For information on the H8/300 machine instruction set, see @cite{H8/300
1969 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1970 Programming Manual} (Renesas).
1973 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1974 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1975 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1976 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1979 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1983 @c I think this is premature---doc@cygnus.com, 17jan1991
1985 Throughout this manual, we assume that you are running @dfn{GNU},
1986 the portable operating system from the @dfn{Free Software
1987 Foundation, Inc.}. This restricts our attention to certain kinds of
1988 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1989 once this assumption is granted examples and definitions need less
1992 @command{@value{AS}} is part of a team of programs that turn a high-level
1993 human-readable series of instructions into a low-level
1994 computer-readable series of instructions. Different versions of
1995 @command{@value{AS}} are used for different kinds of computer.
1998 @c There used to be a section "Terminology" here, which defined
1999 @c "contents", "byte", "word", and "long". Defining "word" to any
2000 @c particular size is confusing when the .word directive may generate 16
2001 @c bits on one machine and 32 bits on another; in general, for the user
2002 @c version of this manual, none of these terms seem essential to define.
2003 @c They were used very little even in the former draft of the manual;
2004 @c this draft makes an effort to avoid them (except in names of
2008 @section The GNU Assembler
2010 @c man begin DESCRIPTION
2012 @sc{gnu} @command{as} is really a family of assemblers.
2014 This manual describes @command{@value{AS}}, a member of that family which is
2015 configured for the @value{TARGET} architectures.
2017 If you use (or have used) the @sc{gnu} assembler on one architecture, you
2018 should find a fairly similar environment when you use it on another
2019 architecture. Each version has much in common with the others,
2020 including object file formats, most assembler directives (often called
2021 @dfn{pseudo-ops}) and assembler syntax.@refill
2023 @cindex purpose of @sc{gnu} assembler
2024 @command{@value{AS}} is primarily intended to assemble the output of the
2025 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
2026 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
2027 assemble correctly everything that other assemblers for the same
2028 machine would assemble.
2030 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
2033 @c This remark should appear in generic version of manual; assumption
2034 @c here is that generic version sets M680x0.
2035 This doesn't mean @command{@value{AS}} always uses the same syntax as another
2036 assembler for the same architecture; for example, we know of several
2037 incompatible versions of 680x0 assembly language syntax.
2042 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
2043 program in one pass of the source file. This has a subtle impact on the
2044 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
2046 @node Object Formats
2047 @section Object File Formats
2049 @cindex object file format
2050 The @sc{gnu} assembler can be configured to produce several alternative
2051 object file formats. For the most part, this does not affect how you
2052 write assembly language programs; but directives for debugging symbols
2053 are typically different in different file formats. @xref{Symbol
2054 Attributes,,Symbol Attributes}.
2057 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
2058 @value{OBJ-NAME} format object files.
2060 @c The following should exhaust all configs that set MULTI-OBJ, ideally
2062 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
2063 SOM or ELF format object files.
2068 @section Command Line
2070 @cindex command line conventions
2072 After the program name @command{@value{AS}}, the command line may contain
2073 options and file names. Options may appear in any order, and may be
2074 before, after, or between file names. The order of file names is
2077 @cindex standard input, as input file
2079 @file{--} (two hyphens) by itself names the standard input file
2080 explicitly, as one of the files for @command{@value{AS}} to assemble.
2082 @cindex options, command line
2083 Except for @samp{--} any command-line argument that begins with a
2084 hyphen (@samp{-}) is an option. Each option changes the behavior of
2085 @command{@value{AS}}. No option changes the way another option works. An
2086 option is a @samp{-} followed by one or more letters; the case of
2087 the letter is important. All options are optional.
2089 Some options expect exactly one file name to follow them. The file
2090 name may either immediately follow the option's letter (compatible
2091 with older assemblers) or it may be the next command argument (@sc{gnu}
2092 standard). These two command lines are equivalent:
2095 @value{AS} -o my-object-file.o mumble.s
2096 @value{AS} -omy-object-file.o mumble.s
2100 @section Input Files
2103 @cindex source program
2104 @cindex files, input
2105 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2106 describe the program input to one run of @command{@value{AS}}. The program may
2107 be in one or more files; how the source is partitioned into files
2108 doesn't change the meaning of the source.
2110 @c I added "con" prefix to "catenation" just to prove I can overcome my
2111 @c APL training... doc@cygnus.com
2112 The source program is a concatenation of the text in all the files, in the
2115 @c man begin DESCRIPTION
2116 Each time you run @command{@value{AS}} it assembles exactly one source
2117 program. The source program is made up of one or more files.
2118 (The standard input is also a file.)
2120 You give @command{@value{AS}} a command line that has zero or more input file
2121 names. The input files are read (from left file name to right). A
2122 command-line argument (in any position) that has no special meaning
2123 is taken to be an input file name.
2125 If you give @command{@value{AS}} no file names it attempts to read one input file
2126 from the @command{@value{AS}} standard input, which is normally your terminal. You
2127 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2130 Use @samp{--} if you need to explicitly name the standard input file
2131 in your command line.
2133 If the source is empty, @command{@value{AS}} produces a small, empty object
2138 @subheading Filenames and Line-numbers
2140 @cindex input file linenumbers
2141 @cindex line numbers, in input files
2142 There are two ways of locating a line in the input file (or files) and
2143 either may be used in reporting error messages. One way refers to a line
2144 number in a physical file; the other refers to a line number in a
2145 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2147 @dfn{Physical files} are those files named in the command line given
2148 to @command{@value{AS}}.
2150 @dfn{Logical files} are simply names declared explicitly by assembler
2151 directives; they bear no relation to physical files. Logical file names help
2152 error messages reflect the original source file, when @command{@value{AS}} source
2153 is itself synthesized from other files. @command{@value{AS}} understands the
2154 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2155 @ref{File,,@code{.file}}.
2158 @section Output (Object) File
2164 Every time you run @command{@value{AS}} it produces an output file, which is
2165 your assembly language program translated into numbers. This file
2166 is the object file. Its default name is @code{a.out}.
2167 You can give it another name by using the @option{-o} option. Conventionally,
2168 object file names end with @file{.o}. The default name is used for historical
2169 reasons: older assemblers were capable of assembling self-contained programs
2170 directly into a runnable program. (For some formats, this isn't currently
2171 possible, but it can be done for the @code{a.out} format.)
2175 The object file is meant for input to the linker @code{@value{LD}}. It contains
2176 assembled program code, information to help @code{@value{LD}} integrate
2177 the assembled program into a runnable file, and (optionally) symbolic
2178 information for the debugger.
2180 @c link above to some info file(s) like the description of a.out.
2181 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2184 @section Error and Warning Messages
2186 @c man begin DESCRIPTION
2188 @cindex error messages
2189 @cindex warning messages
2190 @cindex messages from assembler
2191 @command{@value{AS}} may write warnings and error messages to the standard error
2192 file (usually your terminal). This should not happen when a compiler
2193 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2194 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2195 grave problem that stops the assembly.
2199 @cindex format of warning messages
2200 Warning messages have the format
2203 file_name:@b{NNN}:Warning Message Text
2207 @cindex file names and line numbers, in warnings/errors
2208 (where @b{NNN} is a line number). If both a logical file name
2209 (@pxref{File,,@code{.file}}) and a logical line number
2211 (@pxref{Line,,@code{.line}})
2213 have been given then they will be used, otherwise the file name and line number
2214 in the current assembler source file will be used. The message text is
2215 intended to be self explanatory (in the grand Unix tradition).
2217 Note the file name must be set via the logical version of the @code{.file}
2218 directive, not the DWARF2 version of the @code{.file} directive. For example:
2222 error_assembler_source
2228 produces this output:
2232 asm.s:2: Error: no such instruction: `error_assembler_source'
2233 foo.c:31: Error: no such instruction: `error_c_source'
2236 @cindex format of error messages
2237 Error messages have the format
2240 file_name:@b{NNN}:FATAL:Error Message Text
2243 The file name and line number are derived as for warning
2244 messages. The actual message text may be rather less explanatory
2245 because many of them aren't supposed to happen.
2248 @chapter Command-Line Options
2250 @cindex options, all versions of assembler
2251 This chapter describes command-line options available in @emph{all}
2252 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2253 for options specific
2255 to the @value{TARGET} target.
2258 to particular machine architectures.
2261 @c man begin DESCRIPTION
2263 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2264 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2265 The assembler arguments must be separated from each other (and the @samp{-Wa})
2266 by commas. For example:
2269 gcc -c -g -O -Wa,-alh,-L file.c
2273 This passes two options to the assembler: @samp{-alh} (emit a listing to
2274 standard output with high-level and assembly source) and @samp{-L} (retain
2275 local symbols in the symbol table).
2277 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2278 command-line options are automatically passed to the assembler by the compiler.
2279 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2280 precisely what options it passes to each compilation pass, including the
2286 * a:: -a[cdghlns] enable listings
2287 * alternate:: --alternate enable alternate macro syntax
2288 * D:: -D for compatibility
2289 * f:: -f to work faster
2290 * I:: -I for .include search path
2291 @ifclear DIFF-TBL-KLUGE
2292 * K:: -K for compatibility
2294 @ifset DIFF-TBL-KLUGE
2295 * K:: -K for difference tables
2298 * L:: -L to retain local symbols
2299 * listing:: --listing-XXX to configure listing output
2300 * M:: -M or --mri to assemble in MRI compatibility mode
2301 * MD:: --MD for dependency tracking
2302 * no-pad-sections:: --no-pad-sections to stop section padding
2303 * o:: -o to name the object file
2304 * R:: -R to join data and text sections
2305 * statistics:: --statistics to see statistics about assembly
2306 * traditional-format:: --traditional-format for compatible output
2307 * v:: -v to announce version
2308 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2309 * Z:: -Z to make object file even after errors
2313 @section Enable Listings: @option{-a[cdghlns]}
2323 @cindex listings, enabling
2324 @cindex assembly listings, enabling
2326 These options enable listing output from the assembler. By itself,
2327 @samp{-a} requests high-level, assembly, and symbols listing.
2328 You can use other letters to select specific options for the list:
2329 @samp{-ah} requests a high-level language listing,
2330 @samp{-al} requests an output-program assembly listing, and
2331 @samp{-as} requests a symbol table listing.
2332 High-level listings require that a compiler debugging option like
2333 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2336 Use the @samp{-ag} option to print a first section with general assembly
2337 information, like @value{AS} version, switches passed, or time stamp.
2339 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2340 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2341 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2342 omitted from the listing.
2344 Use the @samp{-ad} option to omit debugging directives from the
2347 Once you have specified one of these options, you can further control
2348 listing output and its appearance using the directives @code{.list},
2349 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2351 The @samp{-an} option turns off all forms processing.
2352 If you do not request listing output with one of the @samp{-a} options, the
2353 listing-control directives have no effect.
2355 The letters after @samp{-a} may be combined into one option,
2356 @emph{e.g.}, @samp{-aln}.
2358 Note if the assembler source is coming from the standard input (e.g.,
2360 is being created by @code{@value{GCC}} and the @samp{-pipe} command-line switch
2361 is being used) then the listing will not contain any comments or preprocessor
2362 directives. This is because the listing code buffers input source lines from
2363 stdin only after they have been preprocessed by the assembler. This reduces
2364 memory usage and makes the code more efficient.
2367 @section @option{--alternate}
2370 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2373 @section @option{-D}
2376 This option has no effect whatsoever, but it is accepted to make it more
2377 likely that scripts written for other assemblers also work with
2378 @command{@value{AS}}.
2381 @section Work Faster: @option{-f}
2384 @cindex trusted compiler
2385 @cindex faster processing (@option{-f})
2386 @samp{-f} should only be used when assembling programs written by a
2387 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2388 and comment preprocessing on
2389 the input file(s) before assembling them. @xref{Preprocessing,
2393 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2394 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2399 @section @code{.include} Search Path: @option{-I} @var{path}
2401 @kindex -I @var{path}
2402 @cindex paths for @code{.include}
2403 @cindex search path for @code{.include}
2404 @cindex @code{include} directive search path
2405 Use this option to add a @var{path} to the list of directories
2406 @command{@value{AS}} searches for files specified in @code{.include}
2407 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2408 many times as necessary to include a variety of paths. The current
2409 working directory is always searched first; after that, @command{@value{AS}}
2410 searches any @samp{-I} directories in the same order as they were
2411 specified (left to right) on the command line.
2414 @section Difference Tables: @option{-K}
2417 @ifclear DIFF-TBL-KLUGE
2418 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2419 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2420 where it can be used to warn when the assembler alters the machine code
2421 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2422 family does not have the addressing limitations that sometimes lead to this
2423 alteration on other platforms.
2426 @ifset DIFF-TBL-KLUGE
2427 @cindex difference tables, warning
2428 @cindex warning for altered difference tables
2429 @command{@value{AS}} sometimes alters the code emitted for directives of the
2430 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2431 You can use the @samp{-K} option if you want a warning issued when this
2436 @section Include Local Symbols: @option{-L}
2439 @cindex local symbols, retaining in output
2440 Symbols beginning with system-specific local label prefixes, typically
2441 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2442 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2443 such symbols when debugging, because they are intended for the use of
2444 programs (like compilers) that compose assembler programs, not for your
2445 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2446 such symbols, so you do not normally debug with them.
2448 This option tells @command{@value{AS}} to retain those local symbols
2449 in the object file. Usually if you do this you also tell the linker
2450 @code{@value{LD}} to preserve those symbols.
2453 @section Configuring listing output: @option{--listing}
2455 The listing feature of the assembler can be enabled via the command-line switch
2456 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2457 hex dump of the corresponding locations in the output object file, and displays
2458 them as a listing file. The format of this listing can be controlled by
2459 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2460 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2461 @code{.psize} (@pxref{Psize}), and
2462 @code{.eject} (@pxref{Eject}) and also by the following switches:
2465 @item --listing-lhs-width=@samp{number}
2466 @kindex --listing-lhs-width
2467 @cindex Width of first line disassembly output
2468 Sets the maximum width, in words, of the first line of the hex byte dump. This
2469 dump appears on the left hand side of the listing output.
2471 @item --listing-lhs-width2=@samp{number}
2472 @kindex --listing-lhs-width2
2473 @cindex Width of continuation lines of disassembly output
2474 Sets the maximum width, in words, of any further lines of the hex byte dump for
2475 a given input source line. If this value is not specified, it defaults to being
2476 the same as the value specified for @samp{--listing-lhs-width}. If neither
2477 switch is used the default is to one.
2479 @item --listing-rhs-width=@samp{number}
2480 @kindex --listing-rhs-width
2481 @cindex Width of source line output
2482 Sets the maximum width, in characters, of the source line that is displayed
2483 alongside the hex dump. The default value for this parameter is 100. The
2484 source line is displayed on the right hand side of the listing output.
2486 @item --listing-cont-lines=@samp{number}
2487 @kindex --listing-cont-lines
2488 @cindex Maximum number of continuation lines
2489 Sets the maximum number of continuation lines of hex dump that will be
2490 displayed for a given single line of source input. The default value is 4.
2494 @section Assemble in MRI Compatibility Mode: @option{-M}
2497 @cindex MRI compatibility mode
2498 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2499 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2500 compatible with the @code{ASM68K} assembler from Microtec Research.
2501 The exact nature of the
2502 MRI syntax will not be documented here; see the MRI manuals for more
2503 information. Note in particular that the handling of macros and macro
2504 arguments is somewhat different. The purpose of this option is to permit
2505 assembling existing MRI assembler code using @command{@value{AS}}.
2507 The MRI compatibility is not complete. Certain operations of the MRI assembler
2508 depend upon its object file format, and can not be supported using other object
2509 file formats. Supporting these would require enhancing each object file format
2510 individually. These are:
2513 @item global symbols in common section
2515 The m68k MRI assembler supports common sections which are merged by the linker.
2516 Other object file formats do not support this. @command{@value{AS}} handles
2517 common sections by treating them as a single common symbol. It permits local
2518 symbols to be defined within a common section, but it can not support global
2519 symbols, since it has no way to describe them.
2521 @item complex relocations
2523 The MRI assemblers support relocations against a negated section address, and
2524 relocations which combine the start addresses of two or more sections. These
2525 are not support by other object file formats.
2527 @item @code{END} pseudo-op specifying start address
2529 The MRI @code{END} pseudo-op permits the specification of a start address.
2530 This is not supported by other object file formats. The start address may
2531 instead be specified using the @option{-e} option to the linker, or in a linker
2534 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2536 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2537 name to the output file. This is not supported by other object file formats.
2539 @item @code{ORG} pseudo-op
2541 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2542 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2543 which changes the location within the current section. Absolute sections are
2544 not supported by other object file formats. The address of a section may be
2545 assigned within a linker script.
2548 There are some other features of the MRI assembler which are not supported by
2549 @command{@value{AS}}, typically either because they are difficult or because they
2550 seem of little consequence. Some of these may be supported in future releases.
2554 @item EBCDIC strings
2556 EBCDIC strings are not supported.
2558 @item packed binary coded decimal
2560 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2561 and @code{DCB.P} pseudo-ops are not supported.
2563 @item @code{FEQU} pseudo-op
2565 The m68k @code{FEQU} pseudo-op is not supported.
2567 @item @code{NOOBJ} pseudo-op
2569 The m68k @code{NOOBJ} pseudo-op is not supported.
2571 @item @code{OPT} branch control options
2573 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2574 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2575 relaxes all branches, whether forward or backward, to an appropriate size, so
2576 these options serve no purpose.
2578 @item @code{OPT} list control options
2580 The following m68k @code{OPT} list control options are ignored: @code{C},
2581 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2582 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2584 @item other @code{OPT} options
2586 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2587 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2589 @item @code{OPT} @code{D} option is default
2591 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2592 @code{OPT NOD} may be used to turn it off.
2594 @item @code{XREF} pseudo-op.
2596 The m68k @code{XREF} pseudo-op is ignored.
2601 @section Dependency Tracking: @option{--MD}
2604 @cindex dependency tracking
2607 @command{@value{AS}} can generate a dependency file for the file it creates. This
2608 file consists of a single rule suitable for @code{make} describing the
2609 dependencies of the main source file.
2611 The rule is written to the file named in its argument.
2613 This feature is used in the automatic updating of makefiles.
2615 @node no-pad-sections
2616 @section Output Section Padding
2617 @kindex --no-pad-sections
2618 @cindex output section padding
2619 Normally the assembler will pad the end of each output section up to its
2620 alignment boundary. But this can waste space, which can be significant on
2621 memory constrained targets. So the @option{--no-pad-sections} option will
2622 disable this behaviour.
2625 @section Name the Object File: @option{-o}
2628 @cindex naming object file
2629 @cindex object file name
2630 There is always one object file output when you run @command{@value{AS}}. By
2631 default it has the name @file{a.out}.
2632 You use this option (which takes exactly one filename) to give the
2633 object file a different name.
2635 Whatever the object file is called, @command{@value{AS}} overwrites any
2636 existing file of the same name.
2639 @section Join Data and Text Sections: @option{-R}
2642 @cindex data and text sections, joining
2643 @cindex text and data sections, joining
2644 @cindex joining text and data sections
2645 @cindex merging text and data sections
2646 @option{-R} tells @command{@value{AS}} to write the object file as if all
2647 data-section data lives in the text section. This is only done at
2648 the very last moment: your binary data are the same, but data
2649 section parts are relocated differently. The data section part of
2650 your object file is zero bytes long because all its bytes are
2651 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2653 When you specify @option{-R} it would be possible to generate shorter
2654 address displacements (because we do not have to cross between text and
2655 data section). We refrain from doing this simply for compatibility with
2656 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2659 When @command{@value{AS}} is configured for COFF or ELF output,
2660 this option is only useful if you use sections named @samp{.text} and
2665 @option{-R} is not supported for any of the HPPA targets. Using
2666 @option{-R} generates a warning from @command{@value{AS}}.
2670 @section Display Assembly Statistics: @option{--statistics}
2672 @kindex --statistics
2673 @cindex statistics, about assembly
2674 @cindex time, total for assembly
2675 @cindex space used, maximum for assembly
2676 Use @samp{--statistics} to display two statistics about the resources used by
2677 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2678 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2681 @node traditional-format
2682 @section Compatible Output: @option{--traditional-format}
2684 @kindex --traditional-format
2685 For some targets, the output of @command{@value{AS}} is different in some ways
2686 from the output of some existing assembler. This switch requests
2687 @command{@value{AS}} to use the traditional format instead.
2689 For example, it disables the exception frame optimizations which
2690 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2693 @section Announce Version: @option{-v}
2697 @cindex assembler version
2698 @cindex version of assembler
2699 You can find out what version of as is running by including the
2700 option @samp{-v} (which you can also spell as @samp{-version}) on the
2704 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2706 @command{@value{AS}} should never give a warning or error message when
2707 assembling compiler output. But programs written by people often
2708 cause @command{@value{AS}} to give a warning that a particular assumption was
2709 made. All such warnings are directed to the standard error file.
2713 @cindex suppressing warnings
2714 @cindex warnings, suppressing
2715 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2716 This only affects the warning messages: it does not change any particular of
2717 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2720 @kindex --fatal-warnings
2721 @cindex errors, caused by warnings
2722 @cindex warnings, causing error
2723 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2724 files that generate warnings to be in error.
2727 @cindex warnings, switching on
2728 You can switch these options off again by specifying @option{--warn}, which
2729 causes warnings to be output as usual.
2732 @section Generate Object File in Spite of Errors: @option{-Z}
2733 @cindex object file, after errors
2734 @cindex errors, continuing after
2735 After an error message, @command{@value{AS}} normally produces no output. If for
2736 some reason you are interested in object file output even after
2737 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2738 option. If there are any errors, @command{@value{AS}} continues anyways, and
2739 writes an object file after a final warning message of the form @samp{@var{n}
2740 errors, @var{m} warnings, generating bad object file.}
2745 @cindex machine-independent syntax
2746 @cindex syntax, machine-independent
2747 This chapter describes the machine-independent syntax allowed in a
2748 source file. @command{@value{AS}} syntax is similar to what many other
2749 assemblers use; it is inspired by the BSD 4.2
2754 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2758 * Preprocessing:: Preprocessing
2759 * Whitespace:: Whitespace
2760 * Comments:: Comments
2761 * Symbol Intro:: Symbols
2762 * Statements:: Statements
2763 * Constants:: Constants
2767 @section Preprocessing
2769 @cindex preprocessing
2770 The @command{@value{AS}} internal preprocessor:
2772 @cindex whitespace, removed by preprocessor
2774 adjusts and removes extra whitespace. It leaves one space or tab before
2775 the keywords on a line, and turns any other whitespace on the line into
2778 @cindex comments, removed by preprocessor
2780 removes all comments, replacing them with a single space, or an
2781 appropriate number of newlines.
2783 @cindex constants, converted by preprocessor
2785 converts character constants into the appropriate numeric values.
2788 It does not do macro processing, include file handling, or
2789 anything else you may get from your C compiler's preprocessor. You can
2790 do include file processing with the @code{.include} directive
2791 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2792 to get other ``CPP'' style preprocessing by giving the input file a
2793 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2794 Output, gcc info, Using GNU CC}.
2796 Excess whitespace, comments, and character constants
2797 cannot be used in the portions of the input text that are not
2800 @cindex turning preprocessing on and off
2801 @cindex preprocessing, turning on and off
2804 If the first line of an input file is @code{#NO_APP} or if you use the
2805 @samp{-f} option, whitespace and comments are not removed from the input file.
2806 Within an input file, you can ask for whitespace and comment removal in
2807 specific portions of the by putting a line that says @code{#APP} before the
2808 text that may contain whitespace or comments, and putting a line that says
2809 @code{#NO_APP} after this text. This feature is mainly intend to support
2810 @code{asm} statements in compilers whose output is otherwise free of comments
2817 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2818 Whitespace is used to separate symbols, and to make programs neater for
2819 people to read. Unless within character constants
2820 (@pxref{Characters,,Character Constants}), any whitespace means the same
2821 as exactly one space.
2827 There are two ways of rendering comments to @command{@value{AS}}. In both
2828 cases the comment is equivalent to one space.
2830 Anything from @samp{/*} through the next @samp{*/} is a comment.
2831 This means you may not nest these comments.
2835 The only way to include a newline ('\n') in a comment
2836 is to use this sort of comment.
2839 /* This sort of comment does not nest. */
2842 @cindex line comment character
2843 Anything from a @dfn{line comment} character up to the next newline is
2844 considered a comment and is ignored. The line comment character is target
2845 specific, and some targets multiple comment characters. Some targets also have
2846 line comment characters that only work if they are the first character on a
2847 line. Some targets use a sequence of two characters to introduce a line
2848 comment. Some targets can also change their line comment characters depending
2849 upon command-line options that have been used. For more details see the
2850 @emph{Syntax} section in the documentation for individual targets.
2852 If the line comment character is the hash sign (@samp{#}) then it still has the
2853 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2854 to specify logical line numbers:
2857 @cindex lines starting with @code{#}
2858 @cindex logical line numbers
2859 To be compatible with past assemblers, lines that begin with @samp{#} have a
2860 special interpretation. Following the @samp{#} should be an absolute
2861 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2862 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2863 new logical file name. The rest of the line, if any, should be whitespace.
2865 If the first non-whitespace characters on the line are not numeric,
2866 the line is ignored. (Just like a comment.)
2869 # This is an ordinary comment.
2870 # 42-6 "new_file_name" # New logical file name
2871 # This is logical line # 36.
2873 This feature is deprecated, and may disappear from future versions
2874 of @command{@value{AS}}.
2879 @cindex characters used in symbols
2880 @ifclear SPECIAL-SYMS
2881 A @dfn{symbol} is one or more characters chosen from the set of all
2882 letters (both upper and lower case), digits and the three characters
2888 A @dfn{symbol} is one or more characters chosen from the set of all
2889 letters (both upper and lower case), digits and the three characters
2890 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2896 On most machines, you can also use @code{$} in symbol names; exceptions
2897 are noted in @ref{Machine Dependencies}.
2899 No symbol may begin with a digit. Case is significant.
2900 There is no length limit; all characters are significant. Multibyte characters
2901 are supported. Symbols are delimited by characters not in that set, or by the
2902 beginning of a file (since the source program must end with a newline, the end
2903 of a file is not a possible symbol delimiter). @xref{Symbols}.
2905 Symbol names may also be enclosed in double quote @code{"} characters. In such
2906 cases any characters are allowed, except for the NUL character. If a double
2907 quote character is to be included in the symbol name it must be preceeded by a
2908 backslash @code{\} character.
2909 @cindex length of symbols
2914 @cindex statements, structure of
2915 @cindex line separator character
2916 @cindex statement separator character
2918 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2919 @dfn{line separator character}. The line separator character is target
2920 specific and described in the @emph{Syntax} section of each
2921 target's documentation. Not all targets support a line separator character.
2922 The newline or line separator character is considered to be part of the
2923 preceding statement. Newlines and separators within character constants are an
2924 exception: they do not end statements.
2926 @cindex newline, required at file end
2927 @cindex EOF, newline must precede
2928 It is an error to end any statement with end-of-file: the last
2929 character of any input file should be a newline.@refill
2931 An empty statement is allowed, and may include whitespace. It is ignored.
2933 @cindex instructions and directives
2934 @cindex directives and instructions
2935 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2936 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2938 A statement begins with zero or more labels, optionally followed by a
2939 key symbol which determines what kind of statement it is. The key
2940 symbol determines the syntax of the rest of the statement. If the
2941 symbol begins with a dot @samp{.} then the statement is an assembler
2942 directive: typically valid for any computer. If the symbol begins with
2943 a letter the statement is an assembly language @dfn{instruction}: it
2944 assembles into a machine language instruction.
2946 Different versions of @command{@value{AS}} for different computers
2947 recognize different instructions. In fact, the same symbol may
2948 represent a different instruction in a different computer's assembly
2952 @cindex @code{:} (label)
2953 @cindex label (@code{:})
2954 A label is a symbol immediately followed by a colon (@code{:}).
2955 Whitespace before a label or after a colon is permitted, but you may not
2956 have whitespace between a label's symbol and its colon. @xref{Labels}.
2959 For HPPA targets, labels need not be immediately followed by a colon, but
2960 the definition of a label must begin in column zero. This also implies that
2961 only one label may be defined on each line.
2965 label: .directive followed by something
2966 another_label: # This is an empty statement.
2967 instruction operand_1, operand_2, @dots{}
2974 A constant is a number, written so that its value is known by
2975 inspection, without knowing any context. Like this:
2978 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2979 .ascii "Ring the bell\7" # A string constant.
2980 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2981 .float 0f-314159265358979323846264338327\
2982 95028841971.693993751E-40 # - pi, a flonum.
2987 * Characters:: Character Constants
2988 * Numbers:: Number Constants
2992 @subsection Character Constants
2994 @cindex character constants
2995 @cindex constants, character
2996 There are two kinds of character constants. A @dfn{character} stands
2997 for one character in one byte and its value may be used in
2998 numeric expressions. String constants (properly called string
2999 @emph{literals}) are potentially many bytes and their values may not be
3000 used in arithmetic expressions.
3004 * Chars:: Characters
3008 @subsubsection Strings
3010 @cindex string constants
3011 @cindex constants, string
3012 A @dfn{string} is written between double-quotes. It may contain
3013 double-quotes or null characters. The way to get special characters
3014 into a string is to @dfn{escape} these characters: precede them with
3015 a backslash @samp{\} character. For example @samp{\\} represents
3016 one backslash: the first @code{\} is an escape which tells
3017 @command{@value{AS}} to interpret the second character literally as a backslash
3018 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
3019 escape character). The complete list of escapes follows.
3021 @cindex escape codes, character
3022 @cindex character escape codes
3023 @c NOTE: Cindex entries must not start with a backlash character.
3024 @c NOTE: This confuses the pdf2texi script when it is creating the
3025 @c NOTE: index based upon the first character and so it generates:
3026 @c NOTE: \initial {\\}
3027 @c NOTE: which then results in the error message:
3028 @c NOTE: Argument of \\ has an extra }.
3029 @c NOTE: So in the index entries below a space character has been
3030 @c NOTE: prepended to avoid this problem.
3033 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3035 @cindex @code{ \b} (backspace character)
3036 @cindex backspace (@code{\b})
3038 Mnemonic for backspace; for ASCII this is octal code 010.
3041 @c Mnemonic for EOText; for ASCII this is octal code 004.
3043 @cindex @code{ \f} (formfeed character)
3044 @cindex formfeed (@code{\f})
3046 Mnemonic for FormFeed; for ASCII this is octal code 014.
3048 @cindex @code{ \n} (newline character)
3049 @cindex newline (@code{\n})
3051 Mnemonic for newline; for ASCII this is octal code 012.
3054 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3056 @cindex @code{ \r} (carriage return character)
3057 @cindex carriage return (@code{backslash-r})
3059 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3062 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3063 @c other assemblers.
3065 @cindex @code{ \t} (tab)
3066 @cindex tab (@code{\t})
3068 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3071 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3072 @c @item \x @var{digit} @var{digit} @var{digit}
3073 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3075 @cindex @code{ \@var{ddd}} (octal character code)
3076 @cindex octal character code (@code{\@var{ddd}})
3077 @item \ @var{digit} @var{digit} @var{digit}
3078 An octal character code. The numeric code is 3 octal digits.
3079 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3080 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3082 @cindex @code{ \@var{xd...}} (hex character code)
3083 @cindex hex character code (@code{\@var{xd...}})
3084 @item \@code{x} @var{hex-digits...}
3085 A hex character code. All trailing hex digits are combined. Either upper or
3086 lower case @code{x} works.
3088 @cindex @code{ \\} (@samp{\} character)
3089 @cindex backslash (@code{\\})
3091 Represents one @samp{\} character.
3094 @c Represents one @samp{'} (accent acute) character.
3095 @c This is needed in single character literals
3096 @c (@xref{Characters,,Character Constants}.) to represent
3099 @cindex @code{ \"} (doublequote character)
3100 @cindex doublequote (@code{\"})
3102 Represents one @samp{"} character. Needed in strings to represent
3103 this character, because an unescaped @samp{"} would end the string.
3105 @item \ @var{anything-else}
3106 Any other character when escaped by @kbd{\} gives a warning, but
3107 assembles as if the @samp{\} was not present. The idea is that if
3108 you used an escape sequence you clearly didn't want the literal
3109 interpretation of the following character. However @command{@value{AS}} has no
3110 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3111 code and warns you of the fact.
3114 Which characters are escapable, and what those escapes represent,
3115 varies widely among assemblers. The current set is what we think
3116 the BSD 4.2 assembler recognizes, and is a subset of what most C
3117 compilers recognize. If you are in doubt, do not use an escape
3121 @subsubsection Characters
3123 @cindex single character constant
3124 @cindex character, single
3125 @cindex constant, single character
3126 A single character may be written as a single quote immediately followed by
3127 that character. Some backslash escapes apply to characters, @code{\b},
3128 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3129 as for strings, plus @code{\'} for a single quote. So if you want to write the
3130 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3131 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3134 @ifclear abnormal-separator
3135 (or semicolon @samp{;})
3137 @ifset abnormal-separator
3139 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3144 immediately following an acute accent is taken as a literal character
3145 and does not count as the end of a statement. The value of a character
3146 constant in a numeric expression is the machine's byte-wide code for
3147 that character. @command{@value{AS}} assumes your character code is ASCII:
3148 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3151 @subsection Number Constants
3153 @cindex constants, number
3154 @cindex number constants
3155 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3156 are stored in the target machine. @emph{Integers} are numbers that
3157 would fit into an @code{int} in the C language. @emph{Bignums} are
3158 integers, but they are stored in more than 32 bits. @emph{Flonums}
3159 are floating point numbers, described below.
3162 * Integers:: Integers
3170 @subsubsection Integers
3172 @cindex constants, integer
3174 @cindex binary integers
3175 @cindex integers, binary
3176 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3177 the binary digits @samp{01}.
3179 @cindex octal integers
3180 @cindex integers, octal
3181 An octal integer is @samp{0} followed by zero or more of the octal
3182 digits (@samp{01234567}).
3184 @cindex decimal integers
3185 @cindex integers, decimal
3186 A decimal integer starts with a non-zero digit followed by zero or
3187 more digits (@samp{0123456789}).
3189 @cindex hexadecimal integers
3190 @cindex integers, hexadecimal
3191 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3192 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3194 Integers have the usual values. To denote a negative integer, use
3195 the prefix operator @samp{-} discussed under expressions
3196 (@pxref{Prefix Ops,,Prefix Operators}).
3199 @subsubsection Bignums
3202 @cindex constants, bignum
3203 A @dfn{bignum} has the same syntax and semantics as an integer
3204 except that the number (or its negative) takes more than 32 bits to
3205 represent in binary. The distinction is made because in some places
3206 integers are permitted while bignums are not.
3209 @subsubsection Flonums
3211 @cindex floating point numbers
3212 @cindex constants, floating point
3214 @cindex precision, floating point
3215 A @dfn{flonum} represents a floating point number. The translation is
3216 indirect: a decimal floating point number from the text is converted by
3217 @command{@value{AS}} to a generic binary floating point number of more than
3218 sufficient precision. This generic floating point number is converted
3219 to a particular computer's floating point format (or formats) by a
3220 portion of @command{@value{AS}} specialized to that computer.
3222 A flonum is written by writing (in order)
3227 (@samp{0} is optional on the HPPA.)
3231 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3233 @kbd{e} is recommended. Case is not important.
3235 @c FIXME: verify if flonum syntax really this vague for most cases
3236 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3237 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3240 On the H8/300 and Renesas / SuperH SH architectures, the letter must be
3241 one of the letters @samp{DFPRSX} (in upper or lower case).
3243 On the ARC, the letter must be one of the letters @samp{DFRS}
3244 (in upper or lower case).
3246 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3250 One of the letters @samp{DFRS} (in upper or lower case).
3253 One of the letters @samp{DFPRSX} (in upper or lower case).
3256 The letter @samp{E} (upper case only).
3261 An optional sign: either @samp{+} or @samp{-}.
3264 An optional @dfn{integer part}: zero or more decimal digits.
3267 An optional @dfn{fractional part}: @samp{.} followed by zero
3268 or more decimal digits.
3271 An optional exponent, consisting of:
3275 An @samp{E} or @samp{e}.
3276 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3277 @c principle this can perfectly well be different on different targets.
3279 Optional sign: either @samp{+} or @samp{-}.
3281 One or more decimal digits.
3286 At least one of the integer part or the fractional part must be
3287 present. The floating point number has the usual base-10 value.
3289 @command{@value{AS}} does all processing using integers. Flonums are computed
3290 independently of any floating point hardware in the computer running
3291 @command{@value{AS}}.
3294 @chapter Sections and Relocation
3299 * Secs Background:: Background
3300 * Ld Sections:: Linker Sections
3301 * As Sections:: Assembler Internal Sections
3302 * Sub-Sections:: Sub-Sections
3306 @node Secs Background
3309 Roughly, a section is a range of addresses, with no gaps; all data
3310 ``in'' those addresses is treated the same for some particular purpose.
3311 For example there may be a ``read only'' section.
3313 @cindex linker, and assembler
3314 @cindex assembler, and linker
3315 The linker @code{@value{LD}} reads many object files (partial programs) and
3316 combines their contents to form a runnable program. When @command{@value{AS}}
3317 emits an object file, the partial program is assumed to start at address 0.
3318 @code{@value{LD}} assigns the final addresses for the partial program, so that
3319 different partial programs do not overlap. This is actually an
3320 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3323 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3324 addresses. These blocks slide to their run-time addresses as rigid
3325 units; their length does not change and neither does the order of bytes
3326 within them. Such a rigid unit is called a @emph{section}. Assigning
3327 run-time addresses to sections is called @dfn{relocation}. It includes
3328 the task of adjusting mentions of object-file addresses so they refer to
3329 the proper run-time addresses.
3331 For the H8/300, and for the Renesas / SuperH SH,
3332 @command{@value{AS}} pads sections if needed to
3333 ensure they end on a word (sixteen bit) boundary.
3336 @cindex standard assembler sections
3337 An object file written by @command{@value{AS}} has at least three sections, any
3338 of which may be empty. These are named @dfn{text}, @dfn{data} and
3343 When it generates COFF or ELF output,
3345 @command{@value{AS}} can also generate whatever other named sections you specify
3346 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3347 If you do not use any directives that place output in the @samp{.text}
3348 or @samp{.data} sections, these sections still exist, but are empty.
3353 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3355 @command{@value{AS}} can also generate whatever other named sections you
3356 specify using the @samp{.space} and @samp{.subspace} directives. See
3357 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3358 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3359 assembler directives.
3362 Additionally, @command{@value{AS}} uses different names for the standard
3363 text, data, and bss sections when generating SOM output. Program text
3364 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3365 BSS into @samp{$BSS$}.
3369 Within the object file, the text section starts at address @code{0}, the
3370 data section follows, and the bss section follows the data section.
3373 When generating either SOM or ELF output files on the HPPA, the text
3374 section starts at address @code{0}, the data section at address
3375 @code{0x4000000}, and the bss section follows the data section.
3378 To let @code{@value{LD}} know which data changes when the sections are
3379 relocated, and how to change that data, @command{@value{AS}} also writes to the
3380 object file details of the relocation needed. To perform relocation
3381 @code{@value{LD}} must know, each time an address in the object
3385 Where in the object file is the beginning of this reference to
3388 How long (in bytes) is this reference?
3390 Which section does the address refer to? What is the numeric value of
3392 (@var{address}) @minus{} (@var{start-address of section})?
3395 Is the reference to an address ``Program-Counter relative''?
3398 @cindex addresses, format of
3399 @cindex section-relative addressing
3400 In fact, every address @command{@value{AS}} ever uses is expressed as
3402 (@var{section}) + (@var{offset into section})
3405 Further, most expressions @command{@value{AS}} computes have this section-relative
3408 (For some object formats, such as SOM for the HPPA, some expressions are
3409 symbol-relative instead.)
3412 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3413 @var{N} into section @var{secname}.''
3415 Apart from text, data and bss sections you need to know about the
3416 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3417 addresses in the absolute section remain unchanged. For example, address
3418 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3419 @code{@value{LD}}. Although the linker never arranges two partial programs'
3420 data sections with overlapping addresses after linking, @emph{by definition}
3421 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3422 part of a program is always the same address when the program is running as
3423 address @code{@{absolute@ 239@}} in any other part of the program.
3425 The idea of sections is extended to the @dfn{undefined} section. Any
3426 address whose section is unknown at assembly time is by definition
3427 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3428 Since numbers are always defined, the only way to generate an undefined
3429 address is to mention an undefined symbol. A reference to a named
3430 common block would be such a symbol: its value is unknown at assembly
3431 time so it has section @emph{undefined}.
3433 By analogy the word @emph{section} is used to describe groups of sections in
3434 the linked program. @code{@value{LD}} puts all partial programs' text
3435 sections in contiguous addresses in the linked program. It is
3436 customary to refer to the @emph{text section} of a program, meaning all
3437 the addresses of all partial programs' text sections. Likewise for
3438 data and bss sections.
3440 Some sections are manipulated by @code{@value{LD}}; others are invented for
3441 use of @command{@value{AS}} and have no meaning except during assembly.
3444 @section Linker Sections
3445 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3450 @cindex named sections
3451 @cindex sections, named
3452 @item named sections
3455 @cindex text section
3456 @cindex data section
3460 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3461 separate but equal sections. Anything you can say of one section is
3464 When the program is running, however, it is
3465 customary for the text section to be unalterable. The
3466 text section is often shared among processes: it contains
3467 instructions, constants and the like. The data section of a running
3468 program is usually alterable: for example, C variables would be stored
3469 in the data section.
3474 This section contains zeroed bytes when your program begins running. It
3475 is used to hold uninitialized variables or common storage. The length of
3476 each partial program's bss section is important, but because it starts
3477 out containing zeroed bytes there is no need to store explicit zero
3478 bytes in the object file. The bss section was invented to eliminate
3479 those explicit zeros from object files.
3481 @cindex absolute section
3482 @item absolute section
3483 Address 0 of this section is always ``relocated'' to runtime address 0.
3484 This is useful if you want to refer to an address that @code{@value{LD}} must
3485 not change when relocating. In this sense we speak of absolute
3486 addresses being ``unrelocatable'': they do not change during relocation.
3488 @cindex undefined section
3489 @item undefined section
3490 This ``section'' is a catch-all for address references to objects not in
3491 the preceding sections.
3492 @c FIXME: ref to some other doc on obj-file formats could go here.
3495 @cindex relocation example
3496 An idealized example of three relocatable sections follows.
3498 The example uses the traditional section names @samp{.text} and @samp{.data}.
3500 Memory addresses are on the horizontal axis.
3504 @c END TEXI2ROFF-KILL
3507 partial program # 1: |ttttt|dddd|00|
3514 partial program # 2: |TTT|DDD|000|
3517 +--+---+-----+--+----+---+-----+~~
3518 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3519 +--+---+-----+--+----+---+-----+~~
3521 addresses: 0 @dots{}
3528 \line{\it Partial program \#1: \hfil}
3529 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3530 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3532 \line{\it Partial program \#2: \hfil}
3533 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3534 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3536 \line{\it linked program: \hfil}
3537 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3538 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3539 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3540 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3542 \line{\it addresses: \hfil}
3546 @c END TEXI2ROFF-KILL
3549 @section Assembler Internal Sections
3551 @cindex internal assembler sections
3552 @cindex sections in messages, internal
3553 These sections are meant only for the internal use of @command{@value{AS}}. They
3554 have no meaning at run-time. You do not really need to know about these
3555 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3556 warning messages, so it might be helpful to have an idea of their
3557 meanings to @command{@value{AS}}. These sections are used to permit the
3558 value of every expression in your assembly language program to be a
3559 section-relative address.
3562 @cindex assembler internal logic error
3563 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3564 An internal assembler logic error has been found. This means there is a
3565 bug in the assembler.
3567 @cindex expr (internal section)
3569 The assembler stores complex expression internally as combinations of
3570 symbols. When it needs to represent an expression as a symbol, it puts
3571 it in the expr section.
3573 @c FIXME item transfer[t] vector preload
3574 @c FIXME item transfer[t] vector postload
3575 @c FIXME item register
3579 @section Sub-Sections
3581 @cindex numbered subsections
3582 @cindex grouping data
3588 fall into two sections: text and data.
3590 You may have separate groups of
3592 data in named sections
3596 data in named sections
3602 that you want to end up near to each other in the object file, even though they
3603 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3604 use @dfn{subsections} for this purpose. Within each section, there can be
3605 numbered subsections with values from 0 to 8192. Objects assembled into the
3606 same subsection go into the object file together with other objects in the same
3607 subsection. For example, a compiler might want to store constants in the text
3608 section, but might not want to have them interspersed with the program being
3609 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3610 section of code being output, and a @samp{.text 1} before each group of
3611 constants being output.
3613 Subsections are optional. If you do not use subsections, everything
3614 goes in subsection number zero.
3617 Each subsection is zero-padded up to a multiple of four bytes.
3618 (Subsections may be padded a different amount on different flavors
3619 of @command{@value{AS}}.)
3623 On the H8/300 platform, each subsection is zero-padded to a word
3624 boundary (two bytes).
3625 The same is true on the Renesas SH.
3629 Subsections appear in your object file in numeric order, lowest numbered
3630 to highest. (All this to be compatible with other people's assemblers.)
3631 The object file contains no representation of subsections; @code{@value{LD}} and
3632 other programs that manipulate object files see no trace of them.
3633 They just see all your text subsections as a text section, and all your
3634 data subsections as a data section.
3636 To specify which subsection you want subsequent statements assembled
3637 into, use a numeric argument to specify it, in a @samp{.text
3638 @var{expression}} or a @samp{.data @var{expression}} statement.
3641 When generating COFF output, you
3646 can also use an extra subsection
3647 argument with arbitrary named sections: @samp{.section @var{name},
3652 When generating ELF output, you
3657 can also use the @code{.subsection} directive (@pxref{SubSection})
3658 to specify a subsection: @samp{.subsection @var{expression}}.
3660 @var{Expression} should be an absolute expression
3661 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3662 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3663 begins in @code{text 0}. For instance:
3665 .text 0 # The default subsection is text 0 anyway.
3666 .ascii "This lives in the first text subsection. *"
3668 .ascii "But this lives in the second text subsection."
3670 .ascii "This lives in the data section,"
3671 .ascii "in the first data subsection."
3673 .ascii "This lives in the first text section,"
3674 .ascii "immediately following the asterisk (*)."
3677 Each section has a @dfn{location counter} incremented by one for every byte
3678 assembled into that section. Because subsections are merely a convenience
3679 restricted to @command{@value{AS}} there is no concept of a subsection location
3680 counter. There is no way to directly manipulate a location counter---but the
3681 @code{.align} directive changes it, and any label definition captures its
3682 current value. The location counter of the section where statements are being
3683 assembled is said to be the @dfn{active} location counter.
3686 @section bss Section
3689 @cindex common variable storage
3690 The bss section is used for local common variable storage.
3691 You may allocate address space in the bss section, but you may
3692 not dictate data to load into it before your program executes. When
3693 your program starts running, all the contents of the bss
3694 section are zeroed bytes.
3696 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3697 @ref{Lcomm,,@code{.lcomm}}.
3699 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3700 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3703 When assembling for a target which supports multiple sections, such as ELF or
3704 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3705 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3706 section. Typically the section will only contain symbol definitions and
3707 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3714 Symbols are a central concept: the programmer uses symbols to name
3715 things, the linker uses symbols to link, and the debugger uses symbols
3719 @cindex debuggers, and symbol order
3720 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3721 the same order they were declared. This may break some debuggers.
3726 * Setting Symbols:: Giving Symbols Other Values
3727 * Symbol Names:: Symbol Names
3728 * Dot:: The Special Dot Symbol
3729 * Symbol Attributes:: Symbol Attributes
3736 A @dfn{label} is written as a symbol immediately followed by a colon
3737 @samp{:}. The symbol then represents the current value of the
3738 active location counter, and is, for example, a suitable instruction
3739 operand. You are warned if you use the same symbol to represent two
3740 different locations: the first definition overrides any other
3744 On the HPPA, the usual form for a label need not be immediately followed by a
3745 colon, but instead must start in column zero. Only one label may be defined on
3746 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3747 provides a special directive @code{.label} for defining labels more flexibly.
3750 @node Setting Symbols
3751 @section Giving Symbols Other Values
3753 @cindex assigning values to symbols
3754 @cindex symbol values, assigning
3755 A symbol can be given an arbitrary value by writing a symbol, followed
3756 by an equals sign @samp{=}, followed by an expression
3757 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3758 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3759 equals sign @samp{=}@samp{=} here represents an equivalent of the
3760 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3763 Blackfin does not support symbol assignment with @samp{=}.
3767 @section Symbol Names
3769 @cindex symbol names
3770 @cindex names, symbol
3771 @ifclear SPECIAL-SYMS
3772 Symbol names begin with a letter or with one of @samp{._}. On most
3773 machines, you can also use @code{$} in symbol names; exceptions are
3774 noted in @ref{Machine Dependencies}. That character may be followed by any
3775 string of digits, letters, dollar signs (unless otherwise noted for a
3776 particular target machine), and underscores.
3780 Symbol names begin with a letter or with one of @samp{._}. On the
3781 Renesas SH you can also use @code{$} in symbol names. That
3782 character may be followed by any string of digits, letters, dollar signs (save
3783 on the H8/300), and underscores.
3787 Case of letters is significant: @code{foo} is a different symbol name
3790 Symbol names do not start with a digit. An exception to this rule is made for
3791 Local Labels. See below.
3793 Multibyte characters are supported. To generate a symbol name containing
3794 multibyte characters enclose it within double quotes and use escape codes. cf
3795 @xref{Strings}. Generating a multibyte symbol name from a label is not
3796 currently supported.
3798 Each symbol has exactly one name. Each name in an assembly language program
3799 refers to exactly one symbol. You may use that symbol name any number of times
3802 @subheading Local Symbol Names
3804 @cindex local symbol names
3805 @cindex symbol names, local
3806 A local symbol is any symbol beginning with certain local label prefixes.
3807 By default, the local label prefix is @samp{.L} for ELF systems or
3808 @samp{L} for traditional a.out systems, but each target may have its own
3809 set of local label prefixes.
3811 On the HPPA local symbols begin with @samp{L$}.
3814 Local symbols are defined and used within the assembler, but they are
3815 normally not saved in object files. Thus, they are not visible when debugging.
3816 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3817 to retain the local symbols in the object files.
3819 @subheading Local Labels
3821 @cindex local labels
3822 @cindex temporary symbol names
3823 @cindex symbol names, temporary
3824 Local labels are different from local symbols. Local labels help compilers and
3825 programmers use names temporarily. They create symbols which are guaranteed to
3826 be unique over the entire scope of the input source code and which can be
3827 referred to by a simple notation. To define a local label, write a label of
3828 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3829 To refer to the most recent previous definition of that label write
3830 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3831 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3832 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3834 There is no restriction on how you can use these labels, and you can reuse them
3835 too. So that it is possible to repeatedly define the same local label (using
3836 the same number @samp{@b{N}}), although you can only refer to the most recently
3837 defined local label of that number (for a backwards reference) or the next
3838 definition of a specific local label for a forward reference. It is also worth
3839 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3840 implemented in a slightly more efficient manner than the others.
3851 Which is the equivalent of:
3854 label_1: branch label_3
3855 label_2: branch label_1
3856 label_3: branch label_4
3857 label_4: branch label_3
3860 Local label names are only a notational device. They are immediately
3861 transformed into more conventional symbol names before the assembler uses them.
3862 The symbol names are stored in the symbol table, appear in error messages, and
3863 are optionally emitted to the object file. The names are constructed using
3867 @item @emph{local label prefix}
3868 All local symbols begin with the system-specific local label prefix.
3869 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3870 that start with the local label prefix. These labels are
3871 used for symbols you are never intended to see. If you use the
3872 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3873 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3874 you may use them in debugging.
3877 This is the number that was used in the local label definition. So if the
3878 label is written @samp{55:} then the number is @samp{55}.
3881 This unusual character is included so you do not accidentally invent a symbol
3882 of the same name. The character has ASCII value of @samp{\002} (control-B).
3884 @item @emph{ordinal number}
3885 This is a serial number to keep the labels distinct. The first definition of
3886 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3887 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3888 the number @samp{1} and its 15th definition gets @samp{15} as well.
3891 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3892 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3894 @subheading Dollar Local Labels
3895 @cindex dollar local symbols
3897 On some targets @code{@value{AS}} also supports an even more local form of
3898 local labels called dollar labels. These labels go out of scope (i.e., they
3899 become undefined) as soon as a non-local label is defined. Thus they remain
3900 valid for only a small region of the input source code. Normal local labels,
3901 by contrast, remain in scope for the entire file, or until they are redefined
3902 by another occurrence of the same local label.
3904 Dollar labels are defined in exactly the same way as ordinary local labels,
3905 except that they have a dollar sign suffix to their numeric value, e.g.,
3908 They can also be distinguished from ordinary local labels by their transformed
3909 names which use ASCII character @samp{\001} (control-A) as the magic character
3910 to distinguish them from ordinary labels. For example, the fifth definition of
3911 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3914 @section The Special Dot Symbol
3916 @cindex dot (symbol)
3917 @cindex @code{.} (symbol)
3918 @cindex current address
3919 @cindex location counter
3920 The special symbol @samp{.} refers to the current address that
3921 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3922 .long .} defines @code{melvin} to contain its own address.
3923 Assigning a value to @code{.} is treated the same as a @code{.org}
3925 @ifclear no-space-dir
3926 Thus, the expression @samp{.=.+4} is the same as saying
3930 @node Symbol Attributes
3931 @section Symbol Attributes
3933 @cindex symbol attributes
3934 @cindex attributes, symbol
3935 Every symbol has, as well as its name, the attributes ``Value'' and
3936 ``Type''. Depending on output format, symbols can also have auxiliary
3939 The detailed definitions are in @file{a.out.h}.
3942 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3943 all these attributes, and probably won't warn you. This makes the
3944 symbol an externally defined symbol, which is generally what you
3948 * Symbol Value:: Value
3949 * Symbol Type:: Type
3951 * a.out Symbols:: Symbol Attributes: @code{a.out}
3954 * COFF Symbols:: Symbol Attributes for COFF
3957 * SOM Symbols:: Symbol Attributes for SOM
3964 @cindex value of a symbol
3965 @cindex symbol value
3966 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3967 location in the text, data, bss or absolute sections the value is the
3968 number of addresses from the start of that section to the label.
3969 Naturally for text, data and bss sections the value of a symbol changes
3970 as @code{@value{LD}} changes section base addresses during linking. Absolute
3971 symbols' values do not change during linking: that is why they are
3974 The value of an undefined symbol is treated in a special way. If it is
3975 0 then the symbol is not defined in this assembler source file, and
3976 @code{@value{LD}} tries to determine its value from other files linked into the
3977 same program. You make this kind of symbol simply by mentioning a symbol
3978 name without defining it. A non-zero value represents a @code{.comm}
3979 common declaration. The value is how much common storage to reserve, in
3980 bytes (addresses). The symbol refers to the first address of the
3986 @cindex type of a symbol
3988 The type attribute of a symbol contains relocation (section)
3989 information, any flag settings indicating that a symbol is external, and
3990 (optionally), other information for linkers and debuggers. The exact
3991 format depends on the object-code output format in use.
3995 @subsection Symbol Attributes: @code{a.out}
3997 @cindex @code{a.out} symbol attributes
3998 @cindex symbol attributes, @code{a.out}
4001 * Symbol Desc:: Descriptor
4002 * Symbol Other:: Other
4006 @subsubsection Descriptor
4008 @cindex descriptor, of @code{a.out} symbol
4009 This is an arbitrary 16-bit value. You may establish a symbol's
4010 descriptor value by using a @code{.desc} statement
4011 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4012 @command{@value{AS}}.
4015 @subsubsection Other
4017 @cindex other attribute, of @code{a.out} symbol
4018 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4023 @subsection Symbol Attributes for COFF
4025 @cindex COFF symbol attributes
4026 @cindex symbol attributes, COFF
4028 The COFF format supports a multitude of auxiliary symbol attributes;
4029 like the primary symbol attributes, they are set between @code{.def} and
4030 @code{.endef} directives.
4032 @subsubsection Primary Attributes
4034 @cindex primary attributes, COFF symbols
4035 The symbol name is set with @code{.def}; the value and type,
4036 respectively, with @code{.val} and @code{.type}.
4038 @subsubsection Auxiliary Attributes
4040 @cindex auxiliary attributes, COFF symbols
4041 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4042 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4043 table information for COFF.
4048 @subsection Symbol Attributes for SOM
4050 @cindex SOM symbol attributes
4051 @cindex symbol attributes, SOM
4053 The SOM format for the HPPA supports a multitude of symbol attributes set with
4054 the @code{.EXPORT} and @code{.IMPORT} directives.
4056 The attributes are described in @cite{HP9000 Series 800 Assembly
4057 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4058 @code{EXPORT} assembler directive documentation.
4062 @chapter Expressions
4066 @cindex numeric values
4067 An @dfn{expression} specifies an address or numeric value.
4068 Whitespace may precede and/or follow an expression.
4070 The result of an expression must be an absolute number, or else an offset into
4071 a particular section. If an expression is not absolute, and there is not
4072 enough information when @command{@value{AS}} sees the expression to know its
4073 section, a second pass over the source program might be necessary to interpret
4074 the expression---but the second pass is currently not implemented.
4075 @command{@value{AS}} aborts with an error message in this situation.
4078 * Empty Exprs:: Empty Expressions
4079 * Integer Exprs:: Integer Expressions
4083 @section Empty Expressions
4085 @cindex empty expressions
4086 @cindex expressions, empty
4087 An empty expression has no value: it is just whitespace or null.
4088 Wherever an absolute expression is required, you may omit the
4089 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4090 is compatible with other assemblers.
4093 @section Integer Expressions
4095 @cindex integer expressions
4096 @cindex expressions, integer
4097 An @dfn{integer expression} is one or more @emph{arguments} delimited
4098 by @emph{operators}.
4101 * Arguments:: Arguments
4102 * Operators:: Operators
4103 * Prefix Ops:: Prefix Operators
4104 * Infix Ops:: Infix Operators
4108 @subsection Arguments
4110 @cindex expression arguments
4111 @cindex arguments in expressions
4112 @cindex operands in expressions
4113 @cindex arithmetic operands
4114 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4115 contexts arguments are sometimes called ``arithmetic operands''. In
4116 this manual, to avoid confusing them with the ``instruction operands'' of
4117 the machine language, we use the term ``argument'' to refer to parts of
4118 expressions only, reserving the word ``operand'' to refer only to machine
4119 instruction operands.
4121 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4122 @var{section} is one of text, data, bss, absolute,
4123 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4126 Numbers are usually integers.
4128 A number can be a flonum or bignum. In this case, you are warned
4129 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4130 these 32 bits are an integer. You may write integer-manipulating
4131 instructions that act on exotic constants, compatible with other
4134 @cindex subexpressions
4135 Subexpressions are a left parenthesis @samp{(} followed by an integer
4136 expression, followed by a right parenthesis @samp{)}; or a prefix
4137 operator followed by an argument.
4140 @subsection Operators
4142 @cindex operators, in expressions
4143 @cindex arithmetic functions
4144 @cindex functions, in expressions
4145 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4146 operators are followed by an argument. Infix operators appear
4147 between their arguments. Operators may be preceded and/or followed by
4151 @subsection Prefix Operator
4153 @cindex prefix operators
4154 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4155 one argument, which must be absolute.
4157 @c the tex/end tex stuff surrounding this small table is meant to make
4158 @c it align, on the printed page, with the similar table in the next
4159 @c section (which is inside an enumerate).
4161 \global\advance\leftskip by \itemindent
4166 @dfn{Negation}. Two's complement negation.
4168 @dfn{Complementation}. Bitwise not.
4172 \global\advance\leftskip by -\itemindent
4176 @subsection Infix Operators
4178 @cindex infix operators
4179 @cindex operators, permitted arguments
4180 @dfn{Infix operators} take two arguments, one on either side. Operators
4181 have precedence, but operations with equal precedence are performed left
4182 to right. Apart from @code{+} or @option{-}, both arguments must be
4183 absolute, and the result is absolute.
4186 @cindex operator precedence
4187 @cindex precedence of operators
4194 @dfn{Multiplication}.
4197 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4203 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4206 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4210 Intermediate precedence
4215 @dfn{Bitwise Inclusive Or}.
4221 @dfn{Bitwise Exclusive Or}.
4224 @dfn{Bitwise Or Not}.
4231 @cindex addition, permitted arguments
4232 @cindex plus, permitted arguments
4233 @cindex arguments for addition
4235 @dfn{Addition}. If either argument is absolute, the result has the section of
4236 the other argument. You may not add together arguments from different
4239 @cindex subtraction, permitted arguments
4240 @cindex minus, permitted arguments
4241 @cindex arguments for subtraction
4243 @dfn{Subtraction}. If the right argument is absolute, the
4244 result has the section of the left argument.
4245 If both arguments are in the same section, the result is absolute.
4246 You may not subtract arguments from different sections.
4247 @c FIXME is there still something useful to say about undefined - undefined ?
4249 @cindex comparison expressions
4250 @cindex expressions, comparison
4255 @dfn{Is Not Equal To}
4259 @dfn{Is Greater Than}
4261 @dfn{Is Greater Than Or Equal To}
4263 @dfn{Is Less Than Or Equal To}
4265 The comparison operators can be used as infix operators. A true results has a
4266 value of -1 whereas a false result has a value of 0. Note, these operators
4267 perform signed comparisons.
4270 @item Lowest Precedence
4279 These two logical operations can be used to combine the results of sub
4280 expressions. Note, unlike the comparison operators a true result returns a
4281 value of 1 but a false results does still return 0. Also note that the logical
4282 or operator has a slightly lower precedence than logical and.
4287 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4288 address; you can only have a defined section in one of the two arguments.
4291 @chapter Assembler Directives
4293 @cindex directives, machine independent
4294 @cindex pseudo-ops, machine independent
4295 @cindex machine independent directives
4296 All assembler directives have names that begin with a period (@samp{.}).
4297 The names are case insensitive for most targets, and usually written
4300 This chapter discusses directives that are available regardless of the
4301 target machine configuration for the @sc{gnu} assembler.
4303 Some machine configurations provide additional directives.
4304 @xref{Machine Dependencies}.
4307 @ifset machine-directives
4308 @xref{Machine Dependencies}, for additional directives.
4313 * Abort:: @code{.abort}
4315 * ABORT (COFF):: @code{.ABORT}
4318 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4319 * Altmacro:: @code{.altmacro}
4320 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4321 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4322 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4323 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4324 * Byte:: @code{.byte @var{expressions}}
4325 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4326 * Comm:: @code{.comm @var{symbol} , @var{length} }
4327 * Data:: @code{.data @var{subsection}}
4328 * Dc:: @code{.dc[@var{size}] @var{expressions}}
4329 * Dcb:: @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
4330 * Ds:: @code{.ds[@var{size}] @var{number} [,@var{fill}]}
4332 * Def:: @code{.def @var{name}}
4335 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4341 * Double:: @code{.double @var{flonums}}
4342 * Eject:: @code{.eject}
4343 * Else:: @code{.else}
4344 * Elseif:: @code{.elseif}
4347 * Endef:: @code{.endef}
4350 * Endfunc:: @code{.endfunc}
4351 * Endif:: @code{.endif}
4352 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4353 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4354 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4356 * Error:: @code{.error @var{string}}
4357 * Exitm:: @code{.exitm}
4358 * Extern:: @code{.extern}
4359 * Fail:: @code{.fail}
4360 * File:: @code{.file}
4361 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4362 * Float:: @code{.float @var{flonums}}
4363 * Func:: @code{.func}
4364 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4366 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4367 * Hidden:: @code{.hidden @var{names}}
4370 * hword:: @code{.hword @var{expressions}}
4371 * Ident:: @code{.ident}
4372 * If:: @code{.if @var{absolute expression}}
4373 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4374 * Include:: @code{.include "@var{file}"}
4375 * Int:: @code{.int @var{expressions}}
4377 * Internal:: @code{.internal @var{names}}
4380 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4381 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4382 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4383 * Lflags:: @code{.lflags}
4384 @ifclear no-line-dir
4385 * Line:: @code{.line @var{line-number}}
4388 * Linkonce:: @code{.linkonce [@var{type}]}
4389 * List:: @code{.list}
4390 * Ln:: @code{.ln @var{line-number}}
4391 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4392 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4394 * Local:: @code{.local @var{names}}
4397 * Long:: @code{.long @var{expressions}}
4399 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4402 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4403 * MRI:: @code{.mri @var{val}}
4404 * Noaltmacro:: @code{.noaltmacro}
4405 * Nolist:: @code{.nolist}
4406 * Nops:: @code{.nops @var{size}[, @var{control}]}
4407 * Octa:: @code{.octa @var{bignums}}
4408 * Offset:: @code{.offset @var{loc}}
4409 * Org:: @code{.org @var{new-lc}, @var{fill}}
4410 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4412 * PopSection:: @code{.popsection}
4413 * Previous:: @code{.previous}
4416 * Print:: @code{.print @var{string}}
4418 * Protected:: @code{.protected @var{names}}
4421 * Psize:: @code{.psize @var{lines}, @var{columns}}
4422 * Purgem:: @code{.purgem @var{name}}
4424 * PushSection:: @code{.pushsection @var{name}}
4427 * Quad:: @code{.quad @var{bignums}}
4428 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4429 * Rept:: @code{.rept @var{count}}
4430 * Sbttl:: @code{.sbttl "@var{subheading}"}
4432 * Scl:: @code{.scl @var{class}}
4435 * Section:: @code{.section @var{name}[, @var{flags}]}
4438 * Set:: @code{.set @var{symbol}, @var{expression}}
4439 * Short:: @code{.short @var{expressions}}
4440 * Single:: @code{.single @var{flonums}}
4442 * Size:: @code{.size [@var{name} , @var{expression}]}
4444 @ifclear no-space-dir
4445 * Skip:: @code{.skip @var{size} [,@var{fill}]}
4448 * Sleb128:: @code{.sleb128 @var{expressions}}
4449 @ifclear no-space-dir
4450 * Space:: @code{.space @var{size} [,@var{fill}]}
4453 * Stab:: @code{.stabd, .stabn, .stabs}
4456 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4457 * Struct:: @code{.struct @var{expression}}
4459 * SubSection:: @code{.subsection}
4460 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4464 * Tag:: @code{.tag @var{structname}}
4467 * Text:: @code{.text @var{subsection}}
4468 * Title:: @code{.title "@var{heading}"}
4470 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4473 * Uleb128:: @code{.uleb128 @var{expressions}}
4475 * Val:: @code{.val @var{addr}}
4479 * Version:: @code{.version "@var{string}"}
4480 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4481 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4484 * Warning:: @code{.warning @var{string}}
4485 * Weak:: @code{.weak @var{names}}
4486 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4487 * Word:: @code{.word @var{expressions}}
4488 @ifclear no-space-dir
4489 * Zero:: @code{.zero @var{size}}
4492 * 2byte:: @code{.2byte @var{expressions}}
4493 * 4byte:: @code{.4byte @var{expressions}}
4494 * 8byte:: @code{.8byte @var{bignums}}
4496 * Deprecated:: Deprecated Directives
4500 @section @code{.abort}
4502 @cindex @code{abort} directive
4503 @cindex stopping the assembly
4504 This directive stops the assembly immediately. It is for
4505 compatibility with other assemblers. The original idea was that the
4506 assembly language source would be piped into the assembler. If the sender
4507 of the source quit, it could use this directive tells @command{@value{AS}} to
4508 quit also. One day @code{.abort} will not be supported.
4512 @section @code{.ABORT} (COFF)
4514 @cindex @code{ABORT} directive
4515 When producing COFF output, @command{@value{AS}} accepts this directive as a
4516 synonym for @samp{.abort}.
4521 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4523 @cindex padding the location counter
4524 @cindex @code{align} directive
4525 Pad the location counter (in the current subsection) to a particular storage
4526 boundary. The first expression (which must be absolute) is the alignment
4527 required, as described below.
4529 The second expression (also absolute) gives the fill value to be stored in the
4530 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4531 padding bytes are normally zero. However, on most systems, if the section is
4532 marked as containing code and the fill value is omitted, the space is filled
4533 with no-op instructions.
4535 The third expression is also absolute, and is also optional. If it is present,
4536 it is the maximum number of bytes that should be skipped by this alignment
4537 directive. If doing the alignment would require skipping more bytes than the
4538 specified maximum, then the alignment is not done at all. You can omit the
4539 fill value (the second argument) entirely by simply using two commas after the
4540 required alignment; this can be useful if you want the alignment to be filled
4541 with no-op instructions when appropriate.
4543 The way the required alignment is specified varies from system to system.
4544 For the arc, hppa, i386 using ELF, iq2000, m68k, or1k,
4545 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4546 alignment request in bytes. For example @samp{.align 8} advances
4547 the location counter until it is a multiple of 8. If the location counter
4548 is already a multiple of 8, no change is needed. For the tic54x, the
4549 first expression is the alignment request in words.
4551 For other systems, including ppc, i386 using a.out format, arm and
4552 strongarm, it is the
4553 number of low-order zero bits the location counter must have after
4554 advancement. For example @samp{.align 3} advances the location
4555 counter until it a multiple of 8. If the location counter is already a
4556 multiple of 8, no change is needed.
4558 This inconsistency is due to the different behaviors of the various
4559 native assemblers for these systems which GAS must emulate.
4560 GAS also provides @code{.balign} and @code{.p2align} directives,
4561 described later, which have a consistent behavior across all
4562 architectures (but are specific to GAS).
4565 @section @code{.altmacro}
4566 Enable alternate macro mode, enabling:
4569 @item LOCAL @var{name} [ , @dots{} ]
4570 One additional directive, @code{LOCAL}, is available. It is used to
4571 generate a string replacement for each of the @var{name} arguments, and
4572 replace any instances of @var{name} in each macro expansion. The
4573 replacement string is unique in the assembly, and different for each
4574 separate macro expansion. @code{LOCAL} allows you to write macros that
4575 define symbols, without fear of conflict between separate macro expansions.
4577 @item String delimiters
4578 You can write strings delimited in these other ways besides
4579 @code{"@var{string}"}:
4582 @item '@var{string}'
4583 You can delimit strings with single-quote characters.
4585 @item <@var{string}>
4586 You can delimit strings with matching angle brackets.
4589 @item single-character string escape
4590 To include any single character literally in a string (even if the
4591 character would otherwise have some special meaning), you can prefix the
4592 character with @samp{!} (an exclamation mark). For example, you can
4593 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4595 @item Expression results as strings
4596 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4597 and use the result as a string.
4601 @section @code{.ascii "@var{string}"}@dots{}
4603 @cindex @code{ascii} directive
4604 @cindex string literals
4605 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4606 separated by commas. It assembles each string (with no automatic
4607 trailing zero byte) into consecutive addresses.
4610 @section @code{.asciz "@var{string}"}@dots{}
4612 @cindex @code{asciz} directive
4613 @cindex zero-terminated strings
4614 @cindex null-terminated strings
4615 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4616 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4619 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4621 @cindex padding the location counter given number of bytes
4622 @cindex @code{balign} directive
4623 Pad the location counter (in the current subsection) to a particular
4624 storage boundary. The first expression (which must be absolute) is the
4625 alignment request in bytes. For example @samp{.balign 8} advances
4626 the location counter until it is a multiple of 8. If the location counter
4627 is already a multiple of 8, no change is needed.
4629 The second expression (also absolute) gives the fill value to be stored in the
4630 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4631 padding bytes are normally zero. However, on most systems, if the section is
4632 marked as containing code and the fill value is omitted, the space is filled
4633 with no-op instructions.
4635 The third expression is also absolute, and is also optional. If it is present,
4636 it is the maximum number of bytes that should be skipped by this alignment
4637 directive. If doing the alignment would require skipping more bytes than the
4638 specified maximum, then the alignment is not done at all. You can omit the
4639 fill value (the second argument) entirely by simply using two commas after the
4640 required alignment; this can be useful if you want the alignment to be filled
4641 with no-op instructions when appropriate.
4643 @cindex @code{balignw} directive
4644 @cindex @code{balignl} directive
4645 The @code{.balignw} and @code{.balignl} directives are variants of the
4646 @code{.balign} directive. The @code{.balignw} directive treats the fill
4647 pattern as a two byte word value. The @code{.balignl} directives treats the
4648 fill pattern as a four byte longword value. For example, @code{.balignw
4649 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4650 filled in with the value 0x368d (the exact placement of the bytes depends upon
4651 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4654 @node Bundle directives
4655 @section Bundle directives
4656 @subsection @code{.bundle_align_mode @var{abs-expr}}
4657 @cindex @code{bundle_align_mode} directive
4659 @cindex instruction bundle
4660 @cindex aligned instruction bundle
4661 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4662 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4663 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4664 disabled (which is the default state). If the argument it not zero, it
4665 gives the size of an instruction bundle as a power of two (as for the
4666 @code{.p2align} directive, @pxref{P2align}).
4668 For some targets, it's an ABI requirement that no instruction may span a
4669 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4670 instructions that starts on an aligned boundary. For example, if
4671 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4672 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4673 effect, no single instruction may span a boundary between bundles. If an
4674 instruction would start too close to the end of a bundle for the length of
4675 that particular instruction to fit within the bundle, then the space at the
4676 end of that bundle is filled with no-op instructions so the instruction
4677 starts in the next bundle. As a corollary, it's an error if any single
4678 instruction's encoding is longer than the bundle size.
4680 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4681 @cindex @code{bundle_lock} directive
4682 @cindex @code{bundle_unlock} directive
4683 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4684 allow explicit control over instruction bundle padding. These directives
4685 are only valid when @code{.bundle_align_mode} has been used to enable
4686 aligned instruction bundle mode. It's an error if they appear when
4687 @code{.bundle_align_mode} has not been used at all, or when the last
4688 directive was @w{@code{.bundle_align_mode 0}}.
4690 @cindex bundle-locked
4691 For some targets, it's an ABI requirement that certain instructions may
4692 appear only as part of specified permissible sequences of multiple
4693 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4694 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4695 instruction sequence. For purposes of aligned instruction bundle mode, a
4696 sequence starting with @code{.bundle_lock} and ending with
4697 @code{.bundle_unlock} is treated as a single instruction. That is, the
4698 entire sequence must fit into a single bundle and may not span a bundle
4699 boundary. If necessary, no-op instructions will be inserted before the
4700 first instruction of the sequence so that the whole sequence starts on an
4701 aligned bundle boundary. It's an error if the sequence is longer than the
4704 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4705 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4706 nested. That is, a second @code{.bundle_lock} directive before the next
4707 @code{.bundle_unlock} directive has no effect except that it must be
4708 matched by another closing @code{.bundle_unlock} so that there is the
4709 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4712 @section @code{.byte @var{expressions}}
4714 @cindex @code{byte} directive
4715 @cindex integers, one byte
4716 @code{.byte} expects zero or more expressions, separated by commas.
4717 Each expression is assembled into the next byte.
4719 @node CFI directives
4720 @section CFI directives
4721 @subsection @code{.cfi_sections @var{section_list}}
4722 @cindex @code{cfi_sections} directive
4723 @code{.cfi_sections} may be used to specify whether CFI directives
4724 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4725 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4726 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4727 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4728 directive is not used is @code{.cfi_sections .eh_frame}.
4730 On targets that support compact unwinding tables these can be generated
4731 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4733 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4734 which is used by the @value{TIC6X} target.
4736 The @code{.cfi_sections} directive can be repeated, with the same or different
4737 arguments, provided that CFI generation has not yet started. Once CFI
4738 generation has started however the section list is fixed and any attempts to
4739 redefine it will result in an error.
4741 @subsection @code{.cfi_startproc [simple]}
4742 @cindex @code{cfi_startproc} directive
4743 @code{.cfi_startproc} is used at the beginning of each function that
4744 should have an entry in @code{.eh_frame}. It initializes some internal
4745 data structures. Don't forget to close the function by
4746 @code{.cfi_endproc}.
4748 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4749 it also emits some architecture dependent initial CFI instructions.
4751 @subsection @code{.cfi_endproc}
4752 @cindex @code{cfi_endproc} directive
4753 @code{.cfi_endproc} is used at the end of a function where it closes its
4754 unwind entry previously opened by
4755 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4757 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4758 @cindex @code{cfi_personality} directive
4759 @code{.cfi_personality} defines personality routine and its encoding.
4760 @var{encoding} must be a constant determining how the personality
4761 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4762 argument is not present, otherwise second argument should be
4763 a constant or a symbol name. When using indirect encodings,
4764 the symbol provided should be the location where personality
4765 can be loaded from, not the personality routine itself.
4766 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4767 no personality routine.
4769 @subsection @code{.cfi_personality_id @var{id}}
4770 @cindex @code{cfi_personality_id} directive
4771 @code{cfi_personality_id} defines a personality routine by its index as
4772 defined in a compact unwinding format.
4773 Only valid when generating compact EH frames (i.e.
4774 with @code{.cfi_sections eh_frame_entry}.
4776 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4777 @cindex @code{cfi_fde_data} directive
4778 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4779 used for the current function. These are emitted inline in the
4780 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4781 in the @code{.gnu.extab} section otherwise.
4782 Only valid when generating compact EH frames (i.e.
4783 with @code{.cfi_sections eh_frame_entry}.
4785 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4786 @code{.cfi_lsda} defines LSDA and its encoding.
4787 @var{encoding} must be a constant determining how the LSDA
4788 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4789 argument is not present, otherwise the second argument should be a constant
4790 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4791 meaning that no LSDA is present.
4793 @subsection @code{.cfi_inline_lsda} [@var{align}]
4794 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4795 switches to the corresponding @code{.gnu.extab} section.
4796 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4797 Only valid when generating compact EH frames (i.e.
4798 with @code{.cfi_sections eh_frame_entry}.
4800 The table header and unwinding opcodes will be generated at this point,
4801 so that they are immediately followed by the LSDA data. The symbol
4802 referenced by the @code{.cfi_lsda} directive should still be defined
4803 in case a fallback FDE based encoding is used. The LSDA data is terminated
4804 by a section directive.
4806 The optional @var{align} argument specifies the alignment required.
4807 The alignment is specified as a power of two, as with the
4808 @code{.p2align} directive.
4810 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4811 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4812 address from @var{register} and add @var{offset} to it}.
4814 @subsection @code{.cfi_def_cfa_register @var{register}}
4815 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4816 now on @var{register} will be used instead of the old one. Offset
4819 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4820 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4821 remains the same, but @var{offset} is new. Note that it is the
4822 absolute offset that will be added to a defined register to compute
4825 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4826 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4827 value that is added/subtracted from the previous offset.
4829 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4830 Previous value of @var{register} is saved at offset @var{offset} from
4833 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4834 Previous value of @var{register} is CFA + @var{offset}.
4836 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4837 Previous value of @var{register} is saved at offset @var{offset} from
4838 the current CFA register. This is transformed to @code{.cfi_offset}
4839 using the known displacement of the CFA register from the CFA.
4840 This is often easier to use, because the number will match the
4841 code it's annotating.
4843 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4844 Previous value of @var{register1} is saved in register @var{register2}.
4846 @subsection @code{.cfi_restore @var{register}}
4847 @code{.cfi_restore} says that the rule for @var{register} is now the
4848 same as it was at the beginning of the function, after all initial
4849 instruction added by @code{.cfi_startproc} were executed.
4851 @subsection @code{.cfi_undefined @var{register}}
4852 From now on the previous value of @var{register} can't be restored anymore.
4854 @subsection @code{.cfi_same_value @var{register}}
4855 Current value of @var{register} is the same like in the previous frame,
4856 i.e. no restoration needed.
4858 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4859 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4860 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4861 places them in the current row. This is useful for situations where you have
4862 multiple @code{.cfi_*} directives that need to be undone due to the control
4863 flow of the program. For example, we could have something like this (assuming
4864 the CFA is the value of @code{rbp}):
4874 .cfi_def_cfa %rsp, 8
4877 /* Do something else */
4880 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4881 to the instructions before @code{label}. This means we'd have to add multiple
4882 @code{.cfi} directives after @code{label} to recreate the original save
4883 locations of the registers, as well as setting the CFA back to the value of
4884 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4896 .cfi_def_cfa %rsp, 8
4900 /* Do something else */
4903 That way, the rules for the instructions after @code{label} will be the same
4904 as before the first @code{.cfi_restore} without having to use multiple
4905 @code{.cfi} directives.
4907 @subsection @code{.cfi_return_column @var{register}}
4908 Change return column @var{register}, i.e. the return address is either
4909 directly in @var{register} or can be accessed by rules for @var{register}.
4911 @subsection @code{.cfi_signal_frame}
4912 Mark current function as signal trampoline.
4914 @subsection @code{.cfi_window_save}
4915 SPARC register window has been saved.
4917 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4918 Allows the user to add arbitrary bytes to the unwind info. One
4919 might use this to add OS-specific CFI opcodes, or generic CFI
4920 opcodes that GAS does not yet support.
4922 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4923 The current value of @var{register} is @var{label}. The value of @var{label}
4924 will be encoded in the output file according to @var{encoding}; see the
4925 description of @code{.cfi_personality} for details on this encoding.
4927 The usefulness of equating a register to a fixed label is probably
4928 limited to the return address register. Here, it can be useful to
4929 mark a code segment that has only one return address which is reached
4930 by a direct branch and no copy of the return address exists in memory
4931 or another register.
4934 @section @code{.comm @var{symbol} , @var{length} }
4936 @cindex @code{comm} directive
4937 @cindex symbol, common
4938 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4939 common symbol in one object file may be merged with a defined or common symbol
4940 of the same name in another object file. If @code{@value{LD}} does not see a
4941 definition for the symbol--just one or more common symbols--then it will
4942 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4943 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4944 the same name, and they do not all have the same size, it will allocate space
4945 using the largest size.
4948 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4949 an optional third argument. This is the desired alignment of the symbol,
4950 specified for ELF as a byte boundary (for example, an alignment of 16 means
4951 that the least significant 4 bits of the address should be zero), and for PE
4952 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4953 boundary). The alignment must be an absolute expression, and it must be a
4954 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4955 common symbol, it will use the alignment when placing the symbol. If no
4956 alignment is specified, @command{@value{AS}} will set the alignment to the
4957 largest power of two less than or equal to the size of the symbol, up to a
4958 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4959 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4960 @samp{--section-alignment} option; image file sections in PE are aligned to
4961 multiples of 4096, which is far too large an alignment for ordinary variables.
4962 It is rather the default alignment for (non-debug) sections within object
4963 (@samp{*.o}) files, which are less strictly aligned.}.
4967 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4968 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4972 @section @code{.data @var{subsection}}
4973 @cindex @code{data} directive
4975 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4976 end of the data subsection numbered @var{subsection} (which is an
4977 absolute expression). If @var{subsection} is omitted, it defaults
4981 @section @code{.dc[@var{size}] @var{expressions}}
4982 @cindex @code{dc} directive
4984 The @code{.dc} directive expects zero or more @var{expressions} separated by
4985 commas. These expressions are evaluated and their values inserted into the
4986 current section. The size of the emitted value depends upon the suffix to the
4987 @code{.dc} directive:
4991 Emits N-bit values, where N is the size of an address on the target system.
4995 Emits double precision floating-point values.
4997 Emits 32-bit values.
4999 Emits single precision floating-point values.
5001 Emits 16-bit values.
5002 Note - this is true even on targets where the @code{.word} directive would emit
5005 Emits long double precision floating-point values.
5008 If no suffix is used then @samp{.w} is assumed.
5010 The byte ordering is target dependent, as is the size and format of floating
5014 @section @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
5015 @cindex @code{dcb} directive
5016 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5017 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5018 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5019 @var{size} suffix, if present, must be one of:
5023 Emits single byte values.
5025 Emits double-precision floating point values.
5027 Emits 4-byte values.
5029 Emits single-precision floating point values.
5031 Emits 2-byte values.
5033 Emits long double-precision floating point values.
5036 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5038 The byte ordering is target dependent, as is the size and format of floating
5042 @section @code{.ds[@var{size}] @var{number} [,@var{fill}]}
5043 @cindex @code{ds} directive
5044 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5045 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5046 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5047 @var{size} suffix, if present, must be one of:
5051 Emits single byte values.
5053 Emits 8-byte values.
5055 Emits 4-byte values.
5057 Emits 12-byte values.
5059 Emits 4-byte values.
5061 Emits 2-byte values.
5063 Emits 12-byte values.
5066 Note - unlike the @code{.dcb} directive the @samp{.d}, @samp{.s} and @samp{.x}
5067 suffixes do not indicate that floating-point values are to be inserted.
5069 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5071 The byte ordering is target dependent.
5076 @section @code{.def @var{name}}
5078 @cindex @code{def} directive
5079 @cindex COFF symbols, debugging
5080 @cindex debugging COFF symbols
5081 Begin defining debugging information for a symbol @var{name}; the
5082 definition extends until the @code{.endef} directive is encountered.
5087 @section @code{.desc @var{symbol}, @var{abs-expression}}
5089 @cindex @code{desc} directive
5090 @cindex COFF symbol descriptor
5091 @cindex symbol descriptor, COFF
5092 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5093 to the low 16 bits of an absolute expression.
5096 The @samp{.desc} directive is not available when @command{@value{AS}} is
5097 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5098 object format. For the sake of compatibility, @command{@value{AS}} accepts
5099 it, but produces no output, when configured for COFF.
5105 @section @code{.dim}
5107 @cindex @code{dim} directive
5108 @cindex COFF auxiliary symbol information
5109 @cindex auxiliary symbol information, COFF
5110 This directive is generated by compilers to include auxiliary debugging
5111 information in the symbol table. It is only permitted inside
5112 @code{.def}/@code{.endef} pairs.
5116 @section @code{.double @var{flonums}}
5118 @cindex @code{double} directive
5119 @cindex floating point numbers (double)
5120 @code{.double} expects zero or more flonums, separated by commas. It
5121 assembles floating point numbers.
5123 The exact kind of floating point numbers emitted depends on how
5124 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5128 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5129 in @sc{ieee} format.
5134 @section @code{.eject}
5136 @cindex @code{eject} directive
5137 @cindex new page, in listings
5138 @cindex page, in listings
5139 @cindex listing control: new page
5140 Force a page break at this point, when generating assembly listings.
5143 @section @code{.else}
5145 @cindex @code{else} directive
5146 @code{.else} is part of the @command{@value{AS}} support for conditional
5147 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5148 of code to be assembled if the condition for the preceding @code{.if}
5152 @section @code{.elseif}
5154 @cindex @code{elseif} directive
5155 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5156 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5157 @code{.if} block that would otherwise fill the entire @code{.else} section.
5160 @section @code{.end}
5162 @cindex @code{end} directive
5163 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5164 process anything in the file past the @code{.end} directive.
5168 @section @code{.endef}
5170 @cindex @code{endef} directive
5171 This directive flags the end of a symbol definition begun with
5176 @section @code{.endfunc}
5177 @cindex @code{endfunc} directive
5178 @code{.endfunc} marks the end of a function specified with @code{.func}.
5181 @section @code{.endif}
5183 @cindex @code{endif} directive
5184 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5185 it marks the end of a block of code that is only assembled
5186 conditionally. @xref{If,,@code{.if}}.
5189 @section @code{.equ @var{symbol}, @var{expression}}
5191 @cindex @code{equ} directive
5192 @cindex assigning values to symbols
5193 @cindex symbols, assigning values to
5194 This directive sets the value of @var{symbol} to @var{expression}.
5195 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5198 The syntax for @code{equ} on the HPPA is
5199 @samp{@var{symbol} .equ @var{expression}}.
5203 The syntax for @code{equ} on the Z80 is
5204 @samp{@var{symbol} equ @var{expression}}.
5205 On the Z80 it is an error if @var{symbol} is already defined,
5206 but the symbol is not protected from later redefinition.
5207 Compare @ref{Equiv}.
5211 @section @code{.equiv @var{symbol}, @var{expression}}
5212 @cindex @code{equiv} directive
5213 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5214 the assembler will signal an error if @var{symbol} is already defined. Note a
5215 symbol which has been referenced but not actually defined is considered to be
5218 Except for the contents of the error message, this is roughly equivalent to
5225 plus it protects the symbol from later redefinition.
5228 @section @code{.eqv @var{symbol}, @var{expression}}
5229 @cindex @code{eqv} directive
5230 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5231 evaluate the expression or any part of it immediately. Instead each time
5232 the resulting symbol is used in an expression, a snapshot of its current
5236 @section @code{.err}
5237 @cindex @code{err} directive
5238 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5239 message and, unless the @option{-Z} option was used, it will not generate an
5240 object file. This can be used to signal an error in conditionally compiled code.
5243 @section @code{.error "@var{string}"}
5244 @cindex error directive
5246 Similarly to @code{.err}, this directive emits an error, but you can specify a
5247 string that will be emitted as the error message. If you don't specify the
5248 message, it defaults to @code{".error directive invoked in source file"}.
5249 @xref{Errors, ,Error and Warning Messages}.
5252 .error "This code has not been assembled and tested."
5256 @section @code{.exitm}
5257 Exit early from the current macro definition. @xref{Macro}.
5260 @section @code{.extern}
5262 @cindex @code{extern} directive
5263 @code{.extern} is accepted in the source program---for compatibility
5264 with other assemblers---but it is ignored. @command{@value{AS}} treats
5265 all undefined symbols as external.
5268 @section @code{.fail @var{expression}}
5270 @cindex @code{fail} directive
5271 Generates an error or a warning. If the value of the @var{expression} is 500
5272 or more, @command{@value{AS}} will print a warning message. If the value is less
5273 than 500, @command{@value{AS}} will print an error message. The message will
5274 include the value of @var{expression}. This can occasionally be useful inside
5275 complex nested macros or conditional assembly.
5278 @section @code{.file}
5279 @cindex @code{file} directive
5281 @ifclear no-file-dir
5282 There are two different versions of the @code{.file} directive. Targets
5283 that support DWARF2 line number information use the DWARF2 version of
5284 @code{.file}. Other targets use the default version.
5286 @subheading Default Version
5288 @cindex logical file name
5289 @cindex file name, logical
5290 This version of the @code{.file} directive tells @command{@value{AS}} that we
5291 are about to start a new logical file. The syntax is:
5297 @var{string} is the new file name. In general, the filename is
5298 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5299 to specify an empty file name, you must give the quotes--@code{""}. This
5300 statement may go away in future: it is only recognized to be compatible with
5301 old @command{@value{AS}} programs.
5303 @subheading DWARF2 Version
5306 When emitting DWARF2 line number information, @code{.file} assigns filenames
5307 to the @code{.debug_line} file name table. The syntax is:
5310 .file @var{fileno} @var{filename}
5313 The @var{fileno} operand should be a unique positive integer to use as the
5314 index of the entry in the table. The @var{filename} operand is a C string
5317 The detail of filename indices is exposed to the user because the filename
5318 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5319 information, and thus the user must know the exact indices that table
5323 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5325 @cindex @code{fill} directive
5326 @cindex writing patterns in memory
5327 @cindex patterns, writing in memory
5328 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5329 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5330 may be zero or more. @var{Size} may be zero or more, but if it is
5331 more than 8, then it is deemed to have the value 8, compatible with
5332 other people's assemblers. The contents of each @var{repeat} bytes
5333 is taken from an 8-byte number. The highest order 4 bytes are
5334 zero. The lowest order 4 bytes are @var{value} rendered in the
5335 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5336 Each @var{size} bytes in a repetition is taken from the lowest order
5337 @var{size} bytes of this number. Again, this bizarre behavior is
5338 compatible with other people's assemblers.
5340 @var{size} and @var{value} are optional.
5341 If the second comma and @var{value} are absent, @var{value} is
5342 assumed zero. If the first comma and following tokens are absent,
5343 @var{size} is assumed to be 1.
5346 @section @code{.float @var{flonums}}
5348 @cindex floating point numbers (single)
5349 @cindex @code{float} directive
5350 This directive assembles zero or more flonums, separated by commas. It
5351 has the same effect as @code{.single}.
5353 The exact kind of floating point numbers emitted depends on how
5354 @command{@value{AS}} is configured.
5355 @xref{Machine Dependencies}.
5359 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5360 in @sc{ieee} format.
5365 @section @code{.func @var{name}[,@var{label}]}
5366 @cindex @code{func} directive
5367 @code{.func} emits debugging information to denote function @var{name}, and
5368 is ignored unless the file is assembled with debugging enabled.
5369 Only @samp{--gstabs[+]} is currently supported.
5370 @var{label} is the entry point of the function and if omitted @var{name}
5371 prepended with the @samp{leading char} is used.
5372 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5373 All functions are currently defined to have @code{void} return type.
5374 The function must be terminated with @code{.endfunc}.
5377 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5379 @cindex @code{global} directive
5380 @cindex symbol, making visible to linker
5381 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5382 @var{symbol} in your partial program, its value is made available to
5383 other partial programs that are linked with it. Otherwise,
5384 @var{symbol} takes its attributes from a symbol of the same name
5385 from another file linked into the same program.
5387 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5388 compatibility with other assemblers.
5391 On the HPPA, @code{.global} is not always enough to make it accessible to other
5392 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5393 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5398 @section @code{.gnu_attribute @var{tag},@var{value}}
5399 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5402 @section @code{.hidden @var{names}}
5404 @cindex @code{hidden} directive
5406 This is one of the ELF visibility directives. The other two are
5407 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5408 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5410 This directive overrides the named symbols default visibility (which is set by
5411 their binding: local, global or weak). The directive sets the visibility to
5412 @code{hidden} which means that the symbols are not visible to other components.
5413 Such symbols are always considered to be @code{protected} as well.
5417 @section @code{.hword @var{expressions}}
5419 @cindex @code{hword} directive
5420 @cindex integers, 16-bit
5421 @cindex numbers, 16-bit
5422 @cindex sixteen bit integers
5423 This expects zero or more @var{expressions}, and emits
5424 a 16 bit number for each.
5427 This directive is a synonym for @samp{.short}; depending on the target
5428 architecture, it may also be a synonym for @samp{.word}.
5432 This directive is a synonym for @samp{.short}.
5435 This directive is a synonym for both @samp{.short} and @samp{.word}.
5440 @section @code{.ident}
5442 @cindex @code{ident} directive
5444 This directive is used by some assemblers to place tags in object files. The
5445 behavior of this directive varies depending on the target. When using the
5446 a.out object file format, @command{@value{AS}} simply accepts the directive for
5447 source-file compatibility with existing assemblers, but does not emit anything
5448 for it. When using COFF, comments are emitted to the @code{.comment} or
5449 @code{.rdata} section, depending on the target. When using ELF, comments are
5450 emitted to the @code{.comment} section.
5453 @section @code{.if @var{absolute expression}}
5455 @cindex conditional assembly
5456 @cindex @code{if} directive
5457 @code{.if} marks the beginning of a section of code which is only
5458 considered part of the source program being assembled if the argument
5459 (which must be an @var{absolute expression}) is non-zero. The end of
5460 the conditional section of code must be marked by @code{.endif}
5461 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5462 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5463 If you have several conditions to check, @code{.elseif} may be used to avoid
5464 nesting blocks if/else within each subsequent @code{.else} block.
5466 The following variants of @code{.if} are also supported:
5468 @cindex @code{ifdef} directive
5469 @item .ifdef @var{symbol}
5470 Assembles the following section of code if the specified @var{symbol}
5471 has been defined. Note a symbol which has been referenced but not yet defined
5472 is considered to be undefined.
5474 @cindex @code{ifb} directive
5475 @item .ifb @var{text}
5476 Assembles the following section of code if the operand is blank (empty).
5478 @cindex @code{ifc} directive
5479 @item .ifc @var{string1},@var{string2}
5480 Assembles the following section of code if the two strings are the same. The
5481 strings may be optionally quoted with single quotes. If they are not quoted,
5482 the first string stops at the first comma, and the second string stops at the
5483 end of the line. Strings which contain whitespace should be quoted. The
5484 string comparison is case sensitive.
5486 @cindex @code{ifeq} directive
5487 @item .ifeq @var{absolute expression}
5488 Assembles the following section of code if the argument is zero.
5490 @cindex @code{ifeqs} directive
5491 @item .ifeqs @var{string1},@var{string2}
5492 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5494 @cindex @code{ifge} directive
5495 @item .ifge @var{absolute expression}
5496 Assembles the following section of code if the argument is greater than or
5499 @cindex @code{ifgt} directive
5500 @item .ifgt @var{absolute expression}
5501 Assembles the following section of code if the argument is greater than zero.
5503 @cindex @code{ifle} directive
5504 @item .ifle @var{absolute expression}
5505 Assembles the following section of code if the argument is less than or equal
5508 @cindex @code{iflt} directive
5509 @item .iflt @var{absolute expression}
5510 Assembles the following section of code if the argument is less than zero.
5512 @cindex @code{ifnb} directive
5513 @item .ifnb @var{text}
5514 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5515 following section of code if the operand is non-blank (non-empty).
5517 @cindex @code{ifnc} directive
5518 @item .ifnc @var{string1},@var{string2}.
5519 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5520 following section of code if the two strings are not the same.
5522 @cindex @code{ifndef} directive
5523 @cindex @code{ifnotdef} directive
5524 @item .ifndef @var{symbol}
5525 @itemx .ifnotdef @var{symbol}
5526 Assembles the following section of code if the specified @var{symbol}
5527 has not been defined. Both spelling variants are equivalent. Note a symbol
5528 which has been referenced but not yet defined is considered to be undefined.
5530 @cindex @code{ifne} directive
5531 @item .ifne @var{absolute expression}
5532 Assembles the following section of code if the argument is not equal to zero
5533 (in other words, this is equivalent to @code{.if}).
5535 @cindex @code{ifnes} directive
5536 @item .ifnes @var{string1},@var{string2}
5537 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5538 following section of code if the two strings are not the same.
5542 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5544 @cindex @code{incbin} directive
5545 @cindex binary files, including
5546 The @code{incbin} directive includes @var{file} verbatim at the current
5547 location. You can control the search paths used with the @samp{-I} command-line
5548 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5551 The @var{skip} argument skips a number of bytes from the start of the
5552 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5553 read. Note that the data is not aligned in any way, so it is the user's
5554 responsibility to make sure that proper alignment is provided both before and
5555 after the @code{incbin} directive.
5558 @section @code{.include "@var{file}"}
5560 @cindex @code{include} directive
5561 @cindex supporting files, including
5562 @cindex files, including
5563 This directive provides a way to include supporting files at specified
5564 points in your source program. The code from @var{file} is assembled as
5565 if it followed the point of the @code{.include}; when the end of the
5566 included file is reached, assembly of the original file continues. You
5567 can control the search paths used with the @samp{-I} command-line option
5568 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5572 @section @code{.int @var{expressions}}
5574 @cindex @code{int} directive
5575 @cindex integers, 32-bit
5576 Expect zero or more @var{expressions}, of any section, separated by commas.
5577 For each expression, emit a number that, at run time, is the value of that
5578 expression. The byte order and bit size of the number depends on what kind
5579 of target the assembly is for.
5583 On most forms of the H8/300, @code{.int} emits 16-bit
5584 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5591 @section @code{.internal @var{names}}
5593 @cindex @code{internal} directive
5595 This is one of the ELF visibility directives. The other two are
5596 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5597 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5599 This directive overrides the named symbols default visibility (which is set by
5600 their binding: local, global or weak). The directive sets the visibility to
5601 @code{internal} which means that the symbols are considered to be @code{hidden}
5602 (i.e., not visible to other components), and that some extra, processor specific
5603 processing must also be performed upon the symbols as well.
5607 @section @code{.irp @var{symbol},@var{values}}@dots{}
5609 @cindex @code{irp} directive
5610 Evaluate a sequence of statements assigning different values to @var{symbol}.
5611 The sequence of statements starts at the @code{.irp} directive, and is
5612 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5613 set to @var{value}, and the sequence of statements is assembled. If no
5614 @var{value} is listed, the sequence of statements is assembled once, with
5615 @var{symbol} set to the null string. To refer to @var{symbol} within the
5616 sequence of statements, use @var{\symbol}.
5618 For example, assembling
5626 is equivalent to assembling
5634 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5637 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5639 @cindex @code{irpc} directive
5640 Evaluate a sequence of statements assigning different values to @var{symbol}.
5641 The sequence of statements starts at the @code{.irpc} directive, and is
5642 terminated by an @code{.endr} directive. For each character in @var{value},
5643 @var{symbol} is set to the character, and the sequence of statements is
5644 assembled. If no @var{value} is listed, the sequence of statements is
5645 assembled once, with @var{symbol} set to the null string. To refer to
5646 @var{symbol} within the sequence of statements, use @var{\symbol}.
5648 For example, assembling
5656 is equivalent to assembling
5664 For some caveats with the spelling of @var{symbol}, see also the discussion
5668 @section @code{.lcomm @var{symbol} , @var{length}}
5670 @cindex @code{lcomm} directive
5671 @cindex local common symbols
5672 @cindex symbols, local common
5673 Reserve @var{length} (an absolute expression) bytes for a local common
5674 denoted by @var{symbol}. The section and value of @var{symbol} are
5675 those of the new local common. The addresses are allocated in the bss
5676 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5677 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5678 not visible to @code{@value{LD}}.
5681 Some targets permit a third argument to be used with @code{.lcomm}. This
5682 argument specifies the desired alignment of the symbol in the bss section.
5686 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5687 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5691 @section @code{.lflags}
5693 @cindex @code{lflags} directive (ignored)
5694 @command{@value{AS}} accepts this directive, for compatibility with other
5695 assemblers, but ignores it.
5697 @ifclear no-line-dir
5699 @section @code{.line @var{line-number}}
5701 @cindex @code{line} directive
5702 @cindex logical line number
5704 Change the logical line number. @var{line-number} must be an absolute
5705 expression. The next line has that logical line number. Therefore any other
5706 statements on the current line (after a statement separator character) are
5707 reported as on logical line number @var{line-number} @minus{} 1. One day
5708 @command{@value{AS}} will no longer support this directive: it is recognized only
5709 for compatibility with existing assembler programs.
5712 Even though this is a directive associated with the @code{a.out} or
5713 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5714 when producing COFF output, and treats @samp{.line} as though it
5715 were the COFF @samp{.ln} @emph{if} it is found outside a
5716 @code{.def}/@code{.endef} pair.
5718 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5719 used by compilers to generate auxiliary symbol information for
5724 @section @code{.linkonce [@var{type}]}
5726 @cindex @code{linkonce} directive
5727 @cindex common sections
5728 Mark the current section so that the linker only includes a single copy of it.
5729 This may be used to include the same section in several different object files,
5730 but ensure that the linker will only include it once in the final output file.
5731 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5732 Duplicate sections are detected based on the section name, so it should be
5735 This directive is only supported by a few object file formats; as of this
5736 writing, the only object file format which supports it is the Portable
5737 Executable format used on Windows NT.
5739 The @var{type} argument is optional. If specified, it must be one of the
5740 following strings. For example:
5744 Not all types may be supported on all object file formats.
5748 Silently discard duplicate sections. This is the default.
5751 Warn if there are duplicate sections, but still keep only one copy.
5754 Warn if any of the duplicates have different sizes.
5757 Warn if any of the duplicates do not have exactly the same contents.
5761 @section @code{.list}
5763 @cindex @code{list} directive
5764 @cindex listing control, turning on
5765 Control (in conjunction with the @code{.nolist} directive) whether or
5766 not assembly listings are generated. These two directives maintain an
5767 internal counter (which is zero initially). @code{.list} increments the
5768 counter, and @code{.nolist} decrements it. Assembly listings are
5769 generated whenever the counter is greater than zero.
5771 By default, listings are disabled. When you enable them (with the
5772 @samp{-a} command-line option; @pxref{Invoking,,Command-Line Options}),
5773 the initial value of the listing counter is one.
5776 @section @code{.ln @var{line-number}}
5778 @cindex @code{ln} directive
5779 @ifclear no-line-dir
5780 @samp{.ln} is a synonym for @samp{.line}.
5783 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5784 must be an absolute expression. The next line has that logical
5785 line number, so any other statements on the current line (after a
5786 statement separator character @code{;}) are reported as on logical
5787 line number @var{line-number} @minus{} 1.
5791 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5792 @cindex @code{loc} directive
5793 When emitting DWARF2 line number information,
5794 the @code{.loc} directive will add a row to the @code{.debug_line} line
5795 number matrix corresponding to the immediately following assembly
5796 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5797 arguments will be applied to the @code{.debug_line} state machine before
5800 The @var{options} are a sequence of the following tokens in any order:
5804 This option will set the @code{basic_block} register in the
5805 @code{.debug_line} state machine to @code{true}.
5808 This option will set the @code{prologue_end} register in the
5809 @code{.debug_line} state machine to @code{true}.
5811 @item epilogue_begin
5812 This option will set the @code{epilogue_begin} register in the
5813 @code{.debug_line} state machine to @code{true}.
5815 @item is_stmt @var{value}
5816 This option will set the @code{is_stmt} register in the
5817 @code{.debug_line} state machine to @code{value}, which must be
5820 @item isa @var{value}
5821 This directive will set the @code{isa} register in the @code{.debug_line}
5822 state machine to @var{value}, which must be an unsigned integer.
5824 @item discriminator @var{value}
5825 This directive will set the @code{discriminator} register in the @code{.debug_line}
5826 state machine to @var{value}, which must be an unsigned integer.
5828 @item view @var{value}
5829 This option causes a row to be added to @code{.debug_line} in reference to the
5830 current address (which might not be the same as that of the following assembly
5831 instruction), and to associate @var{value} with the @code{view} register in the
5832 @code{.debug_line} state machine. If @var{value} is a label, both the
5833 @code{view} register and the label are set to the number of prior @code{.loc}
5834 directives at the same program location. If @var{value} is the literal
5835 @code{0}, the @code{view} register is set to zero, and the assembler asserts
5836 that there aren't any prior @code{.loc} directives at the same program
5837 location. If @var{value} is the literal @code{-0}, the assembler arrange for
5838 the @code{view} register to be reset in this row, even if there are prior
5839 @code{.loc} directives at the same program location.
5843 @node Loc_mark_labels
5844 @section @code{.loc_mark_labels @var{enable}}
5845 @cindex @code{loc_mark_labels} directive
5846 When emitting DWARF2 line number information,
5847 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5848 to the @code{.debug_line} line number matrix with the @code{basic_block}
5849 register in the state machine set whenever a code label is seen.
5850 The @var{enable} argument should be either 1 or 0, to enable or disable
5851 this function respectively.
5855 @section @code{.local @var{names}}
5857 @cindex @code{local} directive
5858 This directive, which is available for ELF targets, marks each symbol in
5859 the comma-separated list of @code{names} as a local symbol so that it
5860 will not be externally visible. If the symbols do not already exist,
5861 they will be created.
5863 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5864 accept an alignment argument, which is the case for most ELF targets,
5865 the @code{.local} directive can be used in combination with @code{.comm}
5866 (@pxref{Comm}) to define aligned local common data.
5870 @section @code{.long @var{expressions}}
5872 @cindex @code{long} directive
5873 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5876 @c no one seems to know what this is for or whether this description is
5877 @c what it really ought to do
5879 @section @code{.lsym @var{symbol}, @var{expression}}
5881 @cindex @code{lsym} directive
5882 @cindex symbol, not referenced in assembly
5883 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5884 the hash table, ensuring it cannot be referenced by name during the
5885 rest of the assembly. This sets the attributes of the symbol to be
5886 the same as the expression value:
5888 @var{other} = @var{descriptor} = 0
5889 @var{type} = @r{(section of @var{expression})}
5890 @var{value} = @var{expression}
5893 The new symbol is not flagged as external.
5897 @section @code{.macro}
5900 The commands @code{.macro} and @code{.endm} allow you to define macros that
5901 generate assembly output. For example, this definition specifies a macro
5902 @code{sum} that puts a sequence of numbers into memory:
5905 .macro sum from=0, to=5
5914 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5926 @item .macro @var{macname}
5927 @itemx .macro @var{macname} @var{macargs} @dots{}
5928 @cindex @code{macro} directive
5929 Begin the definition of a macro called @var{macname}. If your macro
5930 definition requires arguments, specify their names after the macro name,
5931 separated by commas or spaces. You can qualify the macro argument to
5932 indicate whether all invocations must specify a non-blank value (through
5933 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5934 (through @samp{:@code{vararg}}). You can supply a default value for any
5935 macro argument by following the name with @samp{=@var{deflt}}. You
5936 cannot define two macros with the same @var{macname} unless it has been
5937 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5938 definitions. For example, these are all valid @code{.macro} statements:
5942 Begin the definition of a macro called @code{comm}, which takes no
5945 @item .macro plus1 p, p1
5946 @itemx .macro plus1 p p1
5947 Either statement begins the definition of a macro called @code{plus1},
5948 which takes two arguments; within the macro definition, write
5949 @samp{\p} or @samp{\p1} to evaluate the arguments.
5951 @item .macro reserve_str p1=0 p2
5952 Begin the definition of a macro called @code{reserve_str}, with two
5953 arguments. The first argument has a default value, but not the second.
5954 After the definition is complete, you can call the macro either as
5955 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5956 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5957 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5958 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5960 @item .macro m p1:req, p2=0, p3:vararg
5961 Begin the definition of a macro called @code{m}, with at least three
5962 arguments. The first argument must always have a value specified, but
5963 not the second, which instead has a default value. The third formal
5964 will get assigned all remaining arguments specified at invocation time.
5966 When you call a macro, you can specify the argument values either by
5967 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5968 @samp{sum to=17, from=9}.
5972 Note that since each of the @var{macargs} can be an identifier exactly
5973 as any other one permitted by the target architecture, there may be
5974 occasional problems if the target hand-crafts special meanings to certain
5975 characters when they occur in a special position. For example, if the colon
5976 (@code{:}) is generally permitted to be part of a symbol name, but the
5977 architecture specific code special-cases it when occurring as the final
5978 character of a symbol (to denote a label), then the macro parameter
5979 replacement code will have no way of knowing that and consider the whole
5980 construct (including the colon) an identifier, and check only this
5981 identifier for being the subject to parameter substitution. So for example
5982 this macro definition:
5990 might not work as expected. Invoking @samp{label foo} might not create a label
5991 called @samp{foo} but instead just insert the text @samp{\l:} into the
5992 assembler source, probably generating an error about an unrecognised
5995 Similarly problems might occur with the period character (@samp{.})
5996 which is often allowed inside opcode names (and hence identifier names). So
5997 for example constructing a macro to build an opcode from a base name and a
5998 length specifier like this:
6001 .macro opcode base length
6006 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
6007 instruction but instead generate some kind of error as the assembler tries to
6008 interpret the text @samp{\base.\length}.
6010 There are several possible ways around this problem:
6013 @item Insert white space
6014 If it is possible to use white space characters then this is the simplest
6023 @item Use @samp{\()}
6024 The string @samp{\()} can be used to separate the end of a macro argument from
6025 the following text. eg:
6028 .macro opcode base length
6033 @item Use the alternate macro syntax mode
6034 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6035 used as a separator. eg:
6045 Note: this problem of correctly identifying string parameters to pseudo ops
6046 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6047 and @code{.irpc} (@pxref{Irpc}) as well.
6050 @cindex @code{endm} directive
6051 Mark the end of a macro definition.
6054 @cindex @code{exitm} directive
6055 Exit early from the current macro definition.
6057 @cindex number of macros executed
6058 @cindex macros, count executed
6060 @command{@value{AS}} maintains a counter of how many macros it has
6061 executed in this pseudo-variable; you can copy that number to your
6062 output with @samp{\@@}, but @emph{only within a macro definition}.
6064 @item LOCAL @var{name} [ , @dots{} ]
6065 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6066 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6067 @xref{Altmacro,,@code{.altmacro}}.
6071 @section @code{.mri @var{val}}
6073 @cindex @code{mri} directive
6074 @cindex MRI mode, temporarily
6075 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6076 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6077 affects code assembled until the next @code{.mri} directive, or until the end
6078 of the file. @xref{M, MRI mode, MRI mode}.
6081 @section @code{.noaltmacro}
6082 Disable alternate macro mode. @xref{Altmacro}.
6085 @section @code{.nolist}
6087 @cindex @code{nolist} directive
6088 @cindex listing control, turning off
6089 Control (in conjunction with the @code{.list} directive) whether or
6090 not assembly listings are generated. These two directives maintain an
6091 internal counter (which is zero initially). @code{.list} increments the
6092 counter, and @code{.nolist} decrements it. Assembly listings are
6093 generated whenever the counter is greater than zero.
6096 @section @code{.nops @var{size}[, @var{control}]}
6098 @cindex @code{nops} directive
6099 @cindex filling memory with no-op instructions
6100 This directive emits @var{size} bytes filled with no-op instructions.
6101 @var{size} is absolute expression, which must be a positve value.
6102 @var{control} controls how no-op instructions should be generated. If
6103 the comma and @var{control} are omitted, @var{control} is assumed to be
6106 Note: For Intel 80386 and AMD x86-64 targets, @var{control} specifies
6107 the size limit of a no-op instruction. The valid values of @var{control}
6108 are between 0 and 4 in 16-bit mode, between 0 and 7 when tuning for
6109 older processors in 32-bit mode, between 0 and 11 in 64-bit mode or when
6110 tuning for newer processors in 32-bit mode. When 0 is used, the no-op
6111 instruction size limit is set to the maximum supported size.
6114 @section @code{.octa @var{bignums}}
6116 @c FIXME: double size emitted for "octa" on some? Or warn?
6117 @cindex @code{octa} directive
6118 @cindex integer, 16-byte
6119 @cindex sixteen byte integer
6120 This directive expects zero or more bignums, separated by commas. For each
6121 bignum, it emits a 16-byte integer.
6123 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6124 hence @emph{octa}-word for 16 bytes.
6127 @section @code{.offset @var{loc}}
6129 @cindex @code{offset} directive
6130 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6131 be an absolute expression. This directive may be useful for defining
6132 symbols with absolute values. Do not confuse it with the @code{.org}
6136 @section @code{.org @var{new-lc} , @var{fill}}
6138 @cindex @code{org} directive
6139 @cindex location counter, advancing
6140 @cindex advancing location counter
6141 @cindex current address, advancing
6142 Advance the location counter of the current section to
6143 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6144 expression with the same section as the current subsection. That is,
6145 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6146 wrong section, the @code{.org} directive is ignored. To be compatible
6147 with former assemblers, if the section of @var{new-lc} is absolute,
6148 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6149 is the same as the current subsection.
6151 @code{.org} may only increase the location counter, or leave it
6152 unchanged; you cannot use @code{.org} to move the location counter
6155 @c double negative used below "not undefined" because this is a specific
6156 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6157 @c section. doc@cygnus.com 18feb91
6158 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6159 may not be undefined. If you really detest this restriction we eagerly await
6160 a chance to share your improved assembler.
6162 Beware that the origin is relative to the start of the section, not
6163 to the start of the subsection. This is compatible with other
6164 people's assemblers.
6166 When the location counter (of the current subsection) is advanced, the
6167 intervening bytes are filled with @var{fill} which should be an
6168 absolute expression. If the comma and @var{fill} are omitted,
6169 @var{fill} defaults to zero.
6172 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6174 @cindex padding the location counter given a power of two
6175 @cindex @code{p2align} directive
6176 Pad the location counter (in the current subsection) to a particular
6177 storage boundary. The first expression (which must be absolute) is the
6178 number of low-order zero bits the location counter must have after
6179 advancement. For example @samp{.p2align 3} advances the location
6180 counter until it a multiple of 8. If the location counter is already a
6181 multiple of 8, no change is needed.
6183 The second expression (also absolute) gives the fill value to be stored in the
6184 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6185 padding bytes are normally zero. However, on most systems, if the section is
6186 marked as containing code and the fill value is omitted, the space is filled
6187 with no-op instructions.
6189 The third expression is also absolute, and is also optional. If it is present,
6190 it is the maximum number of bytes that should be skipped by this alignment
6191 directive. If doing the alignment would require skipping more bytes than the
6192 specified maximum, then the alignment is not done at all. You can omit the
6193 fill value (the second argument) entirely by simply using two commas after the
6194 required alignment; this can be useful if you want the alignment to be filled
6195 with no-op instructions when appropriate.
6197 @cindex @code{p2alignw} directive
6198 @cindex @code{p2alignl} directive
6199 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6200 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6201 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6202 fill pattern as a four byte longword value. For example, @code{.p2alignw
6203 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6204 filled in with the value 0x368d (the exact placement of the bytes depends upon
6205 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6210 @section @code{.popsection}
6212 @cindex @code{popsection} directive
6213 @cindex Section Stack
6214 This is one of the ELF section stack manipulation directives. The others are
6215 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6216 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6219 This directive replaces the current section (and subsection) with the top
6220 section (and subsection) on the section stack. This section is popped off the
6226 @section @code{.previous}
6228 @cindex @code{previous} directive
6229 @cindex Section Stack
6230 This is one of the ELF section stack manipulation directives. The others are
6231 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6232 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6233 (@pxref{PopSection}).
6235 This directive swaps the current section (and subsection) with most recently
6236 referenced section/subsection pair prior to this one. Multiple
6237 @code{.previous} directives in a row will flip between two sections (and their
6238 subsections). For example:
6250 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6256 # Now in section A subsection 1
6260 # Now in section B subsection 0
6263 # Now in section B subsection 1
6266 # Now in section B subsection 0
6270 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6271 section B and 0x9abc into subsection 1 of section B.
6273 In terms of the section stack, this directive swaps the current section with
6274 the top section on the section stack.
6278 @section @code{.print @var{string}}
6280 @cindex @code{print} directive
6281 @command{@value{AS}} will print @var{string} on the standard output during
6282 assembly. You must put @var{string} in double quotes.
6286 @section @code{.protected @var{names}}
6288 @cindex @code{protected} directive
6290 This is one of the ELF visibility directives. The other two are
6291 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6293 This directive overrides the named symbols default visibility (which is set by
6294 their binding: local, global or weak). The directive sets the visibility to
6295 @code{protected} which means that any references to the symbols from within the
6296 components that defines them must be resolved to the definition in that
6297 component, even if a definition in another component would normally preempt
6302 @section @code{.psize @var{lines} , @var{columns}}
6304 @cindex @code{psize} directive
6305 @cindex listing control: paper size
6306 @cindex paper size, for listings
6307 Use this directive to declare the number of lines---and, optionally, the
6308 number of columns---to use for each page, when generating listings.
6310 If you do not use @code{.psize}, listings use a default line-count
6311 of 60. You may omit the comma and @var{columns} specification; the
6312 default width is 200 columns.
6314 @command{@value{AS}} generates formfeeds whenever the specified number of
6315 lines is exceeded (or whenever you explicitly request one, using
6318 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6319 those explicitly specified with @code{.eject}.
6322 @section @code{.purgem @var{name}}
6324 @cindex @code{purgem} directive
6325 Undefine the macro @var{name}, so that later uses of the string will not be
6326 expanded. @xref{Macro}.
6330 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6332 @cindex @code{pushsection} directive
6333 @cindex Section Stack
6334 This is one of the ELF section stack manipulation directives. The others are
6335 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6336 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6339 This directive pushes the current section (and subsection) onto the
6340 top of the section stack, and then replaces the current section and
6341 subsection with @code{name} and @code{subsection}. The optional
6342 @code{flags}, @code{type} and @code{arguments} are treated the same
6343 as in the @code{.section} (@pxref{Section}) directive.
6347 @section @code{.quad @var{bignums}}
6349 @cindex @code{quad} directive
6350 @code{.quad} expects zero or more bignums, separated by commas. For
6351 each bignum, it emits
6353 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6354 warning message; and just takes the lowest order 8 bytes of the bignum.
6355 @cindex eight-byte integer
6356 @cindex integer, 8-byte
6358 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6359 hence @emph{quad}-word for 8 bytes.
6362 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6363 warning message; and just takes the lowest order 16 bytes of the bignum.
6364 @cindex sixteen-byte integer
6365 @cindex integer, 16-byte
6369 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6371 @cindex @code{reloc} directive
6372 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6373 @var{expression}. If @var{offset} is a number, the relocation is generated in
6374 the current section. If @var{offset} is an expression that resolves to a
6375 symbol plus offset, the relocation is generated in the given symbol's section.
6376 @var{expression}, if present, must resolve to a symbol plus addend or to an
6377 absolute value, but note that not all targets support an addend. e.g. ELF REL
6378 targets such as i386 store an addend in the section contents rather than in the
6379 relocation. This low level interface does not support addends stored in the
6383 @section @code{.rept @var{count}}
6385 @cindex @code{rept} directive
6386 Repeat the sequence of lines between the @code{.rept} directive and the next
6387 @code{.endr} directive @var{count} times.
6389 For example, assembling
6397 is equivalent to assembling
6405 A count of zero is allowed, but nothing is generated. Negative counts are not
6406 allowed and if encountered will be treated as if they were zero.
6409 @section @code{.sbttl "@var{subheading}"}
6411 @cindex @code{sbttl} directive
6412 @cindex subtitles for listings
6413 @cindex listing control: subtitle
6414 Use @var{subheading} as the title (third line, immediately after the
6415 title line) when generating assembly listings.
6417 This directive affects subsequent pages, as well as the current page if
6418 it appears within ten lines of the top of a page.
6422 @section @code{.scl @var{class}}
6424 @cindex @code{scl} directive
6425 @cindex symbol storage class (COFF)
6426 @cindex COFF symbol storage class
6427 Set the storage-class value for a symbol. This directive may only be
6428 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6429 whether a symbol is static or external, or it may record further
6430 symbolic debugging information.
6435 @section @code{.section @var{name}}
6437 @cindex named section
6438 Use the @code{.section} directive to assemble the following code into a section
6441 This directive is only supported for targets that actually support arbitrarily
6442 named sections; on @code{a.out} targets, for example, it is not accepted, even
6443 with a standard @code{a.out} section name.
6447 @c only print the extra heading if both COFF and ELF are set
6448 @subheading COFF Version
6451 @cindex @code{section} directive (COFF version)
6452 For COFF targets, the @code{.section} directive is used in one of the following
6456 .section @var{name}[, "@var{flags}"]
6457 .section @var{name}[, @var{subsection}]
6460 If the optional argument is quoted, it is taken as flags to use for the
6461 section. Each flag is a single character. The following flags are recognized:
6465 bss section (uninitialized data)
6467 section is not loaded
6473 exclude section from linking
6479 shared section (meaningful for PE targets)
6481 ignored. (For compatibility with the ELF version)
6483 section is not readable (meaningful for PE targets)
6485 single-digit power-of-two section alignment (GNU extension)
6488 If no flags are specified, the default flags depend upon the section name. If
6489 the section name is not recognized, the default will be for the section to be
6490 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6491 from the section, rather than adding them, so if they are used on their own it
6492 will be as if no flags had been specified at all.
6494 If the optional argument to the @code{.section} directive is not quoted, it is
6495 taken as a subsection number (@pxref{Sub-Sections}).
6500 @c only print the extra heading if both COFF and ELF are set
6501 @subheading ELF Version
6504 @cindex Section Stack
6505 This is one of the ELF section stack manipulation directives. The others are
6506 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6507 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6508 @code{.previous} (@pxref{Previous}).
6510 @cindex @code{section} directive (ELF version)
6511 For ELF targets, the @code{.section} directive is used like this:
6514 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6517 @anchor{Section Name Substitutions}
6518 @kindex --sectname-subst
6519 @cindex section name substitution
6520 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6521 argument may contain a substitution sequence. Only @code{%S} is supported
6522 at the moment, and substitutes the current section name. For example:
6525 .macro exception_code
6526 .section %S.exception
6527 [exception code here]
6542 The two @code{exception_code} invocations above would create the
6543 @code{.text.exception} and @code{.init.exception} sections respectively.
6544 This is useful e.g. to discriminate between ancillary sections that are
6545 tied to setup code to be discarded after use from ancillary sections that
6546 need to stay resident without having to define multiple @code{exception_code}
6547 macros just for that purpose.
6549 The optional @var{flags} argument is a quoted string which may contain any
6550 combination of the following characters:
6554 section is allocatable
6556 section is a GNU_MBIND section
6558 section is excluded from executable and shared library.
6562 section is executable
6564 section is mergeable
6566 section contains zero terminated strings
6568 section is a member of a section group
6570 section is used for thread-local-storage
6572 section is a member of the previously-current section's group, if any
6573 @item @code{<number>}
6574 a numeric value indicating the bits to be set in the ELF section header's flags
6575 field. Note - if one or more of the alphabetic characters described above is
6576 also included in the flags field, their bit values will be ORed into the
6578 @item @code{<target specific>}
6579 some targets extend this list with their own flag characters
6582 Note - once a section's flags have been set they cannot be changed. There are
6583 a few exceptions to this rule however. Processor and application specific
6584 flags can be added to an already defined section. The @code{.interp},
6585 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6586 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6587 section may have the executable (@code{x}) flag added.
6589 The optional @var{type} argument may contain one of the following constants:
6593 section contains data
6595 section does not contain data (i.e., section only occupies space)
6597 section contains data which is used by things other than the program
6599 section contains an array of pointers to init functions
6601 section contains an array of pointers to finish functions
6602 @item @@preinit_array
6603 section contains an array of pointers to pre-init functions
6604 @item @@@code{<number>}
6605 a numeric value to be set as the ELF section header's type field.
6606 @item @@@code{<target specific>}
6607 some targets extend this list with their own types
6610 Many targets only support the first three section types. The type may be
6611 enclosed in double quotes if necessary.
6613 Note on targets where the @code{@@} character is the start of a comment (eg
6614 ARM) then another character is used instead. For example the ARM port uses the
6617 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6618 special and have fixed types. Any attempt to declare them with a different
6619 type will generate an error from the assembler.
6621 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6622 be specified as well as an extra argument---@var{entsize}---like this:
6625 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6628 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6629 constants, each @var{entsize} octets long. Sections with both @code{M} and
6630 @code{S} must contain zero terminated strings where each character is
6631 @var{entsize} bytes long. The linker may remove duplicates within sections with
6632 the same name, same entity size and same flags. @var{entsize} must be an
6633 absolute expression. For sections with both @code{M} and @code{S}, a string
6634 which is a suffix of a larger string is considered a duplicate. Thus
6635 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6636 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6638 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6639 be present along with an additional field like this:
6642 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6645 The @var{GroupName} field specifies the name of the section group to which this
6646 particular section belongs. The optional linkage field can contain:
6650 indicates that only one copy of this section should be retained
6655 Note: if both the @var{M} and @var{G} flags are present then the fields for
6656 the Merge flag should come first, like this:
6659 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6662 If @var{flags} contains the @code{?} symbol then it may not also contain the
6663 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6664 present. Instead, @code{?} says to consider the section that's current before
6665 this directive. If that section used @code{G}, then the new section will use
6666 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6667 If not, then the @code{?} symbol has no effect.
6669 If no flags are specified, the default flags depend upon the section name. If
6670 the section name is not recognized, the default will be for the section to have
6671 none of the above flags: it will not be allocated in memory, nor writable, nor
6672 executable. The section will contain data.
6674 For ELF targets, the assembler supports another type of @code{.section}
6675 directive for compatibility with the Solaris assembler:
6678 .section "@var{name}"[, @var{flags}...]
6681 Note that the section name is quoted. There may be a sequence of comma
6686 section is allocatable
6690 section is executable
6692 section is excluded from executable and shared library.
6694 section is used for thread local storage
6697 This directive replaces the current section and subsection. See the
6698 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6699 some examples of how this directive and the other section stack directives
6705 @section @code{.set @var{symbol}, @var{expression}}
6707 @cindex @code{set} directive
6708 @cindex symbol value, setting
6709 Set the value of @var{symbol} to @var{expression}. This
6710 changes @var{symbol}'s value and type to conform to
6711 @var{expression}. If @var{symbol} was flagged as external, it remains
6712 flagged (@pxref{Symbol Attributes}).
6714 You may @code{.set} a symbol many times in the same assembly provided that the
6715 values given to the symbol are constants. Values that are based on expressions
6716 involving other symbols are allowed, but some targets may restrict this to only
6717 being done once per assembly. This is because those targets do not set the
6718 addresses of symbols at assembly time, but rather delay the assignment until a
6719 final link is performed. This allows the linker a chance to change the code in
6720 the files, changing the location of, and the relative distance between, various
6723 If you @code{.set} a global symbol, the value stored in the object
6724 file is the last value stored into it.
6727 On Z80 @code{set} is a real instruction, use
6728 @samp{@var{symbol} defl @var{expression}} instead.
6732 @section @code{.short @var{expressions}}
6734 @cindex @code{short} directive
6736 @code{.short} is normally the same as @samp{.word}.
6737 @xref{Word,,@code{.word}}.
6739 In some configurations, however, @code{.short} and @code{.word} generate
6740 numbers of different lengths. @xref{Machine Dependencies}.
6744 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6747 This expects zero or more @var{expressions}, and emits
6748 a 16 bit number for each.
6753 @section @code{.single @var{flonums}}
6755 @cindex @code{single} directive
6756 @cindex floating point numbers (single)
6757 This directive assembles zero or more flonums, separated by commas. It
6758 has the same effect as @code{.float}.
6760 The exact kind of floating point numbers emitted depends on how
6761 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6765 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6766 numbers in @sc{ieee} format.
6772 @section @code{.size}
6774 This directive is used to set the size associated with a symbol.
6778 @c only print the extra heading if both COFF and ELF are set
6779 @subheading COFF Version
6782 @cindex @code{size} directive (COFF version)
6783 For COFF targets, the @code{.size} directive is only permitted inside
6784 @code{.def}/@code{.endef} pairs. It is used like this:
6787 .size @var{expression}
6794 @c only print the extra heading if both COFF and ELF are set
6795 @subheading ELF Version
6798 @cindex @code{size} directive (ELF version)
6799 For ELF targets, the @code{.size} directive is used like this:
6802 .size @var{name} , @var{expression}
6805 This directive sets the size associated with a symbol @var{name}.
6806 The size in bytes is computed from @var{expression} which can make use of label
6807 arithmetic. This directive is typically used to set the size of function
6812 @ifclear no-space-dir
6814 @section @code{.skip @var{size} [,@var{fill}]}
6816 @cindex @code{skip} directive
6817 @cindex filling memory
6818 This directive emits @var{size} bytes, each of value @var{fill}. Both
6819 @var{size} and @var{fill} are absolute expressions. If the comma and
6820 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6825 @section @code{.sleb128 @var{expressions}}
6827 @cindex @code{sleb128} directive
6828 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6829 compact, variable length representation of numbers used by the DWARF
6830 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6832 @ifclear no-space-dir
6834 @section @code{.space @var{size} [,@var{fill}]}
6836 @cindex @code{space} directive
6837 @cindex filling memory
6838 This directive emits @var{size} bytes, each of value @var{fill}. Both
6839 @var{size} and @var{fill} are absolute expressions. If the comma
6840 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6845 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6846 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6847 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6848 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6856 @section @code{.stabd, .stabn, .stabs}
6858 @cindex symbolic debuggers, information for
6859 @cindex @code{stab@var{x}} directives
6860 There are three directives that begin @samp{.stab}.
6861 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6862 The symbols are not entered in the @command{@value{AS}} hash table: they
6863 cannot be referenced elsewhere in the source file.
6864 Up to five fields are required:
6868 This is the symbol's name. It may contain any character except
6869 @samp{\000}, so is more general than ordinary symbol names. Some
6870 debuggers used to code arbitrarily complex structures into symbol names
6874 An absolute expression. The symbol's type is set to the low 8 bits of
6875 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6876 and debuggers choke on silly bit patterns.
6879 An absolute expression. The symbol's ``other'' attribute is set to the
6880 low 8 bits of this expression.
6883 An absolute expression. The symbol's descriptor is set to the low 16
6884 bits of this expression.
6887 An absolute expression which becomes the symbol's value.
6890 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6891 or @code{.stabs} statement, the symbol has probably already been created;
6892 you get a half-formed symbol in your object file. This is
6893 compatible with earlier assemblers!
6896 @cindex @code{stabd} directive
6897 @item .stabd @var{type} , @var{other} , @var{desc}
6899 The ``name'' of the symbol generated is not even an empty string.
6900 It is a null pointer, for compatibility. Older assemblers used a
6901 null pointer so they didn't waste space in object files with empty
6904 The symbol's value is set to the location counter,
6905 relocatably. When your program is linked, the value of this symbol
6906 is the address of the location counter when the @code{.stabd} was
6909 @cindex @code{stabn} directive
6910 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6911 The name of the symbol is set to the empty string @code{""}.
6913 @cindex @code{stabs} directive
6914 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6915 All five fields are specified.
6921 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6922 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6924 @cindex string, copying to object file
6925 @cindex string8, copying to object file
6926 @cindex string16, copying to object file
6927 @cindex string32, copying to object file
6928 @cindex string64, copying to object file
6929 @cindex @code{string} directive
6930 @cindex @code{string8} directive
6931 @cindex @code{string16} directive
6932 @cindex @code{string32} directive
6933 @cindex @code{string64} directive
6935 Copy the characters in @var{str} to the object file. You may specify more than
6936 one string to copy, separated by commas. Unless otherwise specified for a
6937 particular machine, the assembler marks the end of each string with a 0 byte.
6938 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6940 The variants @code{string16}, @code{string32} and @code{string64} differ from
6941 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6942 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6943 are stored in target endianness byte order.
6949 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6950 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6955 @section @code{.struct @var{expression}}
6957 @cindex @code{struct} directive
6958 Switch to the absolute section, and set the section offset to @var{expression},
6959 which must be an absolute expression. You might use this as follows:
6968 This would define the symbol @code{field1} to have the value 0, the symbol
6969 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6970 value 8. Assembly would be left in the absolute section, and you would need to
6971 use a @code{.section} directive of some sort to change to some other section
6972 before further assembly.
6976 @section @code{.subsection @var{name}}
6978 @cindex @code{subsection} directive
6979 @cindex Section Stack
6980 This is one of the ELF section stack manipulation directives. The others are
6981 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6982 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6985 This directive replaces the current subsection with @code{name}. The current
6986 section is not changed. The replaced subsection is put onto the section stack
6987 in place of the then current top of stack subsection.
6992 @section @code{.symver}
6993 @cindex @code{symver} directive
6994 @cindex symbol versioning
6995 @cindex versions of symbols
6996 Use the @code{.symver} directive to bind symbols to specific version nodes
6997 within a source file. This is only supported on ELF platforms, and is
6998 typically used when assembling files to be linked into a shared library.
6999 There are cases where it may make sense to use this in objects to be bound
7000 into an application itself so as to override a versioned symbol from a
7003 For ELF targets, the @code{.symver} directive can be used like this:
7005 .symver @var{name}, @var{name2@@nodename}
7007 If the symbol @var{name} is defined within the file
7008 being assembled, the @code{.symver} directive effectively creates a symbol
7009 alias with the name @var{name2@@nodename}, and in fact the main reason that we
7010 just don't try and create a regular alias is that the @var{@@} character isn't
7011 permitted in symbol names. The @var{name2} part of the name is the actual name
7012 of the symbol by which it will be externally referenced. The name @var{name}
7013 itself is merely a name of convenience that is used so that it is possible to
7014 have definitions for multiple versions of a function within a single source
7015 file, and so that the compiler can unambiguously know which version of a
7016 function is being mentioned. The @var{nodename} portion of the alias should be
7017 the name of a node specified in the version script supplied to the linker when
7018 building a shared library. If you are attempting to override a versioned
7019 symbol from a shared library, then @var{nodename} should correspond to the
7020 nodename of the symbol you are trying to override.
7022 If the symbol @var{name} is not defined within the file being assembled, all
7023 references to @var{name} will be changed to @var{name2@@nodename}. If no
7024 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
7027 Another usage of the @code{.symver} directive is:
7029 .symver @var{name}, @var{name2@@@@nodename}
7031 In this case, the symbol @var{name} must exist and be defined within
7032 the file being assembled. It is similar to @var{name2@@nodename}. The
7033 difference is @var{name2@@@@nodename} will also be used to resolve
7034 references to @var{name2} by the linker.
7036 The third usage of the @code{.symver} directive is:
7038 .symver @var{name}, @var{name2@@@@@@nodename}
7040 When @var{name} is not defined within the
7041 file being assembled, it is treated as @var{name2@@nodename}. When
7042 @var{name} is defined within the file being assembled, the symbol
7043 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7048 @section @code{.tag @var{structname}}
7050 @cindex COFF structure debugging
7051 @cindex structure debugging, COFF
7052 @cindex @code{tag} directive
7053 This directive is generated by compilers to include auxiliary debugging
7054 information in the symbol table. It is only permitted inside
7055 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7056 definitions in the symbol table with instances of those structures.
7060 @section @code{.text @var{subsection}}
7062 @cindex @code{text} directive
7063 Tells @command{@value{AS}} to assemble the following statements onto the end of
7064 the text subsection numbered @var{subsection}, which is an absolute
7065 expression. If @var{subsection} is omitted, subsection number zero
7069 @section @code{.title "@var{heading}"}
7071 @cindex @code{title} directive
7072 @cindex listing control: title line
7073 Use @var{heading} as the title (second line, immediately after the
7074 source file name and pagenumber) when generating assembly listings.
7076 This directive affects subsequent pages, as well as the current page if
7077 it appears within ten lines of the top of a page.
7081 @section @code{.type}
7083 This directive is used to set the type of a symbol.
7087 @c only print the extra heading if both COFF and ELF are set
7088 @subheading COFF Version
7091 @cindex COFF symbol type
7092 @cindex symbol type, COFF
7093 @cindex @code{type} directive (COFF version)
7094 For COFF targets, this directive is permitted only within
7095 @code{.def}/@code{.endef} pairs. It is used like this:
7101 This records the integer @var{int} as the type attribute of a symbol table
7108 @c only print the extra heading if both COFF and ELF are set
7109 @subheading ELF Version
7112 @cindex ELF symbol type
7113 @cindex symbol type, ELF
7114 @cindex @code{type} directive (ELF version)
7115 For ELF targets, the @code{.type} directive is used like this:
7118 .type @var{name} , @var{type description}
7121 This sets the type of symbol @var{name} to be either a
7122 function symbol or an object symbol. There are five different syntaxes
7123 supported for the @var{type description} field, in order to provide
7124 compatibility with various other assemblers.
7126 Because some of the characters used in these syntaxes (such as @samp{@@} and
7127 @samp{#}) are comment characters for some architectures, some of the syntaxes
7128 below do not work on all architectures. The first variant will be accepted by
7129 the GNU assembler on all architectures so that variant should be used for
7130 maximum portability, if you do not need to assemble your code with other
7133 The syntaxes supported are:
7136 .type <name> STT_<TYPE_IN_UPPER_CASE>
7137 .type <name>,#<type>
7138 .type <name>,@@<type>
7139 .type <name>,%<type>
7140 .type <name>,"<type>"
7143 The types supported are:
7148 Mark the symbol as being a function name.
7151 @itemx gnu_indirect_function
7152 Mark the symbol as an indirect function when evaluated during reloc
7153 processing. (This is only supported on assemblers targeting GNU systems).
7157 Mark the symbol as being a data object.
7161 Mark the symbol as being a thread-local data object.
7165 Mark the symbol as being a common data object.
7169 Does not mark the symbol in any way. It is supported just for completeness.
7171 @item gnu_unique_object
7172 Marks the symbol as being a globally unique data object. The dynamic linker
7173 will make sure that in the entire process there is just one symbol with this
7174 name and type in use. (This is only supported on assemblers targeting GNU
7179 Note: Some targets support extra types in addition to those listed above.
7185 @section @code{.uleb128 @var{expressions}}
7187 @cindex @code{uleb128} directive
7188 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7189 compact, variable length representation of numbers used by the DWARF
7190 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7194 @section @code{.val @var{addr}}
7196 @cindex @code{val} directive
7197 @cindex COFF value attribute
7198 @cindex value attribute, COFF
7199 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7200 records the address @var{addr} as the value attribute of a symbol table
7206 @section @code{.version "@var{string}"}
7208 @cindex @code{version} directive
7209 This directive creates a @code{.note} section and places into it an ELF
7210 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7215 @section @code{.vtable_entry @var{table}, @var{offset}}
7217 @cindex @code{vtable_entry} directive
7218 This directive finds or creates a symbol @code{table} and creates a
7219 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7222 @section @code{.vtable_inherit @var{child}, @var{parent}}
7224 @cindex @code{vtable_inherit} directive
7225 This directive finds the symbol @code{child} and finds or creates the symbol
7226 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7227 parent whose addend is the value of the child symbol. As a special case the
7228 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7232 @section @code{.warning "@var{string}"}
7233 @cindex warning directive
7234 Similar to the directive @code{.error}
7235 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7238 @section @code{.weak @var{names}}
7240 @cindex @code{weak} directive
7241 This directive sets the weak attribute on the comma separated list of symbol
7242 @code{names}. If the symbols do not already exist, they will be created.
7244 On COFF targets other than PE, weak symbols are a GNU extension. This
7245 directive sets the weak attribute on the comma separated list of symbol
7246 @code{names}. If the symbols do not already exist, they will be created.
7248 On the PE target, weak symbols are supported natively as weak aliases.
7249 When a weak symbol is created that is not an alias, GAS creates an
7250 alternate symbol to hold the default value.
7253 @section @code{.weakref @var{alias}, @var{target}}
7255 @cindex @code{weakref} directive
7256 This directive creates an alias to the target symbol that enables the symbol to
7257 be referenced with weak-symbol semantics, but without actually making it weak.
7258 If direct references or definitions of the symbol are present, then the symbol
7259 will not be weak, but if all references to it are through weak references, the
7260 symbol will be marked as weak in the symbol table.
7262 The effect is equivalent to moving all references to the alias to a separate
7263 assembly source file, renaming the alias to the symbol in it, declaring the
7264 symbol as weak there, and running a reloadable link to merge the object files
7265 resulting from the assembly of the new source file and the old source file that
7266 had the references to the alias removed.
7268 The alias itself never makes to the symbol table, and is entirely handled
7269 within the assembler.
7272 @section @code{.word @var{expressions}}
7274 @cindex @code{word} directive
7275 This directive expects zero or more @var{expressions}, of any section,
7276 separated by commas.
7279 For each expression, @command{@value{AS}} emits a 32-bit number.
7282 For each expression, @command{@value{AS}} emits a 16-bit number.
7287 The size of the number emitted, and its byte order,
7288 depend on what target computer the assembly is for.
7291 @c on sparc the "special treatment to support compilers" doesn't
7292 @c happen---32-bit addressability, period; no long/short jumps.
7293 @ifset DIFF-TBL-KLUGE
7294 @cindex difference tables altered
7295 @cindex altered difference tables
7297 @emph{Warning: Special Treatment to support Compilers}
7301 Machines with a 32-bit address space, but that do less than 32-bit
7302 addressing, require the following special treatment. If the machine of
7303 interest to you does 32-bit addressing (or doesn't require it;
7304 @pxref{Machine Dependencies}), you can ignore this issue.
7307 In order to assemble compiler output into something that works,
7308 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7309 Directives of the form @samp{.word sym1-sym2} are often emitted by
7310 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7311 directive of the form @samp{.word sym1-sym2}, and the difference between
7312 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7313 creates a @dfn{secondary jump table}, immediately before the next label.
7314 This secondary jump table is preceded by a short-jump to the
7315 first byte after the secondary table. This short-jump prevents the flow
7316 of control from accidentally falling into the new table. Inside the
7317 table is a long-jump to @code{sym2}. The original @samp{.word}
7318 contains @code{sym1} minus the address of the long-jump to
7321 If there were several occurrences of @samp{.word sym1-sym2} before the
7322 secondary jump table, all of them are adjusted. If there was a
7323 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7324 long-jump to @code{sym4} is included in the secondary jump table,
7325 and the @code{.word} directives are adjusted to contain @code{sym3}
7326 minus the address of the long-jump to @code{sym4}; and so on, for as many
7327 entries in the original jump table as necessary.
7330 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7331 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7332 assembly language programmers.
7335 @c end DIFF-TBL-KLUGE
7337 @ifclear no-space-dir
7339 @section @code{.zero @var{size}}
7341 @cindex @code{zero} directive
7342 @cindex filling memory with zero bytes
7343 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7344 expression. This directive is actually an alias for the @samp{.skip} directive
7345 so in can take an optional second argument of the value to store in the bytes
7346 instead of zero. Using @samp{.zero} in this way would be confusing however.
7351 @section @code{.2byte @var{expression} [, @var{expression}]*}
7352 @cindex @code{2byte} directive
7353 @cindex two-byte integer
7354 @cindex integer, 2-byte
7356 This directive expects zero or more expressions, separated by commas. If there
7357 are no expressions then the directive does nothing. Otherwise each expression
7358 is evaluated in turn and placed in the next two bytes of the current output
7359 section, using the endian model of the target. If an expression will not fit
7360 in two bytes, a warning message is displayed and the least significant two
7361 bytes of the expression's value are used. If an expression cannot be evaluated
7362 at assembly time then relocations will be generated in order to compute the
7365 This directive does not apply any alignment before or after inserting the
7366 values. As a result of this, if relocations are generated, they may be
7367 different from those used for inserting values with a guaranteed alignment.
7369 This directive is only available for ELF targets,
7372 @section @code{.4byte @var{expression} [, @var{expression}]*}
7373 @cindex @code{4byte} directive
7374 @cindex four-byte integer
7375 @cindex integer, 4-byte
7377 Like the @option{.2byte} directive, except that it inserts unaligned, four byte
7378 long values into the output.
7381 @section @code{.8byte @var{expression} [, @var{expression}]*}
7382 @cindex @code{8byte} directive
7383 @cindex eight-byte integer
7384 @cindex integer, 8-byte
7386 Like the @option{.2byte} directive, except that it inserts unaligned, eight
7387 byte long bignum values into the output.
7392 @section Deprecated Directives
7394 @cindex deprecated directives
7395 @cindex obsolescent directives
7396 One day these directives won't work.
7397 They are included for compatibility with older assemblers.
7404 @node Object Attributes
7405 @chapter Object Attributes
7406 @cindex object attributes
7408 @command{@value{AS}} assembles source files written for a specific architecture
7409 into object files for that architecture. But not all object files are alike.
7410 Many architectures support incompatible variations. For instance, floating
7411 point arguments might be passed in floating point registers if the object file
7412 requires hardware floating point support---or floating point arguments might be
7413 passed in integer registers if the object file supports processors with no
7414 hardware floating point unit. Or, if two objects are built for different
7415 generations of the same architecture, the combination may require the
7416 newer generation at run-time.
7418 This information is useful during and after linking. At link time,
7419 @command{@value{LD}} can warn about incompatible object files. After link
7420 time, tools like @command{gdb} can use it to process the linked file
7423 Compatibility information is recorded as a series of object attributes. Each
7424 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7425 string, and indicates who sets the meaning of the tag. The tag is an integer,
7426 and indicates what property the attribute describes. The value may be a string
7427 or an integer, and indicates how the property affects this object. Missing
7428 attributes are the same as attributes with a zero value or empty string value.
7430 Object attributes were developed as part of the ABI for the ARM Architecture.
7431 The file format is documented in @cite{ELF for the ARM Architecture}.
7434 * GNU Object Attributes:: @sc{gnu} Object Attributes
7435 * Defining New Object Attributes:: Defining New Object Attributes
7438 @node GNU Object Attributes
7439 @section @sc{gnu} Object Attributes
7441 The @code{.gnu_attribute} directive records an object attribute
7442 with vendor @samp{gnu}.
7444 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7445 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7446 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7447 2} is set for architecture-independent attributes and clear for
7448 architecture-dependent ones.
7450 @subsection Common @sc{gnu} attributes
7452 These attributes are valid on all architectures.
7455 @item Tag_compatibility (32)
7456 The compatibility attribute takes an integer flag value and a vendor name. If
7457 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7458 then the file is only compatible with the named toolchain. If it is greater
7459 than 1, the file can only be processed by other toolchains under some private
7460 arrangement indicated by the flag value and the vendor name.
7463 @subsection MIPS Attributes
7466 @item Tag_GNU_MIPS_ABI_FP (4)
7467 The floating-point ABI used by this object file. The value will be:
7471 0 for files not affected by the floating-point ABI.
7473 1 for files using the hardware floating-point ABI with a standard
7474 double-precision FPU.
7476 2 for files using the hardware floating-point ABI with a single-precision FPU.
7478 3 for files using the software floating-point ABI.
7480 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7481 floating-point registers, 32-bit general-purpose registers and increased the
7482 number of callee-saved floating-point registers.
7484 5 for files using the hardware floating-point ABI with a double-precision FPU
7485 with either 32-bit or 64-bit floating-point registers and 32-bit
7486 general-purpose registers.
7488 6 for files using the hardware floating-point ABI with 64-bit floating-point
7489 registers and 32-bit general-purpose registers.
7491 7 for files using the hardware floating-point ABI with 64-bit floating-point
7492 registers, 32-bit general-purpose registers and a rule that forbids the
7493 direct use of odd-numbered single-precision floating-point registers.
7497 @subsection PowerPC Attributes
7500 @item Tag_GNU_Power_ABI_FP (4)
7501 The floating-point ABI used by this object file. The value will be:
7505 0 for files not affected by the floating-point ABI.
7507 1 for files using double-precision hardware floating-point ABI.
7509 2 for files using the software floating-point ABI.
7511 3 for files using single-precision hardware floating-point ABI.
7514 @item Tag_GNU_Power_ABI_Vector (8)
7515 The vector ABI used by this object file. The value will be:
7519 0 for files not affected by the vector ABI.
7521 1 for files using general purpose registers to pass vectors.
7523 2 for files using AltiVec registers to pass vectors.
7525 3 for files using SPE registers to pass vectors.
7529 @subsection IBM z Systems Attributes
7532 @item Tag_GNU_S390_ABI_Vector (8)
7533 The vector ABI used by this object file. The value will be:
7537 0 for files not affected by the vector ABI.
7539 1 for files using software vector ABI.
7541 2 for files using hardware vector ABI.
7545 @node Defining New Object Attributes
7546 @section Defining New Object Attributes
7548 If you want to define a new @sc{gnu} object attribute, here are the places you
7549 will need to modify. New attributes should be discussed on the @samp{binutils}
7554 This manual, which is the official register of attributes.
7556 The header for your architecture @file{include/elf}, to define the tag.
7558 The @file{bfd} support file for your architecture, to merge the attribute
7559 and issue any appropriate link warnings.
7561 Test cases in @file{ld/testsuite} for merging and link warnings.
7563 @file{binutils/readelf.c} to display your attribute.
7565 GCC, if you want the compiler to mark the attribute automatically.
7571 @node Machine Dependencies
7572 @chapter Machine Dependent Features
7574 @cindex machine dependencies
7575 The machine instruction sets are (almost by definition) different on
7576 each machine where @command{@value{AS}} runs. Floating point representations
7577 vary as well, and @command{@value{AS}} often supports a few additional
7578 directives or command-line options for compatibility with other
7579 assemblers on a particular platform. Finally, some versions of
7580 @command{@value{AS}} support special pseudo-instructions for branch
7583 This chapter discusses most of these differences, though it does not
7584 include details on any machine's instruction set. For details on that
7585 subject, see the hardware manufacturer's manual.
7589 * AArch64-Dependent:: AArch64 Dependent Features
7592 * Alpha-Dependent:: Alpha Dependent Features
7595 * ARC-Dependent:: ARC Dependent Features
7598 * ARM-Dependent:: ARM Dependent Features
7601 * AVR-Dependent:: AVR Dependent Features
7604 * Blackfin-Dependent:: Blackfin Dependent Features
7607 * CR16-Dependent:: CR16 Dependent Features
7610 * CRIS-Dependent:: CRIS Dependent Features
7613 * C-SKY-Dependent:: C-SKY Dependent Features
7616 * D10V-Dependent:: D10V Dependent Features
7619 * D30V-Dependent:: D30V Dependent Features
7622 * Epiphany-Dependent:: EPIPHANY Dependent Features
7625 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7628 * HPPA-Dependent:: HPPA Dependent Features
7631 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7634 * IA-64-Dependent:: Intel IA-64 Dependent Features
7637 * IP2K-Dependent:: IP2K Dependent Features
7640 * LM32-Dependent:: LM32 Dependent Features
7643 * M32C-Dependent:: M32C Dependent Features
7646 * M32R-Dependent:: M32R Dependent Features
7649 * M68K-Dependent:: M680x0 Dependent Features
7652 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7655 * S12Z-Dependent:: S12Z Dependent Features
7658 * Meta-Dependent :: Meta Dependent Features
7661 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7664 * MIPS-Dependent:: MIPS Dependent Features
7667 * MMIX-Dependent:: MMIX Dependent Features
7670 * MSP430-Dependent:: MSP430 Dependent Features
7673 * NDS32-Dependent:: Andes NDS32 Dependent Features
7676 * NiosII-Dependent:: Altera Nios II Dependent Features
7679 * NS32K-Dependent:: NS32K Dependent Features
7682 * PDP-11-Dependent:: PDP-11 Dependent Features
7685 * PJ-Dependent:: picoJava Dependent Features
7688 * PPC-Dependent:: PowerPC Dependent Features
7691 * PRU-Dependent:: PRU Dependent Features
7694 * RISC-V-Dependent:: RISC-V Dependent Features
7697 * RL78-Dependent:: RL78 Dependent Features
7700 * RX-Dependent:: RX Dependent Features
7703 * S/390-Dependent:: IBM S/390 Dependent Features
7706 * SCORE-Dependent:: SCORE Dependent Features
7709 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7712 * Sparc-Dependent:: SPARC Dependent Features
7715 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7718 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7721 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7724 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7727 * V850-Dependent:: V850 Dependent Features
7730 * Vax-Dependent:: VAX Dependent Features
7733 * Visium-Dependent:: Visium Dependent Features
7736 * WebAssembly-Dependent:: WebAssembly Dependent Features
7739 * XGATE-Dependent:: XGATE Dependent Features
7742 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7745 * Xtensa-Dependent:: Xtensa Dependent Features
7748 * Z80-Dependent:: Z80 Dependent Features
7751 * Z8000-Dependent:: Z8000 Dependent Features
7758 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7759 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7760 @c peculiarity: to preserve cross-references, there must be a node called
7761 @c "Machine Dependencies". Hence the conditional nodenames in each
7762 @c major node below. Node defaulting in makeinfo requires adjacency of
7763 @c node and sectioning commands; hence the repetition of @chapter BLAH
7764 @c in both conditional blocks.
7767 @include c-aarch64.texi
7771 @include c-alpha.texi
7787 @include c-bfin.texi
7791 @include c-cr16.texi
7795 @include c-cris.texi
7799 @include c-csky.texi
7804 @node Machine Dependencies
7805 @chapter Machine Dependent Features
7807 The machine instruction sets are different on each Renesas chip family,
7808 and there are also some syntax differences among the families. This
7809 chapter describes the specific @command{@value{AS}} features for each
7813 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7814 * SH-Dependent:: Renesas SH Dependent Features
7821 @include c-d10v.texi
7825 @include c-d30v.texi
7829 @include c-epiphany.texi
7833 @include c-h8300.texi
7837 @include c-hppa.texi
7841 @include c-i386.texi
7845 @include c-ia64.texi
7849 @include c-ip2k.texi
7853 @include c-lm32.texi
7857 @include c-m32c.texi
7861 @include c-m32r.texi
7865 @include c-m68k.texi
7869 @include c-m68hc11.texi
7873 @include c-s12z.texi
7877 @include c-metag.texi
7881 @include c-microblaze.texi
7885 @include c-mips.texi
7889 @include c-mmix.texi
7893 @include c-msp430.texi
7897 @include c-nds32.texi
7901 @include c-nios2.texi
7905 @include c-ns32k.texi
7909 @include c-pdp11.texi
7925 @include c-riscv.texi
7929 @include c-rl78.texi
7937 @include c-s390.texi
7941 @include c-score.texi
7949 @include c-sparc.texi
7953 @include c-tic54x.texi
7957 @include c-tic6x.texi
7961 @include c-tilegx.texi
7965 @include c-tilepro.texi
7969 @include c-v850.texi
7977 @include c-visium.texi
7981 @include c-wasm32.texi
7985 @include c-xgate.texi
7989 @include c-xstormy16.texi
7993 @include c-xtensa.texi
8005 @c reverse effect of @down at top of generic Machine-Dep chapter
8009 @node Reporting Bugs
8010 @chapter Reporting Bugs
8011 @cindex bugs in assembler
8012 @cindex reporting bugs in assembler
8014 Your bug reports play an essential role in making @command{@value{AS}} reliable.
8016 Reporting a bug may help you by bringing a solution to your problem, or it may
8017 not. But in any case the principal function of a bug report is to help the
8018 entire community by making the next version of @command{@value{AS}} work better.
8019 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
8021 In order for a bug report to serve its purpose, you must include the
8022 information that enables us to fix the bug.
8025 * Bug Criteria:: Have you found a bug?
8026 * Bug Reporting:: How to report bugs
8030 @section Have You Found a Bug?
8031 @cindex bug criteria
8033 If you are not sure whether you have found a bug, here are some guidelines:
8036 @cindex fatal signal
8037 @cindex assembler crash
8038 @cindex crash of assembler
8040 If the assembler gets a fatal signal, for any input whatever, that is a
8041 @command{@value{AS}} bug. Reliable assemblers never crash.
8043 @cindex error on valid input
8045 If @command{@value{AS}} produces an error message for valid input, that is a bug.
8047 @cindex invalid input
8049 If @command{@value{AS}} does not produce an error message for invalid input, that
8050 is a bug. However, you should note that your idea of ``invalid input'' might
8051 be our idea of ``an extension'' or ``support for traditional practice''.
8054 If you are an experienced user of assemblers, your suggestions for improvement
8055 of @command{@value{AS}} are welcome in any case.
8059 @section How to Report Bugs
8061 @cindex assembler bugs, reporting
8063 A number of companies and individuals offer support for @sc{gnu} products. If
8064 you obtained @command{@value{AS}} from a support organization, we recommend you
8065 contact that organization first.
8067 You can find contact information for many support companies and
8068 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8072 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8076 The fundamental principle of reporting bugs usefully is this:
8077 @strong{report all the facts}. If you are not sure whether to state a
8078 fact or leave it out, state it!
8080 Often people omit facts because they think they know what causes the problem
8081 and assume that some details do not matter. Thus, you might assume that the
8082 name of a symbol you use in an example does not matter. Well, probably it does
8083 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8084 happens to fetch from the location where that name is stored in memory;
8085 perhaps, if the name were different, the contents of that location would fool
8086 the assembler into doing the right thing despite the bug. Play it safe and
8087 give a specific, complete example. That is the easiest thing for you to do,
8088 and the most helpful.
8090 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8091 it is new to us. Therefore, always write your bug reports on the assumption
8092 that the bug has not been reported previously.
8094 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8095 bell?'' This cannot help us fix a bug, so it is basically useless. We
8096 respond by asking for enough details to enable us to investigate.
8097 You might as well expedite matters by sending them to begin with.
8099 To enable us to fix the bug, you should include all these things:
8103 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8104 it with the @samp{--version} argument.
8106 Without this, we will not know whether there is any point in looking for
8107 the bug in the current version of @command{@value{AS}}.
8110 Any patches you may have applied to the @command{@value{AS}} source.
8113 The type of machine you are using, and the operating system name and
8117 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8121 The command arguments you gave the assembler to assemble your example and
8122 observe the bug. To guarantee you will not omit something important, list them
8123 all. A copy of the Makefile (or the output from make) is sufficient.
8125 If we were to try to guess the arguments, we would probably guess wrong
8126 and then we might not encounter the bug.
8129 A complete input file that will reproduce the bug. If the bug is observed when
8130 the assembler is invoked via a compiler, send the assembler source, not the
8131 high level language source. Most compilers will produce the assembler source
8132 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8133 the options @samp{-v --save-temps}; this will save the assembler source in a
8134 file with an extension of @file{.s}, and also show you exactly how
8135 @command{@value{AS}} is being run.
8138 A description of what behavior you observe that you believe is
8139 incorrect. For example, ``It gets a fatal signal.''
8141 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8142 will certainly notice it. But if the bug is incorrect output, we might not
8143 notice unless it is glaringly wrong. You might as well not give us a chance to
8146 Even if the problem you experience is a fatal signal, you should still say so
8147 explicitly. Suppose something strange is going on, such as, your copy of
8148 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8149 library on your system. (This has happened!) Your copy might crash and ours
8150 would not. If you told us to expect a crash, then when ours fails to crash, we
8151 would know that the bug was not happening for us. If you had not told us to
8152 expect a crash, then we would not be able to draw any conclusion from our
8156 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8157 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8158 option. Always send diffs from the old file to the new file. If you even
8159 discuss something in the @command{@value{AS}} source, refer to it by context, not
8162 The line numbers in our development sources will not match those in your
8163 sources. Your line numbers would convey no useful information to us.
8166 Here are some things that are not necessary:
8170 A description of the envelope of the bug.
8172 Often people who encounter a bug spend a lot of time investigating
8173 which changes to the input file will make the bug go away and which
8174 changes will not affect it.
8176 This is often time consuming and not very useful, because the way we
8177 will find the bug is by running a single example under the debugger
8178 with breakpoints, not by pure deduction from a series of examples.
8179 We recommend that you save your time for something else.
8181 Of course, if you can find a simpler example to report @emph{instead}
8182 of the original one, that is a convenience for us. Errors in the
8183 output will be easier to spot, running under the debugger will take
8184 less time, and so on.
8186 However, simplification is not vital; if you do not want to do this,
8187 report the bug anyway and send us the entire test case you used.
8190 A patch for the bug.
8192 A patch for the bug does help us if it is a good one. But do not omit
8193 the necessary information, such as the test case, on the assumption that
8194 a patch is all we need. We might see problems with your patch and decide
8195 to fix the problem another way, or we might not understand it at all.
8197 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8198 construct an example that will make the program follow a certain path through
8199 the code. If you do not send us the example, we will not be able to construct
8200 one, so we will not be able to verify that the bug is fixed.
8202 And if we cannot understand what bug you are trying to fix, or why your
8203 patch should be an improvement, we will not install it. A test case will
8204 help us to understand.
8207 A guess about what the bug is or what it depends on.
8209 Such guesses are usually wrong. Even we cannot guess right about such
8210 things without first using the debugger to find the facts.
8213 @node Acknowledgements
8214 @chapter Acknowledgements
8216 If you have contributed to GAS and your name isn't listed here,
8217 it is not meant as a slight. We just don't know about it. Send mail to the
8218 maintainer, and we'll correct the situation. Currently
8220 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8222 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8225 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8226 information and the 68k series machines, most of the preprocessing pass, and
8227 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8229 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8230 many bug fixes, including merging support for several processors, breaking GAS
8231 up to handle multiple object file format back ends (including heavy rewrite,
8232 testing, an integration of the coff and b.out back ends), adding configuration
8233 including heavy testing and verification of cross assemblers and file splits
8234 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8235 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8236 port (including considerable amounts of reverse engineering), a SPARC opcode
8237 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8238 assertions and made them work, much other reorganization, cleanup, and lint.
8240 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8241 in format-specific I/O modules.
8243 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8244 has done much work with it since.
8246 The Intel 80386 machine description was written by Eliot Dresselhaus.
8248 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8250 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8251 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8253 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8254 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8255 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8256 support a.out format.
8258 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8259 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8260 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8261 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8264 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8265 simplified the configuration of which versions accept which directives. He
8266 updated the 68k machine description so that Motorola's opcodes always produced
8267 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8268 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8269 cross-compilation support, and one bug in relaxation that took a week and
8270 required the proverbial one-bit fix.
8272 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8273 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8274 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8275 PowerPC assembler, and made a few other minor patches.
8277 Steve Chamberlain made GAS able to generate listings.
8279 Hewlett-Packard contributed support for the HP9000/300.
8281 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8282 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8283 formats). This work was supported by both the Center for Software Science at
8284 the University of Utah and Cygnus Support.
8286 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8287 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8288 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8289 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8290 and some initial 64-bit support).
8292 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8294 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8295 support for openVMS/Alpha.
8297 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8300 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8301 Inc.@: added support for Xtensa processors.
8303 Several engineers at Cygnus Support have also provided many small bug fixes and
8304 configuration enhancements.
8306 Jon Beniston added support for the Lattice Mico32 architecture.
8308 Many others have contributed large or small bugfixes and enhancements. If
8309 you have contributed significant work and are not mentioned on this list, and
8310 want to be, let us know. Some of the history has been lost; we are not
8311 intentionally leaving anyone out.
8313 @node GNU Free Documentation License
8314 @appendix GNU Free Documentation License
8318 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob