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{-minsn32}] [@b{-mno-insn32}]
450 [@b{-mfix7000}] [@b{-mno-fix7000}]
451 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
452 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
453 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
454 [@b{-mdebug}] [@b{-no-mdebug}]
455 [@b{-mpdr}] [@b{-mno-pdr}]
459 @emph{Target MMIX options:}
460 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
461 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
462 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
463 [@b{--linker-allocated-gregs}]
467 @emph{Target Nios II options:}
468 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
473 @emph{Target NDS32 options:}
474 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
475 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
476 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
477 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
478 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
479 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
480 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
485 @emph{Target PDP11 options:}
486 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
487 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
488 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
492 @emph{Target picoJava options:}
497 @emph{Target PowerPC options:}
499 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
500 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mgekko}|
501 @b{-mbroadway}|@b{-mppc64}|@b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|
502 @b{-me6500}|@b{-mppc64bridge}|@b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|
503 @b{-mpower6}|@b{-mpwr6}|@b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
504 @b{-mcell}|@b{-mspe}|@b{-mspe2}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
505 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
506 [@b{-mregnames}|@b{-mno-regnames}]
507 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
508 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
509 [@b{-msolaris}|@b{-mno-solaris}]
510 [@b{-nops=@var{count}}]
514 @emph{Target PRU options:}
517 [@b{-mno-warn-regname-label}]
521 @emph{Target RISC-V options:}
522 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
523 [@b{-march}=@var{ISA}]
524 [@b{-mabi}=@var{ABI}]
528 @emph{Target RL78 options:}
530 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
534 @emph{Target RX options:}
535 [@b{-mlittle-endian}|@b{-mbig-endian}]
536 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
537 [@b{-muse-conventional-section-names}]
538 [@b{-msmall-data-limit}]
541 [@b{-mint-register=@var{number}}]
542 [@b{-mgcc-abi}|@b{-mrx-abi}]
546 @emph{Target s390 options:}
547 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
548 [@b{-mregnames}|@b{-mno-regnames}]
549 [@b{-mwarn-areg-zero}]
553 @emph{Target SCORE options:}
554 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
555 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
556 [@b{-march=score7}][@b{-march=score3}]
557 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
561 @emph{Target SPARC options:}
562 @c The order here is important. See c-sparc.texi.
563 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
564 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
565 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
566 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
567 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
568 @b{-Asparcvisr}|@b{-Asparc5}]
569 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
570 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
571 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
572 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
573 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
574 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
577 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
581 @emph{Target TIC54X options:}
582 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
583 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
587 @emph{Target TIC6X options:}
588 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
589 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
590 [@b{-mpic}|@b{-mno-pic}]
594 @emph{Target TILE-Gx options:}
595 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
598 @c TILEPro has no machine-dependent assembler options
602 @emph{Target Visium options:}
603 [@b{-mtune=@var{arch}}]
607 @emph{Target Xtensa options:}
608 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
609 [@b{--[no-]absolute-literals}]
610 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
611 [@b{--[no-]transform}]
612 [@b{--rename-section} @var{oldname}=@var{newname}]
613 [@b{--[no-]trampolines}]
617 @emph{Target Z80 options:}
618 [@b{-z80}] [@b{-r800}]
619 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
620 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
621 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
622 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
623 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
624 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
628 @c Z8000 has no machine-dependent assembler options
637 @include at-file.texi
640 Turn on listings, in any of a variety of ways:
644 omit false conditionals
647 omit debugging directives
650 include general information, like @value{AS} version and options passed
653 include high-level source
659 include macro expansions
662 omit forms processing
668 set the name of the listing file
671 You may combine these options; for example, use @samp{-aln} for assembly
672 listing without forms processing. The @samp{=file} option, if used, must be
673 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
676 Begin in alternate macro mode.
678 @xref{Altmacro,,@code{.altmacro}}.
681 @item --compress-debug-sections
682 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
683 ELF ABI. The resulting object file may not be compatible with older
684 linkers and object file utilities. Note if compression would make a
685 given section @emph{larger} then it is not compressed.
688 @cindex @samp{--compress-debug-sections=} option
689 @item --compress-debug-sections=none
690 @itemx --compress-debug-sections=zlib
691 @itemx --compress-debug-sections=zlib-gnu
692 @itemx --compress-debug-sections=zlib-gabi
693 These options control how DWARF debug sections are compressed.
694 @option{--compress-debug-sections=none} is equivalent to
695 @option{--nocompress-debug-sections}.
696 @option{--compress-debug-sections=zlib} and
697 @option{--compress-debug-sections=zlib-gabi} are equivalent to
698 @option{--compress-debug-sections}.
699 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
700 sections using zlib. The debug sections are renamed to begin with
701 @samp{.zdebug}. Note if compression would make a given section
702 @emph{larger} then it is not compressed nor renamed.
706 @item --nocompress-debug-sections
707 Do not compress DWARF debug sections. This is usually the default for all
708 targets except the x86/x86_64, but a configure time option can be used to
712 Ignored. This option is accepted for script compatibility with calls to
715 @item --debug-prefix-map @var{old}=@var{new}
716 When assembling files in directory @file{@var{old}}, record debugging
717 information describing them as in @file{@var{new}} instead.
719 @item --defsym @var{sym}=@var{value}
720 Define the symbol @var{sym} to be @var{value} before assembling the input file.
721 @var{value} must be an integer constant. As in C, a leading @samp{0x}
722 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
723 value. The value of the symbol can be overridden inside a source file via the
724 use of a @code{.set} pseudo-op.
727 ``fast''---skip whitespace and comment preprocessing (assume source is
732 Generate debugging information for each assembler source line using whichever
733 debug format is preferred by the target. This currently means either STABS,
737 Generate stabs debugging information for each assembler line. This
738 may help debugging assembler code, if the debugger can handle it.
741 Generate stabs debugging information for each assembler line, with GNU
742 extensions that probably only gdb can handle, and that could make other
743 debuggers crash or refuse to read your program. This
744 may help debugging assembler code. Currently the only GNU extension is
745 the location of the current working directory at assembling time.
748 Generate DWARF2 debugging information for each assembler line. This
749 may help debugging assembler code, if the debugger can handle it. Note---this
750 option is only supported by some targets, not all of them.
752 @item --gdwarf-sections
753 Instead of creating a .debug_line section, create a series of
754 .debug_line.@var{foo} sections where @var{foo} is the name of the
755 corresponding code section. For example a code section called @var{.text.func}
756 will have its dwarf line number information placed into a section called
757 @var{.debug_line.text.func}. If the code section is just called @var{.text}
758 then debug line section will still be called just @var{.debug_line} without any
762 @item --size-check=error
763 @itemx --size-check=warning
764 Issue an error or warning for invalid ELF .size directive.
766 @item --elf-stt-common=no
767 @itemx --elf-stt-common=yes
768 These options control whether the ELF assembler should generate common
769 symbols with the @code{STT_COMMON} type. The default can be controlled
770 by a configure option @option{--enable-elf-stt-common}.
772 @item --generate-missing-build-notes=yes
773 @itemx --generate-missing-build-notes=no
774 These options control whether the ELF assembler should generate GNU Build
775 attribute notes if none are present in the input sources.
776 The default can be controlled by the @option{--enable-generate-build-notes}
782 Print a summary of the command-line options and exit.
785 Print a summary of all target specific options and exit.
788 Add directory @var{dir} to the search list for @code{.include} directives.
791 Don't warn about signed overflow.
794 @ifclear DIFF-TBL-KLUGE
795 This option is accepted but has no effect on the @value{TARGET} family.
797 @ifset DIFF-TBL-KLUGE
798 Issue warnings when difference tables altered for long displacements.
803 Keep (in the symbol table) local symbols. These symbols start with
804 system-specific local label prefixes, typically @samp{.L} for ELF systems
805 or @samp{L} for traditional a.out systems.
810 @item --listing-lhs-width=@var{number}
811 Set the maximum width, in words, of the output data column for an assembler
812 listing to @var{number}.
814 @item --listing-lhs-width2=@var{number}
815 Set the maximum width, in words, of the output data column for continuation
816 lines in an assembler listing to @var{number}.
818 @item --listing-rhs-width=@var{number}
819 Set the maximum width of an input source line, as displayed in a listing, to
822 @item --listing-cont-lines=@var{number}
823 Set the maximum number of lines printed in a listing for a single line of input
826 @item --no-pad-sections
827 Stop the assembler for padding the ends of output sections to the alignment
828 of that section. The default is to pad the sections, but this can waste space
829 which might be needed on targets which have tight memory constraints.
831 @item -o @var{objfile}
832 Name the object-file output from @command{@value{AS}} @var{objfile}.
835 Fold the data section into the text section.
837 @item --hash-size=@var{number}
838 Set the default size of GAS's hash tables to a prime number close to
839 @var{number}. Increasing this value can reduce the length of time it takes the
840 assembler to perform its tasks, at the expense of increasing the assembler's
841 memory requirements. Similarly reducing this value can reduce the memory
842 requirements at the expense of speed.
844 @item --reduce-memory-overheads
845 This option reduces GAS's memory requirements, at the expense of making the
846 assembly processes slower. Currently this switch is a synonym for
847 @samp{--hash-size=4051}, but in the future it may have other effects as well.
850 @item --sectname-subst
851 Honor substitution sequences in section names.
853 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
858 Print the maximum space (in bytes) and total time (in seconds) used by
861 @item --strip-local-absolute
862 Remove local absolute symbols from the outgoing symbol table.
866 Print the @command{as} version.
869 Print the @command{as} version and exit.
873 Suppress warning messages.
875 @item --fatal-warnings
876 Treat warnings as errors.
879 Don't suppress warning messages or treat them as errors.
888 Generate an object file even after errors.
890 @item -- | @var{files} @dots{}
891 Standard input, or source files to assemble.
899 @xref{AArch64 Options}, for the options available when @value{AS} is configured
900 for the 64-bit mode of the ARM Architecture (AArch64).
905 The following options are available when @value{AS} is configured for the
906 64-bit mode of the ARM Architecture (AArch64).
909 @include c-aarch64.texi
910 @c ended inside the included file
918 @xref{Alpha Options}, for the options available when @value{AS} is configured
919 for an Alpha processor.
924 The following options are available when @value{AS} is configured for an Alpha
928 @include c-alpha.texi
929 @c ended inside the included file
936 The following options are available when @value{AS} is configured for an ARC
940 @item -mcpu=@var{cpu}
941 This option selects the core processor variant.
943 Select either big-endian (-EB) or little-endian (-EL) output.
945 Enable Code Density extenssion instructions.
950 The following options are available when @value{AS} is configured for the ARM
954 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
955 Specify which ARM processor variant is the target.
956 @item -march=@var{architecture}[+@var{extension}@dots{}]
957 Specify which ARM architecture variant is used by the target.
958 @item -mfpu=@var{floating-point-format}
959 Select which Floating Point architecture is the target.
960 @item -mfloat-abi=@var{abi}
961 Select which floating point ABI is in use.
963 Enable Thumb only instruction decoding.
964 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
965 Select which procedure calling convention is in use.
967 Select either big-endian (-EB) or little-endian (-EL) output.
968 @item -mthumb-interwork
969 Specify that the code has been generated with interworking between Thumb and
972 Turns on CodeComposer Studio assembly syntax compatibility mode.
974 Specify that PIC code has been generated.
982 @xref{Blackfin Options}, for the options available when @value{AS} is
983 configured for the Blackfin processor family.
988 The following options are available when @value{AS} is configured for
989 the Blackfin processor family.
993 @c ended inside the included file
1000 See the info pages for documentation of the CRIS-specific options.
1006 @xref{C-SKY Options}, for the options available when @value{AS} is
1007 configured for the C-SKY processor family.
1011 @c man begin OPTIONS
1012 The following options are available when @value{AS} is configured for
1013 the C-SKY processor family.
1015 @c man begin INCLUDE
1016 @include c-csky.texi
1017 @c ended inside the included file
1023 The following options are available when @value{AS} is configured for
1026 @cindex D10V optimization
1027 @cindex optimization, D10V
1029 Optimize output by parallelizing instructions.
1034 The following options are available when @value{AS} is configured for a D30V
1037 @cindex D30V optimization
1038 @cindex optimization, D30V
1040 Optimize output by parallelizing instructions.
1044 Warn when nops are generated.
1046 @cindex D30V nops after 32-bit multiply
1048 Warn when a nop after a 32-bit multiply instruction is generated.
1054 The following options are available when @value{AS} is configured for the
1055 Adapteva EPIPHANY series.
1058 @xref{Epiphany Options}, for the options available when @value{AS} is
1059 configured for an Epiphany processor.
1063 @c man begin OPTIONS
1064 The following options are available when @value{AS} is configured for
1065 an Epiphany processor.
1067 @c man begin INCLUDE
1068 @include c-epiphany.texi
1069 @c ended inside the included file
1077 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1078 for an H8/300 processor.
1082 @c man begin OPTIONS
1083 The following options are available when @value{AS} is configured for an H8/300
1086 @c man begin INCLUDE
1087 @include c-h8300.texi
1088 @c ended inside the included file
1096 @xref{i386-Options}, for the options available when @value{AS} is
1097 configured for an i386 processor.
1101 @c man begin OPTIONS
1102 The following options are available when @value{AS} is configured for
1105 @c man begin INCLUDE
1106 @include c-i386.texi
1107 @c ended inside the included file
1112 @c man begin OPTIONS
1114 The following options are available when @value{AS} is configured for the
1120 Specifies that the extended IP2022 instructions are allowed.
1123 Restores the default behaviour, which restricts the permitted instructions to
1124 just the basic IP2022 ones.
1130 The following options are available when @value{AS} is configured for the
1131 Renesas M32C and M16C processors.
1136 Assemble M32C instructions.
1139 Assemble M16C instructions (the default).
1142 Enable support for link-time relaxations.
1145 Support H'00 style hex constants in addition to 0x00 style.
1151 The following options are available when @value{AS} is configured for the
1152 Renesas M32R (formerly Mitsubishi M32R) series.
1157 Specify which processor in the M32R family is the target. The default
1158 is normally the M32R, but this option changes it to the M32RX.
1160 @item --warn-explicit-parallel-conflicts or --Wp
1161 Produce warning messages when questionable parallel constructs are
1164 @item --no-warn-explicit-parallel-conflicts or --Wnp
1165 Do not produce warning messages when questionable parallel constructs are
1172 The following options are available when @value{AS} is configured for the
1173 Motorola 68000 series.
1178 Shorten references to undefined symbols, to one word instead of two.
1180 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1181 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1182 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1183 Specify what processor in the 68000 family is the target. The default
1184 is normally the 68020, but this can be changed at configuration time.
1186 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1187 The target machine does (or does not) have a floating-point coprocessor.
1188 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1189 the basic 68000 is not compatible with the 68881, a combination of the
1190 two can be specified, since it's possible to do emulation of the
1191 coprocessor instructions with the main processor.
1193 @item -m68851 | -mno-68851
1194 The target machine does (or does not) have a memory-management
1195 unit coprocessor. The default is to assume an MMU for 68020 and up.
1203 @xref{Nios II Options}, for the options available when @value{AS} is configured
1204 for an Altera Nios II processor.
1208 @c man begin OPTIONS
1209 The following options are available when @value{AS} is configured for an
1210 Altera Nios II processor.
1212 @c man begin INCLUDE
1213 @include c-nios2.texi
1214 @c ended inside the included file
1220 For details about the PDP-11 machine dependent features options,
1221 see @ref{PDP-11-Options}.
1224 @item -mpic | -mno-pic
1225 Generate position-independent (or position-dependent) code. The
1226 default is @option{-mpic}.
1229 @itemx -mall-extensions
1230 Enable all instruction set extensions. This is the default.
1232 @item -mno-extensions
1233 Disable all instruction set extensions.
1235 @item -m@var{extension} | -mno-@var{extension}
1236 Enable (or disable) a particular instruction set extension.
1239 Enable the instruction set extensions supported by a particular CPU, and
1240 disable all other extensions.
1242 @item -m@var{machine}
1243 Enable the instruction set extensions supported by a particular machine
1244 model, and disable all other extensions.
1250 The following options are available when @value{AS} is configured for
1251 a picoJava processor.
1255 @cindex PJ endianness
1256 @cindex endianness, PJ
1257 @cindex big endian output, PJ
1259 Generate ``big endian'' format output.
1261 @cindex little endian output, PJ
1263 Generate ``little endian'' format output.
1271 @xref{PRU Options}, for the options available when @value{AS} is configured
1272 for a PRU processor.
1276 @c man begin OPTIONS
1277 The following options are available when @value{AS} is configured for a
1280 @c man begin INCLUDE
1282 @c ended inside the included file
1287 The following options are available when @value{AS} is configured for the
1288 Motorola 68HC11 or 68HC12 series.
1292 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1293 Specify what processor is the target. The default is
1294 defined by the configuration option when building the assembler.
1296 @item --xgate-ramoffset
1297 Instruct the linker to offset RAM addresses from S12X address space into
1298 XGATE address space.
1301 Specify to use the 16-bit integer ABI.
1304 Specify to use the 32-bit integer ABI.
1306 @item -mshort-double
1307 Specify to use the 32-bit double ABI.
1310 Specify to use the 64-bit double ABI.
1312 @item --force-long-branches
1313 Relative branches are turned into absolute ones. This concerns
1314 conditional branches, unconditional branches and branches to a
1317 @item -S | --short-branches
1318 Do not turn relative branches into absolute ones
1319 when the offset is out of range.
1321 @item --strict-direct-mode
1322 Do not turn the direct addressing mode into extended addressing mode
1323 when the instruction does not support direct addressing mode.
1325 @item --print-insn-syntax
1326 Print the syntax of instruction in case of error.
1328 @item --print-opcodes
1329 Print the list of instructions with syntax and then exit.
1331 @item --generate-example
1332 Print an example of instruction for each possible instruction and then exit.
1333 This option is only useful for testing @command{@value{AS}}.
1339 The following options are available when @command{@value{AS}} is configured
1340 for the SPARC architecture:
1343 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1344 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1345 Explicitly select a variant of the SPARC architecture.
1347 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1348 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1350 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1351 UltraSPARC extensions.
1353 @item -xarch=v8plus | -xarch=v8plusa
1354 For compatibility with the Solaris v9 assembler. These options are
1355 equivalent to -Av8plus and -Av8plusa, respectively.
1358 Warn when the assembler switches to another architecture.
1363 The following options are available when @value{AS} is configured for the 'c54x
1368 Enable extended addressing mode. All addresses and relocations will assume
1369 extended addressing (usually 23 bits).
1370 @item -mcpu=@var{CPU_VERSION}
1371 Sets the CPU version being compiled for.
1372 @item -merrors-to-file @var{FILENAME}
1373 Redirect error output to a file, for broken systems which don't support such
1374 behaviour in the shell.
1379 @c man begin OPTIONS
1380 The following options are available when @value{AS} is configured for
1385 This option sets the largest size of an object that can be referenced
1386 implicitly with the @code{gp} register. It is only accepted for targets that
1387 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1389 @cindex MIPS endianness
1390 @cindex endianness, MIPS
1391 @cindex big endian output, MIPS
1393 Generate ``big endian'' format output.
1395 @cindex little endian output, MIPS
1397 Generate ``little endian'' format output.
1415 Generate code for a particular MIPS Instruction Set Architecture level.
1416 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1417 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1418 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1419 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1420 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1421 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1422 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1423 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1424 MIPS64 Release 6 ISA processors, respectively.
1426 @item -march=@var{cpu}
1427 Generate code for a particular MIPS CPU.
1429 @item -mtune=@var{cpu}
1430 Schedule and tune for a particular MIPS CPU.
1434 Cause nops to be inserted if the read of the destination register
1435 of an mfhi or mflo instruction occurs in the following two instructions.
1438 @itemx -mno-fix-rm7000
1439 Cause nops to be inserted if a dmult or dmultu instruction is
1440 followed by a load instruction.
1444 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1445 section instead of the standard ELF .stabs sections.
1449 Control generation of @code{.pdr} sections.
1453 The register sizes are normally inferred from the ISA and ABI, but these
1454 flags force a certain group of registers to be treated as 32 bits wide at
1455 all times. @samp{-mgp32} controls the size of general-purpose registers
1456 and @samp{-mfp32} controls the size of floating-point registers.
1460 The register sizes are normally inferred from the ISA and ABI, but these
1461 flags force a certain group of registers to be treated as 64 bits wide at
1462 all times. @samp{-mgp64} controls the size of general-purpose registers
1463 and @samp{-mfp64} controls the size of floating-point registers.
1466 The register sizes are normally inferred from the ISA and ABI, but using
1467 this flag in combination with @samp{-mabi=32} enables an ABI variant
1468 which will operate correctly with floating-point registers which are
1472 @itemx -mno-odd-spreg
1473 Enable use of floating-point operations on odd-numbered single-precision
1474 registers when supported by the ISA. @samp{-mfpxx} implies
1475 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1479 Generate code for the MIPS 16 processor. This is equivalent to putting
1480 @code{.module mips16} at the start of the assembly file. @samp{-no-mips16}
1481 turns off this option.
1484 @itemx -mno-mips16e2
1485 Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent
1486 to putting @code{.module mips16e2} at the start of the assembly file.
1487 @samp{-mno-mips16e2} turns off this option.
1490 @itemx -mno-micromips
1491 Generate code for the microMIPS processor. This is equivalent to putting
1492 @code{.module micromips} at the start of the assembly file.
1493 @samp{-mno-micromips} turns off this option. This is equivalent to putting
1494 @code{.module nomicromips} at the start of the assembly file.
1497 @itemx -mno-smartmips
1498 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1499 equivalent to putting @code{.module smartmips} at the start of the assembly
1500 file. @samp{-mno-smartmips} turns off this option.
1504 Generate code for the MIPS-3D Application Specific Extension.
1505 This tells the assembler to accept MIPS-3D instructions.
1506 @samp{-no-mips3d} turns off this option.
1510 Generate code for the MDMX Application Specific Extension.
1511 This tells the assembler to accept MDMX instructions.
1512 @samp{-no-mdmx} turns off this option.
1516 Generate code for the DSP Release 1 Application Specific Extension.
1517 This tells the assembler to accept DSP Release 1 instructions.
1518 @samp{-mno-dsp} turns off this option.
1522 Generate code for the DSP Release 2 Application Specific Extension.
1523 This option implies @samp{-mdsp}.
1524 This tells the assembler to accept DSP Release 2 instructions.
1525 @samp{-mno-dspr2} turns off this option.
1529 Generate code for the DSP Release 3 Application Specific Extension.
1530 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1531 This tells the assembler to accept DSP Release 3 instructions.
1532 @samp{-mno-dspr3} turns off this option.
1536 Generate code for the MIPS SIMD Architecture Extension.
1537 This tells the assembler to accept MSA instructions.
1538 @samp{-mno-msa} turns off this option.
1542 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1543 This tells the assembler to accept XPA instructions.
1544 @samp{-mno-xpa} turns off this option.
1548 Generate code for the MT Application Specific Extension.
1549 This tells the assembler to accept MT instructions.
1550 @samp{-mno-mt} turns off this option.
1554 Generate code for the MCU Application Specific Extension.
1555 This tells the assembler to accept MCU instructions.
1556 @samp{-mno-mcu} turns off this option.
1560 Generate code for the MIPS cyclic redundancy check (CRC) Application
1561 Specific Extension. This tells the assembler to accept CRC instructions.
1562 @samp{-mno-crc} turns off this option.
1566 Generate code for the Global INValidate (GINV) Application Specific
1567 Extension. This tells the assembler to accept GINV instructions.
1568 @samp{-mno-ginv} turns off this option.
1570 @item -mloongson-mmi
1571 @itemx -mno-loongson-mmi
1572 Generate code for the Loongson MultiMedia extensions Instructions (MMI)
1573 Application Specific Extension. This tells the assembler to accept MMI
1575 @samp{-mno-loongson-mmi} turns off this option.
1577 @item -mloongson-cam
1578 @itemx -mno-loongson-cam
1579 Generate code for the Loongson Content Address Memory (CAM) instructions.
1580 This tells the assembler to accept Loongson CAM instructions.
1581 @samp{-mno-loongson-cam} turns off this option.
1585 Only use 32-bit instruction encodings when generating code for the
1586 microMIPS processor. This option inhibits the use of any 16-bit
1587 instructions. This is equivalent to putting @code{.set insn32} at
1588 the start of the assembly file. @samp{-mno-insn32} turns off this
1589 option. This is equivalent to putting @code{.set noinsn32} at the
1590 start of the assembly file. By default @samp{-mno-insn32} is
1591 selected, allowing all instructions to be used.
1593 @item --construct-floats
1594 @itemx --no-construct-floats
1595 The @samp{--no-construct-floats} option disables the construction of
1596 double width floating point constants by loading the two halves of the
1597 value into the two single width floating point registers that make up
1598 the double width register. By default @samp{--construct-floats} is
1599 selected, allowing construction of these floating point constants.
1601 @item --relax-branch
1602 @itemx --no-relax-branch
1603 The @samp{--relax-branch} option enables the relaxation of out-of-range
1604 branches. By default @samp{--no-relax-branch} is selected, causing any
1605 out-of-range branches to produce an error.
1607 @item -mignore-branch-isa
1608 @itemx -mno-ignore-branch-isa
1609 Ignore branch checks for invalid transitions between ISA modes. The
1610 semantics of branches does not provide for an ISA mode switch, so in
1611 most cases the ISA mode a branch has been encoded for has to be the
1612 same as the ISA mode of the branch's target label. Therefore GAS has
1613 checks implemented that verify in branch assembly that the two ISA
1614 modes match. @samp{-mignore-branch-isa} disables these checks. By
1615 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1616 branch requiring a transition between ISA modes to produce an error.
1618 @item -mnan=@var{encoding}
1619 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1620 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1623 @item --emulation=@var{name}
1624 This option was formerly used to switch between ELF and ECOFF output
1625 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1626 removed in GAS 2.24, so the option now serves little purpose.
1627 It is retained for backwards compatibility.
1629 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1630 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1631 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1632 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1633 preferred options instead.
1636 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1643 Control how to deal with multiplication overflow and division by zero.
1644 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1645 (and only work for Instruction Set Architecture level 2 and higher);
1646 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1650 When this option is used, @command{@value{AS}} will issue a warning every
1651 time it generates a nop instruction from a macro.
1657 The following options are available when @value{AS} is configured for
1663 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1664 The command-line option @samp{-nojsri2bsr} can be used to disable it.
1668 Enable or disable the silicon filter behaviour. By default this is disabled.
1669 The default can be overridden by the @samp{-sifilter} command-line option.
1672 Alter jump instructions for long displacements.
1674 @item -mcpu=[210|340]
1675 Select the cpu type on the target hardware. This controls which instructions
1679 Assemble for a big endian target.
1682 Assemble for a little endian target.
1691 @xref{Meta Options}, for the options available when @value{AS} is configured
1692 for a Meta processor.
1696 @c man begin OPTIONS
1697 The following options are available when @value{AS} is configured for a
1700 @c man begin INCLUDE
1701 @include c-metag.texi
1702 @c ended inside the included file
1707 @c man begin OPTIONS
1709 See the info pages for documentation of the MMIX-specific options.
1715 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1716 for a NDS32 processor.
1718 @c ended inside the included file
1722 @c man begin OPTIONS
1723 The following options are available when @value{AS} is configured for a
1726 @c man begin INCLUDE
1727 @include c-nds32.texi
1728 @c ended inside the included file
1735 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1736 for a PowerPC processor.
1740 @c man begin OPTIONS
1741 The following options are available when @value{AS} is configured for a
1744 @c man begin INCLUDE
1746 @c ended inside the included file
1754 @xref{RISC-V-Options}, for the options available when @value{AS} is configured
1755 for a RISC-V processor.
1759 @c man begin OPTIONS
1760 The following options are available when @value{AS} is configured for a
1763 @c man begin INCLUDE
1764 @include c-riscv.texi
1765 @c ended inside the included file
1770 @c man begin OPTIONS
1772 See the info pages for documentation of the RX-specific options.
1776 The following options are available when @value{AS} is configured for the s390
1782 Select the word size, either 31/32 bits or 64 bits.
1785 Select the architecture mode, either the Enterprise System
1786 Architecture (esa) or the z/Architecture mode (zarch).
1787 @item -march=@var{processor}
1788 Specify which s390 processor variant is the target, @samp{g5} (or
1789 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1790 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1791 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1792 @samp{z13} (or @samp{arch11}), or @samp{z14} (or @samp{arch12}).
1794 @itemx -mno-regnames
1795 Allow or disallow symbolic names for registers.
1796 @item -mwarn-areg-zero
1797 Warn whenever the operand for a base or index register has been specified
1798 but evaluates to zero.
1806 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1807 for a TMS320C6000 processor.
1811 @c man begin OPTIONS
1812 The following options are available when @value{AS} is configured for a
1813 TMS320C6000 processor.
1815 @c man begin INCLUDE
1816 @include c-tic6x.texi
1817 @c ended inside the included file
1825 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1826 for a TILE-Gx processor.
1830 @c man begin OPTIONS
1831 The following options are available when @value{AS} is configured for a TILE-Gx
1834 @c man begin INCLUDE
1835 @include c-tilegx.texi
1836 @c ended inside the included file
1844 @xref{Visium Options}, for the options available when @value{AS} is configured
1845 for a Visium processor.
1849 @c man begin OPTIONS
1850 The following option is available when @value{AS} is configured for a Visium
1853 @c man begin INCLUDE
1854 @include c-visium.texi
1855 @c ended inside the included file
1863 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1864 for an Xtensa processor.
1868 @c man begin OPTIONS
1869 The following options are available when @value{AS} is configured for an
1872 @c man begin INCLUDE
1873 @include c-xtensa.texi
1874 @c ended inside the included file
1879 @c man begin OPTIONS
1882 The following options are available when @value{AS} is configured for
1883 a Z80 family processor.
1886 Assemble for Z80 processor.
1888 Assemble for R800 processor.
1889 @item -ignore-undocumented-instructions
1891 Assemble undocumented Z80 instructions that also work on R800 without warning.
1892 @item -ignore-unportable-instructions
1894 Assemble all undocumented Z80 instructions without warning.
1895 @item -warn-undocumented-instructions
1897 Issue a warning for undocumented Z80 instructions that also work on R800.
1898 @item -warn-unportable-instructions
1900 Issue a warning for undocumented Z80 instructions that do not work on R800.
1901 @item -forbid-undocumented-instructions
1903 Treat all undocumented instructions as errors.
1904 @item -forbid-unportable-instructions
1906 Treat undocumented Z80 instructions that do not work on R800 as errors.
1913 * Manual:: Structure of this Manual
1914 * GNU Assembler:: The GNU Assembler
1915 * Object Formats:: Object File Formats
1916 * Command Line:: Command Line
1917 * Input Files:: Input Files
1918 * Object:: Output (Object) File
1919 * Errors:: Error and Warning Messages
1923 @section Structure of this Manual
1925 @cindex manual, structure and purpose
1926 This manual is intended to describe what you need to know to use
1927 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1928 notation for symbols, constants, and expressions; the directives that
1929 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1932 We also cover special features in the @value{TARGET}
1933 configuration of @command{@value{AS}}, including assembler directives.
1936 This manual also describes some of the machine-dependent features of
1937 various flavors of the assembler.
1940 @cindex machine instructions (not covered)
1941 On the other hand, this manual is @emph{not} intended as an introduction
1942 to programming in assembly language---let alone programming in general!
1943 In a similar vein, we make no attempt to introduce the machine
1944 architecture; we do @emph{not} describe the instruction set, standard
1945 mnemonics, registers or addressing modes that are standard to a
1946 particular architecture.
1948 You may want to consult the manufacturer's
1949 machine architecture manual for this information.
1953 For information on the H8/300 machine instruction set, see @cite{H8/300
1954 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1955 Programming Manual} (Renesas).
1958 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1959 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1960 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1961 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1964 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1968 @c I think this is premature---doc@cygnus.com, 17jan1991
1970 Throughout this manual, we assume that you are running @dfn{GNU},
1971 the portable operating system from the @dfn{Free Software
1972 Foundation, Inc.}. This restricts our attention to certain kinds of
1973 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1974 once this assumption is granted examples and definitions need less
1977 @command{@value{AS}} is part of a team of programs that turn a high-level
1978 human-readable series of instructions into a low-level
1979 computer-readable series of instructions. Different versions of
1980 @command{@value{AS}} are used for different kinds of computer.
1983 @c There used to be a section "Terminology" here, which defined
1984 @c "contents", "byte", "word", and "long". Defining "word" to any
1985 @c particular size is confusing when the .word directive may generate 16
1986 @c bits on one machine and 32 bits on another; in general, for the user
1987 @c version of this manual, none of these terms seem essential to define.
1988 @c They were used very little even in the former draft of the manual;
1989 @c this draft makes an effort to avoid them (except in names of
1993 @section The GNU Assembler
1995 @c man begin DESCRIPTION
1997 @sc{gnu} @command{as} is really a family of assemblers.
1999 This manual describes @command{@value{AS}}, a member of that family which is
2000 configured for the @value{TARGET} architectures.
2002 If you use (or have used) the @sc{gnu} assembler on one architecture, you
2003 should find a fairly similar environment when you use it on another
2004 architecture. Each version has much in common with the others,
2005 including object file formats, most assembler directives (often called
2006 @dfn{pseudo-ops}) and assembler syntax.@refill
2008 @cindex purpose of @sc{gnu} assembler
2009 @command{@value{AS}} is primarily intended to assemble the output of the
2010 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
2011 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
2012 assemble correctly everything that other assemblers for the same
2013 machine would assemble.
2015 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
2018 @c This remark should appear in generic version of manual; assumption
2019 @c here is that generic version sets M680x0.
2020 This doesn't mean @command{@value{AS}} always uses the same syntax as another
2021 assembler for the same architecture; for example, we know of several
2022 incompatible versions of 680x0 assembly language syntax.
2027 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
2028 program in one pass of the source file. This has a subtle impact on the
2029 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
2031 @node Object Formats
2032 @section Object File Formats
2034 @cindex object file format
2035 The @sc{gnu} assembler can be configured to produce several alternative
2036 object file formats. For the most part, this does not affect how you
2037 write assembly language programs; but directives for debugging symbols
2038 are typically different in different file formats. @xref{Symbol
2039 Attributes,,Symbol Attributes}.
2042 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
2043 @value{OBJ-NAME} format object files.
2045 @c The following should exhaust all configs that set MULTI-OBJ, ideally
2047 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
2048 SOM or ELF format object files.
2053 @section Command Line
2055 @cindex command line conventions
2057 After the program name @command{@value{AS}}, the command line may contain
2058 options and file names. Options may appear in any order, and may be
2059 before, after, or between file names. The order of file names is
2062 @cindex standard input, as input file
2064 @file{--} (two hyphens) by itself names the standard input file
2065 explicitly, as one of the files for @command{@value{AS}} to assemble.
2067 @cindex options, command line
2068 Except for @samp{--} any command-line argument that begins with a
2069 hyphen (@samp{-}) is an option. Each option changes the behavior of
2070 @command{@value{AS}}. No option changes the way another option works. An
2071 option is a @samp{-} followed by one or more letters; the case of
2072 the letter is important. All options are optional.
2074 Some options expect exactly one file name to follow them. The file
2075 name may either immediately follow the option's letter (compatible
2076 with older assemblers) or it may be the next command argument (@sc{gnu}
2077 standard). These two command lines are equivalent:
2080 @value{AS} -o my-object-file.o mumble.s
2081 @value{AS} -omy-object-file.o mumble.s
2085 @section Input Files
2088 @cindex source program
2089 @cindex files, input
2090 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2091 describe the program input to one run of @command{@value{AS}}. The program may
2092 be in one or more files; how the source is partitioned into files
2093 doesn't change the meaning of the source.
2095 @c I added "con" prefix to "catenation" just to prove I can overcome my
2096 @c APL training... doc@cygnus.com
2097 The source program is a concatenation of the text in all the files, in the
2100 @c man begin DESCRIPTION
2101 Each time you run @command{@value{AS}} it assembles exactly one source
2102 program. The source program is made up of one or more files.
2103 (The standard input is also a file.)
2105 You give @command{@value{AS}} a command line that has zero or more input file
2106 names. The input files are read (from left file name to right). A
2107 command-line argument (in any position) that has no special meaning
2108 is taken to be an input file name.
2110 If you give @command{@value{AS}} no file names it attempts to read one input file
2111 from the @command{@value{AS}} standard input, which is normally your terminal. You
2112 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2115 Use @samp{--} if you need to explicitly name the standard input file
2116 in your command line.
2118 If the source is empty, @command{@value{AS}} produces a small, empty object
2123 @subheading Filenames and Line-numbers
2125 @cindex input file linenumbers
2126 @cindex line numbers, in input files
2127 There are two ways of locating a line in the input file (or files) and
2128 either may be used in reporting error messages. One way refers to a line
2129 number in a physical file; the other refers to a line number in a
2130 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2132 @dfn{Physical files} are those files named in the command line given
2133 to @command{@value{AS}}.
2135 @dfn{Logical files} are simply names declared explicitly by assembler
2136 directives; they bear no relation to physical files. Logical file names help
2137 error messages reflect the original source file, when @command{@value{AS}} source
2138 is itself synthesized from other files. @command{@value{AS}} understands the
2139 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2140 @ref{File,,@code{.file}}.
2143 @section Output (Object) File
2149 Every time you run @command{@value{AS}} it produces an output file, which is
2150 your assembly language program translated into numbers. This file
2151 is the object file. Its default name is @code{a.out}.
2152 You can give it another name by using the @option{-o} option. Conventionally,
2153 object file names end with @file{.o}. The default name is used for historical
2154 reasons: older assemblers were capable of assembling self-contained programs
2155 directly into a runnable program. (For some formats, this isn't currently
2156 possible, but it can be done for the @code{a.out} format.)
2160 The object file is meant for input to the linker @code{@value{LD}}. It contains
2161 assembled program code, information to help @code{@value{LD}} integrate
2162 the assembled program into a runnable file, and (optionally) symbolic
2163 information for the debugger.
2165 @c link above to some info file(s) like the description of a.out.
2166 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2169 @section Error and Warning Messages
2171 @c man begin DESCRIPTION
2173 @cindex error messages
2174 @cindex warning messages
2175 @cindex messages from assembler
2176 @command{@value{AS}} may write warnings and error messages to the standard error
2177 file (usually your terminal). This should not happen when a compiler
2178 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2179 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2180 grave problem that stops the assembly.
2184 @cindex format of warning messages
2185 Warning messages have the format
2188 file_name:@b{NNN}:Warning Message Text
2192 @cindex file names and line numbers, in warnings/errors
2193 (where @b{NNN} is a line number). If both a logical file name
2194 (@pxref{File,,@code{.file}}) and a logical line number
2196 (@pxref{Line,,@code{.line}})
2198 have been given then they will be used, otherwise the file name and line number
2199 in the current assembler source file will be used. The message text is
2200 intended to be self explanatory (in the grand Unix tradition).
2202 Note the file name must be set via the logical version of the @code{.file}
2203 directive, not the DWARF2 version of the @code{.file} directive. For example:
2207 error_assembler_source
2213 produces this output:
2217 asm.s:2: Error: no such instruction: `error_assembler_source'
2218 foo.c:31: Error: no such instruction: `error_c_source'
2221 @cindex format of error messages
2222 Error messages have the format
2225 file_name:@b{NNN}:FATAL:Error Message Text
2228 The file name and line number are derived as for warning
2229 messages. The actual message text may be rather less explanatory
2230 because many of them aren't supposed to happen.
2233 @chapter Command-Line Options
2235 @cindex options, all versions of assembler
2236 This chapter describes command-line options available in @emph{all}
2237 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2238 for options specific
2240 to the @value{TARGET} target.
2243 to particular machine architectures.
2246 @c man begin DESCRIPTION
2248 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2249 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2250 The assembler arguments must be separated from each other (and the @samp{-Wa})
2251 by commas. For example:
2254 gcc -c -g -O -Wa,-alh,-L file.c
2258 This passes two options to the assembler: @samp{-alh} (emit a listing to
2259 standard output with high-level and assembly source) and @samp{-L} (retain
2260 local symbols in the symbol table).
2262 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2263 command-line options are automatically passed to the assembler by the compiler.
2264 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2265 precisely what options it passes to each compilation pass, including the
2271 * a:: -a[cdghlns] enable listings
2272 * alternate:: --alternate enable alternate macro syntax
2273 * D:: -D for compatibility
2274 * f:: -f to work faster
2275 * I:: -I for .include search path
2276 @ifclear DIFF-TBL-KLUGE
2277 * K:: -K for compatibility
2279 @ifset DIFF-TBL-KLUGE
2280 * K:: -K for difference tables
2283 * L:: -L to retain local symbols
2284 * listing:: --listing-XXX to configure listing output
2285 * M:: -M or --mri to assemble in MRI compatibility mode
2286 * MD:: --MD for dependency tracking
2287 * no-pad-sections:: --no-pad-sections to stop section padding
2288 * o:: -o to name the object file
2289 * R:: -R to join data and text sections
2290 * statistics:: --statistics to see statistics about assembly
2291 * traditional-format:: --traditional-format for compatible output
2292 * v:: -v to announce version
2293 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2294 * Z:: -Z to make object file even after errors
2298 @section Enable Listings: @option{-a[cdghlns]}
2308 @cindex listings, enabling
2309 @cindex assembly listings, enabling
2311 These options enable listing output from the assembler. By itself,
2312 @samp{-a} requests high-level, assembly, and symbols listing.
2313 You can use other letters to select specific options for the list:
2314 @samp{-ah} requests a high-level language listing,
2315 @samp{-al} requests an output-program assembly listing, and
2316 @samp{-as} requests a symbol table listing.
2317 High-level listings require that a compiler debugging option like
2318 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2321 Use the @samp{-ag} option to print a first section with general assembly
2322 information, like @value{AS} version, switches passed, or time stamp.
2324 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2325 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2326 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2327 omitted from the listing.
2329 Use the @samp{-ad} option to omit debugging directives from the
2332 Once you have specified one of these options, you can further control
2333 listing output and its appearance using the directives @code{.list},
2334 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2336 The @samp{-an} option turns off all forms processing.
2337 If you do not request listing output with one of the @samp{-a} options, the
2338 listing-control directives have no effect.
2340 The letters after @samp{-a} may be combined into one option,
2341 @emph{e.g.}, @samp{-aln}.
2343 Note if the assembler source is coming from the standard input (e.g.,
2345 is being created by @code{@value{GCC}} and the @samp{-pipe} command-line switch
2346 is being used) then the listing will not contain any comments or preprocessor
2347 directives. This is because the listing code buffers input source lines from
2348 stdin only after they have been preprocessed by the assembler. This reduces
2349 memory usage and makes the code more efficient.
2352 @section @option{--alternate}
2355 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2358 @section @option{-D}
2361 This option has no effect whatsoever, but it is accepted to make it more
2362 likely that scripts written for other assemblers also work with
2363 @command{@value{AS}}.
2366 @section Work Faster: @option{-f}
2369 @cindex trusted compiler
2370 @cindex faster processing (@option{-f})
2371 @samp{-f} should only be used when assembling programs written by a
2372 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2373 and comment preprocessing on
2374 the input file(s) before assembling them. @xref{Preprocessing,
2378 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2379 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2384 @section @code{.include} Search Path: @option{-I} @var{path}
2386 @kindex -I @var{path}
2387 @cindex paths for @code{.include}
2388 @cindex search path for @code{.include}
2389 @cindex @code{include} directive search path
2390 Use this option to add a @var{path} to the list of directories
2391 @command{@value{AS}} searches for files specified in @code{.include}
2392 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2393 many times as necessary to include a variety of paths. The current
2394 working directory is always searched first; after that, @command{@value{AS}}
2395 searches any @samp{-I} directories in the same order as they were
2396 specified (left to right) on the command line.
2399 @section Difference Tables: @option{-K}
2402 @ifclear DIFF-TBL-KLUGE
2403 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2404 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2405 where it can be used to warn when the assembler alters the machine code
2406 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2407 family does not have the addressing limitations that sometimes lead to this
2408 alteration on other platforms.
2411 @ifset DIFF-TBL-KLUGE
2412 @cindex difference tables, warning
2413 @cindex warning for altered difference tables
2414 @command{@value{AS}} sometimes alters the code emitted for directives of the
2415 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2416 You can use the @samp{-K} option if you want a warning issued when this
2421 @section Include Local Symbols: @option{-L}
2424 @cindex local symbols, retaining in output
2425 Symbols beginning with system-specific local label prefixes, typically
2426 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2427 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2428 such symbols when debugging, because they are intended for the use of
2429 programs (like compilers) that compose assembler programs, not for your
2430 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2431 such symbols, so you do not normally debug with them.
2433 This option tells @command{@value{AS}} to retain those local symbols
2434 in the object file. Usually if you do this you also tell the linker
2435 @code{@value{LD}} to preserve those symbols.
2438 @section Configuring listing output: @option{--listing}
2440 The listing feature of the assembler can be enabled via the command-line switch
2441 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2442 hex dump of the corresponding locations in the output object file, and displays
2443 them as a listing file. The format of this listing can be controlled by
2444 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2445 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2446 @code{.psize} (@pxref{Psize}), and
2447 @code{.eject} (@pxref{Eject}) and also by the following switches:
2450 @item --listing-lhs-width=@samp{number}
2451 @kindex --listing-lhs-width
2452 @cindex Width of first line disassembly output
2453 Sets the maximum width, in words, of the first line of the hex byte dump. This
2454 dump appears on the left hand side of the listing output.
2456 @item --listing-lhs-width2=@samp{number}
2457 @kindex --listing-lhs-width2
2458 @cindex Width of continuation lines of disassembly output
2459 Sets the maximum width, in words, of any further lines of the hex byte dump for
2460 a given input source line. If this value is not specified, it defaults to being
2461 the same as the value specified for @samp{--listing-lhs-width}. If neither
2462 switch is used the default is to one.
2464 @item --listing-rhs-width=@samp{number}
2465 @kindex --listing-rhs-width
2466 @cindex Width of source line output
2467 Sets the maximum width, in characters, of the source line that is displayed
2468 alongside the hex dump. The default value for this parameter is 100. The
2469 source line is displayed on the right hand side of the listing output.
2471 @item --listing-cont-lines=@samp{number}
2472 @kindex --listing-cont-lines
2473 @cindex Maximum number of continuation lines
2474 Sets the maximum number of continuation lines of hex dump that will be
2475 displayed for a given single line of source input. The default value is 4.
2479 @section Assemble in MRI Compatibility Mode: @option{-M}
2482 @cindex MRI compatibility mode
2483 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2484 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2485 compatible with the @code{ASM68K} assembler from Microtec Research.
2486 The exact nature of the
2487 MRI syntax will not be documented here; see the MRI manuals for more
2488 information. Note in particular that the handling of macros and macro
2489 arguments is somewhat different. The purpose of this option is to permit
2490 assembling existing MRI assembler code using @command{@value{AS}}.
2492 The MRI compatibility is not complete. Certain operations of the MRI assembler
2493 depend upon its object file format, and can not be supported using other object
2494 file formats. Supporting these would require enhancing each object file format
2495 individually. These are:
2498 @item global symbols in common section
2500 The m68k MRI assembler supports common sections which are merged by the linker.
2501 Other object file formats do not support this. @command{@value{AS}} handles
2502 common sections by treating them as a single common symbol. It permits local
2503 symbols to be defined within a common section, but it can not support global
2504 symbols, since it has no way to describe them.
2506 @item complex relocations
2508 The MRI assemblers support relocations against a negated section address, and
2509 relocations which combine the start addresses of two or more sections. These
2510 are not support by other object file formats.
2512 @item @code{END} pseudo-op specifying start address
2514 The MRI @code{END} pseudo-op permits the specification of a start address.
2515 This is not supported by other object file formats. The start address may
2516 instead be specified using the @option{-e} option to the linker, or in a linker
2519 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2521 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2522 name to the output file. This is not supported by other object file formats.
2524 @item @code{ORG} pseudo-op
2526 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2527 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2528 which changes the location within the current section. Absolute sections are
2529 not supported by other object file formats. The address of a section may be
2530 assigned within a linker script.
2533 There are some other features of the MRI assembler which are not supported by
2534 @command{@value{AS}}, typically either because they are difficult or because they
2535 seem of little consequence. Some of these may be supported in future releases.
2539 @item EBCDIC strings
2541 EBCDIC strings are not supported.
2543 @item packed binary coded decimal
2545 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2546 and @code{DCB.P} pseudo-ops are not supported.
2548 @item @code{FEQU} pseudo-op
2550 The m68k @code{FEQU} pseudo-op is not supported.
2552 @item @code{NOOBJ} pseudo-op
2554 The m68k @code{NOOBJ} pseudo-op is not supported.
2556 @item @code{OPT} branch control options
2558 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2559 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2560 relaxes all branches, whether forward or backward, to an appropriate size, so
2561 these options serve no purpose.
2563 @item @code{OPT} list control options
2565 The following m68k @code{OPT} list control options are ignored: @code{C},
2566 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2567 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2569 @item other @code{OPT} options
2571 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2572 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2574 @item @code{OPT} @code{D} option is default
2576 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2577 @code{OPT NOD} may be used to turn it off.
2579 @item @code{XREF} pseudo-op.
2581 The m68k @code{XREF} pseudo-op is ignored.
2586 @section Dependency Tracking: @option{--MD}
2589 @cindex dependency tracking
2592 @command{@value{AS}} can generate a dependency file for the file it creates. This
2593 file consists of a single rule suitable for @code{make} describing the
2594 dependencies of the main source file.
2596 The rule is written to the file named in its argument.
2598 This feature is used in the automatic updating of makefiles.
2600 @node no-pad-sections
2601 @section Output Section Padding
2602 @kindex --no-pad-sections
2603 @cindex output section padding
2604 Normally the assembler will pad the end of each output section up to its
2605 alignment boundary. But this can waste space, which can be significant on
2606 memory constrained targets. So the @option{--no-pad-sections} option will
2607 disable this behaviour.
2610 @section Name the Object File: @option{-o}
2613 @cindex naming object file
2614 @cindex object file name
2615 There is always one object file output when you run @command{@value{AS}}. By
2616 default it has the name @file{a.out}.
2617 You use this option (which takes exactly one filename) to give the
2618 object file a different name.
2620 Whatever the object file is called, @command{@value{AS}} overwrites any
2621 existing file of the same name.
2624 @section Join Data and Text Sections: @option{-R}
2627 @cindex data and text sections, joining
2628 @cindex text and data sections, joining
2629 @cindex joining text and data sections
2630 @cindex merging text and data sections
2631 @option{-R} tells @command{@value{AS}} to write the object file as if all
2632 data-section data lives in the text section. This is only done at
2633 the very last moment: your binary data are the same, but data
2634 section parts are relocated differently. The data section part of
2635 your object file is zero bytes long because all its bytes are
2636 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2638 When you specify @option{-R} it would be possible to generate shorter
2639 address displacements (because we do not have to cross between text and
2640 data section). We refrain from doing this simply for compatibility with
2641 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2644 When @command{@value{AS}} is configured for COFF or ELF output,
2645 this option is only useful if you use sections named @samp{.text} and
2650 @option{-R} is not supported for any of the HPPA targets. Using
2651 @option{-R} generates a warning from @command{@value{AS}}.
2655 @section Display Assembly Statistics: @option{--statistics}
2657 @kindex --statistics
2658 @cindex statistics, about assembly
2659 @cindex time, total for assembly
2660 @cindex space used, maximum for assembly
2661 Use @samp{--statistics} to display two statistics about the resources used by
2662 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2663 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2666 @node traditional-format
2667 @section Compatible Output: @option{--traditional-format}
2669 @kindex --traditional-format
2670 For some targets, the output of @command{@value{AS}} is different in some ways
2671 from the output of some existing assembler. This switch requests
2672 @command{@value{AS}} to use the traditional format instead.
2674 For example, it disables the exception frame optimizations which
2675 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2678 @section Announce Version: @option{-v}
2682 @cindex assembler version
2683 @cindex version of assembler
2684 You can find out what version of as is running by including the
2685 option @samp{-v} (which you can also spell as @samp{-version}) on the
2689 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2691 @command{@value{AS}} should never give a warning or error message when
2692 assembling compiler output. But programs written by people often
2693 cause @command{@value{AS}} to give a warning that a particular assumption was
2694 made. All such warnings are directed to the standard error file.
2698 @cindex suppressing warnings
2699 @cindex warnings, suppressing
2700 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2701 This only affects the warning messages: it does not change any particular of
2702 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2705 @kindex --fatal-warnings
2706 @cindex errors, caused by warnings
2707 @cindex warnings, causing error
2708 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2709 files that generate warnings to be in error.
2712 @cindex warnings, switching on
2713 You can switch these options off again by specifying @option{--warn}, which
2714 causes warnings to be output as usual.
2717 @section Generate Object File in Spite of Errors: @option{-Z}
2718 @cindex object file, after errors
2719 @cindex errors, continuing after
2720 After an error message, @command{@value{AS}} normally produces no output. If for
2721 some reason you are interested in object file output even after
2722 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2723 option. If there are any errors, @command{@value{AS}} continues anyways, and
2724 writes an object file after a final warning message of the form @samp{@var{n}
2725 errors, @var{m} warnings, generating bad object file.}
2730 @cindex machine-independent syntax
2731 @cindex syntax, machine-independent
2732 This chapter describes the machine-independent syntax allowed in a
2733 source file. @command{@value{AS}} syntax is similar to what many other
2734 assemblers use; it is inspired by the BSD 4.2
2739 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2743 * Preprocessing:: Preprocessing
2744 * Whitespace:: Whitespace
2745 * Comments:: Comments
2746 * Symbol Intro:: Symbols
2747 * Statements:: Statements
2748 * Constants:: Constants
2752 @section Preprocessing
2754 @cindex preprocessing
2755 The @command{@value{AS}} internal preprocessor:
2757 @cindex whitespace, removed by preprocessor
2759 adjusts and removes extra whitespace. It leaves one space or tab before
2760 the keywords on a line, and turns any other whitespace on the line into
2763 @cindex comments, removed by preprocessor
2765 removes all comments, replacing them with a single space, or an
2766 appropriate number of newlines.
2768 @cindex constants, converted by preprocessor
2770 converts character constants into the appropriate numeric values.
2773 It does not do macro processing, include file handling, or
2774 anything else you may get from your C compiler's preprocessor. You can
2775 do include file processing with the @code{.include} directive
2776 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2777 to get other ``CPP'' style preprocessing by giving the input file a
2778 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2779 Output, gcc info, Using GNU CC}.
2781 Excess whitespace, comments, and character constants
2782 cannot be used in the portions of the input text that are not
2785 @cindex turning preprocessing on and off
2786 @cindex preprocessing, turning on and off
2789 If the first line of an input file is @code{#NO_APP} or if you use the
2790 @samp{-f} option, whitespace and comments are not removed from the input file.
2791 Within an input file, you can ask for whitespace and comment removal in
2792 specific portions of the by putting a line that says @code{#APP} before the
2793 text that may contain whitespace or comments, and putting a line that says
2794 @code{#NO_APP} after this text. This feature is mainly intend to support
2795 @code{asm} statements in compilers whose output is otherwise free of comments
2802 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2803 Whitespace is used to separate symbols, and to make programs neater for
2804 people to read. Unless within character constants
2805 (@pxref{Characters,,Character Constants}), any whitespace means the same
2806 as exactly one space.
2812 There are two ways of rendering comments to @command{@value{AS}}. In both
2813 cases the comment is equivalent to one space.
2815 Anything from @samp{/*} through the next @samp{*/} is a comment.
2816 This means you may not nest these comments.
2820 The only way to include a newline ('\n') in a comment
2821 is to use this sort of comment.
2824 /* This sort of comment does not nest. */
2827 @cindex line comment character
2828 Anything from a @dfn{line comment} character up to the next newline is
2829 considered a comment and is ignored. The line comment character is target
2830 specific, and some targets multiple comment characters. Some targets also have
2831 line comment characters that only work if they are the first character on a
2832 line. Some targets use a sequence of two characters to introduce a line
2833 comment. Some targets can also change their line comment characters depending
2834 upon command-line options that have been used. For more details see the
2835 @emph{Syntax} section in the documentation for individual targets.
2837 If the line comment character is the hash sign (@samp{#}) then it still has the
2838 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2839 to specify logical line numbers:
2842 @cindex lines starting with @code{#}
2843 @cindex logical line numbers
2844 To be compatible with past assemblers, lines that begin with @samp{#} have a
2845 special interpretation. Following the @samp{#} should be an absolute
2846 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2847 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2848 new logical file name. The rest of the line, if any, should be whitespace.
2850 If the first non-whitespace characters on the line are not numeric,
2851 the line is ignored. (Just like a comment.)
2854 # This is an ordinary comment.
2855 # 42-6 "new_file_name" # New logical file name
2856 # This is logical line # 36.
2858 This feature is deprecated, and may disappear from future versions
2859 of @command{@value{AS}}.
2864 @cindex characters used in symbols
2865 @ifclear SPECIAL-SYMS
2866 A @dfn{symbol} is one or more characters chosen from the set of all
2867 letters (both upper and lower case), digits and the three characters
2873 A @dfn{symbol} is one or more characters chosen from the set of all
2874 letters (both upper and lower case), digits and the three characters
2875 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2881 On most machines, you can also use @code{$} in symbol names; exceptions
2882 are noted in @ref{Machine Dependencies}.
2884 No symbol may begin with a digit. Case is significant.
2885 There is no length limit; all characters are significant. Multibyte characters
2886 are supported. Symbols are delimited by characters not in that set, or by the
2887 beginning of a file (since the source program must end with a newline, the end
2888 of a file is not a possible symbol delimiter). @xref{Symbols}.
2890 Symbol names may also be enclosed in double quote @code{"} characters. In such
2891 cases any characters are allowed, except for the NUL character. If a double
2892 quote character is to be included in the symbol name it must be preceeded by a
2893 backslash @code{\} character.
2894 @cindex length of symbols
2899 @cindex statements, structure of
2900 @cindex line separator character
2901 @cindex statement separator character
2903 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2904 @dfn{line separator character}. The line separator character is target
2905 specific and described in the @emph{Syntax} section of each
2906 target's documentation. Not all targets support a line separator character.
2907 The newline or line separator character is considered to be part of the
2908 preceding statement. Newlines and separators within character constants are an
2909 exception: they do not end statements.
2911 @cindex newline, required at file end
2912 @cindex EOF, newline must precede
2913 It is an error to end any statement with end-of-file: the last
2914 character of any input file should be a newline.@refill
2916 An empty statement is allowed, and may include whitespace. It is ignored.
2918 @cindex instructions and directives
2919 @cindex directives and instructions
2920 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2921 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2923 A statement begins with zero or more labels, optionally followed by a
2924 key symbol which determines what kind of statement it is. The key
2925 symbol determines the syntax of the rest of the statement. If the
2926 symbol begins with a dot @samp{.} then the statement is an assembler
2927 directive: typically valid for any computer. If the symbol begins with
2928 a letter the statement is an assembly language @dfn{instruction}: it
2929 assembles into a machine language instruction.
2931 Different versions of @command{@value{AS}} for different computers
2932 recognize different instructions. In fact, the same symbol may
2933 represent a different instruction in a different computer's assembly
2937 @cindex @code{:} (label)
2938 @cindex label (@code{:})
2939 A label is a symbol immediately followed by a colon (@code{:}).
2940 Whitespace before a label or after a colon is permitted, but you may not
2941 have whitespace between a label's symbol and its colon. @xref{Labels}.
2944 For HPPA targets, labels need not be immediately followed by a colon, but
2945 the definition of a label must begin in column zero. This also implies that
2946 only one label may be defined on each line.
2950 label: .directive followed by something
2951 another_label: # This is an empty statement.
2952 instruction operand_1, operand_2, @dots{}
2959 A constant is a number, written so that its value is known by
2960 inspection, without knowing any context. Like this:
2963 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2964 .ascii "Ring the bell\7" # A string constant.
2965 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2966 .float 0f-314159265358979323846264338327\
2967 95028841971.693993751E-40 # - pi, a flonum.
2972 * Characters:: Character Constants
2973 * Numbers:: Number Constants
2977 @subsection Character Constants
2979 @cindex character constants
2980 @cindex constants, character
2981 There are two kinds of character constants. A @dfn{character} stands
2982 for one character in one byte and its value may be used in
2983 numeric expressions. String constants (properly called string
2984 @emph{literals}) are potentially many bytes and their values may not be
2985 used in arithmetic expressions.
2989 * Chars:: Characters
2993 @subsubsection Strings
2995 @cindex string constants
2996 @cindex constants, string
2997 A @dfn{string} is written between double-quotes. It may contain
2998 double-quotes or null characters. The way to get special characters
2999 into a string is to @dfn{escape} these characters: precede them with
3000 a backslash @samp{\} character. For example @samp{\\} represents
3001 one backslash: the first @code{\} is an escape which tells
3002 @command{@value{AS}} to interpret the second character literally as a backslash
3003 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
3004 escape character). The complete list of escapes follows.
3006 @cindex escape codes, character
3007 @cindex character escape codes
3008 @c NOTE: Cindex entries must not start with a backlash character.
3009 @c NOTE: This confuses the pdf2texi script when it is creating the
3010 @c NOTE: index based upon the first character and so it generates:
3011 @c NOTE: \initial {\\}
3012 @c NOTE: which then results in the error message:
3013 @c NOTE: Argument of \\ has an extra }.
3014 @c NOTE: So in the index entries below a space character has been
3015 @c NOTE: prepended to avoid this problem.
3018 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3020 @cindex @code{ \b} (backspace character)
3021 @cindex backspace (@code{\b})
3023 Mnemonic for backspace; for ASCII this is octal code 010.
3026 @c Mnemonic for EOText; for ASCII this is octal code 004.
3028 @cindex @code{ \f} (formfeed character)
3029 @cindex formfeed (@code{\f})
3031 Mnemonic for FormFeed; for ASCII this is octal code 014.
3033 @cindex @code{ \n} (newline character)
3034 @cindex newline (@code{\n})
3036 Mnemonic for newline; for ASCII this is octal code 012.
3039 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3041 @cindex @code{ \r} (carriage return character)
3042 @cindex carriage return (@code{backslash-r})
3044 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3047 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3048 @c other assemblers.
3050 @cindex @code{ \t} (tab)
3051 @cindex tab (@code{\t})
3053 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3056 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3057 @c @item \x @var{digit} @var{digit} @var{digit}
3058 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3060 @cindex @code{ \@var{ddd}} (octal character code)
3061 @cindex octal character code (@code{\@var{ddd}})
3062 @item \ @var{digit} @var{digit} @var{digit}
3063 An octal character code. The numeric code is 3 octal digits.
3064 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3065 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3067 @cindex @code{ \@var{xd...}} (hex character code)
3068 @cindex hex character code (@code{\@var{xd...}})
3069 @item \@code{x} @var{hex-digits...}
3070 A hex character code. All trailing hex digits are combined. Either upper or
3071 lower case @code{x} works.
3073 @cindex @code{ \\} (@samp{\} character)
3074 @cindex backslash (@code{\\})
3076 Represents one @samp{\} character.
3079 @c Represents one @samp{'} (accent acute) character.
3080 @c This is needed in single character literals
3081 @c (@xref{Characters,,Character Constants}.) to represent
3084 @cindex @code{ \"} (doublequote character)
3085 @cindex doublequote (@code{\"})
3087 Represents one @samp{"} character. Needed in strings to represent
3088 this character, because an unescaped @samp{"} would end the string.
3090 @item \ @var{anything-else}
3091 Any other character when escaped by @kbd{\} gives a warning, but
3092 assembles as if the @samp{\} was not present. The idea is that if
3093 you used an escape sequence you clearly didn't want the literal
3094 interpretation of the following character. However @command{@value{AS}} has no
3095 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3096 code and warns you of the fact.
3099 Which characters are escapable, and what those escapes represent,
3100 varies widely among assemblers. The current set is what we think
3101 the BSD 4.2 assembler recognizes, and is a subset of what most C
3102 compilers recognize. If you are in doubt, do not use an escape
3106 @subsubsection Characters
3108 @cindex single character constant
3109 @cindex character, single
3110 @cindex constant, single character
3111 A single character may be written as a single quote immediately followed by
3112 that character. Some backslash escapes apply to characters, @code{\b},
3113 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3114 as for strings, plus @code{\'} for a single quote. So if you want to write the
3115 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3116 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3119 @ifclear abnormal-separator
3120 (or semicolon @samp{;})
3122 @ifset abnormal-separator
3124 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3129 immediately following an acute accent is taken as a literal character
3130 and does not count as the end of a statement. The value of a character
3131 constant in a numeric expression is the machine's byte-wide code for
3132 that character. @command{@value{AS}} assumes your character code is ASCII:
3133 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3136 @subsection Number Constants
3138 @cindex constants, number
3139 @cindex number constants
3140 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3141 are stored in the target machine. @emph{Integers} are numbers that
3142 would fit into an @code{int} in the C language. @emph{Bignums} are
3143 integers, but they are stored in more than 32 bits. @emph{Flonums}
3144 are floating point numbers, described below.
3147 * Integers:: Integers
3155 @subsubsection Integers
3157 @cindex constants, integer
3159 @cindex binary integers
3160 @cindex integers, binary
3161 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3162 the binary digits @samp{01}.
3164 @cindex octal integers
3165 @cindex integers, octal
3166 An octal integer is @samp{0} followed by zero or more of the octal
3167 digits (@samp{01234567}).
3169 @cindex decimal integers
3170 @cindex integers, decimal
3171 A decimal integer starts with a non-zero digit followed by zero or
3172 more digits (@samp{0123456789}).
3174 @cindex hexadecimal integers
3175 @cindex integers, hexadecimal
3176 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3177 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3179 Integers have the usual values. To denote a negative integer, use
3180 the prefix operator @samp{-} discussed under expressions
3181 (@pxref{Prefix Ops,,Prefix Operators}).
3184 @subsubsection Bignums
3187 @cindex constants, bignum
3188 A @dfn{bignum} has the same syntax and semantics as an integer
3189 except that the number (or its negative) takes more than 32 bits to
3190 represent in binary. The distinction is made because in some places
3191 integers are permitted while bignums are not.
3194 @subsubsection Flonums
3196 @cindex floating point numbers
3197 @cindex constants, floating point
3199 @cindex precision, floating point
3200 A @dfn{flonum} represents a floating point number. The translation is
3201 indirect: a decimal floating point number from the text is converted by
3202 @command{@value{AS}} to a generic binary floating point number of more than
3203 sufficient precision. This generic floating point number is converted
3204 to a particular computer's floating point format (or formats) by a
3205 portion of @command{@value{AS}} specialized to that computer.
3207 A flonum is written by writing (in order)
3212 (@samp{0} is optional on the HPPA.)
3216 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3218 @kbd{e} is recommended. Case is not important.
3220 @c FIXME: verify if flonum syntax really this vague for most cases
3221 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3222 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3225 On the H8/300 and Renesas / SuperH SH architectures, the letter must be
3226 one of the letters @samp{DFPRSX} (in upper or lower case).
3228 On the ARC, the letter must be one of the letters @samp{DFRS}
3229 (in upper or lower case).
3231 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3235 One of the letters @samp{DFRS} (in upper or lower case).
3238 One of the letters @samp{DFPRSX} (in upper or lower case).
3241 The letter @samp{E} (upper case only).
3246 An optional sign: either @samp{+} or @samp{-}.
3249 An optional @dfn{integer part}: zero or more decimal digits.
3252 An optional @dfn{fractional part}: @samp{.} followed by zero
3253 or more decimal digits.
3256 An optional exponent, consisting of:
3260 An @samp{E} or @samp{e}.
3261 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3262 @c principle this can perfectly well be different on different targets.
3264 Optional sign: either @samp{+} or @samp{-}.
3266 One or more decimal digits.
3271 At least one of the integer part or the fractional part must be
3272 present. The floating point number has the usual base-10 value.
3274 @command{@value{AS}} does all processing using integers. Flonums are computed
3275 independently of any floating point hardware in the computer running
3276 @command{@value{AS}}.
3279 @chapter Sections and Relocation
3284 * Secs Background:: Background
3285 * Ld Sections:: Linker Sections
3286 * As Sections:: Assembler Internal Sections
3287 * Sub-Sections:: Sub-Sections
3291 @node Secs Background
3294 Roughly, a section is a range of addresses, with no gaps; all data
3295 ``in'' those addresses is treated the same for some particular purpose.
3296 For example there may be a ``read only'' section.
3298 @cindex linker, and assembler
3299 @cindex assembler, and linker
3300 The linker @code{@value{LD}} reads many object files (partial programs) and
3301 combines their contents to form a runnable program. When @command{@value{AS}}
3302 emits an object file, the partial program is assumed to start at address 0.
3303 @code{@value{LD}} assigns the final addresses for the partial program, so that
3304 different partial programs do not overlap. This is actually an
3305 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3308 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3309 addresses. These blocks slide to their run-time addresses as rigid
3310 units; their length does not change and neither does the order of bytes
3311 within them. Such a rigid unit is called a @emph{section}. Assigning
3312 run-time addresses to sections is called @dfn{relocation}. It includes
3313 the task of adjusting mentions of object-file addresses so they refer to
3314 the proper run-time addresses.
3316 For the H8/300, and for the Renesas / SuperH SH,
3317 @command{@value{AS}} pads sections if needed to
3318 ensure they end on a word (sixteen bit) boundary.
3321 @cindex standard assembler sections
3322 An object file written by @command{@value{AS}} has at least three sections, any
3323 of which may be empty. These are named @dfn{text}, @dfn{data} and
3328 When it generates COFF or ELF output,
3330 @command{@value{AS}} can also generate whatever other named sections you specify
3331 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3332 If you do not use any directives that place output in the @samp{.text}
3333 or @samp{.data} sections, these sections still exist, but are empty.
3338 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3340 @command{@value{AS}} can also generate whatever other named sections you
3341 specify using the @samp{.space} and @samp{.subspace} directives. See
3342 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3343 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3344 assembler directives.
3347 Additionally, @command{@value{AS}} uses different names for the standard
3348 text, data, and bss sections when generating SOM output. Program text
3349 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3350 BSS into @samp{$BSS$}.
3354 Within the object file, the text section starts at address @code{0}, the
3355 data section follows, and the bss section follows the data section.
3358 When generating either SOM or ELF output files on the HPPA, the text
3359 section starts at address @code{0}, the data section at address
3360 @code{0x4000000}, and the bss section follows the data section.
3363 To let @code{@value{LD}} know which data changes when the sections are
3364 relocated, and how to change that data, @command{@value{AS}} also writes to the
3365 object file details of the relocation needed. To perform relocation
3366 @code{@value{LD}} must know, each time an address in the object
3370 Where in the object file is the beginning of this reference to
3373 How long (in bytes) is this reference?
3375 Which section does the address refer to? What is the numeric value of
3377 (@var{address}) @minus{} (@var{start-address of section})?
3380 Is the reference to an address ``Program-Counter relative''?
3383 @cindex addresses, format of
3384 @cindex section-relative addressing
3385 In fact, every address @command{@value{AS}} ever uses is expressed as
3387 (@var{section}) + (@var{offset into section})
3390 Further, most expressions @command{@value{AS}} computes have this section-relative
3393 (For some object formats, such as SOM for the HPPA, some expressions are
3394 symbol-relative instead.)
3397 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3398 @var{N} into section @var{secname}.''
3400 Apart from text, data and bss sections you need to know about the
3401 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3402 addresses in the absolute section remain unchanged. For example, address
3403 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3404 @code{@value{LD}}. Although the linker never arranges two partial programs'
3405 data sections with overlapping addresses after linking, @emph{by definition}
3406 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3407 part of a program is always the same address when the program is running as
3408 address @code{@{absolute@ 239@}} in any other part of the program.
3410 The idea of sections is extended to the @dfn{undefined} section. Any
3411 address whose section is unknown at assembly time is by definition
3412 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3413 Since numbers are always defined, the only way to generate an undefined
3414 address is to mention an undefined symbol. A reference to a named
3415 common block would be such a symbol: its value is unknown at assembly
3416 time so it has section @emph{undefined}.
3418 By analogy the word @emph{section} is used to describe groups of sections in
3419 the linked program. @code{@value{LD}} puts all partial programs' text
3420 sections in contiguous addresses in the linked program. It is
3421 customary to refer to the @emph{text section} of a program, meaning all
3422 the addresses of all partial programs' text sections. Likewise for
3423 data and bss sections.
3425 Some sections are manipulated by @code{@value{LD}}; others are invented for
3426 use of @command{@value{AS}} and have no meaning except during assembly.
3429 @section Linker Sections
3430 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3435 @cindex named sections
3436 @cindex sections, named
3437 @item named sections
3440 @cindex text section
3441 @cindex data section
3445 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3446 separate but equal sections. Anything you can say of one section is
3449 When the program is running, however, it is
3450 customary for the text section to be unalterable. The
3451 text section is often shared among processes: it contains
3452 instructions, constants and the like. The data section of a running
3453 program is usually alterable: for example, C variables would be stored
3454 in the data section.
3459 This section contains zeroed bytes when your program begins running. It
3460 is used to hold uninitialized variables or common storage. The length of
3461 each partial program's bss section is important, but because it starts
3462 out containing zeroed bytes there is no need to store explicit zero
3463 bytes in the object file. The bss section was invented to eliminate
3464 those explicit zeros from object files.
3466 @cindex absolute section
3467 @item absolute section
3468 Address 0 of this section is always ``relocated'' to runtime address 0.
3469 This is useful if you want to refer to an address that @code{@value{LD}} must
3470 not change when relocating. In this sense we speak of absolute
3471 addresses being ``unrelocatable'': they do not change during relocation.
3473 @cindex undefined section
3474 @item undefined section
3475 This ``section'' is a catch-all for address references to objects not in
3476 the preceding sections.
3477 @c FIXME: ref to some other doc on obj-file formats could go here.
3480 @cindex relocation example
3481 An idealized example of three relocatable sections follows.
3483 The example uses the traditional section names @samp{.text} and @samp{.data}.
3485 Memory addresses are on the horizontal axis.
3489 @c END TEXI2ROFF-KILL
3492 partial program # 1: |ttttt|dddd|00|
3499 partial program # 2: |TTT|DDD|000|
3502 +--+---+-----+--+----+---+-----+~~
3503 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3504 +--+---+-----+--+----+---+-----+~~
3506 addresses: 0 @dots{}
3513 \line{\it Partial program \#1: \hfil}
3514 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3515 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3517 \line{\it Partial program \#2: \hfil}
3518 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3519 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3521 \line{\it linked program: \hfil}
3522 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3523 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3524 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3525 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3527 \line{\it addresses: \hfil}
3531 @c END TEXI2ROFF-KILL
3534 @section Assembler Internal Sections
3536 @cindex internal assembler sections
3537 @cindex sections in messages, internal
3538 These sections are meant only for the internal use of @command{@value{AS}}. They
3539 have no meaning at run-time. You do not really need to know about these
3540 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3541 warning messages, so it might be helpful to have an idea of their
3542 meanings to @command{@value{AS}}. These sections are used to permit the
3543 value of every expression in your assembly language program to be a
3544 section-relative address.
3547 @cindex assembler internal logic error
3548 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3549 An internal assembler logic error has been found. This means there is a
3550 bug in the assembler.
3552 @cindex expr (internal section)
3554 The assembler stores complex expression internally as combinations of
3555 symbols. When it needs to represent an expression as a symbol, it puts
3556 it in the expr section.
3558 @c FIXME item transfer[t] vector preload
3559 @c FIXME item transfer[t] vector postload
3560 @c FIXME item register
3564 @section Sub-Sections
3566 @cindex numbered subsections
3567 @cindex grouping data
3573 fall into two sections: text and data.
3575 You may have separate groups of
3577 data in named sections
3581 data in named sections
3587 that you want to end up near to each other in the object file, even though they
3588 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3589 use @dfn{subsections} for this purpose. Within each section, there can be
3590 numbered subsections with values from 0 to 8192. Objects assembled into the
3591 same subsection go into the object file together with other objects in the same
3592 subsection. For example, a compiler might want to store constants in the text
3593 section, but might not want to have them interspersed with the program being
3594 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3595 section of code being output, and a @samp{.text 1} before each group of
3596 constants being output.
3598 Subsections are optional. If you do not use subsections, everything
3599 goes in subsection number zero.
3602 Each subsection is zero-padded up to a multiple of four bytes.
3603 (Subsections may be padded a different amount on different flavors
3604 of @command{@value{AS}}.)
3608 On the H8/300 platform, each subsection is zero-padded to a word
3609 boundary (two bytes).
3610 The same is true on the Renesas SH.
3614 Subsections appear in your object file in numeric order, lowest numbered
3615 to highest. (All this to be compatible with other people's assemblers.)
3616 The object file contains no representation of subsections; @code{@value{LD}} and
3617 other programs that manipulate object files see no trace of them.
3618 They just see all your text subsections as a text section, and all your
3619 data subsections as a data section.
3621 To specify which subsection you want subsequent statements assembled
3622 into, use a numeric argument to specify it, in a @samp{.text
3623 @var{expression}} or a @samp{.data @var{expression}} statement.
3626 When generating COFF output, you
3631 can also use an extra subsection
3632 argument with arbitrary named sections: @samp{.section @var{name},
3637 When generating ELF output, you
3642 can also use the @code{.subsection} directive (@pxref{SubSection})
3643 to specify a subsection: @samp{.subsection @var{expression}}.
3645 @var{Expression} should be an absolute expression
3646 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3647 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3648 begins in @code{text 0}. For instance:
3650 .text 0 # The default subsection is text 0 anyway.
3651 .ascii "This lives in the first text subsection. *"
3653 .ascii "But this lives in the second text subsection."
3655 .ascii "This lives in the data section,"
3656 .ascii "in the first data subsection."
3658 .ascii "This lives in the first text section,"
3659 .ascii "immediately following the asterisk (*)."
3662 Each section has a @dfn{location counter} incremented by one for every byte
3663 assembled into that section. Because subsections are merely a convenience
3664 restricted to @command{@value{AS}} there is no concept of a subsection location
3665 counter. There is no way to directly manipulate a location counter---but the
3666 @code{.align} directive changes it, and any label definition captures its
3667 current value. The location counter of the section where statements are being
3668 assembled is said to be the @dfn{active} location counter.
3671 @section bss Section
3674 @cindex common variable storage
3675 The bss section is used for local common variable storage.
3676 You may allocate address space in the bss section, but you may
3677 not dictate data to load into it before your program executes. When
3678 your program starts running, all the contents of the bss
3679 section are zeroed bytes.
3681 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3682 @ref{Lcomm,,@code{.lcomm}}.
3684 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3685 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3688 When assembling for a target which supports multiple sections, such as ELF or
3689 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3690 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3691 section. Typically the section will only contain symbol definitions and
3692 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3699 Symbols are a central concept: the programmer uses symbols to name
3700 things, the linker uses symbols to link, and the debugger uses symbols
3704 @cindex debuggers, and symbol order
3705 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3706 the same order they were declared. This may break some debuggers.
3711 * Setting Symbols:: Giving Symbols Other Values
3712 * Symbol Names:: Symbol Names
3713 * Dot:: The Special Dot Symbol
3714 * Symbol Attributes:: Symbol Attributes
3721 A @dfn{label} is written as a symbol immediately followed by a colon
3722 @samp{:}. The symbol then represents the current value of the
3723 active location counter, and is, for example, a suitable instruction
3724 operand. You are warned if you use the same symbol to represent two
3725 different locations: the first definition overrides any other
3729 On the HPPA, the usual form for a label need not be immediately followed by a
3730 colon, but instead must start in column zero. Only one label may be defined on
3731 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3732 provides a special directive @code{.label} for defining labels more flexibly.
3735 @node Setting Symbols
3736 @section Giving Symbols Other Values
3738 @cindex assigning values to symbols
3739 @cindex symbol values, assigning
3740 A symbol can be given an arbitrary value by writing a symbol, followed
3741 by an equals sign @samp{=}, followed by an expression
3742 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3743 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3744 equals sign @samp{=}@samp{=} here represents an equivalent of the
3745 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3748 Blackfin does not support symbol assignment with @samp{=}.
3752 @section Symbol Names
3754 @cindex symbol names
3755 @cindex names, symbol
3756 @ifclear SPECIAL-SYMS
3757 Symbol names begin with a letter or with one of @samp{._}. On most
3758 machines, you can also use @code{$} in symbol names; exceptions are
3759 noted in @ref{Machine Dependencies}. That character may be followed by any
3760 string of digits, letters, dollar signs (unless otherwise noted for a
3761 particular target machine), and underscores.
3765 Symbol names begin with a letter or with one of @samp{._}. On the
3766 Renesas SH you can also use @code{$} in symbol names. That
3767 character may be followed by any string of digits, letters, dollar signs (save
3768 on the H8/300), and underscores.
3772 Case of letters is significant: @code{foo} is a different symbol name
3775 Symbol names do not start with a digit. An exception to this rule is made for
3776 Local Labels. See below.
3778 Multibyte characters are supported. To generate a symbol name containing
3779 multibyte characters enclose it within double quotes and use escape codes. cf
3780 @xref{Strings}. Generating a multibyte symbol name from a label is not
3781 currently supported.
3783 Each symbol has exactly one name. Each name in an assembly language program
3784 refers to exactly one symbol. You may use that symbol name any number of times
3787 @subheading Local Symbol Names
3789 @cindex local symbol names
3790 @cindex symbol names, local
3791 A local symbol is any symbol beginning with certain local label prefixes.
3792 By default, the local label prefix is @samp{.L} for ELF systems or
3793 @samp{L} for traditional a.out systems, but each target may have its own
3794 set of local label prefixes.
3796 On the HPPA local symbols begin with @samp{L$}.
3799 Local symbols are defined and used within the assembler, but they are
3800 normally not saved in object files. Thus, they are not visible when debugging.
3801 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3802 to retain the local symbols in the object files.
3804 @subheading Local Labels
3806 @cindex local labels
3807 @cindex temporary symbol names
3808 @cindex symbol names, temporary
3809 Local labels are different from local symbols. Local labels help compilers and
3810 programmers use names temporarily. They create symbols which are guaranteed to
3811 be unique over the entire scope of the input source code and which can be
3812 referred to by a simple notation. To define a local label, write a label of
3813 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3814 To refer to the most recent previous definition of that label write
3815 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3816 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3817 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3819 There is no restriction on how you can use these labels, and you can reuse them
3820 too. So that it is possible to repeatedly define the same local label (using
3821 the same number @samp{@b{N}}), although you can only refer to the most recently
3822 defined local label of that number (for a backwards reference) or the next
3823 definition of a specific local label for a forward reference. It is also worth
3824 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3825 implemented in a slightly more efficient manner than the others.
3836 Which is the equivalent of:
3839 label_1: branch label_3
3840 label_2: branch label_1
3841 label_3: branch label_4
3842 label_4: branch label_3
3845 Local label names are only a notational device. They are immediately
3846 transformed into more conventional symbol names before the assembler uses them.
3847 The symbol names are stored in the symbol table, appear in error messages, and
3848 are optionally emitted to the object file. The names are constructed using
3852 @item @emph{local label prefix}
3853 All local symbols begin with the system-specific local label prefix.
3854 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3855 that start with the local label prefix. These labels are
3856 used for symbols you are never intended to see. If you use the
3857 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3858 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3859 you may use them in debugging.
3862 This is the number that was used in the local label definition. So if the
3863 label is written @samp{55:} then the number is @samp{55}.
3866 This unusual character is included so you do not accidentally invent a symbol
3867 of the same name. The character has ASCII value of @samp{\002} (control-B).
3869 @item @emph{ordinal number}
3870 This is a serial number to keep the labels distinct. The first definition of
3871 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3872 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3873 the number @samp{1} and its 15th definition gets @samp{15} as well.
3876 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3877 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3879 @subheading Dollar Local Labels
3880 @cindex dollar local symbols
3882 On some targets @code{@value{AS}} also supports an even more local form of
3883 local labels called dollar labels. These labels go out of scope (i.e., they
3884 become undefined) as soon as a non-local label is defined. Thus they remain
3885 valid for only a small region of the input source code. Normal local labels,
3886 by contrast, remain in scope for the entire file, or until they are redefined
3887 by another occurrence of the same local label.
3889 Dollar labels are defined in exactly the same way as ordinary local labels,
3890 except that they have a dollar sign suffix to their numeric value, e.g.,
3893 They can also be distinguished from ordinary local labels by their transformed
3894 names which use ASCII character @samp{\001} (control-A) as the magic character
3895 to distinguish them from ordinary labels. For example, the fifth definition of
3896 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3899 @section The Special Dot Symbol
3901 @cindex dot (symbol)
3902 @cindex @code{.} (symbol)
3903 @cindex current address
3904 @cindex location counter
3905 The special symbol @samp{.} refers to the current address that
3906 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3907 .long .} defines @code{melvin} to contain its own address.
3908 Assigning a value to @code{.} is treated the same as a @code{.org}
3910 @ifclear no-space-dir
3911 Thus, the expression @samp{.=.+4} is the same as saying
3915 @node Symbol Attributes
3916 @section Symbol Attributes
3918 @cindex symbol attributes
3919 @cindex attributes, symbol
3920 Every symbol has, as well as its name, the attributes ``Value'' and
3921 ``Type''. Depending on output format, symbols can also have auxiliary
3924 The detailed definitions are in @file{a.out.h}.
3927 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3928 all these attributes, and probably won't warn you. This makes the
3929 symbol an externally defined symbol, which is generally what you
3933 * Symbol Value:: Value
3934 * Symbol Type:: Type
3936 * a.out Symbols:: Symbol Attributes: @code{a.out}
3939 * COFF Symbols:: Symbol Attributes for COFF
3942 * SOM Symbols:: Symbol Attributes for SOM
3949 @cindex value of a symbol
3950 @cindex symbol value
3951 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3952 location in the text, data, bss or absolute sections the value is the
3953 number of addresses from the start of that section to the label.
3954 Naturally for text, data and bss sections the value of a symbol changes
3955 as @code{@value{LD}} changes section base addresses during linking. Absolute
3956 symbols' values do not change during linking: that is why they are
3959 The value of an undefined symbol is treated in a special way. If it is
3960 0 then the symbol is not defined in this assembler source file, and
3961 @code{@value{LD}} tries to determine its value from other files linked into the
3962 same program. You make this kind of symbol simply by mentioning a symbol
3963 name without defining it. A non-zero value represents a @code{.comm}
3964 common declaration. The value is how much common storage to reserve, in
3965 bytes (addresses). The symbol refers to the first address of the
3971 @cindex type of a symbol
3973 The type attribute of a symbol contains relocation (section)
3974 information, any flag settings indicating that a symbol is external, and
3975 (optionally), other information for linkers and debuggers. The exact
3976 format depends on the object-code output format in use.
3980 @subsection Symbol Attributes: @code{a.out}
3982 @cindex @code{a.out} symbol attributes
3983 @cindex symbol attributes, @code{a.out}
3986 * Symbol Desc:: Descriptor
3987 * Symbol Other:: Other
3991 @subsubsection Descriptor
3993 @cindex descriptor, of @code{a.out} symbol
3994 This is an arbitrary 16-bit value. You may establish a symbol's
3995 descriptor value by using a @code{.desc} statement
3996 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3997 @command{@value{AS}}.
4000 @subsubsection Other
4002 @cindex other attribute, of @code{a.out} symbol
4003 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4008 @subsection Symbol Attributes for COFF
4010 @cindex COFF symbol attributes
4011 @cindex symbol attributes, COFF
4013 The COFF format supports a multitude of auxiliary symbol attributes;
4014 like the primary symbol attributes, they are set between @code{.def} and
4015 @code{.endef} directives.
4017 @subsubsection Primary Attributes
4019 @cindex primary attributes, COFF symbols
4020 The symbol name is set with @code{.def}; the value and type,
4021 respectively, with @code{.val} and @code{.type}.
4023 @subsubsection Auxiliary Attributes
4025 @cindex auxiliary attributes, COFF symbols
4026 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4027 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4028 table information for COFF.
4033 @subsection Symbol Attributes for SOM
4035 @cindex SOM symbol attributes
4036 @cindex symbol attributes, SOM
4038 The SOM format for the HPPA supports a multitude of symbol attributes set with
4039 the @code{.EXPORT} and @code{.IMPORT} directives.
4041 The attributes are described in @cite{HP9000 Series 800 Assembly
4042 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4043 @code{EXPORT} assembler directive documentation.
4047 @chapter Expressions
4051 @cindex numeric values
4052 An @dfn{expression} specifies an address or numeric value.
4053 Whitespace may precede and/or follow an expression.
4055 The result of an expression must be an absolute number, or else an offset into
4056 a particular section. If an expression is not absolute, and there is not
4057 enough information when @command{@value{AS}} sees the expression to know its
4058 section, a second pass over the source program might be necessary to interpret
4059 the expression---but the second pass is currently not implemented.
4060 @command{@value{AS}} aborts with an error message in this situation.
4063 * Empty Exprs:: Empty Expressions
4064 * Integer Exprs:: Integer Expressions
4068 @section Empty Expressions
4070 @cindex empty expressions
4071 @cindex expressions, empty
4072 An empty expression has no value: it is just whitespace or null.
4073 Wherever an absolute expression is required, you may omit the
4074 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4075 is compatible with other assemblers.
4078 @section Integer Expressions
4080 @cindex integer expressions
4081 @cindex expressions, integer
4082 An @dfn{integer expression} is one or more @emph{arguments} delimited
4083 by @emph{operators}.
4086 * Arguments:: Arguments
4087 * Operators:: Operators
4088 * Prefix Ops:: Prefix Operators
4089 * Infix Ops:: Infix Operators
4093 @subsection Arguments
4095 @cindex expression arguments
4096 @cindex arguments in expressions
4097 @cindex operands in expressions
4098 @cindex arithmetic operands
4099 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4100 contexts arguments are sometimes called ``arithmetic operands''. In
4101 this manual, to avoid confusing them with the ``instruction operands'' of
4102 the machine language, we use the term ``argument'' to refer to parts of
4103 expressions only, reserving the word ``operand'' to refer only to machine
4104 instruction operands.
4106 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4107 @var{section} is one of text, data, bss, absolute,
4108 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4111 Numbers are usually integers.
4113 A number can be a flonum or bignum. In this case, you are warned
4114 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4115 these 32 bits are an integer. You may write integer-manipulating
4116 instructions that act on exotic constants, compatible with other
4119 @cindex subexpressions
4120 Subexpressions are a left parenthesis @samp{(} followed by an integer
4121 expression, followed by a right parenthesis @samp{)}; or a prefix
4122 operator followed by an argument.
4125 @subsection Operators
4127 @cindex operators, in expressions
4128 @cindex arithmetic functions
4129 @cindex functions, in expressions
4130 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4131 operators are followed by an argument. Infix operators appear
4132 between their arguments. Operators may be preceded and/or followed by
4136 @subsection Prefix Operator
4138 @cindex prefix operators
4139 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4140 one argument, which must be absolute.
4142 @c the tex/end tex stuff surrounding this small table is meant to make
4143 @c it align, on the printed page, with the similar table in the next
4144 @c section (which is inside an enumerate).
4146 \global\advance\leftskip by \itemindent
4151 @dfn{Negation}. Two's complement negation.
4153 @dfn{Complementation}. Bitwise not.
4157 \global\advance\leftskip by -\itemindent
4161 @subsection Infix Operators
4163 @cindex infix operators
4164 @cindex operators, permitted arguments
4165 @dfn{Infix operators} take two arguments, one on either side. Operators
4166 have precedence, but operations with equal precedence are performed left
4167 to right. Apart from @code{+} or @option{-}, both arguments must be
4168 absolute, and the result is absolute.
4171 @cindex operator precedence
4172 @cindex precedence of operators
4179 @dfn{Multiplication}.
4182 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4188 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4191 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4195 Intermediate precedence
4200 @dfn{Bitwise Inclusive Or}.
4206 @dfn{Bitwise Exclusive Or}.
4209 @dfn{Bitwise Or Not}.
4216 @cindex addition, permitted arguments
4217 @cindex plus, permitted arguments
4218 @cindex arguments for addition
4220 @dfn{Addition}. If either argument is absolute, the result has the section of
4221 the other argument. You may not add together arguments from different
4224 @cindex subtraction, permitted arguments
4225 @cindex minus, permitted arguments
4226 @cindex arguments for subtraction
4228 @dfn{Subtraction}. If the right argument is absolute, the
4229 result has the section of the left argument.
4230 If both arguments are in the same section, the result is absolute.
4231 You may not subtract arguments from different sections.
4232 @c FIXME is there still something useful to say about undefined - undefined ?
4234 @cindex comparison expressions
4235 @cindex expressions, comparison
4240 @dfn{Is Not Equal To}
4244 @dfn{Is Greater Than}
4246 @dfn{Is Greater Than Or Equal To}
4248 @dfn{Is Less Than Or Equal To}
4250 The comparison operators can be used as infix operators. A true results has a
4251 value of -1 whereas a false result has a value of 0. Note, these operators
4252 perform signed comparisons.
4255 @item Lowest Precedence
4264 These two logical operations can be used to combine the results of sub
4265 expressions. Note, unlike the comparison operators a true result returns a
4266 value of 1 but a false results does still return 0. Also note that the logical
4267 or operator has a slightly lower precedence than logical and.
4272 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4273 address; you can only have a defined section in one of the two arguments.
4276 @chapter Assembler Directives
4278 @cindex directives, machine independent
4279 @cindex pseudo-ops, machine independent
4280 @cindex machine independent directives
4281 All assembler directives have names that begin with a period (@samp{.}).
4282 The names are case insensitive for most targets, and usually written
4285 This chapter discusses directives that are available regardless of the
4286 target machine configuration for the @sc{gnu} assembler.
4288 Some machine configurations provide additional directives.
4289 @xref{Machine Dependencies}.
4292 @ifset machine-directives
4293 @xref{Machine Dependencies}, for additional directives.
4298 * Abort:: @code{.abort}
4300 * ABORT (COFF):: @code{.ABORT}
4303 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4304 * Altmacro:: @code{.altmacro}
4305 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4306 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4307 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4308 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4309 * Byte:: @code{.byte @var{expressions}}
4310 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4311 * Comm:: @code{.comm @var{symbol} , @var{length} }
4312 * Data:: @code{.data @var{subsection}}
4313 * Dc:: @code{.dc[@var{size}] @var{expressions}}
4314 * Dcb:: @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
4315 * Ds:: @code{.ds[@var{size}] @var{number} [,@var{fill}]}
4317 * Def:: @code{.def @var{name}}
4320 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4326 * Double:: @code{.double @var{flonums}}
4327 * Eject:: @code{.eject}
4328 * Else:: @code{.else}
4329 * Elseif:: @code{.elseif}
4332 * Endef:: @code{.endef}
4335 * Endfunc:: @code{.endfunc}
4336 * Endif:: @code{.endif}
4337 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4338 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4339 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4341 * Error:: @code{.error @var{string}}
4342 * Exitm:: @code{.exitm}
4343 * Extern:: @code{.extern}
4344 * Fail:: @code{.fail}
4345 * File:: @code{.file}
4346 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4347 * Float:: @code{.float @var{flonums}}
4348 * Func:: @code{.func}
4349 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4351 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4352 * Hidden:: @code{.hidden @var{names}}
4355 * hword:: @code{.hword @var{expressions}}
4356 * Ident:: @code{.ident}
4357 * If:: @code{.if @var{absolute expression}}
4358 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4359 * Include:: @code{.include "@var{file}"}
4360 * Int:: @code{.int @var{expressions}}
4362 * Internal:: @code{.internal @var{names}}
4365 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4366 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4367 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4368 * Lflags:: @code{.lflags}
4369 @ifclear no-line-dir
4370 * Line:: @code{.line @var{line-number}}
4373 * Linkonce:: @code{.linkonce [@var{type}]}
4374 * List:: @code{.list}
4375 * Ln:: @code{.ln @var{line-number}}
4376 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4377 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4379 * Local:: @code{.local @var{names}}
4382 * Long:: @code{.long @var{expressions}}
4384 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4387 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4388 * MRI:: @code{.mri @var{val}}
4389 * Noaltmacro:: @code{.noaltmacro}
4390 * Nolist:: @code{.nolist}
4391 * Nops:: @code{.nops @var{size}[, @var{control}]}
4392 * Octa:: @code{.octa @var{bignums}}
4393 * Offset:: @code{.offset @var{loc}}
4394 * Org:: @code{.org @var{new-lc}, @var{fill}}
4395 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4397 * PopSection:: @code{.popsection}
4398 * Previous:: @code{.previous}
4401 * Print:: @code{.print @var{string}}
4403 * Protected:: @code{.protected @var{names}}
4406 * Psize:: @code{.psize @var{lines}, @var{columns}}
4407 * Purgem:: @code{.purgem @var{name}}
4409 * PushSection:: @code{.pushsection @var{name}}
4412 * Quad:: @code{.quad @var{bignums}}
4413 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4414 * Rept:: @code{.rept @var{count}}
4415 * Sbttl:: @code{.sbttl "@var{subheading}"}
4417 * Scl:: @code{.scl @var{class}}
4420 * Section:: @code{.section @var{name}[, @var{flags}]}
4423 * Set:: @code{.set @var{symbol}, @var{expression}}
4424 * Short:: @code{.short @var{expressions}}
4425 * Single:: @code{.single @var{flonums}}
4427 * Size:: @code{.size [@var{name} , @var{expression}]}
4429 @ifclear no-space-dir
4430 * Skip:: @code{.skip @var{size} [,@var{fill}]}
4433 * Sleb128:: @code{.sleb128 @var{expressions}}
4434 @ifclear no-space-dir
4435 * Space:: @code{.space @var{size} [,@var{fill}]}
4438 * Stab:: @code{.stabd, .stabn, .stabs}
4441 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4442 * Struct:: @code{.struct @var{expression}}
4444 * SubSection:: @code{.subsection}
4445 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4449 * Tag:: @code{.tag @var{structname}}
4452 * Text:: @code{.text @var{subsection}}
4453 * Title:: @code{.title "@var{heading}"}
4455 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4458 * Uleb128:: @code{.uleb128 @var{expressions}}
4460 * Val:: @code{.val @var{addr}}
4464 * Version:: @code{.version "@var{string}"}
4465 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4466 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4469 * Warning:: @code{.warning @var{string}}
4470 * Weak:: @code{.weak @var{names}}
4471 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4472 * Word:: @code{.word @var{expressions}}
4473 @ifclear no-space-dir
4474 * Zero:: @code{.zero @var{size}}
4477 * 2byte:: @code{.2byte @var{expressions}}
4478 * 4byte:: @code{.4byte @var{expressions}}
4479 * 8byte:: @code{.8byte @var{bignums}}
4481 * Deprecated:: Deprecated Directives
4485 @section @code{.abort}
4487 @cindex @code{abort} directive
4488 @cindex stopping the assembly
4489 This directive stops the assembly immediately. It is for
4490 compatibility with other assemblers. The original idea was that the
4491 assembly language source would be piped into the assembler. If the sender
4492 of the source quit, it could use this directive tells @command{@value{AS}} to
4493 quit also. One day @code{.abort} will not be supported.
4497 @section @code{.ABORT} (COFF)
4499 @cindex @code{ABORT} directive
4500 When producing COFF output, @command{@value{AS}} accepts this directive as a
4501 synonym for @samp{.abort}.
4506 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4508 @cindex padding the location counter
4509 @cindex @code{align} directive
4510 Pad the location counter (in the current subsection) to a particular storage
4511 boundary. The first expression (which must be absolute) is the alignment
4512 required, as described below.
4514 The second expression (also absolute) gives the fill value to be stored in the
4515 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4516 padding bytes are normally zero. However, on most systems, if the section is
4517 marked as containing code and the fill value is omitted, the space is filled
4518 with no-op instructions.
4520 The third expression is also absolute, and is also optional. If it is present,
4521 it is the maximum number of bytes that should be skipped by this alignment
4522 directive. If doing the alignment would require skipping more bytes than the
4523 specified maximum, then the alignment is not done at all. You can omit the
4524 fill value (the second argument) entirely by simply using two commas after the
4525 required alignment; this can be useful if you want the alignment to be filled
4526 with no-op instructions when appropriate.
4528 The way the required alignment is specified varies from system to system.
4529 For the arc, hppa, i386 using ELF, iq2000, m68k, or1k,
4530 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4531 alignment request in bytes. For example @samp{.align 8} advances
4532 the location counter until it is a multiple of 8. If the location counter
4533 is already a multiple of 8, no change is needed. For the tic54x, the
4534 first expression is the alignment request in words.
4536 For other systems, including ppc, i386 using a.out format, arm and
4537 strongarm, it is the
4538 number of low-order zero bits the location counter must have after
4539 advancement. For example @samp{.align 3} advances the location
4540 counter until it a multiple of 8. If the location counter is already a
4541 multiple of 8, no change is needed.
4543 This inconsistency is due to the different behaviors of the various
4544 native assemblers for these systems which GAS must emulate.
4545 GAS also provides @code{.balign} and @code{.p2align} directives,
4546 described later, which have a consistent behavior across all
4547 architectures (but are specific to GAS).
4550 @section @code{.altmacro}
4551 Enable alternate macro mode, enabling:
4554 @item LOCAL @var{name} [ , @dots{} ]
4555 One additional directive, @code{LOCAL}, is available. It is used to
4556 generate a string replacement for each of the @var{name} arguments, and
4557 replace any instances of @var{name} in each macro expansion. The
4558 replacement string is unique in the assembly, and different for each
4559 separate macro expansion. @code{LOCAL} allows you to write macros that
4560 define symbols, without fear of conflict between separate macro expansions.
4562 @item String delimiters
4563 You can write strings delimited in these other ways besides
4564 @code{"@var{string}"}:
4567 @item '@var{string}'
4568 You can delimit strings with single-quote characters.
4570 @item <@var{string}>
4571 You can delimit strings with matching angle brackets.
4574 @item single-character string escape
4575 To include any single character literally in a string (even if the
4576 character would otherwise have some special meaning), you can prefix the
4577 character with @samp{!} (an exclamation mark). For example, you can
4578 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4580 @item Expression results as strings
4581 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4582 and use the result as a string.
4586 @section @code{.ascii "@var{string}"}@dots{}
4588 @cindex @code{ascii} directive
4589 @cindex string literals
4590 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4591 separated by commas. It assembles each string (with no automatic
4592 trailing zero byte) into consecutive addresses.
4595 @section @code{.asciz "@var{string}"}@dots{}
4597 @cindex @code{asciz} directive
4598 @cindex zero-terminated strings
4599 @cindex null-terminated strings
4600 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4601 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4604 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4606 @cindex padding the location counter given number of bytes
4607 @cindex @code{balign} directive
4608 Pad the location counter (in the current subsection) to a particular
4609 storage boundary. The first expression (which must be absolute) is the
4610 alignment request in bytes. For example @samp{.balign 8} advances
4611 the location counter until it is a multiple of 8. If the location counter
4612 is already a multiple of 8, no change is needed.
4614 The second expression (also absolute) gives the fill value to be stored in the
4615 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4616 padding bytes are normally zero. However, on most systems, if the section is
4617 marked as containing code and the fill value is omitted, the space is filled
4618 with no-op instructions.
4620 The third expression is also absolute, and is also optional. If it is present,
4621 it is the maximum number of bytes that should be skipped by this alignment
4622 directive. If doing the alignment would require skipping more bytes than the
4623 specified maximum, then the alignment is not done at all. You can omit the
4624 fill value (the second argument) entirely by simply using two commas after the
4625 required alignment; this can be useful if you want the alignment to be filled
4626 with no-op instructions when appropriate.
4628 @cindex @code{balignw} directive
4629 @cindex @code{balignl} directive
4630 The @code{.balignw} and @code{.balignl} directives are variants of the
4631 @code{.balign} directive. The @code{.balignw} directive treats the fill
4632 pattern as a two byte word value. The @code{.balignl} directives treats the
4633 fill pattern as a four byte longword value. For example, @code{.balignw
4634 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4635 filled in with the value 0x368d (the exact placement of the bytes depends upon
4636 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4639 @node Bundle directives
4640 @section Bundle directives
4641 @subsection @code{.bundle_align_mode @var{abs-expr}}
4642 @cindex @code{bundle_align_mode} directive
4644 @cindex instruction bundle
4645 @cindex aligned instruction bundle
4646 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4647 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4648 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4649 disabled (which is the default state). If the argument it not zero, it
4650 gives the size of an instruction bundle as a power of two (as for the
4651 @code{.p2align} directive, @pxref{P2align}).
4653 For some targets, it's an ABI requirement that no instruction may span a
4654 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4655 instructions that starts on an aligned boundary. For example, if
4656 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4657 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4658 effect, no single instruction may span a boundary between bundles. If an
4659 instruction would start too close to the end of a bundle for the length of
4660 that particular instruction to fit within the bundle, then the space at the
4661 end of that bundle is filled with no-op instructions so the instruction
4662 starts in the next bundle. As a corollary, it's an error if any single
4663 instruction's encoding is longer than the bundle size.
4665 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4666 @cindex @code{bundle_lock} directive
4667 @cindex @code{bundle_unlock} directive
4668 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4669 allow explicit control over instruction bundle padding. These directives
4670 are only valid when @code{.bundle_align_mode} has been used to enable
4671 aligned instruction bundle mode. It's an error if they appear when
4672 @code{.bundle_align_mode} has not been used at all, or when the last
4673 directive was @w{@code{.bundle_align_mode 0}}.
4675 @cindex bundle-locked
4676 For some targets, it's an ABI requirement that certain instructions may
4677 appear only as part of specified permissible sequences of multiple
4678 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4679 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4680 instruction sequence. For purposes of aligned instruction bundle mode, a
4681 sequence starting with @code{.bundle_lock} and ending with
4682 @code{.bundle_unlock} is treated as a single instruction. That is, the
4683 entire sequence must fit into a single bundle and may not span a bundle
4684 boundary. If necessary, no-op instructions will be inserted before the
4685 first instruction of the sequence so that the whole sequence starts on an
4686 aligned bundle boundary. It's an error if the sequence is longer than the
4689 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4690 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4691 nested. That is, a second @code{.bundle_lock} directive before the next
4692 @code{.bundle_unlock} directive has no effect except that it must be
4693 matched by another closing @code{.bundle_unlock} so that there is the
4694 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4697 @section @code{.byte @var{expressions}}
4699 @cindex @code{byte} directive
4700 @cindex integers, one byte
4701 @code{.byte} expects zero or more expressions, separated by commas.
4702 Each expression is assembled into the next byte.
4704 @node CFI directives
4705 @section CFI directives
4706 @subsection @code{.cfi_sections @var{section_list}}
4707 @cindex @code{cfi_sections} directive
4708 @code{.cfi_sections} may be used to specify whether CFI directives
4709 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4710 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4711 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4712 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4713 directive is not used is @code{.cfi_sections .eh_frame}.
4715 On targets that support compact unwinding tables these can be generated
4716 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4718 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4719 which is used by the @value{TIC6X} target.
4721 The @code{.cfi_sections} directive can be repeated, with the same or different
4722 arguments, provided that CFI generation has not yet started. Once CFI
4723 generation has started however the section list is fixed and any attempts to
4724 redefine it will result in an error.
4726 @subsection @code{.cfi_startproc [simple]}
4727 @cindex @code{cfi_startproc} directive
4728 @code{.cfi_startproc} is used at the beginning of each function that
4729 should have an entry in @code{.eh_frame}. It initializes some internal
4730 data structures. Don't forget to close the function by
4731 @code{.cfi_endproc}.
4733 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4734 it also emits some architecture dependent initial CFI instructions.
4736 @subsection @code{.cfi_endproc}
4737 @cindex @code{cfi_endproc} directive
4738 @code{.cfi_endproc} is used at the end of a function where it closes its
4739 unwind entry previously opened by
4740 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4742 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4743 @cindex @code{cfi_personality} directive
4744 @code{.cfi_personality} defines personality routine and its encoding.
4745 @var{encoding} must be a constant determining how the personality
4746 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4747 argument is not present, otherwise second argument should be
4748 a constant or a symbol name. When using indirect encodings,
4749 the symbol provided should be the location where personality
4750 can be loaded from, not the personality routine itself.
4751 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4752 no personality routine.
4754 @subsection @code{.cfi_personality_id @var{id}}
4755 @cindex @code{cfi_personality_id} directive
4756 @code{cfi_personality_id} defines a personality routine by its index as
4757 defined in a compact unwinding format.
4758 Only valid when generating compact EH frames (i.e.
4759 with @code{.cfi_sections eh_frame_entry}.
4761 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4762 @cindex @code{cfi_fde_data} directive
4763 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4764 used for the current function. These are emitted inline in the
4765 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4766 in the @code{.gnu.extab} section otherwise.
4767 Only valid when generating compact EH frames (i.e.
4768 with @code{.cfi_sections eh_frame_entry}.
4770 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4771 @code{.cfi_lsda} defines LSDA and its encoding.
4772 @var{encoding} must be a constant determining how the LSDA
4773 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4774 argument is not present, otherwise the second argument should be a constant
4775 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4776 meaning that no LSDA is present.
4778 @subsection @code{.cfi_inline_lsda} [@var{align}]
4779 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4780 switches to the corresponding @code{.gnu.extab} section.
4781 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4782 Only valid when generating compact EH frames (i.e.
4783 with @code{.cfi_sections eh_frame_entry}.
4785 The table header and unwinding opcodes will be generated at this point,
4786 so that they are immediately followed by the LSDA data. The symbol
4787 referenced by the @code{.cfi_lsda} directive should still be defined
4788 in case a fallback FDE based encoding is used. The LSDA data is terminated
4789 by a section directive.
4791 The optional @var{align} argument specifies the alignment required.
4792 The alignment is specified as a power of two, as with the
4793 @code{.p2align} directive.
4795 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4796 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4797 address from @var{register} and add @var{offset} to it}.
4799 @subsection @code{.cfi_def_cfa_register @var{register}}
4800 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4801 now on @var{register} will be used instead of the old one. Offset
4804 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4805 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4806 remains the same, but @var{offset} is new. Note that it is the
4807 absolute offset that will be added to a defined register to compute
4810 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4811 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4812 value that is added/subtracted from the previous offset.
4814 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4815 Previous value of @var{register} is saved at offset @var{offset} from
4818 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4819 Previous value of @var{register} is CFA + @var{offset}.
4821 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4822 Previous value of @var{register} is saved at offset @var{offset} from
4823 the current CFA register. This is transformed to @code{.cfi_offset}
4824 using the known displacement of the CFA register from the CFA.
4825 This is often easier to use, because the number will match the
4826 code it's annotating.
4828 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4829 Previous value of @var{register1} is saved in register @var{register2}.
4831 @subsection @code{.cfi_restore @var{register}}
4832 @code{.cfi_restore} says that the rule for @var{register} is now the
4833 same as it was at the beginning of the function, after all initial
4834 instruction added by @code{.cfi_startproc} were executed.
4836 @subsection @code{.cfi_undefined @var{register}}
4837 From now on the previous value of @var{register} can't be restored anymore.
4839 @subsection @code{.cfi_same_value @var{register}}
4840 Current value of @var{register} is the same like in the previous frame,
4841 i.e. no restoration needed.
4843 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4844 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4845 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4846 places them in the current row. This is useful for situations where you have
4847 multiple @code{.cfi_*} directives that need to be undone due to the control
4848 flow of the program. For example, we could have something like this (assuming
4849 the CFA is the value of @code{rbp}):
4859 .cfi_def_cfa %rsp, 8
4862 /* Do something else */
4865 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4866 to the instructions before @code{label}. This means we'd have to add multiple
4867 @code{.cfi} directives after @code{label} to recreate the original save
4868 locations of the registers, as well as setting the CFA back to the value of
4869 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4881 .cfi_def_cfa %rsp, 8
4885 /* Do something else */
4888 That way, the rules for the instructions after @code{label} will be the same
4889 as before the first @code{.cfi_restore} without having to use multiple
4890 @code{.cfi} directives.
4892 @subsection @code{.cfi_return_column @var{register}}
4893 Change return column @var{register}, i.e. the return address is either
4894 directly in @var{register} or can be accessed by rules for @var{register}.
4896 @subsection @code{.cfi_signal_frame}
4897 Mark current function as signal trampoline.
4899 @subsection @code{.cfi_window_save}
4900 SPARC register window has been saved.
4902 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4903 Allows the user to add arbitrary bytes to the unwind info. One
4904 might use this to add OS-specific CFI opcodes, or generic CFI
4905 opcodes that GAS does not yet support.
4907 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4908 The current value of @var{register} is @var{label}. The value of @var{label}
4909 will be encoded in the output file according to @var{encoding}; see the
4910 description of @code{.cfi_personality} for details on this encoding.
4912 The usefulness of equating a register to a fixed label is probably
4913 limited to the return address register. Here, it can be useful to
4914 mark a code segment that has only one return address which is reached
4915 by a direct branch and no copy of the return address exists in memory
4916 or another register.
4919 @section @code{.comm @var{symbol} , @var{length} }
4921 @cindex @code{comm} directive
4922 @cindex symbol, common
4923 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4924 common symbol in one object file may be merged with a defined or common symbol
4925 of the same name in another object file. If @code{@value{LD}} does not see a
4926 definition for the symbol--just one or more common symbols--then it will
4927 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4928 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4929 the same name, and they do not all have the same size, it will allocate space
4930 using the largest size.
4933 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4934 an optional third argument. This is the desired alignment of the symbol,
4935 specified for ELF as a byte boundary (for example, an alignment of 16 means
4936 that the least significant 4 bits of the address should be zero), and for PE
4937 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4938 boundary). The alignment must be an absolute expression, and it must be a
4939 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4940 common symbol, it will use the alignment when placing the symbol. If no
4941 alignment is specified, @command{@value{AS}} will set the alignment to the
4942 largest power of two less than or equal to the size of the symbol, up to a
4943 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4944 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4945 @samp{--section-alignment} option; image file sections in PE are aligned to
4946 multiples of 4096, which is far too large an alignment for ordinary variables.
4947 It is rather the default alignment for (non-debug) sections within object
4948 (@samp{*.o}) files, which are less strictly aligned.}.
4952 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4953 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4957 @section @code{.data @var{subsection}}
4958 @cindex @code{data} directive
4960 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4961 end of the data subsection numbered @var{subsection} (which is an
4962 absolute expression). If @var{subsection} is omitted, it defaults
4966 @section @code{.dc[@var{size}] @var{expressions}}
4967 @cindex @code{dc} directive
4969 The @code{.dc} directive expects zero or more @var{expressions} separated by
4970 commas. These expressions are evaluated and their values inserted into the
4971 current section. The size of the emitted value depends upon the suffix to the
4972 @code{.dc} directive:
4976 Emits N-bit values, where N is the size of an address on the target system.
4980 Emits double precision floating-point values.
4982 Emits 32-bit values.
4984 Emits single precision floating-point values.
4986 Emits 16-bit values.
4987 Note - this is true even on targets where the @code{.word} directive would emit
4990 Emits long double precision floating-point values.
4993 If no suffix is used then @samp{.w} is assumed.
4995 The byte ordering is target dependent, as is the size and format of floating
4999 @section @code{.dcb[@var{size}] @var{number} [,@var{fill}]}
5000 @cindex @code{dcb} directive
5001 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5002 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5003 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5004 @var{size} suffix, if present, must be one of:
5008 Emits single byte values.
5010 Emits double-precision floating point values.
5012 Emits 4-byte values.
5014 Emits single-precision floating point values.
5016 Emits 2-byte values.
5018 Emits long double-precision floating point values.
5021 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5023 The byte ordering is target dependent, as is the size and format of floating
5027 @section @code{.ds[@var{size}] @var{number} [,@var{fill}]}
5028 @cindex @code{ds} directive
5029 This directive emits @var{number} copies of @var{fill}, each of @var{size}
5030 bytes. Both @var{number} and @var{fill} are absolute expressions. If the
5031 comma and @var{fill} are omitted, @var{fill} is assumed to be zero. The
5032 @var{size} suffix, if present, must be one of:
5036 Emits single byte values.
5038 Emits 8-byte values.
5040 Emits 4-byte values.
5042 Emits 12-byte values.
5044 Emits 4-byte values.
5046 Emits 2-byte values.
5048 Emits 12-byte values.
5051 Note - unlike the @code{.dcb} directive the @samp{.d}, @samp{.s} and @samp{.x}
5052 suffixes do not indicate that floating-point values are to be inserted.
5054 If the @var{size} suffix is omitted then @samp{.w} is assumed.
5056 The byte ordering is target dependent.
5061 @section @code{.def @var{name}}
5063 @cindex @code{def} directive
5064 @cindex COFF symbols, debugging
5065 @cindex debugging COFF symbols
5066 Begin defining debugging information for a symbol @var{name}; the
5067 definition extends until the @code{.endef} directive is encountered.
5072 @section @code{.desc @var{symbol}, @var{abs-expression}}
5074 @cindex @code{desc} directive
5075 @cindex COFF symbol descriptor
5076 @cindex symbol descriptor, COFF
5077 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5078 to the low 16 bits of an absolute expression.
5081 The @samp{.desc} directive is not available when @command{@value{AS}} is
5082 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5083 object format. For the sake of compatibility, @command{@value{AS}} accepts
5084 it, but produces no output, when configured for COFF.
5090 @section @code{.dim}
5092 @cindex @code{dim} directive
5093 @cindex COFF auxiliary symbol information
5094 @cindex auxiliary symbol information, COFF
5095 This directive is generated by compilers to include auxiliary debugging
5096 information in the symbol table. It is only permitted inside
5097 @code{.def}/@code{.endef} pairs.
5101 @section @code{.double @var{flonums}}
5103 @cindex @code{double} directive
5104 @cindex floating point numbers (double)
5105 @code{.double} expects zero or more flonums, separated by commas. It
5106 assembles floating point numbers.
5108 The exact kind of floating point numbers emitted depends on how
5109 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5113 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5114 in @sc{ieee} format.
5119 @section @code{.eject}
5121 @cindex @code{eject} directive
5122 @cindex new page, in listings
5123 @cindex page, in listings
5124 @cindex listing control: new page
5125 Force a page break at this point, when generating assembly listings.
5128 @section @code{.else}
5130 @cindex @code{else} directive
5131 @code{.else} is part of the @command{@value{AS}} support for conditional
5132 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5133 of code to be assembled if the condition for the preceding @code{.if}
5137 @section @code{.elseif}
5139 @cindex @code{elseif} directive
5140 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5141 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5142 @code{.if} block that would otherwise fill the entire @code{.else} section.
5145 @section @code{.end}
5147 @cindex @code{end} directive
5148 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5149 process anything in the file past the @code{.end} directive.
5153 @section @code{.endef}
5155 @cindex @code{endef} directive
5156 This directive flags the end of a symbol definition begun with
5161 @section @code{.endfunc}
5162 @cindex @code{endfunc} directive
5163 @code{.endfunc} marks the end of a function specified with @code{.func}.
5166 @section @code{.endif}
5168 @cindex @code{endif} directive
5169 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5170 it marks the end of a block of code that is only assembled
5171 conditionally. @xref{If,,@code{.if}}.
5174 @section @code{.equ @var{symbol}, @var{expression}}
5176 @cindex @code{equ} directive
5177 @cindex assigning values to symbols
5178 @cindex symbols, assigning values to
5179 This directive sets the value of @var{symbol} to @var{expression}.
5180 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5183 The syntax for @code{equ} on the HPPA is
5184 @samp{@var{symbol} .equ @var{expression}}.
5188 The syntax for @code{equ} on the Z80 is
5189 @samp{@var{symbol} equ @var{expression}}.
5190 On the Z80 it is an error if @var{symbol} is already defined,
5191 but the symbol is not protected from later redefinition.
5192 Compare @ref{Equiv}.
5196 @section @code{.equiv @var{symbol}, @var{expression}}
5197 @cindex @code{equiv} directive
5198 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5199 the assembler will signal an error if @var{symbol} is already defined. Note a
5200 symbol which has been referenced but not actually defined is considered to be
5203 Except for the contents of the error message, this is roughly equivalent to
5210 plus it protects the symbol from later redefinition.
5213 @section @code{.eqv @var{symbol}, @var{expression}}
5214 @cindex @code{eqv} directive
5215 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5216 evaluate the expression or any part of it immediately. Instead each time
5217 the resulting symbol is used in an expression, a snapshot of its current
5221 @section @code{.err}
5222 @cindex @code{err} directive
5223 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5224 message and, unless the @option{-Z} option was used, it will not generate an
5225 object file. This can be used to signal an error in conditionally compiled code.
5228 @section @code{.error "@var{string}"}
5229 @cindex error directive
5231 Similarly to @code{.err}, this directive emits an error, but you can specify a
5232 string that will be emitted as the error message. If you don't specify the
5233 message, it defaults to @code{".error directive invoked in source file"}.
5234 @xref{Errors, ,Error and Warning Messages}.
5237 .error "This code has not been assembled and tested."
5241 @section @code{.exitm}
5242 Exit early from the current macro definition. @xref{Macro}.
5245 @section @code{.extern}
5247 @cindex @code{extern} directive
5248 @code{.extern} is accepted in the source program---for compatibility
5249 with other assemblers---but it is ignored. @command{@value{AS}} treats
5250 all undefined symbols as external.
5253 @section @code{.fail @var{expression}}
5255 @cindex @code{fail} directive
5256 Generates an error or a warning. If the value of the @var{expression} is 500
5257 or more, @command{@value{AS}} will print a warning message. If the value is less
5258 than 500, @command{@value{AS}} will print an error message. The message will
5259 include the value of @var{expression}. This can occasionally be useful inside
5260 complex nested macros or conditional assembly.
5263 @section @code{.file}
5264 @cindex @code{file} directive
5266 @ifclear no-file-dir
5267 There are two different versions of the @code{.file} directive. Targets
5268 that support DWARF2 line number information use the DWARF2 version of
5269 @code{.file}. Other targets use the default version.
5271 @subheading Default Version
5273 @cindex logical file name
5274 @cindex file name, logical
5275 This version of the @code{.file} directive tells @command{@value{AS}} that we
5276 are about to start a new logical file. The syntax is:
5282 @var{string} is the new file name. In general, the filename is
5283 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5284 to specify an empty file name, you must give the quotes--@code{""}. This
5285 statement may go away in future: it is only recognized to be compatible with
5286 old @command{@value{AS}} programs.
5288 @subheading DWARF2 Version
5291 When emitting DWARF2 line number information, @code{.file} assigns filenames
5292 to the @code{.debug_line} file name table. The syntax is:
5295 .file @var{fileno} @var{filename}
5298 The @var{fileno} operand should be a unique positive integer to use as the
5299 index of the entry in the table. The @var{filename} operand is a C string
5302 The detail of filename indices is exposed to the user because the filename
5303 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5304 information, and thus the user must know the exact indices that table
5308 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5310 @cindex @code{fill} directive
5311 @cindex writing patterns in memory
5312 @cindex patterns, writing in memory
5313 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5314 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5315 may be zero or more. @var{Size} may be zero or more, but if it is
5316 more than 8, then it is deemed to have the value 8, compatible with
5317 other people's assemblers. The contents of each @var{repeat} bytes
5318 is taken from an 8-byte number. The highest order 4 bytes are
5319 zero. The lowest order 4 bytes are @var{value} rendered in the
5320 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5321 Each @var{size} bytes in a repetition is taken from the lowest order
5322 @var{size} bytes of this number. Again, this bizarre behavior is
5323 compatible with other people's assemblers.
5325 @var{size} and @var{value} are optional.
5326 If the second comma and @var{value} are absent, @var{value} is
5327 assumed zero. If the first comma and following tokens are absent,
5328 @var{size} is assumed to be 1.
5331 @section @code{.float @var{flonums}}
5333 @cindex floating point numbers (single)
5334 @cindex @code{float} directive
5335 This directive assembles zero or more flonums, separated by commas. It
5336 has the same effect as @code{.single}.
5338 The exact kind of floating point numbers emitted depends on how
5339 @command{@value{AS}} is configured.
5340 @xref{Machine Dependencies}.
5344 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5345 in @sc{ieee} format.
5350 @section @code{.func @var{name}[,@var{label}]}
5351 @cindex @code{func} directive
5352 @code{.func} emits debugging information to denote function @var{name}, and
5353 is ignored unless the file is assembled with debugging enabled.
5354 Only @samp{--gstabs[+]} is currently supported.
5355 @var{label} is the entry point of the function and if omitted @var{name}
5356 prepended with the @samp{leading char} is used.
5357 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5358 All functions are currently defined to have @code{void} return type.
5359 The function must be terminated with @code{.endfunc}.
5362 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5364 @cindex @code{global} directive
5365 @cindex symbol, making visible to linker
5366 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5367 @var{symbol} in your partial program, its value is made available to
5368 other partial programs that are linked with it. Otherwise,
5369 @var{symbol} takes its attributes from a symbol of the same name
5370 from another file linked into the same program.
5372 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5373 compatibility with other assemblers.
5376 On the HPPA, @code{.global} is not always enough to make it accessible to other
5377 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5378 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5383 @section @code{.gnu_attribute @var{tag},@var{value}}
5384 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5387 @section @code{.hidden @var{names}}
5389 @cindex @code{hidden} directive
5391 This is one of the ELF visibility directives. The other two are
5392 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5393 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5395 This directive overrides the named symbols default visibility (which is set by
5396 their binding: local, global or weak). The directive sets the visibility to
5397 @code{hidden} which means that the symbols are not visible to other components.
5398 Such symbols are always considered to be @code{protected} as well.
5402 @section @code{.hword @var{expressions}}
5404 @cindex @code{hword} directive
5405 @cindex integers, 16-bit
5406 @cindex numbers, 16-bit
5407 @cindex sixteen bit integers
5408 This expects zero or more @var{expressions}, and emits
5409 a 16 bit number for each.
5412 This directive is a synonym for @samp{.short}; depending on the target
5413 architecture, it may also be a synonym for @samp{.word}.
5417 This directive is a synonym for @samp{.short}.
5420 This directive is a synonym for both @samp{.short} and @samp{.word}.
5425 @section @code{.ident}
5427 @cindex @code{ident} directive
5429 This directive is used by some assemblers to place tags in object files. The
5430 behavior of this directive varies depending on the target. When using the
5431 a.out object file format, @command{@value{AS}} simply accepts the directive for
5432 source-file compatibility with existing assemblers, but does not emit anything
5433 for it. When using COFF, comments are emitted to the @code{.comment} or
5434 @code{.rdata} section, depending on the target. When using ELF, comments are
5435 emitted to the @code{.comment} section.
5438 @section @code{.if @var{absolute expression}}
5440 @cindex conditional assembly
5441 @cindex @code{if} directive
5442 @code{.if} marks the beginning of a section of code which is only
5443 considered part of the source program being assembled if the argument
5444 (which must be an @var{absolute expression}) is non-zero. The end of
5445 the conditional section of code must be marked by @code{.endif}
5446 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5447 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5448 If you have several conditions to check, @code{.elseif} may be used to avoid
5449 nesting blocks if/else within each subsequent @code{.else} block.
5451 The following variants of @code{.if} are also supported:
5453 @cindex @code{ifdef} directive
5454 @item .ifdef @var{symbol}
5455 Assembles the following section of code if the specified @var{symbol}
5456 has been defined. Note a symbol which has been referenced but not yet defined
5457 is considered to be undefined.
5459 @cindex @code{ifb} directive
5460 @item .ifb @var{text}
5461 Assembles the following section of code if the operand is blank (empty).
5463 @cindex @code{ifc} directive
5464 @item .ifc @var{string1},@var{string2}
5465 Assembles the following section of code if the two strings are the same. The
5466 strings may be optionally quoted with single quotes. If they are not quoted,
5467 the first string stops at the first comma, and the second string stops at the
5468 end of the line. Strings which contain whitespace should be quoted. The
5469 string comparison is case sensitive.
5471 @cindex @code{ifeq} directive
5472 @item .ifeq @var{absolute expression}
5473 Assembles the following section of code if the argument is zero.
5475 @cindex @code{ifeqs} directive
5476 @item .ifeqs @var{string1},@var{string2}
5477 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5479 @cindex @code{ifge} directive
5480 @item .ifge @var{absolute expression}
5481 Assembles the following section of code if the argument is greater than or
5484 @cindex @code{ifgt} directive
5485 @item .ifgt @var{absolute expression}
5486 Assembles the following section of code if the argument is greater than zero.
5488 @cindex @code{ifle} directive
5489 @item .ifle @var{absolute expression}
5490 Assembles the following section of code if the argument is less than or equal
5493 @cindex @code{iflt} directive
5494 @item .iflt @var{absolute expression}
5495 Assembles the following section of code if the argument is less than zero.
5497 @cindex @code{ifnb} directive
5498 @item .ifnb @var{text}
5499 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5500 following section of code if the operand is non-blank (non-empty).
5502 @cindex @code{ifnc} directive
5503 @item .ifnc @var{string1},@var{string2}.
5504 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5505 following section of code if the two strings are not the same.
5507 @cindex @code{ifndef} directive
5508 @cindex @code{ifnotdef} directive
5509 @item .ifndef @var{symbol}
5510 @itemx .ifnotdef @var{symbol}
5511 Assembles the following section of code if the specified @var{symbol}
5512 has not been defined. Both spelling variants are equivalent. Note a symbol
5513 which has been referenced but not yet defined is considered to be undefined.
5515 @cindex @code{ifne} directive
5516 @item .ifne @var{absolute expression}
5517 Assembles the following section of code if the argument is not equal to zero
5518 (in other words, this is equivalent to @code{.if}).
5520 @cindex @code{ifnes} directive
5521 @item .ifnes @var{string1},@var{string2}
5522 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5523 following section of code if the two strings are not the same.
5527 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5529 @cindex @code{incbin} directive
5530 @cindex binary files, including
5531 The @code{incbin} directive includes @var{file} verbatim at the current
5532 location. You can control the search paths used with the @samp{-I} command-line
5533 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5536 The @var{skip} argument skips a number of bytes from the start of the
5537 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5538 read. Note that the data is not aligned in any way, so it is the user's
5539 responsibility to make sure that proper alignment is provided both before and
5540 after the @code{incbin} directive.
5543 @section @code{.include "@var{file}"}
5545 @cindex @code{include} directive
5546 @cindex supporting files, including
5547 @cindex files, including
5548 This directive provides a way to include supporting files at specified
5549 points in your source program. The code from @var{file} is assembled as
5550 if it followed the point of the @code{.include}; when the end of the
5551 included file is reached, assembly of the original file continues. You
5552 can control the search paths used with the @samp{-I} command-line option
5553 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5557 @section @code{.int @var{expressions}}
5559 @cindex @code{int} directive
5560 @cindex integers, 32-bit
5561 Expect zero or more @var{expressions}, of any section, separated by commas.
5562 For each expression, emit a number that, at run time, is the value of that
5563 expression. The byte order and bit size of the number depends on what kind
5564 of target the assembly is for.
5568 On most forms of the H8/300, @code{.int} emits 16-bit
5569 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5576 @section @code{.internal @var{names}}
5578 @cindex @code{internal} directive
5580 This is one of the ELF visibility directives. The other two are
5581 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5582 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5584 This directive overrides the named symbols default visibility (which is set by
5585 their binding: local, global or weak). The directive sets the visibility to
5586 @code{internal} which means that the symbols are considered to be @code{hidden}
5587 (i.e., not visible to other components), and that some extra, processor specific
5588 processing must also be performed upon the symbols as well.
5592 @section @code{.irp @var{symbol},@var{values}}@dots{}
5594 @cindex @code{irp} directive
5595 Evaluate a sequence of statements assigning different values to @var{symbol}.
5596 The sequence of statements starts at the @code{.irp} directive, and is
5597 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5598 set to @var{value}, and the sequence of statements is assembled. If no
5599 @var{value} is listed, the sequence of statements is assembled once, with
5600 @var{symbol} set to the null string. To refer to @var{symbol} within the
5601 sequence of statements, use @var{\symbol}.
5603 For example, assembling
5611 is equivalent to assembling
5619 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5622 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5624 @cindex @code{irpc} directive
5625 Evaluate a sequence of statements assigning different values to @var{symbol}.
5626 The sequence of statements starts at the @code{.irpc} directive, and is
5627 terminated by an @code{.endr} directive. For each character in @var{value},
5628 @var{symbol} is set to the character, and the sequence of statements is
5629 assembled. If no @var{value} is listed, the sequence of statements is
5630 assembled once, with @var{symbol} set to the null string. To refer to
5631 @var{symbol} within the sequence of statements, use @var{\symbol}.
5633 For example, assembling
5641 is equivalent to assembling
5649 For some caveats with the spelling of @var{symbol}, see also the discussion
5653 @section @code{.lcomm @var{symbol} , @var{length}}
5655 @cindex @code{lcomm} directive
5656 @cindex local common symbols
5657 @cindex symbols, local common
5658 Reserve @var{length} (an absolute expression) bytes for a local common
5659 denoted by @var{symbol}. The section and value of @var{symbol} are
5660 those of the new local common. The addresses are allocated in the bss
5661 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5662 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5663 not visible to @code{@value{LD}}.
5666 Some targets permit a third argument to be used with @code{.lcomm}. This
5667 argument specifies the desired alignment of the symbol in the bss section.
5671 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5672 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5676 @section @code{.lflags}
5678 @cindex @code{lflags} directive (ignored)
5679 @command{@value{AS}} accepts this directive, for compatibility with other
5680 assemblers, but ignores it.
5682 @ifclear no-line-dir
5684 @section @code{.line @var{line-number}}
5686 @cindex @code{line} directive
5687 @cindex logical line number
5689 Change the logical line number. @var{line-number} must be an absolute
5690 expression. The next line has that logical line number. Therefore any other
5691 statements on the current line (after a statement separator character) are
5692 reported as on logical line number @var{line-number} @minus{} 1. One day
5693 @command{@value{AS}} will no longer support this directive: it is recognized only
5694 for compatibility with existing assembler programs.
5697 Even though this is a directive associated with the @code{a.out} or
5698 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5699 when producing COFF output, and treats @samp{.line} as though it
5700 were the COFF @samp{.ln} @emph{if} it is found outside a
5701 @code{.def}/@code{.endef} pair.
5703 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5704 used by compilers to generate auxiliary symbol information for
5709 @section @code{.linkonce [@var{type}]}
5711 @cindex @code{linkonce} directive
5712 @cindex common sections
5713 Mark the current section so that the linker only includes a single copy of it.
5714 This may be used to include the same section in several different object files,
5715 but ensure that the linker will only include it once in the final output file.
5716 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5717 Duplicate sections are detected based on the section name, so it should be
5720 This directive is only supported by a few object file formats; as of this
5721 writing, the only object file format which supports it is the Portable
5722 Executable format used on Windows NT.
5724 The @var{type} argument is optional. If specified, it must be one of the
5725 following strings. For example:
5729 Not all types may be supported on all object file formats.
5733 Silently discard duplicate sections. This is the default.
5736 Warn if there are duplicate sections, but still keep only one copy.
5739 Warn if any of the duplicates have different sizes.
5742 Warn if any of the duplicates do not have exactly the same contents.
5746 @section @code{.list}
5748 @cindex @code{list} directive
5749 @cindex listing control, turning on
5750 Control (in conjunction with the @code{.nolist} directive) whether or
5751 not assembly listings are generated. These two directives maintain an
5752 internal counter (which is zero initially). @code{.list} increments the
5753 counter, and @code{.nolist} decrements it. Assembly listings are
5754 generated whenever the counter is greater than zero.
5756 By default, listings are disabled. When you enable them (with the
5757 @samp{-a} command-line option; @pxref{Invoking,,Command-Line Options}),
5758 the initial value of the listing counter is one.
5761 @section @code{.ln @var{line-number}}
5763 @cindex @code{ln} directive
5764 @ifclear no-line-dir
5765 @samp{.ln} is a synonym for @samp{.line}.
5768 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5769 must be an absolute expression. The next line has that logical
5770 line number, so any other statements on the current line (after a
5771 statement separator character @code{;}) are reported as on logical
5772 line number @var{line-number} @minus{} 1.
5776 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5777 @cindex @code{loc} directive
5778 When emitting DWARF2 line number information,
5779 the @code{.loc} directive will add a row to the @code{.debug_line} line
5780 number matrix corresponding to the immediately following assembly
5781 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5782 arguments will be applied to the @code{.debug_line} state machine before
5785 The @var{options} are a sequence of the following tokens in any order:
5789 This option will set the @code{basic_block} register in the
5790 @code{.debug_line} state machine to @code{true}.
5793 This option will set the @code{prologue_end} register in the
5794 @code{.debug_line} state machine to @code{true}.
5796 @item epilogue_begin
5797 This option will set the @code{epilogue_begin} register in the
5798 @code{.debug_line} state machine to @code{true}.
5800 @item is_stmt @var{value}
5801 This option will set the @code{is_stmt} register in the
5802 @code{.debug_line} state machine to @code{value}, which must be
5805 @item isa @var{value}
5806 This directive will set the @code{isa} register in the @code{.debug_line}
5807 state machine to @var{value}, which must be an unsigned integer.
5809 @item discriminator @var{value}
5810 This directive will set the @code{discriminator} register in the @code{.debug_line}
5811 state machine to @var{value}, which must be an unsigned integer.
5813 @item view @var{value}
5814 This option causes a row to be added to @code{.debug_line} in reference to the
5815 current address (which might not be the same as that of the following assembly
5816 instruction), and to associate @var{value} with the @code{view} register in the
5817 @code{.debug_line} state machine. If @var{value} is a label, both the
5818 @code{view} register and the label are set to the number of prior @code{.loc}
5819 directives at the same program location. If @var{value} is the literal
5820 @code{0}, the @code{view} register is set to zero, and the assembler asserts
5821 that there aren't any prior @code{.loc} directives at the same program
5822 location. If @var{value} is the literal @code{-0}, the assembler arrange for
5823 the @code{view} register to be reset in this row, even if there are prior
5824 @code{.loc} directives at the same program location.
5828 @node Loc_mark_labels
5829 @section @code{.loc_mark_labels @var{enable}}
5830 @cindex @code{loc_mark_labels} directive
5831 When emitting DWARF2 line number information,
5832 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5833 to the @code{.debug_line} line number matrix with the @code{basic_block}
5834 register in the state machine set whenever a code label is seen.
5835 The @var{enable} argument should be either 1 or 0, to enable or disable
5836 this function respectively.
5840 @section @code{.local @var{names}}
5842 @cindex @code{local} directive
5843 This directive, which is available for ELF targets, marks each symbol in
5844 the comma-separated list of @code{names} as a local symbol so that it
5845 will not be externally visible. If the symbols do not already exist,
5846 they will be created.
5848 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5849 accept an alignment argument, which is the case for most ELF targets,
5850 the @code{.local} directive can be used in combination with @code{.comm}
5851 (@pxref{Comm}) to define aligned local common data.
5855 @section @code{.long @var{expressions}}
5857 @cindex @code{long} directive
5858 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5861 @c no one seems to know what this is for or whether this description is
5862 @c what it really ought to do
5864 @section @code{.lsym @var{symbol}, @var{expression}}
5866 @cindex @code{lsym} directive
5867 @cindex symbol, not referenced in assembly
5868 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5869 the hash table, ensuring it cannot be referenced by name during the
5870 rest of the assembly. This sets the attributes of the symbol to be
5871 the same as the expression value:
5873 @var{other} = @var{descriptor} = 0
5874 @var{type} = @r{(section of @var{expression})}
5875 @var{value} = @var{expression}
5878 The new symbol is not flagged as external.
5882 @section @code{.macro}
5885 The commands @code{.macro} and @code{.endm} allow you to define macros that
5886 generate assembly output. For example, this definition specifies a macro
5887 @code{sum} that puts a sequence of numbers into memory:
5890 .macro sum from=0, to=5
5899 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5911 @item .macro @var{macname}
5912 @itemx .macro @var{macname} @var{macargs} @dots{}
5913 @cindex @code{macro} directive
5914 Begin the definition of a macro called @var{macname}. If your macro
5915 definition requires arguments, specify their names after the macro name,
5916 separated by commas or spaces. You can qualify the macro argument to
5917 indicate whether all invocations must specify a non-blank value (through
5918 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5919 (through @samp{:@code{vararg}}). You can supply a default value for any
5920 macro argument by following the name with @samp{=@var{deflt}}. You
5921 cannot define two macros with the same @var{macname} unless it has been
5922 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5923 definitions. For example, these are all valid @code{.macro} statements:
5927 Begin the definition of a macro called @code{comm}, which takes no
5930 @item .macro plus1 p, p1
5931 @itemx .macro plus1 p p1
5932 Either statement begins the definition of a macro called @code{plus1},
5933 which takes two arguments; within the macro definition, write
5934 @samp{\p} or @samp{\p1} to evaluate the arguments.
5936 @item .macro reserve_str p1=0 p2
5937 Begin the definition of a macro called @code{reserve_str}, with two
5938 arguments. The first argument has a default value, but not the second.
5939 After the definition is complete, you can call the macro either as
5940 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5941 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5942 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5943 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5945 @item .macro m p1:req, p2=0, p3:vararg
5946 Begin the definition of a macro called @code{m}, with at least three
5947 arguments. The first argument must always have a value specified, but
5948 not the second, which instead has a default value. The third formal
5949 will get assigned all remaining arguments specified at invocation time.
5951 When you call a macro, you can specify the argument values either by
5952 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5953 @samp{sum to=17, from=9}.
5957 Note that since each of the @var{macargs} can be an identifier exactly
5958 as any other one permitted by the target architecture, there may be
5959 occasional problems if the target hand-crafts special meanings to certain
5960 characters when they occur in a special position. For example, if the colon
5961 (@code{:}) is generally permitted to be part of a symbol name, but the
5962 architecture specific code special-cases it when occurring as the final
5963 character of a symbol (to denote a label), then the macro parameter
5964 replacement code will have no way of knowing that and consider the whole
5965 construct (including the colon) an identifier, and check only this
5966 identifier for being the subject to parameter substitution. So for example
5967 this macro definition:
5975 might not work as expected. Invoking @samp{label foo} might not create a label
5976 called @samp{foo} but instead just insert the text @samp{\l:} into the
5977 assembler source, probably generating an error about an unrecognised
5980 Similarly problems might occur with the period character (@samp{.})
5981 which is often allowed inside opcode names (and hence identifier names). So
5982 for example constructing a macro to build an opcode from a base name and a
5983 length specifier like this:
5986 .macro opcode base length
5991 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5992 instruction but instead generate some kind of error as the assembler tries to
5993 interpret the text @samp{\base.\length}.
5995 There are several possible ways around this problem:
5998 @item Insert white space
5999 If it is possible to use white space characters then this is the simplest
6008 @item Use @samp{\()}
6009 The string @samp{\()} can be used to separate the end of a macro argument from
6010 the following text. eg:
6013 .macro opcode base length
6018 @item Use the alternate macro syntax mode
6019 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6020 used as a separator. eg:
6030 Note: this problem of correctly identifying string parameters to pseudo ops
6031 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6032 and @code{.irpc} (@pxref{Irpc}) as well.
6035 @cindex @code{endm} directive
6036 Mark the end of a macro definition.
6039 @cindex @code{exitm} directive
6040 Exit early from the current macro definition.
6042 @cindex number of macros executed
6043 @cindex macros, count executed
6045 @command{@value{AS}} maintains a counter of how many macros it has
6046 executed in this pseudo-variable; you can copy that number to your
6047 output with @samp{\@@}, but @emph{only within a macro definition}.
6049 @item LOCAL @var{name} [ , @dots{} ]
6050 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6051 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6052 @xref{Altmacro,,@code{.altmacro}}.
6056 @section @code{.mri @var{val}}
6058 @cindex @code{mri} directive
6059 @cindex MRI mode, temporarily
6060 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6061 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6062 affects code assembled until the next @code{.mri} directive, or until the end
6063 of the file. @xref{M, MRI mode, MRI mode}.
6066 @section @code{.noaltmacro}
6067 Disable alternate macro mode. @xref{Altmacro}.
6070 @section @code{.nolist}
6072 @cindex @code{nolist} directive
6073 @cindex listing control, turning off
6074 Control (in conjunction with the @code{.list} directive) whether or
6075 not assembly listings are generated. These two directives maintain an
6076 internal counter (which is zero initially). @code{.list} increments the
6077 counter, and @code{.nolist} decrements it. Assembly listings are
6078 generated whenever the counter is greater than zero.
6081 @section @code{.nops @var{size}[, @var{control}]}
6083 @cindex @code{nops} directive
6084 @cindex filling memory with no-op instructions
6085 This directive emits @var{size} bytes filled with no-op instructions.
6086 @var{size} is absolute expression, which must be a positve value.
6087 @var{control} controls how no-op instructions should be generated. If
6088 the comma and @var{control} are omitted, @var{control} is assumed to be
6091 Note: For Intel 80386 and AMD x86-64 targets, @var{control} specifies
6092 the size limit of a no-op instruction. The valid values of @var{control}
6093 are between 0 and 4 in 16-bit mode, between 0 and 7 when tuning for
6094 older processors in 32-bit mode, between 0 and 11 in 64-bit mode or when
6095 tuning for newer processors in 32-bit mode. When 0 is used, the no-op
6096 instruction size limit is set to the maximum supported size.
6099 @section @code{.octa @var{bignums}}
6101 @c FIXME: double size emitted for "octa" on some? Or warn?
6102 @cindex @code{octa} directive
6103 @cindex integer, 16-byte
6104 @cindex sixteen byte integer
6105 This directive expects zero or more bignums, separated by commas. For each
6106 bignum, it emits a 16-byte integer.
6108 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6109 hence @emph{octa}-word for 16 bytes.
6112 @section @code{.offset @var{loc}}
6114 @cindex @code{offset} directive
6115 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6116 be an absolute expression. This directive may be useful for defining
6117 symbols with absolute values. Do not confuse it with the @code{.org}
6121 @section @code{.org @var{new-lc} , @var{fill}}
6123 @cindex @code{org} directive
6124 @cindex location counter, advancing
6125 @cindex advancing location counter
6126 @cindex current address, advancing
6127 Advance the location counter of the current section to
6128 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6129 expression with the same section as the current subsection. That is,
6130 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6131 wrong section, the @code{.org} directive is ignored. To be compatible
6132 with former assemblers, if the section of @var{new-lc} is absolute,
6133 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6134 is the same as the current subsection.
6136 @code{.org} may only increase the location counter, or leave it
6137 unchanged; you cannot use @code{.org} to move the location counter
6140 @c double negative used below "not undefined" because this is a specific
6141 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6142 @c section. doc@cygnus.com 18feb91
6143 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6144 may not be undefined. If you really detest this restriction we eagerly await
6145 a chance to share your improved assembler.
6147 Beware that the origin is relative to the start of the section, not
6148 to the start of the subsection. This is compatible with other
6149 people's assemblers.
6151 When the location counter (of the current subsection) is advanced, the
6152 intervening bytes are filled with @var{fill} which should be an
6153 absolute expression. If the comma and @var{fill} are omitted,
6154 @var{fill} defaults to zero.
6157 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6159 @cindex padding the location counter given a power of two
6160 @cindex @code{p2align} directive
6161 Pad the location counter (in the current subsection) to a particular
6162 storage boundary. The first expression (which must be absolute) is the
6163 number of low-order zero bits the location counter must have after
6164 advancement. For example @samp{.p2align 3} advances the location
6165 counter until it a multiple of 8. If the location counter is already a
6166 multiple of 8, no change is needed.
6168 The second expression (also absolute) gives the fill value to be stored in the
6169 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6170 padding bytes are normally zero. However, on most systems, if the section is
6171 marked as containing code and the fill value is omitted, the space is filled
6172 with no-op instructions.
6174 The third expression is also absolute, and is also optional. If it is present,
6175 it is the maximum number of bytes that should be skipped by this alignment
6176 directive. If doing the alignment would require skipping more bytes than the
6177 specified maximum, then the alignment is not done at all. You can omit the
6178 fill value (the second argument) entirely by simply using two commas after the
6179 required alignment; this can be useful if you want the alignment to be filled
6180 with no-op instructions when appropriate.
6182 @cindex @code{p2alignw} directive
6183 @cindex @code{p2alignl} directive
6184 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6185 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6186 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6187 fill pattern as a four byte longword value. For example, @code{.p2alignw
6188 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6189 filled in with the value 0x368d (the exact placement of the bytes depends upon
6190 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6195 @section @code{.popsection}
6197 @cindex @code{popsection} directive
6198 @cindex Section Stack
6199 This is one of the ELF section stack manipulation directives. The others are
6200 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6201 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6204 This directive replaces the current section (and subsection) with the top
6205 section (and subsection) on the section stack. This section is popped off the
6211 @section @code{.previous}
6213 @cindex @code{previous} directive
6214 @cindex Section Stack
6215 This is one of the ELF section stack manipulation directives. The others are
6216 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6217 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6218 (@pxref{PopSection}).
6220 This directive swaps the current section (and subsection) with most recently
6221 referenced section/subsection pair prior to this one. Multiple
6222 @code{.previous} directives in a row will flip between two sections (and their
6223 subsections). For example:
6235 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6241 # Now in section A subsection 1
6245 # Now in section B subsection 0
6248 # Now in section B subsection 1
6251 # Now in section B subsection 0
6255 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6256 section B and 0x9abc into subsection 1 of section B.
6258 In terms of the section stack, this directive swaps the current section with
6259 the top section on the section stack.
6263 @section @code{.print @var{string}}
6265 @cindex @code{print} directive
6266 @command{@value{AS}} will print @var{string} on the standard output during
6267 assembly. You must put @var{string} in double quotes.
6271 @section @code{.protected @var{names}}
6273 @cindex @code{protected} directive
6275 This is one of the ELF visibility directives. The other two are
6276 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6278 This directive overrides the named symbols default visibility (which is set by
6279 their binding: local, global or weak). The directive sets the visibility to
6280 @code{protected} which means that any references to the symbols from within the
6281 components that defines them must be resolved to the definition in that
6282 component, even if a definition in another component would normally preempt
6287 @section @code{.psize @var{lines} , @var{columns}}
6289 @cindex @code{psize} directive
6290 @cindex listing control: paper size
6291 @cindex paper size, for listings
6292 Use this directive to declare the number of lines---and, optionally, the
6293 number of columns---to use for each page, when generating listings.
6295 If you do not use @code{.psize}, listings use a default line-count
6296 of 60. You may omit the comma and @var{columns} specification; the
6297 default width is 200 columns.
6299 @command{@value{AS}} generates formfeeds whenever the specified number of
6300 lines is exceeded (or whenever you explicitly request one, using
6303 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6304 those explicitly specified with @code{.eject}.
6307 @section @code{.purgem @var{name}}
6309 @cindex @code{purgem} directive
6310 Undefine the macro @var{name}, so that later uses of the string will not be
6311 expanded. @xref{Macro}.
6315 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6317 @cindex @code{pushsection} directive
6318 @cindex Section Stack
6319 This is one of the ELF section stack manipulation directives. The others are
6320 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6321 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6324 This directive pushes the current section (and subsection) onto the
6325 top of the section stack, and then replaces the current section and
6326 subsection with @code{name} and @code{subsection}. The optional
6327 @code{flags}, @code{type} and @code{arguments} are treated the same
6328 as in the @code{.section} (@pxref{Section}) directive.
6332 @section @code{.quad @var{bignums}}
6334 @cindex @code{quad} directive
6335 @code{.quad} expects zero or more bignums, separated by commas. For
6336 each bignum, it emits
6338 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6339 warning message; and just takes the lowest order 8 bytes of the bignum.
6340 @cindex eight-byte integer
6341 @cindex integer, 8-byte
6343 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6344 hence @emph{quad}-word for 8 bytes.
6347 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6348 warning message; and just takes the lowest order 16 bytes of the bignum.
6349 @cindex sixteen-byte integer
6350 @cindex integer, 16-byte
6354 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6356 @cindex @code{reloc} directive
6357 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6358 @var{expression}. If @var{offset} is a number, the relocation is generated in
6359 the current section. If @var{offset} is an expression that resolves to a
6360 symbol plus offset, the relocation is generated in the given symbol's section.
6361 @var{expression}, if present, must resolve to a symbol plus addend or to an
6362 absolute value, but note that not all targets support an addend. e.g. ELF REL
6363 targets such as i386 store an addend in the section contents rather than in the
6364 relocation. This low level interface does not support addends stored in the
6368 @section @code{.rept @var{count}}
6370 @cindex @code{rept} directive
6371 Repeat the sequence of lines between the @code{.rept} directive and the next
6372 @code{.endr} directive @var{count} times.
6374 For example, assembling
6382 is equivalent to assembling
6390 A count of zero is allowed, but nothing is generated. Negative counts are not
6391 allowed and if encountered will be treated as if they were zero.
6394 @section @code{.sbttl "@var{subheading}"}
6396 @cindex @code{sbttl} directive
6397 @cindex subtitles for listings
6398 @cindex listing control: subtitle
6399 Use @var{subheading} as the title (third line, immediately after the
6400 title line) when generating assembly listings.
6402 This directive affects subsequent pages, as well as the current page if
6403 it appears within ten lines of the top of a page.
6407 @section @code{.scl @var{class}}
6409 @cindex @code{scl} directive
6410 @cindex symbol storage class (COFF)
6411 @cindex COFF symbol storage class
6412 Set the storage-class value for a symbol. This directive may only be
6413 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6414 whether a symbol is static or external, or it may record further
6415 symbolic debugging information.
6420 @section @code{.section @var{name}}
6422 @cindex named section
6423 Use the @code{.section} directive to assemble the following code into a section
6426 This directive is only supported for targets that actually support arbitrarily
6427 named sections; on @code{a.out} targets, for example, it is not accepted, even
6428 with a standard @code{a.out} section name.
6432 @c only print the extra heading if both COFF and ELF are set
6433 @subheading COFF Version
6436 @cindex @code{section} directive (COFF version)
6437 For COFF targets, the @code{.section} directive is used in one of the following
6441 .section @var{name}[, "@var{flags}"]
6442 .section @var{name}[, @var{subsection}]
6445 If the optional argument is quoted, it is taken as flags to use for the
6446 section. Each flag is a single character. The following flags are recognized:
6450 bss section (uninitialized data)
6452 section is not loaded
6458 exclude section from linking
6464 shared section (meaningful for PE targets)
6466 ignored. (For compatibility with the ELF version)
6468 section is not readable (meaningful for PE targets)
6470 single-digit power-of-two section alignment (GNU extension)
6473 If no flags are specified, the default flags depend upon the section name. If
6474 the section name is not recognized, the default will be for the section to be
6475 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6476 from the section, rather than adding them, so if they are used on their own it
6477 will be as if no flags had been specified at all.
6479 If the optional argument to the @code{.section} directive is not quoted, it is
6480 taken as a subsection number (@pxref{Sub-Sections}).
6485 @c only print the extra heading if both COFF and ELF are set
6486 @subheading ELF Version
6489 @cindex Section Stack
6490 This is one of the ELF section stack manipulation directives. The others are
6491 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6492 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6493 @code{.previous} (@pxref{Previous}).
6495 @cindex @code{section} directive (ELF version)
6496 For ELF targets, the @code{.section} directive is used like this:
6499 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6502 @anchor{Section Name Substitutions}
6503 @kindex --sectname-subst
6504 @cindex section name substitution
6505 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6506 argument may contain a substitution sequence. Only @code{%S} is supported
6507 at the moment, and substitutes the current section name. For example:
6510 .macro exception_code
6511 .section %S.exception
6512 [exception code here]
6527 The two @code{exception_code} invocations above would create the
6528 @code{.text.exception} and @code{.init.exception} sections respectively.
6529 This is useful e.g. to discriminate between ancillary sections that are
6530 tied to setup code to be discarded after use from ancillary sections that
6531 need to stay resident without having to define multiple @code{exception_code}
6532 macros just for that purpose.
6534 The optional @var{flags} argument is a quoted string which may contain any
6535 combination of the following characters:
6539 section is allocatable
6541 section is a GNU_MBIND section
6543 section is excluded from executable and shared library.
6547 section is executable
6549 section is mergeable
6551 section contains zero terminated strings
6553 section is a member of a section group
6555 section is used for thread-local-storage
6557 section is a member of the previously-current section's group, if any
6558 @item @code{<number>}
6559 a numeric value indicating the bits to be set in the ELF section header's flags
6560 field. Note - if one or more of the alphabetic characters described above is
6561 also included in the flags field, their bit values will be ORed into the
6563 @item @code{<target specific>}
6564 some targets extend this list with their own flag characters
6567 Note - once a section's flags have been set they cannot be changed. There are
6568 a few exceptions to this rule however. Processor and application specific
6569 flags can be added to an already defined section. The @code{.interp},
6570 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6571 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6572 section may have the executable (@code{x}) flag added.
6574 The optional @var{type} argument may contain one of the following constants:
6578 section contains data
6580 section does not contain data (i.e., section only occupies space)
6582 section contains data which is used by things other than the program
6584 section contains an array of pointers to init functions
6586 section contains an array of pointers to finish functions
6587 @item @@preinit_array
6588 section contains an array of pointers to pre-init functions
6589 @item @@@code{<number>}
6590 a numeric value to be set as the ELF section header's type field.
6591 @item @@@code{<target specific>}
6592 some targets extend this list with their own types
6595 Many targets only support the first three section types. The type may be
6596 enclosed in double quotes if necessary.
6598 Note on targets where the @code{@@} character is the start of a comment (eg
6599 ARM) then another character is used instead. For example the ARM port uses the
6602 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6603 special and have fixed types. Any attempt to declare them with a different
6604 type will generate an error from the assembler.
6606 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6607 be specified as well as an extra argument---@var{entsize}---like this:
6610 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6613 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6614 constants, each @var{entsize} octets long. Sections with both @code{M} and
6615 @code{S} must contain zero terminated strings where each character is
6616 @var{entsize} bytes long. The linker may remove duplicates within sections with
6617 the same name, same entity size and same flags. @var{entsize} must be an
6618 absolute expression. For sections with both @code{M} and @code{S}, a string
6619 which is a suffix of a larger string is considered a duplicate. Thus
6620 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6621 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6623 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6624 be present along with an additional field like this:
6627 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6630 The @var{GroupName} field specifies the name of the section group to which this
6631 particular section belongs. The optional linkage field can contain:
6635 indicates that only one copy of this section should be retained
6640 Note: if both the @var{M} and @var{G} flags are present then the fields for
6641 the Merge flag should come first, like this:
6644 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6647 If @var{flags} contains the @code{?} symbol then it may not also contain the
6648 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6649 present. Instead, @code{?} says to consider the section that's current before
6650 this directive. If that section used @code{G}, then the new section will use
6651 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6652 If not, then the @code{?} symbol has no effect.
6654 If no flags are specified, the default flags depend upon the section name. If
6655 the section name is not recognized, the default will be for the section to have
6656 none of the above flags: it will not be allocated in memory, nor writable, nor
6657 executable. The section will contain data.
6659 For ELF targets, the assembler supports another type of @code{.section}
6660 directive for compatibility with the Solaris assembler:
6663 .section "@var{name}"[, @var{flags}...]
6666 Note that the section name is quoted. There may be a sequence of comma
6671 section is allocatable
6675 section is executable
6677 section is excluded from executable and shared library.
6679 section is used for thread local storage
6682 This directive replaces the current section and subsection. See the
6683 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6684 some examples of how this directive and the other section stack directives
6690 @section @code{.set @var{symbol}, @var{expression}}
6692 @cindex @code{set} directive
6693 @cindex symbol value, setting
6694 Set the value of @var{symbol} to @var{expression}. This
6695 changes @var{symbol}'s value and type to conform to
6696 @var{expression}. If @var{symbol} was flagged as external, it remains
6697 flagged (@pxref{Symbol Attributes}).
6699 You may @code{.set} a symbol many times in the same assembly provided that the
6700 values given to the symbol are constants. Values that are based on expressions
6701 involving other symbols are allowed, but some targets may restrict this to only
6702 being done once per assembly. This is because those targets do not set the
6703 addresses of symbols at assembly time, but rather delay the assignment until a
6704 final link is performed. This allows the linker a chance to change the code in
6705 the files, changing the location of, and the relative distance between, various
6708 If you @code{.set} a global symbol, the value stored in the object
6709 file is the last value stored into it.
6712 On Z80 @code{set} is a real instruction, use
6713 @samp{@var{symbol} defl @var{expression}} instead.
6717 @section @code{.short @var{expressions}}
6719 @cindex @code{short} directive
6721 @code{.short} is normally the same as @samp{.word}.
6722 @xref{Word,,@code{.word}}.
6724 In some configurations, however, @code{.short} and @code{.word} generate
6725 numbers of different lengths. @xref{Machine Dependencies}.
6729 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6732 This expects zero or more @var{expressions}, and emits
6733 a 16 bit number for each.
6738 @section @code{.single @var{flonums}}
6740 @cindex @code{single} directive
6741 @cindex floating point numbers (single)
6742 This directive assembles zero or more flonums, separated by commas. It
6743 has the same effect as @code{.float}.
6745 The exact kind of floating point numbers emitted depends on how
6746 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6750 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6751 numbers in @sc{ieee} format.
6757 @section @code{.size}
6759 This directive is used to set the size associated with a symbol.
6763 @c only print the extra heading if both COFF and ELF are set
6764 @subheading COFF Version
6767 @cindex @code{size} directive (COFF version)
6768 For COFF targets, the @code{.size} directive is only permitted inside
6769 @code{.def}/@code{.endef} pairs. It is used like this:
6772 .size @var{expression}
6779 @c only print the extra heading if both COFF and ELF are set
6780 @subheading ELF Version
6783 @cindex @code{size} directive (ELF version)
6784 For ELF targets, the @code{.size} directive is used like this:
6787 .size @var{name} , @var{expression}
6790 This directive sets the size associated with a symbol @var{name}.
6791 The size in bytes is computed from @var{expression} which can make use of label
6792 arithmetic. This directive is typically used to set the size of function
6797 @ifclear no-space-dir
6799 @section @code{.skip @var{size} [,@var{fill}]}
6801 @cindex @code{skip} directive
6802 @cindex filling memory
6803 This directive emits @var{size} bytes, each of value @var{fill}. Both
6804 @var{size} and @var{fill} are absolute expressions. If the comma and
6805 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6810 @section @code{.sleb128 @var{expressions}}
6812 @cindex @code{sleb128} directive
6813 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6814 compact, variable length representation of numbers used by the DWARF
6815 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6817 @ifclear no-space-dir
6819 @section @code{.space @var{size} [,@var{fill}]}
6821 @cindex @code{space} directive
6822 @cindex filling memory
6823 This directive emits @var{size} bytes, each of value @var{fill}. Both
6824 @var{size} and @var{fill} are absolute expressions. If the comma
6825 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6830 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6831 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6832 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6833 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6841 @section @code{.stabd, .stabn, .stabs}
6843 @cindex symbolic debuggers, information for
6844 @cindex @code{stab@var{x}} directives
6845 There are three directives that begin @samp{.stab}.
6846 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6847 The symbols are not entered in the @command{@value{AS}} hash table: they
6848 cannot be referenced elsewhere in the source file.
6849 Up to five fields are required:
6853 This is the symbol's name. It may contain any character except
6854 @samp{\000}, so is more general than ordinary symbol names. Some
6855 debuggers used to code arbitrarily complex structures into symbol names
6859 An absolute expression. The symbol's type is set to the low 8 bits of
6860 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6861 and debuggers choke on silly bit patterns.
6864 An absolute expression. The symbol's ``other'' attribute is set to the
6865 low 8 bits of this expression.
6868 An absolute expression. The symbol's descriptor is set to the low 16
6869 bits of this expression.
6872 An absolute expression which becomes the symbol's value.
6875 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6876 or @code{.stabs} statement, the symbol has probably already been created;
6877 you get a half-formed symbol in your object file. This is
6878 compatible with earlier assemblers!
6881 @cindex @code{stabd} directive
6882 @item .stabd @var{type} , @var{other} , @var{desc}
6884 The ``name'' of the symbol generated is not even an empty string.
6885 It is a null pointer, for compatibility. Older assemblers used a
6886 null pointer so they didn't waste space in object files with empty
6889 The symbol's value is set to the location counter,
6890 relocatably. When your program is linked, the value of this symbol
6891 is the address of the location counter when the @code{.stabd} was
6894 @cindex @code{stabn} directive
6895 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6896 The name of the symbol is set to the empty string @code{""}.
6898 @cindex @code{stabs} directive
6899 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6900 All five fields are specified.
6906 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6907 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6909 @cindex string, copying to object file
6910 @cindex string8, copying to object file
6911 @cindex string16, copying to object file
6912 @cindex string32, copying to object file
6913 @cindex string64, copying to object file
6914 @cindex @code{string} directive
6915 @cindex @code{string8} directive
6916 @cindex @code{string16} directive
6917 @cindex @code{string32} directive
6918 @cindex @code{string64} directive
6920 Copy the characters in @var{str} to the object file. You may specify more than
6921 one string to copy, separated by commas. Unless otherwise specified for a
6922 particular machine, the assembler marks the end of each string with a 0 byte.
6923 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6925 The variants @code{string16}, @code{string32} and @code{string64} differ from
6926 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6927 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6928 are stored in target endianness byte order.
6934 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6935 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6940 @section @code{.struct @var{expression}}
6942 @cindex @code{struct} directive
6943 Switch to the absolute section, and set the section offset to @var{expression},
6944 which must be an absolute expression. You might use this as follows:
6953 This would define the symbol @code{field1} to have the value 0, the symbol
6954 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6955 value 8. Assembly would be left in the absolute section, and you would need to
6956 use a @code{.section} directive of some sort to change to some other section
6957 before further assembly.
6961 @section @code{.subsection @var{name}}
6963 @cindex @code{subsection} directive
6964 @cindex Section Stack
6965 This is one of the ELF section stack manipulation directives. The others are
6966 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6967 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6970 This directive replaces the current subsection with @code{name}. The current
6971 section is not changed. The replaced subsection is put onto the section stack
6972 in place of the then current top of stack subsection.
6977 @section @code{.symver}
6978 @cindex @code{symver} directive
6979 @cindex symbol versioning
6980 @cindex versions of symbols
6981 Use the @code{.symver} directive to bind symbols to specific version nodes
6982 within a source file. This is only supported on ELF platforms, and is
6983 typically used when assembling files to be linked into a shared library.
6984 There are cases where it may make sense to use this in objects to be bound
6985 into an application itself so as to override a versioned symbol from a
6988 For ELF targets, the @code{.symver} directive can be used like this:
6990 .symver @var{name}, @var{name2@@nodename}
6992 If the symbol @var{name} is defined within the file
6993 being assembled, the @code{.symver} directive effectively creates a symbol
6994 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6995 just don't try and create a regular alias is that the @var{@@} character isn't
6996 permitted in symbol names. The @var{name2} part of the name is the actual name
6997 of the symbol by which it will be externally referenced. The name @var{name}
6998 itself is merely a name of convenience that is used so that it is possible to
6999 have definitions for multiple versions of a function within a single source
7000 file, and so that the compiler can unambiguously know which version of a
7001 function is being mentioned. The @var{nodename} portion of the alias should be
7002 the name of a node specified in the version script supplied to the linker when
7003 building a shared library. If you are attempting to override a versioned
7004 symbol from a shared library, then @var{nodename} should correspond to the
7005 nodename of the symbol you are trying to override.
7007 If the symbol @var{name} is not defined within the file being assembled, all
7008 references to @var{name} will be changed to @var{name2@@nodename}. If no
7009 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
7012 Another usage of the @code{.symver} directive is:
7014 .symver @var{name}, @var{name2@@@@nodename}
7016 In this case, the symbol @var{name} must exist and be defined within
7017 the file being assembled. It is similar to @var{name2@@nodename}. The
7018 difference is @var{name2@@@@nodename} will also be used to resolve
7019 references to @var{name2} by the linker.
7021 The third usage of the @code{.symver} directive is:
7023 .symver @var{name}, @var{name2@@@@@@nodename}
7025 When @var{name} is not defined within the
7026 file being assembled, it is treated as @var{name2@@nodename}. When
7027 @var{name} is defined within the file being assembled, the symbol
7028 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7033 @section @code{.tag @var{structname}}
7035 @cindex COFF structure debugging
7036 @cindex structure debugging, COFF
7037 @cindex @code{tag} directive
7038 This directive is generated by compilers to include auxiliary debugging
7039 information in the symbol table. It is only permitted inside
7040 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7041 definitions in the symbol table with instances of those structures.
7045 @section @code{.text @var{subsection}}
7047 @cindex @code{text} directive
7048 Tells @command{@value{AS}} to assemble the following statements onto the end of
7049 the text subsection numbered @var{subsection}, which is an absolute
7050 expression. If @var{subsection} is omitted, subsection number zero
7054 @section @code{.title "@var{heading}"}
7056 @cindex @code{title} directive
7057 @cindex listing control: title line
7058 Use @var{heading} as the title (second line, immediately after the
7059 source file name and pagenumber) when generating assembly listings.
7061 This directive affects subsequent pages, as well as the current page if
7062 it appears within ten lines of the top of a page.
7066 @section @code{.type}
7068 This directive is used to set the type of a symbol.
7072 @c only print the extra heading if both COFF and ELF are set
7073 @subheading COFF Version
7076 @cindex COFF symbol type
7077 @cindex symbol type, COFF
7078 @cindex @code{type} directive (COFF version)
7079 For COFF targets, this directive is permitted only within
7080 @code{.def}/@code{.endef} pairs. It is used like this:
7086 This records the integer @var{int} as the type attribute of a symbol table
7093 @c only print the extra heading if both COFF and ELF are set
7094 @subheading ELF Version
7097 @cindex ELF symbol type
7098 @cindex symbol type, ELF
7099 @cindex @code{type} directive (ELF version)
7100 For ELF targets, the @code{.type} directive is used like this:
7103 .type @var{name} , @var{type description}
7106 This sets the type of symbol @var{name} to be either a
7107 function symbol or an object symbol. There are five different syntaxes
7108 supported for the @var{type description} field, in order to provide
7109 compatibility with various other assemblers.
7111 Because some of the characters used in these syntaxes (such as @samp{@@} and
7112 @samp{#}) are comment characters for some architectures, some of the syntaxes
7113 below do not work on all architectures. The first variant will be accepted by
7114 the GNU assembler on all architectures so that variant should be used for
7115 maximum portability, if you do not need to assemble your code with other
7118 The syntaxes supported are:
7121 .type <name> STT_<TYPE_IN_UPPER_CASE>
7122 .type <name>,#<type>
7123 .type <name>,@@<type>
7124 .type <name>,%<type>
7125 .type <name>,"<type>"
7128 The types supported are:
7133 Mark the symbol as being a function name.
7136 @itemx gnu_indirect_function
7137 Mark the symbol as an indirect function when evaluated during reloc
7138 processing. (This is only supported on assemblers targeting GNU systems).
7142 Mark the symbol as being a data object.
7146 Mark the symbol as being a thread-local data object.
7150 Mark the symbol as being a common data object.
7154 Does not mark the symbol in any way. It is supported just for completeness.
7156 @item gnu_unique_object
7157 Marks the symbol as being a globally unique data object. The dynamic linker
7158 will make sure that in the entire process there is just one symbol with this
7159 name and type in use. (This is only supported on assemblers targeting GNU
7164 Note: Some targets support extra types in addition to those listed above.
7170 @section @code{.uleb128 @var{expressions}}
7172 @cindex @code{uleb128} directive
7173 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7174 compact, variable length representation of numbers used by the DWARF
7175 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7179 @section @code{.val @var{addr}}
7181 @cindex @code{val} directive
7182 @cindex COFF value attribute
7183 @cindex value attribute, COFF
7184 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7185 records the address @var{addr} as the value attribute of a symbol table
7191 @section @code{.version "@var{string}"}
7193 @cindex @code{version} directive
7194 This directive creates a @code{.note} section and places into it an ELF
7195 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7200 @section @code{.vtable_entry @var{table}, @var{offset}}
7202 @cindex @code{vtable_entry} directive
7203 This directive finds or creates a symbol @code{table} and creates a
7204 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7207 @section @code{.vtable_inherit @var{child}, @var{parent}}
7209 @cindex @code{vtable_inherit} directive
7210 This directive finds the symbol @code{child} and finds or creates the symbol
7211 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7212 parent whose addend is the value of the child symbol. As a special case the
7213 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7217 @section @code{.warning "@var{string}"}
7218 @cindex warning directive
7219 Similar to the directive @code{.error}
7220 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7223 @section @code{.weak @var{names}}
7225 @cindex @code{weak} directive
7226 This directive sets the weak attribute on the comma separated list of symbol
7227 @code{names}. If the symbols do not already exist, they will be created.
7229 On COFF targets other than PE, weak symbols are a GNU extension. This
7230 directive sets the weak attribute on the comma separated list of symbol
7231 @code{names}. If the symbols do not already exist, they will be created.
7233 On the PE target, weak symbols are supported natively as weak aliases.
7234 When a weak symbol is created that is not an alias, GAS creates an
7235 alternate symbol to hold the default value.
7238 @section @code{.weakref @var{alias}, @var{target}}
7240 @cindex @code{weakref} directive
7241 This directive creates an alias to the target symbol that enables the symbol to
7242 be referenced with weak-symbol semantics, but without actually making it weak.
7243 If direct references or definitions of the symbol are present, then the symbol
7244 will not be weak, but if all references to it are through weak references, the
7245 symbol will be marked as weak in the symbol table.
7247 The effect is equivalent to moving all references to the alias to a separate
7248 assembly source file, renaming the alias to the symbol in it, declaring the
7249 symbol as weak there, and running a reloadable link to merge the object files
7250 resulting from the assembly of the new source file and the old source file that
7251 had the references to the alias removed.
7253 The alias itself never makes to the symbol table, and is entirely handled
7254 within the assembler.
7257 @section @code{.word @var{expressions}}
7259 @cindex @code{word} directive
7260 This directive expects zero or more @var{expressions}, of any section,
7261 separated by commas.
7264 For each expression, @command{@value{AS}} emits a 32-bit number.
7267 For each expression, @command{@value{AS}} emits a 16-bit number.
7272 The size of the number emitted, and its byte order,
7273 depend on what target computer the assembly is for.
7276 @c on sparc the "special treatment to support compilers" doesn't
7277 @c happen---32-bit addressability, period; no long/short jumps.
7278 @ifset DIFF-TBL-KLUGE
7279 @cindex difference tables altered
7280 @cindex altered difference tables
7282 @emph{Warning: Special Treatment to support Compilers}
7286 Machines with a 32-bit address space, but that do less than 32-bit
7287 addressing, require the following special treatment. If the machine of
7288 interest to you does 32-bit addressing (or doesn't require it;
7289 @pxref{Machine Dependencies}), you can ignore this issue.
7292 In order to assemble compiler output into something that works,
7293 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7294 Directives of the form @samp{.word sym1-sym2} are often emitted by
7295 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7296 directive of the form @samp{.word sym1-sym2}, and the difference between
7297 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7298 creates a @dfn{secondary jump table}, immediately before the next label.
7299 This secondary jump table is preceded by a short-jump to the
7300 first byte after the secondary table. This short-jump prevents the flow
7301 of control from accidentally falling into the new table. Inside the
7302 table is a long-jump to @code{sym2}. The original @samp{.word}
7303 contains @code{sym1} minus the address of the long-jump to
7306 If there were several occurrences of @samp{.word sym1-sym2} before the
7307 secondary jump table, all of them are adjusted. If there was a
7308 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7309 long-jump to @code{sym4} is included in the secondary jump table,
7310 and the @code{.word} directives are adjusted to contain @code{sym3}
7311 minus the address of the long-jump to @code{sym4}; and so on, for as many
7312 entries in the original jump table as necessary.
7315 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7316 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7317 assembly language programmers.
7320 @c end DIFF-TBL-KLUGE
7322 @ifclear no-space-dir
7324 @section @code{.zero @var{size}}
7326 @cindex @code{zero} directive
7327 @cindex filling memory with zero bytes
7328 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7329 expression. This directive is actually an alias for the @samp{.skip} directive
7330 so in can take an optional second argument of the value to store in the bytes
7331 instead of zero. Using @samp{.zero} in this way would be confusing however.
7336 @section @code{.2byte @var{expression} [, @var{expression}]*}
7337 @cindex @code{2byte} directive
7338 @cindex two-byte integer
7339 @cindex integer, 2-byte
7341 This directive expects zero or more expressions, separated by commas. If there
7342 are no expressions then the directive does nothing. Otherwise each expression
7343 is evaluated in turn and placed in the next two bytes of the current output
7344 section, using the endian model of the target. If an expression will not fit
7345 in two bytes, a warning message is displayed and the least significant two
7346 bytes of the expression's value are used. If an expression cannot be evaluated
7347 at assembly time then relocations will be generated in order to compute the
7350 This directive does not apply any alignment before or after inserting the
7351 values. As a result of this, if relocations are generated, they may be
7352 different from those used for inserting values with a guaranteed alignment.
7354 This directive is only available for ELF targets,
7357 @section @code{.4byte @var{expression} [, @var{expression}]*}
7358 @cindex @code{4byte} directive
7359 @cindex four-byte integer
7360 @cindex integer, 4-byte
7362 Like the @option{.2byte} directive, except that it inserts unaligned, four byte
7363 long values into the output.
7366 @section @code{.8byte @var{expression} [, @var{expression}]*}
7367 @cindex @code{8byte} directive
7368 @cindex eight-byte integer
7369 @cindex integer, 8-byte
7371 Like the @option{.2byte} directive, except that it inserts unaligned, eight
7372 byte long bignum values into the output.
7377 @section Deprecated Directives
7379 @cindex deprecated directives
7380 @cindex obsolescent directives
7381 One day these directives won't work.
7382 They are included for compatibility with older assemblers.
7389 @node Object Attributes
7390 @chapter Object Attributes
7391 @cindex object attributes
7393 @command{@value{AS}} assembles source files written for a specific architecture
7394 into object files for that architecture. But not all object files are alike.
7395 Many architectures support incompatible variations. For instance, floating
7396 point arguments might be passed in floating point registers if the object file
7397 requires hardware floating point support---or floating point arguments might be
7398 passed in integer registers if the object file supports processors with no
7399 hardware floating point unit. Or, if two objects are built for different
7400 generations of the same architecture, the combination may require the
7401 newer generation at run-time.
7403 This information is useful during and after linking. At link time,
7404 @command{@value{LD}} can warn about incompatible object files. After link
7405 time, tools like @command{gdb} can use it to process the linked file
7408 Compatibility information is recorded as a series of object attributes. Each
7409 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7410 string, and indicates who sets the meaning of the tag. The tag is an integer,
7411 and indicates what property the attribute describes. The value may be a string
7412 or an integer, and indicates how the property affects this object. Missing
7413 attributes are the same as attributes with a zero value or empty string value.
7415 Object attributes were developed as part of the ABI for the ARM Architecture.
7416 The file format is documented in @cite{ELF for the ARM Architecture}.
7419 * GNU Object Attributes:: @sc{gnu} Object Attributes
7420 * Defining New Object Attributes:: Defining New Object Attributes
7423 @node GNU Object Attributes
7424 @section @sc{gnu} Object Attributes
7426 The @code{.gnu_attribute} directive records an object attribute
7427 with vendor @samp{gnu}.
7429 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7430 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7431 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7432 2} is set for architecture-independent attributes and clear for
7433 architecture-dependent ones.
7435 @subsection Common @sc{gnu} attributes
7437 These attributes are valid on all architectures.
7440 @item Tag_compatibility (32)
7441 The compatibility attribute takes an integer flag value and a vendor name. If
7442 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7443 then the file is only compatible with the named toolchain. If it is greater
7444 than 1, the file can only be processed by other toolchains under some private
7445 arrangement indicated by the flag value and the vendor name.
7448 @subsection MIPS Attributes
7451 @item Tag_GNU_MIPS_ABI_FP (4)
7452 The floating-point ABI used by this object file. The value will be:
7456 0 for files not affected by the floating-point ABI.
7458 1 for files using the hardware floating-point ABI with a standard
7459 double-precision FPU.
7461 2 for files using the hardware floating-point ABI with a single-precision FPU.
7463 3 for files using the software floating-point ABI.
7465 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7466 floating-point registers, 32-bit general-purpose registers and increased the
7467 number of callee-saved floating-point registers.
7469 5 for files using the hardware floating-point ABI with a double-precision FPU
7470 with either 32-bit or 64-bit floating-point registers and 32-bit
7471 general-purpose registers.
7473 6 for files using the hardware floating-point ABI with 64-bit floating-point
7474 registers and 32-bit general-purpose registers.
7476 7 for files using the hardware floating-point ABI with 64-bit floating-point
7477 registers, 32-bit general-purpose registers and a rule that forbids the
7478 direct use of odd-numbered single-precision floating-point registers.
7482 @subsection PowerPC Attributes
7485 @item Tag_GNU_Power_ABI_FP (4)
7486 The floating-point ABI used by this object file. The value will be:
7490 0 for files not affected by the floating-point ABI.
7492 1 for files using double-precision hardware floating-point ABI.
7494 2 for files using the software floating-point ABI.
7496 3 for files using single-precision hardware floating-point ABI.
7499 @item Tag_GNU_Power_ABI_Vector (8)
7500 The vector ABI used by this object file. The value will be:
7504 0 for files not affected by the vector ABI.
7506 1 for files using general purpose registers to pass vectors.
7508 2 for files using AltiVec registers to pass vectors.
7510 3 for files using SPE registers to pass vectors.
7514 @subsection IBM z Systems Attributes
7517 @item Tag_GNU_S390_ABI_Vector (8)
7518 The vector ABI used by this object file. The value will be:
7522 0 for files not affected by the vector ABI.
7524 1 for files using software vector ABI.
7526 2 for files using hardware vector ABI.
7530 @node Defining New Object Attributes
7531 @section Defining New Object Attributes
7533 If you want to define a new @sc{gnu} object attribute, here are the places you
7534 will need to modify. New attributes should be discussed on the @samp{binutils}
7539 This manual, which is the official register of attributes.
7541 The header for your architecture @file{include/elf}, to define the tag.
7543 The @file{bfd} support file for your architecture, to merge the attribute
7544 and issue any appropriate link warnings.
7546 Test cases in @file{ld/testsuite} for merging and link warnings.
7548 @file{binutils/readelf.c} to display your attribute.
7550 GCC, if you want the compiler to mark the attribute automatically.
7556 @node Machine Dependencies
7557 @chapter Machine Dependent Features
7559 @cindex machine dependencies
7560 The machine instruction sets are (almost by definition) different on
7561 each machine where @command{@value{AS}} runs. Floating point representations
7562 vary as well, and @command{@value{AS}} often supports a few additional
7563 directives or command-line options for compatibility with other
7564 assemblers on a particular platform. Finally, some versions of
7565 @command{@value{AS}} support special pseudo-instructions for branch
7568 This chapter discusses most of these differences, though it does not
7569 include details on any machine's instruction set. For details on that
7570 subject, see the hardware manufacturer's manual.
7574 * AArch64-Dependent:: AArch64 Dependent Features
7577 * Alpha-Dependent:: Alpha Dependent Features
7580 * ARC-Dependent:: ARC Dependent Features
7583 * ARM-Dependent:: ARM Dependent Features
7586 * AVR-Dependent:: AVR Dependent Features
7589 * Blackfin-Dependent:: Blackfin Dependent Features
7592 * CR16-Dependent:: CR16 Dependent Features
7595 * CRIS-Dependent:: CRIS Dependent Features
7598 * C-SKY-Dependent:: C-SKY Dependent Features
7601 * D10V-Dependent:: D10V Dependent Features
7604 * D30V-Dependent:: D30V Dependent Features
7607 * Epiphany-Dependent:: EPIPHANY Dependent Features
7610 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7613 * HPPA-Dependent:: HPPA Dependent Features
7616 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7619 * IA-64-Dependent:: Intel IA-64 Dependent Features
7622 * IP2K-Dependent:: IP2K Dependent Features
7625 * LM32-Dependent:: LM32 Dependent Features
7628 * M32C-Dependent:: M32C Dependent Features
7631 * M32R-Dependent:: M32R Dependent Features
7634 * M68K-Dependent:: M680x0 Dependent Features
7637 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7640 * S12Z-Dependent:: S12Z Dependent Features
7643 * Meta-Dependent :: Meta Dependent Features
7646 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7649 * MIPS-Dependent:: MIPS Dependent Features
7652 * MMIX-Dependent:: MMIX Dependent Features
7655 * MSP430-Dependent:: MSP430 Dependent Features
7658 * NDS32-Dependent:: Andes NDS32 Dependent Features
7661 * NiosII-Dependent:: Altera Nios II Dependent Features
7664 * NS32K-Dependent:: NS32K Dependent Features
7667 * PDP-11-Dependent:: PDP-11 Dependent Features
7670 * PJ-Dependent:: picoJava Dependent Features
7673 * PPC-Dependent:: PowerPC Dependent Features
7676 * PRU-Dependent:: PRU Dependent Features
7679 * RISC-V-Dependent:: RISC-V Dependent Features
7682 * RL78-Dependent:: RL78 Dependent Features
7685 * RX-Dependent:: RX Dependent Features
7688 * S/390-Dependent:: IBM S/390 Dependent Features
7691 * SCORE-Dependent:: SCORE Dependent Features
7694 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7697 * Sparc-Dependent:: SPARC Dependent Features
7700 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7703 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7706 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7709 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7712 * V850-Dependent:: V850 Dependent Features
7715 * Vax-Dependent:: VAX Dependent Features
7718 * Visium-Dependent:: Visium Dependent Features
7721 * WebAssembly-Dependent:: WebAssembly Dependent Features
7724 * XGATE-Dependent:: XGATE Dependent Features
7727 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7730 * Xtensa-Dependent:: Xtensa Dependent Features
7733 * Z80-Dependent:: Z80 Dependent Features
7736 * Z8000-Dependent:: Z8000 Dependent Features
7743 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7744 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7745 @c peculiarity: to preserve cross-references, there must be a node called
7746 @c "Machine Dependencies". Hence the conditional nodenames in each
7747 @c major node below. Node defaulting in makeinfo requires adjacency of
7748 @c node and sectioning commands; hence the repetition of @chapter BLAH
7749 @c in both conditional blocks.
7752 @include c-aarch64.texi
7756 @include c-alpha.texi
7772 @include c-bfin.texi
7776 @include c-cr16.texi
7780 @include c-cris.texi
7784 @include c-csky.texi
7789 @node Machine Dependencies
7790 @chapter Machine Dependent Features
7792 The machine instruction sets are different on each Renesas chip family,
7793 and there are also some syntax differences among the families. This
7794 chapter describes the specific @command{@value{AS}} features for each
7798 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7799 * SH-Dependent:: Renesas SH Dependent Features
7806 @include c-d10v.texi
7810 @include c-d30v.texi
7814 @include c-epiphany.texi
7818 @include c-h8300.texi
7822 @include c-hppa.texi
7826 @include c-i386.texi
7830 @include c-ia64.texi
7834 @include c-ip2k.texi
7838 @include c-lm32.texi
7842 @include c-m32c.texi
7846 @include c-m32r.texi
7850 @include c-m68k.texi
7854 @include c-m68hc11.texi
7858 @include c-s12z.texi
7862 @include c-metag.texi
7866 @include c-microblaze.texi
7870 @include c-mips.texi
7874 @include c-mmix.texi
7878 @include c-msp430.texi
7882 @include c-nds32.texi
7886 @include c-nios2.texi
7890 @include c-ns32k.texi
7894 @include c-pdp11.texi
7910 @include c-riscv.texi
7914 @include c-rl78.texi
7922 @include c-s390.texi
7926 @include c-score.texi
7934 @include c-sparc.texi
7938 @include c-tic54x.texi
7942 @include c-tic6x.texi
7946 @include c-tilegx.texi
7950 @include c-tilepro.texi
7954 @include c-v850.texi
7962 @include c-visium.texi
7966 @include c-wasm32.texi
7970 @include c-xgate.texi
7974 @include c-xstormy16.texi
7978 @include c-xtensa.texi
7990 @c reverse effect of @down at top of generic Machine-Dep chapter
7994 @node Reporting Bugs
7995 @chapter Reporting Bugs
7996 @cindex bugs in assembler
7997 @cindex reporting bugs in assembler
7999 Your bug reports play an essential role in making @command{@value{AS}} reliable.
8001 Reporting a bug may help you by bringing a solution to your problem, or it may
8002 not. But in any case the principal function of a bug report is to help the
8003 entire community by making the next version of @command{@value{AS}} work better.
8004 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
8006 In order for a bug report to serve its purpose, you must include the
8007 information that enables us to fix the bug.
8010 * Bug Criteria:: Have you found a bug?
8011 * Bug Reporting:: How to report bugs
8015 @section Have You Found a Bug?
8016 @cindex bug criteria
8018 If you are not sure whether you have found a bug, here are some guidelines:
8021 @cindex fatal signal
8022 @cindex assembler crash
8023 @cindex crash of assembler
8025 If the assembler gets a fatal signal, for any input whatever, that is a
8026 @command{@value{AS}} bug. Reliable assemblers never crash.
8028 @cindex error on valid input
8030 If @command{@value{AS}} produces an error message for valid input, that is a bug.
8032 @cindex invalid input
8034 If @command{@value{AS}} does not produce an error message for invalid input, that
8035 is a bug. However, you should note that your idea of ``invalid input'' might
8036 be our idea of ``an extension'' or ``support for traditional practice''.
8039 If you are an experienced user of assemblers, your suggestions for improvement
8040 of @command{@value{AS}} are welcome in any case.
8044 @section How to Report Bugs
8046 @cindex assembler bugs, reporting
8048 A number of companies and individuals offer support for @sc{gnu} products. If
8049 you obtained @command{@value{AS}} from a support organization, we recommend you
8050 contact that organization first.
8052 You can find contact information for many support companies and
8053 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8057 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8061 The fundamental principle of reporting bugs usefully is this:
8062 @strong{report all the facts}. If you are not sure whether to state a
8063 fact or leave it out, state it!
8065 Often people omit facts because they think they know what causes the problem
8066 and assume that some details do not matter. Thus, you might assume that the
8067 name of a symbol you use in an example does not matter. Well, probably it does
8068 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8069 happens to fetch from the location where that name is stored in memory;
8070 perhaps, if the name were different, the contents of that location would fool
8071 the assembler into doing the right thing despite the bug. Play it safe and
8072 give a specific, complete example. That is the easiest thing for you to do,
8073 and the most helpful.
8075 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8076 it is new to us. Therefore, always write your bug reports on the assumption
8077 that the bug has not been reported previously.
8079 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8080 bell?'' This cannot help us fix a bug, so it is basically useless. We
8081 respond by asking for enough details to enable us to investigate.
8082 You might as well expedite matters by sending them to begin with.
8084 To enable us to fix the bug, you should include all these things:
8088 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8089 it with the @samp{--version} argument.
8091 Without this, we will not know whether there is any point in looking for
8092 the bug in the current version of @command{@value{AS}}.
8095 Any patches you may have applied to the @command{@value{AS}} source.
8098 The type of machine you are using, and the operating system name and
8102 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8106 The command arguments you gave the assembler to assemble your example and
8107 observe the bug. To guarantee you will not omit something important, list them
8108 all. A copy of the Makefile (or the output from make) is sufficient.
8110 If we were to try to guess the arguments, we would probably guess wrong
8111 and then we might not encounter the bug.
8114 A complete input file that will reproduce the bug. If the bug is observed when
8115 the assembler is invoked via a compiler, send the assembler source, not the
8116 high level language source. Most compilers will produce the assembler source
8117 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8118 the options @samp{-v --save-temps}; this will save the assembler source in a
8119 file with an extension of @file{.s}, and also show you exactly how
8120 @command{@value{AS}} is being run.
8123 A description of what behavior you observe that you believe is
8124 incorrect. For example, ``It gets a fatal signal.''
8126 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8127 will certainly notice it. But if the bug is incorrect output, we might not
8128 notice unless it is glaringly wrong. You might as well not give us a chance to
8131 Even if the problem you experience is a fatal signal, you should still say so
8132 explicitly. Suppose something strange is going on, such as, your copy of
8133 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8134 library on your system. (This has happened!) Your copy might crash and ours
8135 would not. If you told us to expect a crash, then when ours fails to crash, we
8136 would know that the bug was not happening for us. If you had not told us to
8137 expect a crash, then we would not be able to draw any conclusion from our
8141 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8142 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8143 option. Always send diffs from the old file to the new file. If you even
8144 discuss something in the @command{@value{AS}} source, refer to it by context, not
8147 The line numbers in our development sources will not match those in your
8148 sources. Your line numbers would convey no useful information to us.
8151 Here are some things that are not necessary:
8155 A description of the envelope of the bug.
8157 Often people who encounter a bug spend a lot of time investigating
8158 which changes to the input file will make the bug go away and which
8159 changes will not affect it.
8161 This is often time consuming and not very useful, because the way we
8162 will find the bug is by running a single example under the debugger
8163 with breakpoints, not by pure deduction from a series of examples.
8164 We recommend that you save your time for something else.
8166 Of course, if you can find a simpler example to report @emph{instead}
8167 of the original one, that is a convenience for us. Errors in the
8168 output will be easier to spot, running under the debugger will take
8169 less time, and so on.
8171 However, simplification is not vital; if you do not want to do this,
8172 report the bug anyway and send us the entire test case you used.
8175 A patch for the bug.
8177 A patch for the bug does help us if it is a good one. But do not omit
8178 the necessary information, such as the test case, on the assumption that
8179 a patch is all we need. We might see problems with your patch and decide
8180 to fix the problem another way, or we might not understand it at all.
8182 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8183 construct an example that will make the program follow a certain path through
8184 the code. If you do not send us the example, we will not be able to construct
8185 one, so we will not be able to verify that the bug is fixed.
8187 And if we cannot understand what bug you are trying to fix, or why your
8188 patch should be an improvement, we will not install it. A test case will
8189 help us to understand.
8192 A guess about what the bug is or what it depends on.
8194 Such guesses are usually wrong. Even we cannot guess right about such
8195 things without first using the debugger to find the facts.
8198 @node Acknowledgements
8199 @chapter Acknowledgements
8201 If you have contributed to GAS and your name isn't listed here,
8202 it is not meant as a slight. We just don't know about it. Send mail to the
8203 maintainer, and we'll correct the situation. Currently
8205 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8207 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8210 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8211 information and the 68k series machines, most of the preprocessing pass, and
8212 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8214 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8215 many bug fixes, including merging support for several processors, breaking GAS
8216 up to handle multiple object file format back ends (including heavy rewrite,
8217 testing, an integration of the coff and b.out back ends), adding configuration
8218 including heavy testing and verification of cross assemblers and file splits
8219 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8220 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8221 port (including considerable amounts of reverse engineering), a SPARC opcode
8222 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8223 assertions and made them work, much other reorganization, cleanup, and lint.
8225 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8226 in format-specific I/O modules.
8228 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8229 has done much work with it since.
8231 The Intel 80386 machine description was written by Eliot Dresselhaus.
8233 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8235 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8236 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8238 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8239 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8240 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8241 support a.out format.
8243 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8244 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8245 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8246 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8249 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8250 simplified the configuration of which versions accept which directives. He
8251 updated the 68k machine description so that Motorola's opcodes always produced
8252 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8253 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8254 cross-compilation support, and one bug in relaxation that took a week and
8255 required the proverbial one-bit fix.
8257 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8258 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8259 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8260 PowerPC assembler, and made a few other minor patches.
8262 Steve Chamberlain made GAS able to generate listings.
8264 Hewlett-Packard contributed support for the HP9000/300.
8266 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8267 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8268 formats). This work was supported by both the Center for Software Science at
8269 the University of Utah and Cygnus Support.
8271 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8272 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8273 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8274 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8275 and some initial 64-bit support).
8277 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8279 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8280 support for openVMS/Alpha.
8282 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8285 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8286 Inc.@: added support for Xtensa processors.
8288 Several engineers at Cygnus Support have also provided many small bug fixes and
8289 configuration enhancements.
8291 Jon Beniston added support for the Lattice Mico32 architecture.
8293 Many others have contributed large or small bugfixes and enhancements. If
8294 you have contributed significant work and are not mentioned on this list, and
8295 want to be, let us know. Some of the history has been lost; we are not
8296 intentionally leaving anyone out.
8298 @node GNU Free Documentation License
8299 @appendix GNU Free Documentation License
8303 @unnumbered AS Index