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
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2018 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2018 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
238 [@b{--no-pad-sections}]
239 [@b{-o} @var{objfile}] [@b{-R}]
240 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
242 [@b{-v}] [@b{-version}] [@b{--version}]
243 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
244 [@b{-Z}] [@b{@@@var{FILE}}]
245 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
246 [@b{--elf-stt-common=[no|yes]}]
247 [@b{--target-help}] [@var{target-options}]
248 [@b{--}|@var{files} @dots{}]
251 @c Target dependent options are listed below. Keep the list sorted.
252 @c Add an empty line for separation.
256 @emph{Target AArch64 options:}
258 [@b{-mabi}=@var{ABI}]
262 @emph{Target Alpha options:}
264 [@b{-mdebug} | @b{-no-mdebug}]
265 [@b{-replace} | @b{-noreplace}]
266 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
267 [@b{-F}] [@b{-32addr}]
271 @emph{Target ARC options:}
272 [@b{-mcpu=@var{cpu}}]
273 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
280 @emph{Target ARM options:}
281 @c Don't document the deprecated options
282 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
283 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
284 [@b{-mfpu}=@var{floating-point-format}]
285 [@b{-mfloat-abi}=@var{abi}]
286 [@b{-meabi}=@var{ver}]
289 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
290 @b{-mapcs-reentrant}]
291 [@b{-mthumb-interwork}] [@b{-k}]
295 @emph{Target Blackfin options:}
296 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
303 @emph{Target CRIS options:}
304 [@b{--underscore} | @b{--no-underscore}]
306 [@b{--emulation=criself} | @b{--emulation=crisaout}]
307 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
308 @c Deprecated -- deliberately not documented.
313 @emph{Target D10V options:}
318 @emph{Target D30V options:}
319 [@b{-O}|@b{-n}|@b{-N}]
323 @emph{Target EPIPHANY options:}
324 [@b{-mepiphany}|@b{-mepiphany16}]
328 @emph{Target H8/300 options:}
332 @c HPPA has no machine-dependent assembler options (yet).
336 @emph{Target i386 options:}
337 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
338 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
342 @emph{Target i960 options:}
343 @c see md_parse_option in tc-i960.c
344 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
346 [@b{-b}] [@b{-no-relax}]
350 @emph{Target IA-64 options:}
351 [@b{-mconstant-gp}|@b{-mauto-pic}]
352 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
354 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
355 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
356 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
357 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
361 @emph{Target IP2K options:}
362 [@b{-mip2022}|@b{-mip2022ext}]
366 @emph{Target M32C options:}
367 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
371 @emph{Target M32R options:}
372 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
377 @emph{Target M680X0 options:}
378 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
382 @emph{Target M68HC11 options:}
383 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
384 [@b{-mshort}|@b{-mlong}]
385 [@b{-mshort-double}|@b{-mlong-double}]
386 [@b{--force-long-branches}] [@b{--short-branches}]
387 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
388 [@b{--print-opcodes}] [@b{--generate-example}]
392 @emph{Target MCORE options:}
393 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
394 [@b{-mcpu=[210|340]}]
398 @emph{Target Meta options:}
399 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
402 @emph{Target MICROBLAZE options:}
403 @c MicroBlaze has no machine-dependent assembler options.
407 @emph{Target MIPS options:}
408 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
409 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
410 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
411 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
412 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
413 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
414 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
415 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
416 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
417 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
418 [@b{-construct-floats}] [@b{-no-construct-floats}]
419 [@b{-mignore-branch-isa}] [@b{-mno-ignore-branch-isa}]
420 [@b{-mnan=@var{encoding}}]
421 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
422 [@b{-mips16}] [@b{-no-mips16}]
423 [@b{-mmips16e2}] [@b{-mno-mips16e2}]
424 [@b{-mmicromips}] [@b{-mno-micromips}]
425 [@b{-msmartmips}] [@b{-mno-smartmips}]
426 [@b{-mips3d}] [@b{-no-mips3d}]
427 [@b{-mdmx}] [@b{-no-mdmx}]
428 [@b{-mdsp}] [@b{-mno-dsp}]
429 [@b{-mdspr2}] [@b{-mno-dspr2}]
430 [@b{-mdspr3}] [@b{-mno-dspr3}]
431 [@b{-mmsa}] [@b{-mno-msa}]
432 [@b{-mxpa}] [@b{-mno-xpa}]
433 [@b{-mmt}] [@b{-mno-mt}]
434 [@b{-mmcu}] [@b{-mno-mcu}]
435 [@b{-minsn32}] [@b{-mno-insn32}]
436 [@b{-mfix7000}] [@b{-mno-fix7000}]
437 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
438 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
439 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
440 [@b{-mdebug}] [@b{-no-mdebug}]
441 [@b{-mpdr}] [@b{-mno-pdr}]
445 @emph{Target MMIX options:}
446 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
447 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
448 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
449 [@b{--linker-allocated-gregs}]
453 @emph{Target Nios II options:}
454 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
459 @emph{Target NDS32 options:}
460 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
461 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
462 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
463 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
464 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
465 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
466 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
471 @emph{Target PDP11 options:}
472 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
473 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
474 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
478 @emph{Target picoJava options:}
483 @emph{Target PowerPC options:}
485 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
486 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
487 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
488 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
489 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
490 @b{-mcell}|@b{-mspe}|@b{-mspe2}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
491 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
492 [@b{-mregnames}|@b{-mno-regnames}]
493 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
494 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
495 [@b{-msolaris}|@b{-mno-solaris}]
496 [@b{-nops=@var{count}}]
500 @emph{Target PRU options:}
503 [@b{-mno-warn-regname-label}]
507 @emph{Target RISC-V options:}
508 [@b{-fpic}|@b{-fPIC}|@b{-fno-pic}]
509 [@b{-march}=@var{ISA}]
510 [@b{-mabi}=@var{ABI}]
514 @emph{Target RL78 options:}
516 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
520 @emph{Target RX options:}
521 [@b{-mlittle-endian}|@b{-mbig-endian}]
522 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
523 [@b{-muse-conventional-section-names}]
524 [@b{-msmall-data-limit}]
527 [@b{-mint-register=@var{number}}]
528 [@b{-mgcc-abi}|@b{-mrx-abi}]
532 @emph{Target s390 options:}
533 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
534 [@b{-mregnames}|@b{-mno-regnames}]
535 [@b{-mwarn-areg-zero}]
539 @emph{Target SCORE options:}
540 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
541 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
542 [@b{-march=score7}][@b{-march=score3}]
543 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
547 @emph{Target SPARC options:}
548 @c The order here is important. See c-sparc.texi.
549 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
550 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
551 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
552 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
553 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
554 @b{-Asparcvisr}|@b{-Asparc5}]
555 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
556 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
557 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
558 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
559 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
560 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
563 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
567 @emph{Target TIC54X options:}
568 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
569 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
573 @emph{Target TIC6X options:}
574 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
575 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
576 [@b{-mpic}|@b{-mno-pic}]
580 @emph{Target TILE-Gx options:}
581 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
584 @c TILEPro has no machine-dependent assembler options
588 @emph{Target Visium options:}
589 [@b{-mtune=@var{arch}}]
593 @emph{Target Xtensa options:}
594 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
595 [@b{--[no-]absolute-literals}]
596 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
597 [@b{--[no-]transform}]
598 [@b{--rename-section} @var{oldname}=@var{newname}]
599 [@b{--[no-]trampolines}]
603 @emph{Target Z80 options:}
604 [@b{-z80}] [@b{-r800}]
605 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
606 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
607 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
608 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
609 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
610 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
614 @c Z8000 has no machine-dependent assembler options
623 @include at-file.texi
626 Turn on listings, in any of a variety of ways:
630 omit false conditionals
633 omit debugging directives
636 include general information, like @value{AS} version and options passed
639 include high-level source
645 include macro expansions
648 omit forms processing
654 set the name of the listing file
657 You may combine these options; for example, use @samp{-aln} for assembly
658 listing without forms processing. The @samp{=file} option, if used, must be
659 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
662 Begin in alternate macro mode.
664 @xref{Altmacro,,@code{.altmacro}}.
667 @item --compress-debug-sections
668 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
669 ELF ABI. The resulting object file may not be compatible with older
670 linkers and object file utilities. Note if compression would make a
671 given section @emph{larger} then it is not compressed.
674 @cindex @samp{--compress-debug-sections=} option
675 @item --compress-debug-sections=none
676 @itemx --compress-debug-sections=zlib
677 @itemx --compress-debug-sections=zlib-gnu
678 @itemx --compress-debug-sections=zlib-gabi
679 These options control how DWARF debug sections are compressed.
680 @option{--compress-debug-sections=none} is equivalent to
681 @option{--nocompress-debug-sections}.
682 @option{--compress-debug-sections=zlib} and
683 @option{--compress-debug-sections=zlib-gabi} are equivalent to
684 @option{--compress-debug-sections}.
685 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
686 sections using zlib. The debug sections are renamed to begin with
687 @samp{.zdebug}. Note if compression would make a given section
688 @emph{larger} then it is not compressed nor renamed.
692 @item --nocompress-debug-sections
693 Do not compress DWARF debug sections. This is usually the default for all
694 targets except the x86/x86_64, but a configure time option can be used to
698 Ignored. This option is accepted for script compatibility with calls to
701 @item --debug-prefix-map @var{old}=@var{new}
702 When assembling files in directory @file{@var{old}}, record debugging
703 information describing them as in @file{@var{new}} instead.
705 @item --defsym @var{sym}=@var{value}
706 Define the symbol @var{sym} to be @var{value} before assembling the input file.
707 @var{value} must be an integer constant. As in C, a leading @samp{0x}
708 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
709 value. The value of the symbol can be overridden inside a source file via the
710 use of a @code{.set} pseudo-op.
713 ``fast''---skip whitespace and comment preprocessing (assume source is
718 Generate debugging information for each assembler source line using whichever
719 debug format is preferred by the target. This currently means either STABS,
723 Generate stabs debugging information for each assembler line. This
724 may help debugging assembler code, if the debugger can handle it.
727 Generate stabs debugging information for each assembler line, with GNU
728 extensions that probably only gdb can handle, and that could make other
729 debuggers crash or refuse to read your program. This
730 may help debugging assembler code. Currently the only GNU extension is
731 the location of the current working directory at assembling time.
734 Generate DWARF2 debugging information for each assembler line. This
735 may help debugging assembler code, if the debugger can handle it. Note---this
736 option is only supported by some targets, not all of them.
738 @item --gdwarf-sections
739 Instead of creating a .debug_line section, create a series of
740 .debug_line.@var{foo} sections where @var{foo} is the name of the
741 corresponding code section. For example a code section called @var{.text.func}
742 will have its dwarf line number information placed into a section called
743 @var{.debug_line.text.func}. If the code section is just called @var{.text}
744 then debug line section will still be called just @var{.debug_line} without any
748 @item --size-check=error
749 @itemx --size-check=warning
750 Issue an error or warning for invalid ELF .size directive.
752 @item --elf-stt-common=no
753 @itemx --elf-stt-common=yes
754 These options control whether the ELF assembler should generate common
755 symbols with the @code{STT_COMMON} type. The default can be controlled
756 by a configure option @option{--enable-elf-stt-common}.
760 Print a summary of the command line options and exit.
763 Print a summary of all target specific options and exit.
766 Add directory @var{dir} to the search list for @code{.include} directives.
769 Don't warn about signed overflow.
772 @ifclear DIFF-TBL-KLUGE
773 This option is accepted but has no effect on the @value{TARGET} family.
775 @ifset DIFF-TBL-KLUGE
776 Issue warnings when difference tables altered for long displacements.
781 Keep (in the symbol table) local symbols. These symbols start with
782 system-specific local label prefixes, typically @samp{.L} for ELF systems
783 or @samp{L} for traditional a.out systems.
788 @item --listing-lhs-width=@var{number}
789 Set the maximum width, in words, of the output data column for an assembler
790 listing to @var{number}.
792 @item --listing-lhs-width2=@var{number}
793 Set the maximum width, in words, of the output data column for continuation
794 lines in an assembler listing to @var{number}.
796 @item --listing-rhs-width=@var{number}
797 Set the maximum width of an input source line, as displayed in a listing, to
800 @item --listing-cont-lines=@var{number}
801 Set the maximum number of lines printed in a listing for a single line of input
804 @item --no-pad-sections
805 Stop the assembler for padding the ends of output sections to the alignment
806 of that section. The default is to pad the sections, but this can waste space
807 which might be needed on targets which have tight memory constraints.
809 @item -o @var{objfile}
810 Name the object-file output from @command{@value{AS}} @var{objfile}.
813 Fold the data section into the text section.
815 @item --hash-size=@var{number}
816 Set the default size of GAS's hash tables to a prime number close to
817 @var{number}. Increasing this value can reduce the length of time it takes the
818 assembler to perform its tasks, at the expense of increasing the assembler's
819 memory requirements. Similarly reducing this value can reduce the memory
820 requirements at the expense of speed.
822 @item --reduce-memory-overheads
823 This option reduces GAS's memory requirements, at the expense of making the
824 assembly processes slower. Currently this switch is a synonym for
825 @samp{--hash-size=4051}, but in the future it may have other effects as well.
828 @item --sectname-subst
829 Honor substitution sequences in section names.
831 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
836 Print the maximum space (in bytes) and total time (in seconds) used by
839 @item --strip-local-absolute
840 Remove local absolute symbols from the outgoing symbol table.
844 Print the @command{as} version.
847 Print the @command{as} version and exit.
851 Suppress warning messages.
853 @item --fatal-warnings
854 Treat warnings as errors.
857 Don't suppress warning messages or treat them as errors.
866 Generate an object file even after errors.
868 @item -- | @var{files} @dots{}
869 Standard input, or source files to assemble.
877 @xref{AArch64 Options}, for the options available when @value{AS} is configured
878 for the 64-bit mode of the ARM Architecture (AArch64).
883 The following options are available when @value{AS} is configured for the
884 64-bit mode of the ARM Architecture (AArch64).
887 @include c-aarch64.texi
888 @c ended inside the included file
896 @xref{Alpha Options}, for the options available when @value{AS} is configured
897 for an Alpha processor.
902 The following options are available when @value{AS} is configured for an Alpha
906 @include c-alpha.texi
907 @c ended inside the included file
914 The following options are available when @value{AS} is configured for an ARC
918 @item -mcpu=@var{cpu}
919 This option selects the core processor variant.
921 Select either big-endian (-EB) or little-endian (-EL) output.
923 Enable Code Density extenssion instructions.
928 The following options are available when @value{AS} is configured for the ARM
932 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
933 Specify which ARM processor variant is the target.
934 @item -march=@var{architecture}[+@var{extension}@dots{}]
935 Specify which ARM architecture variant is used by the target.
936 @item -mfpu=@var{floating-point-format}
937 Select which Floating Point architecture is the target.
938 @item -mfloat-abi=@var{abi}
939 Select which floating point ABI is in use.
941 Enable Thumb only instruction decoding.
942 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
943 Select which procedure calling convention is in use.
945 Select either big-endian (-EB) or little-endian (-EL) output.
946 @item -mthumb-interwork
947 Specify that the code has been generated with interworking between Thumb and
950 Turns on CodeComposer Studio assembly syntax compatibility mode.
952 Specify that PIC code has been generated.
960 @xref{Blackfin Options}, for the options available when @value{AS} is
961 configured for the Blackfin processor family.
966 The following options are available when @value{AS} is configured for
967 the Blackfin processor family.
971 @c ended inside the included file
978 See the info pages for documentation of the CRIS-specific options.
982 The following options are available when @value{AS} is configured for
985 @cindex D10V optimization
986 @cindex optimization, D10V
988 Optimize output by parallelizing instructions.
993 The following options are available when @value{AS} is configured for a D30V
996 @cindex D30V optimization
997 @cindex optimization, D30V
999 Optimize output by parallelizing instructions.
1003 Warn when nops are generated.
1005 @cindex D30V nops after 32-bit multiply
1007 Warn when a nop after a 32-bit multiply instruction is generated.
1013 The following options are available when @value{AS} is configured for the
1014 Adapteva EPIPHANY series.
1017 @xref{Epiphany Options}, for the options available when @value{AS} is
1018 configured for an Epiphany processor.
1022 @c man begin OPTIONS
1023 The following options are available when @value{AS} is configured for
1024 an Epiphany processor.
1026 @c man begin INCLUDE
1027 @include c-epiphany.texi
1028 @c ended inside the included file
1036 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1037 for an H8/300 processor.
1041 @c man begin OPTIONS
1042 The following options are available when @value{AS} is configured for an H8/300
1045 @c man begin INCLUDE
1046 @include c-h8300.texi
1047 @c ended inside the included file
1055 @xref{i386-Options}, for the options available when @value{AS} is
1056 configured for an i386 processor.
1060 @c man begin OPTIONS
1061 The following options are available when @value{AS} is configured for
1064 @c man begin INCLUDE
1065 @include c-i386.texi
1066 @c ended inside the included file
1071 @c man begin OPTIONS
1073 The following options are available when @value{AS} is configured for the
1074 Intel 80960 processor.
1077 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1078 Specify which variant of the 960 architecture is the target.
1081 Add code to collect statistics about branches taken.
1084 Do not alter compare-and-branch instructions for long displacements;
1091 The following options are available when @value{AS} is configured for the
1097 Specifies that the extended IP2022 instructions are allowed.
1100 Restores the default behaviour, which restricts the permitted instructions to
1101 just the basic IP2022 ones.
1107 The following options are available when @value{AS} is configured for the
1108 Renesas M32C and M16C processors.
1113 Assemble M32C instructions.
1116 Assemble M16C instructions (the default).
1119 Enable support for link-time relaxations.
1122 Support H'00 style hex constants in addition to 0x00 style.
1128 The following options are available when @value{AS} is configured for the
1129 Renesas M32R (formerly Mitsubishi M32R) series.
1134 Specify which processor in the M32R family is the target. The default
1135 is normally the M32R, but this option changes it to the M32RX.
1137 @item --warn-explicit-parallel-conflicts or --Wp
1138 Produce warning messages when questionable parallel constructs are
1141 @item --no-warn-explicit-parallel-conflicts or --Wnp
1142 Do not produce warning messages when questionable parallel constructs are
1149 The following options are available when @value{AS} is configured for the
1150 Motorola 68000 series.
1155 Shorten references to undefined symbols, to one word instead of two.
1157 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1158 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1159 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1160 Specify what processor in the 68000 family is the target. The default
1161 is normally the 68020, but this can be changed at configuration time.
1163 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1164 The target machine does (or does not) have a floating-point coprocessor.
1165 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1166 the basic 68000 is not compatible with the 68881, a combination of the
1167 two can be specified, since it's possible to do emulation of the
1168 coprocessor instructions with the main processor.
1170 @item -m68851 | -mno-68851
1171 The target machine does (or does not) have a memory-management
1172 unit coprocessor. The default is to assume an MMU for 68020 and up.
1180 @xref{Nios II Options}, for the options available when @value{AS} is configured
1181 for an Altera Nios II processor.
1185 @c man begin OPTIONS
1186 The following options are available when @value{AS} is configured for an
1187 Altera Nios II processor.
1189 @c man begin INCLUDE
1190 @include c-nios2.texi
1191 @c ended inside the included file
1197 For details about the PDP-11 machine dependent features options,
1198 see @ref{PDP-11-Options}.
1201 @item -mpic | -mno-pic
1202 Generate position-independent (or position-dependent) code. The
1203 default is @option{-mpic}.
1206 @itemx -mall-extensions
1207 Enable all instruction set extensions. This is the default.
1209 @item -mno-extensions
1210 Disable all instruction set extensions.
1212 @item -m@var{extension} | -mno-@var{extension}
1213 Enable (or disable) a particular instruction set extension.
1216 Enable the instruction set extensions supported by a particular CPU, and
1217 disable all other extensions.
1219 @item -m@var{machine}
1220 Enable the instruction set extensions supported by a particular machine
1221 model, and disable all other extensions.
1227 The following options are available when @value{AS} is configured for
1228 a picoJava processor.
1232 @cindex PJ endianness
1233 @cindex endianness, PJ
1234 @cindex big endian output, PJ
1236 Generate ``big endian'' format output.
1238 @cindex little endian output, PJ
1240 Generate ``little endian'' format output.
1248 @xref{PRU Options}, for the options available when @value{AS} is configured
1249 for a PRU processor.
1253 @c man begin OPTIONS
1254 The following options are available when @value{AS} is configured for a
1257 @c man begin INCLUDE
1259 @c ended inside the included file
1264 The following options are available when @value{AS} is configured for the
1265 Motorola 68HC11 or 68HC12 series.
1269 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1270 Specify what processor is the target. The default is
1271 defined by the configuration option when building the assembler.
1273 @item --xgate-ramoffset
1274 Instruct the linker to offset RAM addresses from S12X address space into
1275 XGATE address space.
1278 Specify to use the 16-bit integer ABI.
1281 Specify to use the 32-bit integer ABI.
1283 @item -mshort-double
1284 Specify to use the 32-bit double ABI.
1287 Specify to use the 64-bit double ABI.
1289 @item --force-long-branches
1290 Relative branches are turned into absolute ones. This concerns
1291 conditional branches, unconditional branches and branches to a
1294 @item -S | --short-branches
1295 Do not turn relative branches into absolute ones
1296 when the offset is out of range.
1298 @item --strict-direct-mode
1299 Do not turn the direct addressing mode into extended addressing mode
1300 when the instruction does not support direct addressing mode.
1302 @item --print-insn-syntax
1303 Print the syntax of instruction in case of error.
1305 @item --print-opcodes
1306 Print the list of instructions with syntax and then exit.
1308 @item --generate-example
1309 Print an example of instruction for each possible instruction and then exit.
1310 This option is only useful for testing @command{@value{AS}}.
1316 The following options are available when @command{@value{AS}} is configured
1317 for the SPARC architecture:
1320 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1321 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1322 Explicitly select a variant of the SPARC architecture.
1324 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1325 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1327 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1328 UltraSPARC extensions.
1330 @item -xarch=v8plus | -xarch=v8plusa
1331 For compatibility with the Solaris v9 assembler. These options are
1332 equivalent to -Av8plus and -Av8plusa, respectively.
1335 Warn when the assembler switches to another architecture.
1340 The following options are available when @value{AS} is configured for the 'c54x
1345 Enable extended addressing mode. All addresses and relocations will assume
1346 extended addressing (usually 23 bits).
1347 @item -mcpu=@var{CPU_VERSION}
1348 Sets the CPU version being compiled for.
1349 @item -merrors-to-file @var{FILENAME}
1350 Redirect error output to a file, for broken systems which don't support such
1351 behaviour in the shell.
1356 @c man begin OPTIONS
1357 The following options are available when @value{AS} is configured for
1362 This option sets the largest size of an object that can be referenced
1363 implicitly with the @code{gp} register. It is only accepted for targets that
1364 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1366 @cindex MIPS endianness
1367 @cindex endianness, MIPS
1368 @cindex big endian output, MIPS
1370 Generate ``big endian'' format output.
1372 @cindex little endian output, MIPS
1374 Generate ``little endian'' format output.
1392 Generate code for a particular MIPS Instruction Set Architecture level.
1393 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1394 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1395 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1396 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1397 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1398 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1399 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1400 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1401 MIPS64 Release 6 ISA processors, respectively.
1403 @item -march=@var{cpu}
1404 Generate code for a particular MIPS CPU.
1406 @item -mtune=@var{cpu}
1407 Schedule and tune for a particular MIPS CPU.
1411 Cause nops to be inserted if the read of the destination register
1412 of an mfhi or mflo instruction occurs in the following two instructions.
1415 @itemx -mno-fix-rm7000
1416 Cause nops to be inserted if a dmult or dmultu instruction is
1417 followed by a load instruction.
1421 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1422 section instead of the standard ELF .stabs sections.
1426 Control generation of @code{.pdr} sections.
1430 The register sizes are normally inferred from the ISA and ABI, but these
1431 flags force a certain group of registers to be treated as 32 bits wide at
1432 all times. @samp{-mgp32} controls the size of general-purpose registers
1433 and @samp{-mfp32} controls the size of floating-point registers.
1437 The register sizes are normally inferred from the ISA and ABI, but these
1438 flags force a certain group of registers to be treated as 64 bits wide at
1439 all times. @samp{-mgp64} controls the size of general-purpose registers
1440 and @samp{-mfp64} controls the size of floating-point registers.
1443 The register sizes are normally inferred from the ISA and ABI, but using
1444 this flag in combination with @samp{-mabi=32} enables an ABI variant
1445 which will operate correctly with floating-point registers which are
1449 @itemx -mno-odd-spreg
1450 Enable use of floating-point operations on odd-numbered single-precision
1451 registers when supported by the ISA. @samp{-mfpxx} implies
1452 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1456 Generate code for the MIPS 16 processor. This is equivalent to putting
1457 @code{.module mips16} at the start of the assembly file. @samp{-no-mips16}
1458 turns off this option.
1461 @itemx -mno-mips16e2
1462 Enable the use of MIPS16e2 instructions in MIPS16 mode. This is equivalent
1463 to putting @code{.module mips16e2} at the start of the assembly file.
1464 @samp{-mno-mips16e2} turns off this option.
1467 @itemx -mno-micromips
1468 Generate code for the microMIPS processor. This is equivalent to putting
1469 @code{.module micromips} at the start of the assembly file.
1470 @samp{-mno-micromips} turns off this option. This is equivalent to putting
1471 @code{.module nomicromips} at the start of the assembly file.
1474 @itemx -mno-smartmips
1475 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1476 equivalent to putting @code{.module smartmips} at the start of the assembly
1477 file. @samp{-mno-smartmips} turns off this option.
1481 Generate code for the MIPS-3D Application Specific Extension.
1482 This tells the assembler to accept MIPS-3D instructions.
1483 @samp{-no-mips3d} turns off this option.
1487 Generate code for the MDMX Application Specific Extension.
1488 This tells the assembler to accept MDMX instructions.
1489 @samp{-no-mdmx} turns off this option.
1493 Generate code for the DSP Release 1 Application Specific Extension.
1494 This tells the assembler to accept DSP Release 1 instructions.
1495 @samp{-mno-dsp} turns off this option.
1499 Generate code for the DSP Release 2 Application Specific Extension.
1500 This option implies @samp{-mdsp}.
1501 This tells the assembler to accept DSP Release 2 instructions.
1502 @samp{-mno-dspr2} turns off this option.
1506 Generate code for the DSP Release 3 Application Specific Extension.
1507 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1508 This tells the assembler to accept DSP Release 3 instructions.
1509 @samp{-mno-dspr3} turns off this option.
1513 Generate code for the MIPS SIMD Architecture Extension.
1514 This tells the assembler to accept MSA instructions.
1515 @samp{-mno-msa} turns off this option.
1519 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1520 This tells the assembler to accept XPA instructions.
1521 @samp{-mno-xpa} turns off this option.
1525 Generate code for the MT Application Specific Extension.
1526 This tells the assembler to accept MT instructions.
1527 @samp{-mno-mt} turns off this option.
1531 Generate code for the MCU Application Specific Extension.
1532 This tells the assembler to accept MCU instructions.
1533 @samp{-mno-mcu} turns off this option.
1537 Only use 32-bit instruction encodings when generating code for the
1538 microMIPS processor. This option inhibits the use of any 16-bit
1539 instructions. This is equivalent to putting @code{.set insn32} at
1540 the start of the assembly file. @samp{-mno-insn32} turns off this
1541 option. This is equivalent to putting @code{.set noinsn32} at the
1542 start of the assembly file. By default @samp{-mno-insn32} is
1543 selected, allowing all instructions to be used.
1545 @item --construct-floats
1546 @itemx --no-construct-floats
1547 The @samp{--no-construct-floats} option disables the construction of
1548 double width floating point constants by loading the two halves of the
1549 value into the two single width floating point registers that make up
1550 the double width register. By default @samp{--construct-floats} is
1551 selected, allowing construction of these floating point constants.
1553 @item --relax-branch
1554 @itemx --no-relax-branch
1555 The @samp{--relax-branch} option enables the relaxation of out-of-range
1556 branches. By default @samp{--no-relax-branch} is selected, causing any
1557 out-of-range branches to produce an error.
1559 @item -mignore-branch-isa
1560 @itemx -mno-ignore-branch-isa
1561 Ignore branch checks for invalid transitions between ISA modes. The
1562 semantics of branches does not provide for an ISA mode switch, so in
1563 most cases the ISA mode a branch has been encoded for has to be the
1564 same as the ISA mode of the branch's target label. Therefore GAS has
1565 checks implemented that verify in branch assembly that the two ISA
1566 modes match. @samp{-mignore-branch-isa} disables these checks. By
1567 default @samp{-mno-ignore-branch-isa} is selected, causing any invalid
1568 branch requiring a transition between ISA modes to produce an error.
1570 @item -mnan=@var{encoding}
1571 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1572 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1575 @item --emulation=@var{name}
1576 This option was formerly used to switch between ELF and ECOFF output
1577 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1578 removed in GAS 2.24, so the option now serves little purpose.
1579 It is retained for backwards compatibility.
1581 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1582 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1583 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1584 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1585 preferred options instead.
1588 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1595 Control how to deal with multiplication overflow and division by zero.
1596 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1597 (and only work for Instruction Set Architecture level 2 and higher);
1598 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1602 When this option is used, @command{@value{AS}} will issue a warning every
1603 time it generates a nop instruction from a macro.
1609 The following options are available when @value{AS} is configured for
1615 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1616 The command line option @samp{-nojsri2bsr} can be used to disable it.
1620 Enable or disable the silicon filter behaviour. By default this is disabled.
1621 The default can be overridden by the @samp{-sifilter} command line option.
1624 Alter jump instructions for long displacements.
1626 @item -mcpu=[210|340]
1627 Select the cpu type on the target hardware. This controls which instructions
1631 Assemble for a big endian target.
1634 Assemble for a little endian target.
1643 @xref{Meta Options}, for the options available when @value{AS} is configured
1644 for a Meta processor.
1648 @c man begin OPTIONS
1649 The following options are available when @value{AS} is configured for a
1652 @c man begin INCLUDE
1653 @include c-metag.texi
1654 @c ended inside the included file
1659 @c man begin OPTIONS
1661 See the info pages for documentation of the MMIX-specific options.
1667 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1668 for a NDS32 processor.
1670 @c ended inside the included file
1674 @c man begin OPTIONS
1675 The following options are available when @value{AS} is configured for a
1678 @c man begin INCLUDE
1679 @include c-nds32.texi
1680 @c ended inside the included file
1687 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1688 for a PowerPC processor.
1692 @c man begin OPTIONS
1693 The following options are available when @value{AS} is configured for a
1696 @c man begin INCLUDE
1698 @c ended inside the included file
1706 @xref{RISC-V-Options}, for the options available when @value{AS} is configured
1707 for a RISC-V processor.
1711 @c man begin OPTIONS
1712 The following options are available when @value{AS} is configured for a
1715 @c man begin INCLUDE
1716 @include c-riscv.texi
1717 @c ended inside the included file
1722 @c man begin OPTIONS
1724 See the info pages for documentation of the RX-specific options.
1728 The following options are available when @value{AS} is configured for the s390
1734 Select the word size, either 31/32 bits or 64 bits.
1737 Select the architecture mode, either the Enterprise System
1738 Architecture (esa) or the z/Architecture mode (zarch).
1739 @item -march=@var{processor}
1740 Specify which s390 processor variant is the target, @samp{g5} (or
1741 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1742 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1743 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1744 @samp{z13} (or @samp{arch11}), or @samp{z14} (or @samp{arch12}).
1746 @itemx -mno-regnames
1747 Allow or disallow symbolic names for registers.
1748 @item -mwarn-areg-zero
1749 Warn whenever the operand for a base or index register has been specified
1750 but evaluates to zero.
1758 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1759 for a TMS320C6000 processor.
1763 @c man begin OPTIONS
1764 The following options are available when @value{AS} is configured for a
1765 TMS320C6000 processor.
1767 @c man begin INCLUDE
1768 @include c-tic6x.texi
1769 @c ended inside the included file
1777 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1778 for a TILE-Gx processor.
1782 @c man begin OPTIONS
1783 The following options are available when @value{AS} is configured for a TILE-Gx
1786 @c man begin INCLUDE
1787 @include c-tilegx.texi
1788 @c ended inside the included file
1796 @xref{Visium Options}, for the options available when @value{AS} is configured
1797 for a Visium processor.
1801 @c man begin OPTIONS
1802 The following option is available when @value{AS} is configured for a Visium
1805 @c man begin INCLUDE
1806 @include c-visium.texi
1807 @c ended inside the included file
1815 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1816 for an Xtensa processor.
1820 @c man begin OPTIONS
1821 The following options are available when @value{AS} is configured for an
1824 @c man begin INCLUDE
1825 @include c-xtensa.texi
1826 @c ended inside the included file
1831 @c man begin OPTIONS
1834 The following options are available when @value{AS} is configured for
1835 a Z80 family processor.
1838 Assemble for Z80 processor.
1840 Assemble for R800 processor.
1841 @item -ignore-undocumented-instructions
1843 Assemble undocumented Z80 instructions that also work on R800 without warning.
1844 @item -ignore-unportable-instructions
1846 Assemble all undocumented Z80 instructions without warning.
1847 @item -warn-undocumented-instructions
1849 Issue a warning for undocumented Z80 instructions that also work on R800.
1850 @item -warn-unportable-instructions
1852 Issue a warning for undocumented Z80 instructions that do not work on R800.
1853 @item -forbid-undocumented-instructions
1855 Treat all undocumented instructions as errors.
1856 @item -forbid-unportable-instructions
1858 Treat undocumented Z80 instructions that do not work on R800 as errors.
1865 * Manual:: Structure of this Manual
1866 * GNU Assembler:: The GNU Assembler
1867 * Object Formats:: Object File Formats
1868 * Command Line:: Command Line
1869 * Input Files:: Input Files
1870 * Object:: Output (Object) File
1871 * Errors:: Error and Warning Messages
1875 @section Structure of this Manual
1877 @cindex manual, structure and purpose
1878 This manual is intended to describe what you need to know to use
1879 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1880 notation for symbols, constants, and expressions; the directives that
1881 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1884 We also cover special features in the @value{TARGET}
1885 configuration of @command{@value{AS}}, including assembler directives.
1888 This manual also describes some of the machine-dependent features of
1889 various flavors of the assembler.
1892 @cindex machine instructions (not covered)
1893 On the other hand, this manual is @emph{not} intended as an introduction
1894 to programming in assembly language---let alone programming in general!
1895 In a similar vein, we make no attempt to introduce the machine
1896 architecture; we do @emph{not} describe the instruction set, standard
1897 mnemonics, registers or addressing modes that are standard to a
1898 particular architecture.
1900 You may want to consult the manufacturer's
1901 machine architecture manual for this information.
1905 For information on the H8/300 machine instruction set, see @cite{H8/300
1906 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1907 Programming Manual} (Renesas).
1910 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1911 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1912 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1913 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1916 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1920 @c I think this is premature---doc@cygnus.com, 17jan1991
1922 Throughout this manual, we assume that you are running @dfn{GNU},
1923 the portable operating system from the @dfn{Free Software
1924 Foundation, Inc.}. This restricts our attention to certain kinds of
1925 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1926 once this assumption is granted examples and definitions need less
1929 @command{@value{AS}} is part of a team of programs that turn a high-level
1930 human-readable series of instructions into a low-level
1931 computer-readable series of instructions. Different versions of
1932 @command{@value{AS}} are used for different kinds of computer.
1935 @c There used to be a section "Terminology" here, which defined
1936 @c "contents", "byte", "word", and "long". Defining "word" to any
1937 @c particular size is confusing when the .word directive may generate 16
1938 @c bits on one machine and 32 bits on another; in general, for the user
1939 @c version of this manual, none of these terms seem essential to define.
1940 @c They were used very little even in the former draft of the manual;
1941 @c this draft makes an effort to avoid them (except in names of
1945 @section The GNU Assembler
1947 @c man begin DESCRIPTION
1949 @sc{gnu} @command{as} is really a family of assemblers.
1951 This manual describes @command{@value{AS}}, a member of that family which is
1952 configured for the @value{TARGET} architectures.
1954 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1955 should find a fairly similar environment when you use it on another
1956 architecture. Each version has much in common with the others,
1957 including object file formats, most assembler directives (often called
1958 @dfn{pseudo-ops}) and assembler syntax.@refill
1960 @cindex purpose of @sc{gnu} assembler
1961 @command{@value{AS}} is primarily intended to assemble the output of the
1962 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1963 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1964 assemble correctly everything that other assemblers for the same
1965 machine would assemble.
1967 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1970 @c This remark should appear in generic version of manual; assumption
1971 @c here is that generic version sets M680x0.
1972 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1973 assembler for the same architecture; for example, we know of several
1974 incompatible versions of 680x0 assembly language syntax.
1979 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1980 program in one pass of the source file. This has a subtle impact on the
1981 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1983 @node Object Formats
1984 @section Object File Formats
1986 @cindex object file format
1987 The @sc{gnu} assembler can be configured to produce several alternative
1988 object file formats. For the most part, this does not affect how you
1989 write assembly language programs; but directives for debugging symbols
1990 are typically different in different file formats. @xref{Symbol
1991 Attributes,,Symbol Attributes}.
1994 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1995 @value{OBJ-NAME} format object files.
1997 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1999 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
2000 @code{b.out} or COFF format object files.
2003 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
2004 SOM or ELF format object files.
2009 @section Command Line
2011 @cindex command line conventions
2013 After the program name @command{@value{AS}}, the command line may contain
2014 options and file names. Options may appear in any order, and may be
2015 before, after, or between file names. The order of file names is
2018 @cindex standard input, as input file
2020 @file{--} (two hyphens) by itself names the standard input file
2021 explicitly, as one of the files for @command{@value{AS}} to assemble.
2023 @cindex options, command line
2024 Except for @samp{--} any command line argument that begins with a
2025 hyphen (@samp{-}) is an option. Each option changes the behavior of
2026 @command{@value{AS}}. No option changes the way another option works. An
2027 option is a @samp{-} followed by one or more letters; the case of
2028 the letter is important. All options are optional.
2030 Some options expect exactly one file name to follow them. The file
2031 name may either immediately follow the option's letter (compatible
2032 with older assemblers) or it may be the next command argument (@sc{gnu}
2033 standard). These two command lines are equivalent:
2036 @value{AS} -o my-object-file.o mumble.s
2037 @value{AS} -omy-object-file.o mumble.s
2041 @section Input Files
2044 @cindex source program
2045 @cindex files, input
2046 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2047 describe the program input to one run of @command{@value{AS}}. The program may
2048 be in one or more files; how the source is partitioned into files
2049 doesn't change the meaning of the source.
2051 @c I added "con" prefix to "catenation" just to prove I can overcome my
2052 @c APL training... doc@cygnus.com
2053 The source program is a concatenation of the text in all the files, in the
2056 @c man begin DESCRIPTION
2057 Each time you run @command{@value{AS}} it assembles exactly one source
2058 program. The source program is made up of one or more files.
2059 (The standard input is also a file.)
2061 You give @command{@value{AS}} a command line that has zero or more input file
2062 names. The input files are read (from left file name to right). A
2063 command line argument (in any position) that has no special meaning
2064 is taken to be an input file name.
2066 If you give @command{@value{AS}} no file names it attempts to read one input file
2067 from the @command{@value{AS}} standard input, which is normally your terminal. You
2068 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2071 Use @samp{--} if you need to explicitly name the standard input file
2072 in your command line.
2074 If the source is empty, @command{@value{AS}} produces a small, empty object
2079 @subheading Filenames and Line-numbers
2081 @cindex input file linenumbers
2082 @cindex line numbers, in input files
2083 There are two ways of locating a line in the input file (or files) and
2084 either may be used in reporting error messages. One way refers to a line
2085 number in a physical file; the other refers to a line number in a
2086 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2088 @dfn{Physical files} are those files named in the command line given
2089 to @command{@value{AS}}.
2091 @dfn{Logical files} are simply names declared explicitly by assembler
2092 directives; they bear no relation to physical files. Logical file names help
2093 error messages reflect the original source file, when @command{@value{AS}} source
2094 is itself synthesized from other files. @command{@value{AS}} understands the
2095 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2096 @ref{File,,@code{.file}}.
2099 @section Output (Object) File
2105 Every time you run @command{@value{AS}} it produces an output file, which is
2106 your assembly language program translated into numbers. This file
2107 is the object file. Its default name is
2115 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2117 You can give it another name by using the @option{-o} option. Conventionally,
2118 object file names end with @file{.o}. The default name is used for historical
2119 reasons: older assemblers were capable of assembling self-contained programs
2120 directly into a runnable program. (For some formats, this isn't currently
2121 possible, but it can be done for the @code{a.out} format.)
2125 The object file is meant for input to the linker @code{@value{LD}}. It contains
2126 assembled program code, information to help @code{@value{LD}} integrate
2127 the assembled program into a runnable file, and (optionally) symbolic
2128 information for the debugger.
2130 @c link above to some info file(s) like the description of a.out.
2131 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2134 @section Error and Warning Messages
2136 @c man begin DESCRIPTION
2138 @cindex error messages
2139 @cindex warning messages
2140 @cindex messages from assembler
2141 @command{@value{AS}} may write warnings and error messages to the standard error
2142 file (usually your terminal). This should not happen when a compiler
2143 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2144 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2145 grave problem that stops the assembly.
2149 @cindex format of warning messages
2150 Warning messages have the format
2153 file_name:@b{NNN}:Warning Message Text
2157 @cindex file names and line numbers, in warnings/errors
2158 (where @b{NNN} is a line number). If both a logical file name
2159 (@pxref{File,,@code{.file}}) and a logical line number
2161 (@pxref{Line,,@code{.line}})
2163 have been given then they will be used, otherwise the file name and line number
2164 in the current assembler source file will be used. The message text is
2165 intended to be self explanatory (in the grand Unix tradition).
2167 Note the file name must be set via the logical version of the @code{.file}
2168 directive, not the DWARF2 version of the @code{.file} directive. For example:
2172 error_assembler_source
2178 produces this output:
2182 asm.s:2: Error: no such instruction: `error_assembler_source'
2183 foo.c:31: Error: no such instruction: `error_c_source'
2186 @cindex format of error messages
2187 Error messages have the format
2190 file_name:@b{NNN}:FATAL:Error Message Text
2193 The file name and line number are derived as for warning
2194 messages. The actual message text may be rather less explanatory
2195 because many of them aren't supposed to happen.
2198 @chapter Command-Line Options
2200 @cindex options, all versions of assembler
2201 This chapter describes command-line options available in @emph{all}
2202 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2203 for options specific
2205 to the @value{TARGET} target.
2208 to particular machine architectures.
2211 @c man begin DESCRIPTION
2213 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2214 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2215 The assembler arguments must be separated from each other (and the @samp{-Wa})
2216 by commas. For example:
2219 gcc -c -g -O -Wa,-alh,-L file.c
2223 This passes two options to the assembler: @samp{-alh} (emit a listing to
2224 standard output with high-level and assembly source) and @samp{-L} (retain
2225 local symbols in the symbol table).
2227 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2228 command-line options are automatically passed to the assembler by the compiler.
2229 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2230 precisely what options it passes to each compilation pass, including the
2236 * a:: -a[cdghlns] enable listings
2237 * alternate:: --alternate enable alternate macro syntax
2238 * D:: -D for compatibility
2239 * f:: -f to work faster
2240 * I:: -I for .include search path
2241 @ifclear DIFF-TBL-KLUGE
2242 * K:: -K for compatibility
2244 @ifset DIFF-TBL-KLUGE
2245 * K:: -K for difference tables
2248 * L:: -L to retain local symbols
2249 * listing:: --listing-XXX to configure listing output
2250 * M:: -M or --mri to assemble in MRI compatibility mode
2251 * MD:: --MD for dependency tracking
2252 * no-pad-sections:: --no-pad-sections to stop section padding
2253 * o:: -o to name the object file
2254 * R:: -R to join data and text sections
2255 * statistics:: --statistics to see statistics about assembly
2256 * traditional-format:: --traditional-format for compatible output
2257 * v:: -v to announce version
2258 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2259 * Z:: -Z to make object file even after errors
2263 @section Enable Listings: @option{-a[cdghlns]}
2273 @cindex listings, enabling
2274 @cindex assembly listings, enabling
2276 These options enable listing output from the assembler. By itself,
2277 @samp{-a} requests high-level, assembly, and symbols listing.
2278 You can use other letters to select specific options for the list:
2279 @samp{-ah} requests a high-level language listing,
2280 @samp{-al} requests an output-program assembly listing, and
2281 @samp{-as} requests a symbol table listing.
2282 High-level listings require that a compiler debugging option like
2283 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2286 Use the @samp{-ag} option to print a first section with general assembly
2287 information, like @value{AS} version, switches passed, or time stamp.
2289 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2290 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2291 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2292 omitted from the listing.
2294 Use the @samp{-ad} option to omit debugging directives from the
2297 Once you have specified one of these options, you can further control
2298 listing output and its appearance using the directives @code{.list},
2299 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2301 The @samp{-an} option turns off all forms processing.
2302 If you do not request listing output with one of the @samp{-a} options, the
2303 listing-control directives have no effect.
2305 The letters after @samp{-a} may be combined into one option,
2306 @emph{e.g.}, @samp{-aln}.
2308 Note if the assembler source is coming from the standard input (e.g.,
2310 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2311 is being used) then the listing will not contain any comments or preprocessor
2312 directives. This is because the listing code buffers input source lines from
2313 stdin only after they have been preprocessed by the assembler. This reduces
2314 memory usage and makes the code more efficient.
2317 @section @option{--alternate}
2320 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2323 @section @option{-D}
2326 This option has no effect whatsoever, but it is accepted to make it more
2327 likely that scripts written for other assemblers also work with
2328 @command{@value{AS}}.
2331 @section Work Faster: @option{-f}
2334 @cindex trusted compiler
2335 @cindex faster processing (@option{-f})
2336 @samp{-f} should only be used when assembling programs written by a
2337 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2338 and comment preprocessing on
2339 the input file(s) before assembling them. @xref{Preprocessing,
2343 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2344 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2349 @section @code{.include} Search Path: @option{-I} @var{path}
2351 @kindex -I @var{path}
2352 @cindex paths for @code{.include}
2353 @cindex search path for @code{.include}
2354 @cindex @code{include} directive search path
2355 Use this option to add a @var{path} to the list of directories
2356 @command{@value{AS}} searches for files specified in @code{.include}
2357 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2358 many times as necessary to include a variety of paths. The current
2359 working directory is always searched first; after that, @command{@value{AS}}
2360 searches any @samp{-I} directories in the same order as they were
2361 specified (left to right) on the command line.
2364 @section Difference Tables: @option{-K}
2367 @ifclear DIFF-TBL-KLUGE
2368 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2369 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2370 where it can be used to warn when the assembler alters the machine code
2371 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2372 family does not have the addressing limitations that sometimes lead to this
2373 alteration on other platforms.
2376 @ifset DIFF-TBL-KLUGE
2377 @cindex difference tables, warning
2378 @cindex warning for altered difference tables
2379 @command{@value{AS}} sometimes alters the code emitted for directives of the
2380 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2381 You can use the @samp{-K} option if you want a warning issued when this
2386 @section Include Local Symbols: @option{-L}
2389 @cindex local symbols, retaining in output
2390 Symbols beginning with system-specific local label prefixes, typically
2391 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2392 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2393 such symbols when debugging, because they are intended for the use of
2394 programs (like compilers) that compose assembler programs, not for your
2395 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2396 such symbols, so you do not normally debug with them.
2398 This option tells @command{@value{AS}} to retain those local symbols
2399 in the object file. Usually if you do this you also tell the linker
2400 @code{@value{LD}} to preserve those symbols.
2403 @section Configuring listing output: @option{--listing}
2405 The listing feature of the assembler can be enabled via the command line switch
2406 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2407 hex dump of the corresponding locations in the output object file, and displays
2408 them as a listing file. The format of this listing can be controlled by
2409 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2410 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2411 @code{.psize} (@pxref{Psize}), and
2412 @code{.eject} (@pxref{Eject}) and also by the following switches:
2415 @item --listing-lhs-width=@samp{number}
2416 @kindex --listing-lhs-width
2417 @cindex Width of first line disassembly output
2418 Sets the maximum width, in words, of the first line of the hex byte dump. This
2419 dump appears on the left hand side of the listing output.
2421 @item --listing-lhs-width2=@samp{number}
2422 @kindex --listing-lhs-width2
2423 @cindex Width of continuation lines of disassembly output
2424 Sets the maximum width, in words, of any further lines of the hex byte dump for
2425 a given input source line. If this value is not specified, it defaults to being
2426 the same as the value specified for @samp{--listing-lhs-width}. If neither
2427 switch is used the default is to one.
2429 @item --listing-rhs-width=@samp{number}
2430 @kindex --listing-rhs-width
2431 @cindex Width of source line output
2432 Sets the maximum width, in characters, of the source line that is displayed
2433 alongside the hex dump. The default value for this parameter is 100. The
2434 source line is displayed on the right hand side of the listing output.
2436 @item --listing-cont-lines=@samp{number}
2437 @kindex --listing-cont-lines
2438 @cindex Maximum number of continuation lines
2439 Sets the maximum number of continuation lines of hex dump that will be
2440 displayed for a given single line of source input. The default value is 4.
2444 @section Assemble in MRI Compatibility Mode: @option{-M}
2447 @cindex MRI compatibility mode
2448 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2449 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2450 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2451 configured target) assembler from Microtec Research. The exact nature of the
2452 MRI syntax will not be documented here; see the MRI manuals for more
2453 information. Note in particular that the handling of macros and macro
2454 arguments is somewhat different. The purpose of this option is to permit
2455 assembling existing MRI assembler code using @command{@value{AS}}.
2457 The MRI compatibility is not complete. Certain operations of the MRI assembler
2458 depend upon its object file format, and can not be supported using other object
2459 file formats. Supporting these would require enhancing each object file format
2460 individually. These are:
2463 @item global symbols in common section
2465 The m68k MRI assembler supports common sections which are merged by the linker.
2466 Other object file formats do not support this. @command{@value{AS}} handles
2467 common sections by treating them as a single common symbol. It permits local
2468 symbols to be defined within a common section, but it can not support global
2469 symbols, since it has no way to describe them.
2471 @item complex relocations
2473 The MRI assemblers support relocations against a negated section address, and
2474 relocations which combine the start addresses of two or more sections. These
2475 are not support by other object file formats.
2477 @item @code{END} pseudo-op specifying start address
2479 The MRI @code{END} pseudo-op permits the specification of a start address.
2480 This is not supported by other object file formats. The start address may
2481 instead be specified using the @option{-e} option to the linker, or in a linker
2484 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2486 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2487 name to the output file. This is not supported by other object file formats.
2489 @item @code{ORG} pseudo-op
2491 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2492 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2493 which changes the location within the current section. Absolute sections are
2494 not supported by other object file formats. The address of a section may be
2495 assigned within a linker script.
2498 There are some other features of the MRI assembler which are not supported by
2499 @command{@value{AS}}, typically either because they are difficult or because they
2500 seem of little consequence. Some of these may be supported in future releases.
2504 @item EBCDIC strings
2506 EBCDIC strings are not supported.
2508 @item packed binary coded decimal
2510 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2511 and @code{DCB.P} pseudo-ops are not supported.
2513 @item @code{FEQU} pseudo-op
2515 The m68k @code{FEQU} pseudo-op is not supported.
2517 @item @code{NOOBJ} pseudo-op
2519 The m68k @code{NOOBJ} pseudo-op is not supported.
2521 @item @code{OPT} branch control options
2523 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2524 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2525 relaxes all branches, whether forward or backward, to an appropriate size, so
2526 these options serve no purpose.
2528 @item @code{OPT} list control options
2530 The following m68k @code{OPT} list control options are ignored: @code{C},
2531 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2532 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2534 @item other @code{OPT} options
2536 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2537 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2539 @item @code{OPT} @code{D} option is default
2541 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2542 @code{OPT NOD} may be used to turn it off.
2544 @item @code{XREF} pseudo-op.
2546 The m68k @code{XREF} pseudo-op is ignored.
2548 @item @code{.debug} pseudo-op
2550 The i960 @code{.debug} pseudo-op is not supported.
2552 @item @code{.extended} pseudo-op
2554 The i960 @code{.extended} pseudo-op is not supported.
2556 @item @code{.list} pseudo-op.
2558 The various options of the i960 @code{.list} pseudo-op are not supported.
2560 @item @code{.optimize} pseudo-op
2562 The i960 @code{.optimize} pseudo-op is not supported.
2564 @item @code{.output} pseudo-op
2566 The i960 @code{.output} pseudo-op is not supported.
2568 @item @code{.setreal} pseudo-op
2570 The i960 @code{.setreal} pseudo-op is not supported.
2575 @section Dependency Tracking: @option{--MD}
2578 @cindex dependency tracking
2581 @command{@value{AS}} can generate a dependency file for the file it creates. This
2582 file consists of a single rule suitable for @code{make} describing the
2583 dependencies of the main source file.
2585 The rule is written to the file named in its argument.
2587 This feature is used in the automatic updating of makefiles.
2589 @node no-pad-sections
2590 @section Output Section Padding
2591 @kindex --no-pad-sections
2592 @cindex output section padding
2593 Normally the assembler will pad the end of each output section up to its
2594 alignment boundary. But this can waste space, which can be significant on
2595 memory constrained targets. So the @option{--no-pad-sections} option will
2596 disable this behaviour.
2599 @section Name the Object File: @option{-o}
2602 @cindex naming object file
2603 @cindex object file name
2604 There is always one object file output when you run @command{@value{AS}}. By
2605 default it has the name
2608 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2622 You use this option (which takes exactly one filename) to give the
2623 object file a different name.
2625 Whatever the object file is called, @command{@value{AS}} overwrites any
2626 existing file of the same name.
2629 @section Join Data and Text Sections: @option{-R}
2632 @cindex data and text sections, joining
2633 @cindex text and data sections, joining
2634 @cindex joining text and data sections
2635 @cindex merging text and data sections
2636 @option{-R} tells @command{@value{AS}} to write the object file as if all
2637 data-section data lives in the text section. This is only done at
2638 the very last moment: your binary data are the same, but data
2639 section parts are relocated differently. The data section part of
2640 your object file is zero bytes long because all its bytes are
2641 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2643 When you specify @option{-R} it would be possible to generate shorter
2644 address displacements (because we do not have to cross between text and
2645 data section). We refrain from doing this simply for compatibility with
2646 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2649 When @command{@value{AS}} is configured for COFF or ELF output,
2650 this option is only useful if you use sections named @samp{.text} and
2655 @option{-R} is not supported for any of the HPPA targets. Using
2656 @option{-R} generates a warning from @command{@value{AS}}.
2660 @section Display Assembly Statistics: @option{--statistics}
2662 @kindex --statistics
2663 @cindex statistics, about assembly
2664 @cindex time, total for assembly
2665 @cindex space used, maximum for assembly
2666 Use @samp{--statistics} to display two statistics about the resources used by
2667 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2668 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2671 @node traditional-format
2672 @section Compatible Output: @option{--traditional-format}
2674 @kindex --traditional-format
2675 For some targets, the output of @command{@value{AS}} is different in some ways
2676 from the output of some existing assembler. This switch requests
2677 @command{@value{AS}} to use the traditional format instead.
2679 For example, it disables the exception frame optimizations which
2680 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2683 @section Announce Version: @option{-v}
2687 @cindex assembler version
2688 @cindex version of assembler
2689 You can find out what version of as is running by including the
2690 option @samp{-v} (which you can also spell as @samp{-version}) on the
2694 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2696 @command{@value{AS}} should never give a warning or error message when
2697 assembling compiler output. But programs written by people often
2698 cause @command{@value{AS}} to give a warning that a particular assumption was
2699 made. All such warnings are directed to the standard error file.
2703 @cindex suppressing warnings
2704 @cindex warnings, suppressing
2705 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2706 This only affects the warning messages: it does not change any particular of
2707 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2710 @kindex --fatal-warnings
2711 @cindex errors, caused by warnings
2712 @cindex warnings, causing error
2713 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2714 files that generate warnings to be in error.
2717 @cindex warnings, switching on
2718 You can switch these options off again by specifying @option{--warn}, which
2719 causes warnings to be output as usual.
2722 @section Generate Object File in Spite of Errors: @option{-Z}
2723 @cindex object file, after errors
2724 @cindex errors, continuing after
2725 After an error message, @command{@value{AS}} normally produces no output. If for
2726 some reason you are interested in object file output even after
2727 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2728 option. If there are any errors, @command{@value{AS}} continues anyways, and
2729 writes an object file after a final warning message of the form @samp{@var{n}
2730 errors, @var{m} warnings, generating bad object file.}
2735 @cindex machine-independent syntax
2736 @cindex syntax, machine-independent
2737 This chapter describes the machine-independent syntax allowed in a
2738 source file. @command{@value{AS}} syntax is similar to what many other
2739 assemblers use; it is inspired by the BSD 4.2
2744 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2748 * Preprocessing:: Preprocessing
2749 * Whitespace:: Whitespace
2750 * Comments:: Comments
2751 * Symbol Intro:: Symbols
2752 * Statements:: Statements
2753 * Constants:: Constants
2757 @section Preprocessing
2759 @cindex preprocessing
2760 The @command{@value{AS}} internal preprocessor:
2762 @cindex whitespace, removed by preprocessor
2764 adjusts and removes extra whitespace. It leaves one space or tab before
2765 the keywords on a line, and turns any other whitespace on the line into
2768 @cindex comments, removed by preprocessor
2770 removes all comments, replacing them with a single space, or an
2771 appropriate number of newlines.
2773 @cindex constants, converted by preprocessor
2775 converts character constants into the appropriate numeric values.
2778 It does not do macro processing, include file handling, or
2779 anything else you may get from your C compiler's preprocessor. You can
2780 do include file processing with the @code{.include} directive
2781 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2782 to get other ``CPP'' style preprocessing by giving the input file a
2783 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2784 Output, gcc info, Using GNU CC}.
2786 Excess whitespace, comments, and character constants
2787 cannot be used in the portions of the input text that are not
2790 @cindex turning preprocessing on and off
2791 @cindex preprocessing, turning on and off
2794 If the first line of an input file is @code{#NO_APP} or if you use the
2795 @samp{-f} option, whitespace and comments are not removed from the input file.
2796 Within an input file, you can ask for whitespace and comment removal in
2797 specific portions of the by putting a line that says @code{#APP} before the
2798 text that may contain whitespace or comments, and putting a line that says
2799 @code{#NO_APP} after this text. This feature is mainly intend to support
2800 @code{asm} statements in compilers whose output is otherwise free of comments
2807 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2808 Whitespace is used to separate symbols, and to make programs neater for
2809 people to read. Unless within character constants
2810 (@pxref{Characters,,Character Constants}), any whitespace means the same
2811 as exactly one space.
2817 There are two ways of rendering comments to @command{@value{AS}}. In both
2818 cases the comment is equivalent to one space.
2820 Anything from @samp{/*} through the next @samp{*/} is a comment.
2821 This means you may not nest these comments.
2825 The only way to include a newline ('\n') in a comment
2826 is to use this sort of comment.
2829 /* This sort of comment does not nest. */
2832 @cindex line comment character
2833 Anything from a @dfn{line comment} character up to the next newline is
2834 considered a comment and is ignored. The line comment character is target
2835 specific, and some targets multiple comment characters. Some targets also have
2836 line comment characters that only work if they are the first character on a
2837 line. Some targets use a sequence of two characters to introduce a line
2838 comment. Some targets can also change their line comment characters depending
2839 upon command line options that have been used. For more details see the
2840 @emph{Syntax} section in the documentation for individual targets.
2842 If the line comment character is the hash sign (@samp{#}) then it still has the
2843 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2844 to specify logical line numbers:
2847 @cindex lines starting with @code{#}
2848 @cindex logical line numbers
2849 To be compatible with past assemblers, lines that begin with @samp{#} have a
2850 special interpretation. Following the @samp{#} should be an absolute
2851 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2852 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2853 new logical file name. The rest of the line, if any, should be whitespace.
2855 If the first non-whitespace characters on the line are not numeric,
2856 the line is ignored. (Just like a comment.)
2859 # This is an ordinary comment.
2860 # 42-6 "new_file_name" # New logical file name
2861 # This is logical line # 36.
2863 This feature is deprecated, and may disappear from future versions
2864 of @command{@value{AS}}.
2869 @cindex characters used in symbols
2870 @ifclear SPECIAL-SYMS
2871 A @dfn{symbol} is one or more characters chosen from the set of all
2872 letters (both upper and lower case), digits and the three characters
2878 A @dfn{symbol} is one or more characters chosen from the set of all
2879 letters (both upper and lower case), digits and the three characters
2880 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2886 On most machines, you can also use @code{$} in symbol names; exceptions
2887 are noted in @ref{Machine Dependencies}.
2889 No symbol may begin with a digit. Case is significant.
2890 There is no length limit; all characters are significant. Multibyte characters
2891 are supported. Symbols are delimited by characters not in that set, or by the
2892 beginning of a file (since the source program must end with a newline, the end
2893 of a file is not a possible symbol delimiter). @xref{Symbols}.
2895 Symbol names may also be enclosed in double quote @code{"} characters. In such
2896 cases any characters are allowed, except for the NUL character. If a double
2897 quote character is to be included in the symbol name it must be preceeded by a
2898 backslash @code{\} character.
2899 @cindex length of symbols
2904 @cindex statements, structure of
2905 @cindex line separator character
2906 @cindex statement separator character
2908 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2909 @dfn{line separator character}. The line separator character is target
2910 specific and described in the @emph{Syntax} section of each
2911 target's documentation. Not all targets support a line separator character.
2912 The newline or line separator character is considered to be part of the
2913 preceding statement. Newlines and separators within character constants are an
2914 exception: they do not end statements.
2916 @cindex newline, required at file end
2917 @cindex EOF, newline must precede
2918 It is an error to end any statement with end-of-file: the last
2919 character of any input file should be a newline.@refill
2921 An empty statement is allowed, and may include whitespace. It is ignored.
2923 @cindex instructions and directives
2924 @cindex directives and instructions
2925 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2926 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2928 A statement begins with zero or more labels, optionally followed by a
2929 key symbol which determines what kind of statement it is. The key
2930 symbol determines the syntax of the rest of the statement. If the
2931 symbol begins with a dot @samp{.} then the statement is an assembler
2932 directive: typically valid for any computer. If the symbol begins with
2933 a letter the statement is an assembly language @dfn{instruction}: it
2934 assembles into a machine language instruction.
2936 Different versions of @command{@value{AS}} for different computers
2937 recognize different instructions. In fact, the same symbol may
2938 represent a different instruction in a different computer's assembly
2942 @cindex @code{:} (label)
2943 @cindex label (@code{:})
2944 A label is a symbol immediately followed by a colon (@code{:}).
2945 Whitespace before a label or after a colon is permitted, but you may not
2946 have whitespace between a label's symbol and its colon. @xref{Labels}.
2949 For HPPA targets, labels need not be immediately followed by a colon, but
2950 the definition of a label must begin in column zero. This also implies that
2951 only one label may be defined on each line.
2955 label: .directive followed by something
2956 another_label: # This is an empty statement.
2957 instruction operand_1, operand_2, @dots{}
2964 A constant is a number, written so that its value is known by
2965 inspection, without knowing any context. Like this:
2968 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2969 .ascii "Ring the bell\7" # A string constant.
2970 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2971 .float 0f-314159265358979323846264338327\
2972 95028841971.693993751E-40 # - pi, a flonum.
2977 * Characters:: Character Constants
2978 * Numbers:: Number Constants
2982 @subsection Character Constants
2984 @cindex character constants
2985 @cindex constants, character
2986 There are two kinds of character constants. A @dfn{character} stands
2987 for one character in one byte and its value may be used in
2988 numeric expressions. String constants (properly called string
2989 @emph{literals}) are potentially many bytes and their values may not be
2990 used in arithmetic expressions.
2994 * Chars:: Characters
2998 @subsubsection Strings
3000 @cindex string constants
3001 @cindex constants, string
3002 A @dfn{string} is written between double-quotes. It may contain
3003 double-quotes or null characters. The way to get special characters
3004 into a string is to @dfn{escape} these characters: precede them with
3005 a backslash @samp{\} character. For example @samp{\\} represents
3006 one backslash: the first @code{\} is an escape which tells
3007 @command{@value{AS}} to interpret the second character literally as a backslash
3008 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
3009 escape character). The complete list of escapes follows.
3011 @cindex escape codes, character
3012 @cindex character escape codes
3013 @c NOTE: Cindex entries must not start with a backlash character.
3014 @c NOTE: This confuses the pdf2texi script when it is creating the
3015 @c NOTE: index based upon the first character and so it generates:
3016 @c NOTE: \initial {\\}
3017 @c NOTE: which then results in the error message:
3018 @c NOTE: Argument of \\ has an extra }.
3019 @c NOTE: So in the index entries below a space character has been
3020 @c NOTE: prepended to avoid this problem.
3023 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3025 @cindex @code{ \b} (backspace character)
3026 @cindex backspace (@code{\b})
3028 Mnemonic for backspace; for ASCII this is octal code 010.
3031 @c Mnemonic for EOText; for ASCII this is octal code 004.
3033 @cindex @code{ \f} (formfeed character)
3034 @cindex formfeed (@code{\f})
3036 Mnemonic for FormFeed; for ASCII this is octal code 014.
3038 @cindex @code{ \n} (newline character)
3039 @cindex newline (@code{\n})
3041 Mnemonic for newline; for ASCII this is octal code 012.
3044 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3046 @cindex @code{ \r} (carriage return character)
3047 @cindex carriage return (@code{backslash-r})
3049 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3052 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3053 @c other assemblers.
3055 @cindex @code{ \t} (tab)
3056 @cindex tab (@code{\t})
3058 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3061 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3062 @c @item \x @var{digit} @var{digit} @var{digit}
3063 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3065 @cindex @code{ \@var{ddd}} (octal character code)
3066 @cindex octal character code (@code{\@var{ddd}})
3067 @item \ @var{digit} @var{digit} @var{digit}
3068 An octal character code. The numeric code is 3 octal digits.
3069 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3070 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3072 @cindex @code{ \@var{xd...}} (hex character code)
3073 @cindex hex character code (@code{\@var{xd...}})
3074 @item \@code{x} @var{hex-digits...}
3075 A hex character code. All trailing hex digits are combined. Either upper or
3076 lower case @code{x} works.
3078 @cindex @code{ \\} (@samp{\} character)
3079 @cindex backslash (@code{\\})
3081 Represents one @samp{\} character.
3084 @c Represents one @samp{'} (accent acute) character.
3085 @c This is needed in single character literals
3086 @c (@xref{Characters,,Character Constants}.) to represent
3089 @cindex @code{ \"} (doublequote character)
3090 @cindex doublequote (@code{\"})
3092 Represents one @samp{"} character. Needed in strings to represent
3093 this character, because an unescaped @samp{"} would end the string.
3095 @item \ @var{anything-else}
3096 Any other character when escaped by @kbd{\} gives a warning, but
3097 assembles as if the @samp{\} was not present. The idea is that if
3098 you used an escape sequence you clearly didn't want the literal
3099 interpretation of the following character. However @command{@value{AS}} has no
3100 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3101 code and warns you of the fact.
3104 Which characters are escapable, and what those escapes represent,
3105 varies widely among assemblers. The current set is what we think
3106 the BSD 4.2 assembler recognizes, and is a subset of what most C
3107 compilers recognize. If you are in doubt, do not use an escape
3111 @subsubsection Characters
3113 @cindex single character constant
3114 @cindex character, single
3115 @cindex constant, single character
3116 A single character may be written as a single quote immediately followed by
3117 that character. Some backslash escapes apply to characters, @code{\b},
3118 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3119 as for strings, plus @code{\'} for a single quote. So if you want to write the
3120 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3121 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3124 @ifclear abnormal-separator
3125 (or semicolon @samp{;})
3127 @ifset abnormal-separator
3129 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3134 immediately following an acute accent is taken as a literal character
3135 and does not count as the end of a statement. The value of a character
3136 constant in a numeric expression is the machine's byte-wide code for
3137 that character. @command{@value{AS}} assumes your character code is ASCII:
3138 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3141 @subsection Number Constants
3143 @cindex constants, number
3144 @cindex number constants
3145 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3146 are stored in the target machine. @emph{Integers} are numbers that
3147 would fit into an @code{int} in the C language. @emph{Bignums} are
3148 integers, but they are stored in more than 32 bits. @emph{Flonums}
3149 are floating point numbers, described below.
3152 * Integers:: Integers
3157 * Bit Fields:: Bit Fields
3163 @subsubsection Integers
3165 @cindex constants, integer
3167 @cindex binary integers
3168 @cindex integers, binary
3169 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3170 the binary digits @samp{01}.
3172 @cindex octal integers
3173 @cindex integers, octal
3174 An octal integer is @samp{0} followed by zero or more of the octal
3175 digits (@samp{01234567}).
3177 @cindex decimal integers
3178 @cindex integers, decimal
3179 A decimal integer starts with a non-zero digit followed by zero or
3180 more digits (@samp{0123456789}).
3182 @cindex hexadecimal integers
3183 @cindex integers, hexadecimal
3184 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3185 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3187 Integers have the usual values. To denote a negative integer, use
3188 the prefix operator @samp{-} discussed under expressions
3189 (@pxref{Prefix Ops,,Prefix Operators}).
3192 @subsubsection Bignums
3195 @cindex constants, bignum
3196 A @dfn{bignum} has the same syntax and semantics as an integer
3197 except that the number (or its negative) takes more than 32 bits to
3198 represent in binary. The distinction is made because in some places
3199 integers are permitted while bignums are not.
3202 @subsubsection Flonums
3204 @cindex floating point numbers
3205 @cindex constants, floating point
3207 @cindex precision, floating point
3208 A @dfn{flonum} represents a floating point number. The translation is
3209 indirect: a decimal floating point number from the text is converted by
3210 @command{@value{AS}} to a generic binary floating point number of more than
3211 sufficient precision. This generic floating point number is converted
3212 to a particular computer's floating point format (or formats) by a
3213 portion of @command{@value{AS}} specialized to that computer.
3215 A flonum is written by writing (in order)
3220 (@samp{0} is optional on the HPPA.)
3224 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3226 @kbd{e} is recommended. Case is not important.
3228 @c FIXME: verify if flonum syntax really this vague for most cases
3229 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3230 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3233 On the H8/300, Renesas / SuperH SH,
3234 and AMD 29K architectures, the letter must be
3235 one of the letters @samp{DFPRSX} (in upper or lower case).
3237 On the ARC, the letter must be one of the letters @samp{DFRS}
3238 (in upper or lower case).
3240 On the Intel 960 architecture, the letter must be
3241 one of the letters @samp{DFT} (in upper or lower case).
3243 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3247 One of the letters @samp{DFRS} (in upper or lower case).
3250 One of the letters @samp{DFPRSX} (in upper or lower case).
3253 The letter @samp{E} (upper case only).
3256 One of the letters @samp{DFT} (in upper or lower case).
3261 An optional sign: either @samp{+} or @samp{-}.
3264 An optional @dfn{integer part}: zero or more decimal digits.
3267 An optional @dfn{fractional part}: @samp{.} followed by zero
3268 or more decimal digits.
3271 An optional exponent, consisting of:
3275 An @samp{E} or @samp{e}.
3276 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3277 @c principle this can perfectly well be different on different targets.
3279 Optional sign: either @samp{+} or @samp{-}.
3281 One or more decimal digits.
3286 At least one of the integer part or the fractional part must be
3287 present. The floating point number has the usual base-10 value.
3289 @command{@value{AS}} does all processing using integers. Flonums are computed
3290 independently of any floating point hardware in the computer running
3291 @command{@value{AS}}.
3295 @c Bit fields are written as a general facility but are also controlled
3296 @c by a conditional-compilation flag---which is as of now (21mar91)
3297 @c turned on only by the i960 config of GAS.
3299 @subsubsection Bit Fields
3302 @cindex constants, bit field
3303 You can also define numeric constants as @dfn{bit fields}.
3304 Specify two numbers separated by a colon---
3306 @var{mask}:@var{value}
3309 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3312 The resulting number is then packed
3314 @c this conditional paren in case bit fields turned on elsewhere than 960
3315 (in host-dependent byte order)
3317 into a field whose width depends on which assembler directive has the
3318 bit-field as its argument. Overflow (a result from the bitwise and
3319 requiring more binary digits to represent) is not an error; instead,
3320 more constants are generated, of the specified width, beginning with the
3321 least significant digits.@refill
3323 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3324 @code{.short}, and @code{.word} accept bit-field arguments.
3329 @chapter Sections and Relocation
3334 * Secs Background:: Background
3335 * Ld Sections:: Linker Sections
3336 * As Sections:: Assembler Internal Sections
3337 * Sub-Sections:: Sub-Sections
3341 @node Secs Background
3344 Roughly, a section is a range of addresses, with no gaps; all data
3345 ``in'' those addresses is treated the same for some particular purpose.
3346 For example there may be a ``read only'' section.
3348 @cindex linker, and assembler
3349 @cindex assembler, and linker
3350 The linker @code{@value{LD}} reads many object files (partial programs) and
3351 combines their contents to form a runnable program. When @command{@value{AS}}
3352 emits an object file, the partial program is assumed to start at address 0.
3353 @code{@value{LD}} assigns the final addresses for the partial program, so that
3354 different partial programs do not overlap. This is actually an
3355 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3358 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3359 addresses. These blocks slide to their run-time addresses as rigid
3360 units; their length does not change and neither does the order of bytes
3361 within them. Such a rigid unit is called a @emph{section}. Assigning
3362 run-time addresses to sections is called @dfn{relocation}. It includes
3363 the task of adjusting mentions of object-file addresses so they refer to
3364 the proper run-time addresses.
3366 For the H8/300, and for the Renesas / SuperH SH,
3367 @command{@value{AS}} pads sections if needed to
3368 ensure they end on a word (sixteen bit) boundary.
3371 @cindex standard assembler sections
3372 An object file written by @command{@value{AS}} has at least three sections, any
3373 of which may be empty. These are named @dfn{text}, @dfn{data} and
3378 When it generates COFF or ELF output,
3380 @command{@value{AS}} can also generate whatever other named sections you specify
3381 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3382 If you do not use any directives that place output in the @samp{.text}
3383 or @samp{.data} sections, these sections still exist, but are empty.
3388 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3390 @command{@value{AS}} can also generate whatever other named sections you
3391 specify using the @samp{.space} and @samp{.subspace} directives. See
3392 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3393 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3394 assembler directives.
3397 Additionally, @command{@value{AS}} uses different names for the standard
3398 text, data, and bss sections when generating SOM output. Program text
3399 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3400 BSS into @samp{$BSS$}.
3404 Within the object file, the text section starts at address @code{0}, the
3405 data section follows, and the bss section follows the data section.
3408 When generating either SOM or ELF output files on the HPPA, the text
3409 section starts at address @code{0}, the data section at address
3410 @code{0x4000000}, and the bss section follows the data section.
3413 To let @code{@value{LD}} know which data changes when the sections are
3414 relocated, and how to change that data, @command{@value{AS}} also writes to the
3415 object file details of the relocation needed. To perform relocation
3416 @code{@value{LD}} must know, each time an address in the object
3420 Where in the object file is the beginning of this reference to
3423 How long (in bytes) is this reference?
3425 Which section does the address refer to? What is the numeric value of
3427 (@var{address}) @minus{} (@var{start-address of section})?
3430 Is the reference to an address ``Program-Counter relative''?
3433 @cindex addresses, format of
3434 @cindex section-relative addressing
3435 In fact, every address @command{@value{AS}} ever uses is expressed as
3437 (@var{section}) + (@var{offset into section})
3440 Further, most expressions @command{@value{AS}} computes have this section-relative
3443 (For some object formats, such as SOM for the HPPA, some expressions are
3444 symbol-relative instead.)
3447 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3448 @var{N} into section @var{secname}.''
3450 Apart from text, data and bss sections you need to know about the
3451 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3452 addresses in the absolute section remain unchanged. For example, address
3453 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3454 @code{@value{LD}}. Although the linker never arranges two partial programs'
3455 data sections with overlapping addresses after linking, @emph{by definition}
3456 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3457 part of a program is always the same address when the program is running as
3458 address @code{@{absolute@ 239@}} in any other part of the program.
3460 The idea of sections is extended to the @dfn{undefined} section. Any
3461 address whose section is unknown at assembly time is by definition
3462 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3463 Since numbers are always defined, the only way to generate an undefined
3464 address is to mention an undefined symbol. A reference to a named
3465 common block would be such a symbol: its value is unknown at assembly
3466 time so it has section @emph{undefined}.
3468 By analogy the word @emph{section} is used to describe groups of sections in
3469 the linked program. @code{@value{LD}} puts all partial programs' text
3470 sections in contiguous addresses in the linked program. It is
3471 customary to refer to the @emph{text section} of a program, meaning all
3472 the addresses of all partial programs' text sections. Likewise for
3473 data and bss sections.
3475 Some sections are manipulated by @code{@value{LD}}; others are invented for
3476 use of @command{@value{AS}} and have no meaning except during assembly.
3479 @section Linker Sections
3480 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3485 @cindex named sections
3486 @cindex sections, named
3487 @item named sections
3490 @cindex text section
3491 @cindex data section
3495 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3496 separate but equal sections. Anything you can say of one section is
3499 When the program is running, however, it is
3500 customary for the text section to be unalterable. The
3501 text section is often shared among processes: it contains
3502 instructions, constants and the like. The data section of a running
3503 program is usually alterable: for example, C variables would be stored
3504 in the data section.
3509 This section contains zeroed bytes when your program begins running. It
3510 is used to hold uninitialized variables or common storage. The length of
3511 each partial program's bss section is important, but because it starts
3512 out containing zeroed bytes there is no need to store explicit zero
3513 bytes in the object file. The bss section was invented to eliminate
3514 those explicit zeros from object files.
3516 @cindex absolute section
3517 @item absolute section
3518 Address 0 of this section is always ``relocated'' to runtime address 0.
3519 This is useful if you want to refer to an address that @code{@value{LD}} must
3520 not change when relocating. In this sense we speak of absolute
3521 addresses being ``unrelocatable'': they do not change during relocation.
3523 @cindex undefined section
3524 @item undefined section
3525 This ``section'' is a catch-all for address references to objects not in
3526 the preceding sections.
3527 @c FIXME: ref to some other doc on obj-file formats could go here.
3530 @cindex relocation example
3531 An idealized example of three relocatable sections follows.
3533 The example uses the traditional section names @samp{.text} and @samp{.data}.
3535 Memory addresses are on the horizontal axis.
3539 @c END TEXI2ROFF-KILL
3542 partial program # 1: |ttttt|dddd|00|
3549 partial program # 2: |TTT|DDD|000|
3552 +--+---+-----+--+----+---+-----+~~
3553 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3554 +--+---+-----+--+----+---+-----+~~
3556 addresses: 0 @dots{}
3563 \line{\it Partial program \#1: \hfil}
3564 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3565 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3567 \line{\it Partial program \#2: \hfil}
3568 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3569 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3571 \line{\it linked program: \hfil}
3572 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3573 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3574 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3575 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3577 \line{\it addresses: \hfil}
3581 @c END TEXI2ROFF-KILL
3584 @section Assembler Internal Sections
3586 @cindex internal assembler sections
3587 @cindex sections in messages, internal
3588 These sections are meant only for the internal use of @command{@value{AS}}. They
3589 have no meaning at run-time. You do not really need to know about these
3590 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3591 warning messages, so it might be helpful to have an idea of their
3592 meanings to @command{@value{AS}}. These sections are used to permit the
3593 value of every expression in your assembly language program to be a
3594 section-relative address.
3597 @cindex assembler internal logic error
3598 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3599 An internal assembler logic error has been found. This means there is a
3600 bug in the assembler.
3602 @cindex expr (internal section)
3604 The assembler stores complex expression internally as combinations of
3605 symbols. When it needs to represent an expression as a symbol, it puts
3606 it in the expr section.
3608 @c FIXME item transfer[t] vector preload
3609 @c FIXME item transfer[t] vector postload
3610 @c FIXME item register
3614 @section Sub-Sections
3616 @cindex numbered subsections
3617 @cindex grouping data
3623 fall into two sections: text and data.
3625 You may have separate groups of
3627 data in named sections
3631 data in named sections
3637 that you want to end up near to each other in the object file, even though they
3638 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3639 use @dfn{subsections} for this purpose. Within each section, there can be
3640 numbered subsections with values from 0 to 8192. Objects assembled into the
3641 same subsection go into the object file together with other objects in the same
3642 subsection. For example, a compiler might want to store constants in the text
3643 section, but might not want to have them interspersed with the program being
3644 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3645 section of code being output, and a @samp{.text 1} before each group of
3646 constants being output.
3648 Subsections are optional. If you do not use subsections, everything
3649 goes in subsection number zero.
3652 Each subsection is zero-padded up to a multiple of four bytes.
3653 (Subsections may be padded a different amount on different flavors
3654 of @command{@value{AS}}.)
3658 On the H8/300 platform, each subsection is zero-padded to a word
3659 boundary (two bytes).
3660 The same is true on the Renesas SH.
3663 @c FIXME section padding (alignment)?
3664 @c Rich Pixley says padding here depends on target obj code format; that
3665 @c doesn't seem particularly useful to say without further elaboration,
3666 @c so for now I say nothing about it. If this is a generic BFD issue,
3667 @c these paragraphs might need to vanish from this manual, and be
3668 @c discussed in BFD chapter of binutils (or some such).
3672 Subsections appear in your object file in numeric order, lowest numbered
3673 to highest. (All this to be compatible with other people's assemblers.)
3674 The object file contains no representation of subsections; @code{@value{LD}} and
3675 other programs that manipulate object files see no trace of them.
3676 They just see all your text subsections as a text section, and all your
3677 data subsections as a data section.
3679 To specify which subsection you want subsequent statements assembled
3680 into, use a numeric argument to specify it, in a @samp{.text
3681 @var{expression}} or a @samp{.data @var{expression}} statement.
3684 When generating COFF output, you
3689 can also use an extra subsection
3690 argument with arbitrary named sections: @samp{.section @var{name},
3695 When generating ELF output, you
3700 can also use the @code{.subsection} directive (@pxref{SubSection})
3701 to specify a subsection: @samp{.subsection @var{expression}}.
3703 @var{Expression} should be an absolute expression
3704 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3705 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3706 begins in @code{text 0}. For instance:
3708 .text 0 # The default subsection is text 0 anyway.
3709 .ascii "This lives in the first text subsection. *"
3711 .ascii "But this lives in the second text subsection."
3713 .ascii "This lives in the data section,"
3714 .ascii "in the first data subsection."
3716 .ascii "This lives in the first text section,"
3717 .ascii "immediately following the asterisk (*)."
3720 Each section has a @dfn{location counter} incremented by one for every byte
3721 assembled into that section. Because subsections are merely a convenience
3722 restricted to @command{@value{AS}} there is no concept of a subsection location
3723 counter. There is no way to directly manipulate a location counter---but the
3724 @code{.align} directive changes it, and any label definition captures its
3725 current value. The location counter of the section where statements are being
3726 assembled is said to be the @dfn{active} location counter.
3729 @section bss Section
3732 @cindex common variable storage
3733 The bss section is used for local common variable storage.
3734 You may allocate address space in the bss section, but you may
3735 not dictate data to load into it before your program executes. When
3736 your program starts running, all the contents of the bss
3737 section are zeroed bytes.
3739 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3740 @ref{Lcomm,,@code{.lcomm}}.
3742 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3743 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3746 When assembling for a target which supports multiple sections, such as ELF or
3747 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3748 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3749 section. Typically the section will only contain symbol definitions and
3750 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3757 Symbols are a central concept: the programmer uses symbols to name
3758 things, the linker uses symbols to link, and the debugger uses symbols
3762 @cindex debuggers, and symbol order
3763 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3764 the same order they were declared. This may break some debuggers.
3769 * Setting Symbols:: Giving Symbols Other Values
3770 * Symbol Names:: Symbol Names
3771 * Dot:: The Special Dot Symbol
3772 * Symbol Attributes:: Symbol Attributes
3779 A @dfn{label} is written as a symbol immediately followed by a colon
3780 @samp{:}. The symbol then represents the current value of the
3781 active location counter, and is, for example, a suitable instruction
3782 operand. You are warned if you use the same symbol to represent two
3783 different locations: the first definition overrides any other
3787 On the HPPA, the usual form for a label need not be immediately followed by a
3788 colon, but instead must start in column zero. Only one label may be defined on
3789 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3790 provides a special directive @code{.label} for defining labels more flexibly.
3793 @node Setting Symbols
3794 @section Giving Symbols Other Values
3796 @cindex assigning values to symbols
3797 @cindex symbol values, assigning
3798 A symbol can be given an arbitrary value by writing a symbol, followed
3799 by an equals sign @samp{=}, followed by an expression
3800 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3801 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3802 equals sign @samp{=}@samp{=} here represents an equivalent of the
3803 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3806 Blackfin does not support symbol assignment with @samp{=}.
3810 @section Symbol Names
3812 @cindex symbol names
3813 @cindex names, symbol
3814 @ifclear SPECIAL-SYMS
3815 Symbol names begin with a letter or with one of @samp{._}. On most
3816 machines, you can also use @code{$} in symbol names; exceptions are
3817 noted in @ref{Machine Dependencies}. That character may be followed by any
3818 string of digits, letters, dollar signs (unless otherwise noted for a
3819 particular target machine), and underscores.
3823 Symbol names begin with a letter or with one of @samp{._}. On the
3824 Renesas SH you can also use @code{$} in symbol names. That
3825 character may be followed by any string of digits, letters, dollar signs (save
3826 on the H8/300), and underscores.
3830 Case of letters is significant: @code{foo} is a different symbol name
3833 Symbol names do not start with a digit. An exception to this rule is made for
3834 Local Labels. See below.
3836 Multibyte characters are supported. To generate a symbol name containing
3837 multibyte characters enclose it within double quotes and use escape codes. cf
3838 @xref{Strings}. Generating a multibyte symbol name from a label is not
3839 currently supported.
3841 Each symbol has exactly one name. Each name in an assembly language program
3842 refers to exactly one symbol. You may use that symbol name any number of times
3845 @subheading Local Symbol Names
3847 @cindex local symbol names
3848 @cindex symbol names, local
3849 A local symbol is any symbol beginning with certain local label prefixes.
3850 By default, the local label prefix is @samp{.L} for ELF systems or
3851 @samp{L} for traditional a.out systems, but each target may have its own
3852 set of local label prefixes.
3854 On the HPPA local symbols begin with @samp{L$}.
3857 Local symbols are defined and used within the assembler, but they are
3858 normally not saved in object files. Thus, they are not visible when debugging.
3859 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3860 to retain the local symbols in the object files.
3862 @subheading Local Labels
3864 @cindex local labels
3865 @cindex temporary symbol names
3866 @cindex symbol names, temporary
3867 Local labels are different from local symbols. Local labels help compilers and
3868 programmers use names temporarily. They create symbols which are guaranteed to
3869 be unique over the entire scope of the input source code and which can be
3870 referred to by a simple notation. To define a local label, write a label of
3871 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3872 To refer to the most recent previous definition of that label write
3873 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3874 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3875 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3877 There is no restriction on how you can use these labels, and you can reuse them
3878 too. So that it is possible to repeatedly define the same local label (using
3879 the same number @samp{@b{N}}), although you can only refer to the most recently
3880 defined local label of that number (for a backwards reference) or the next
3881 definition of a specific local label for a forward reference. It is also worth
3882 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3883 implemented in a slightly more efficient manner than the others.
3894 Which is the equivalent of:
3897 label_1: branch label_3
3898 label_2: branch label_1
3899 label_3: branch label_4
3900 label_4: branch label_3
3903 Local label names are only a notational device. They are immediately
3904 transformed into more conventional symbol names before the assembler uses them.
3905 The symbol names are stored in the symbol table, appear in error messages, and
3906 are optionally emitted to the object file. The names are constructed using
3910 @item @emph{local label prefix}
3911 All local symbols begin with the system-specific local label prefix.
3912 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3913 that start with the local label prefix. These labels are
3914 used for symbols you are never intended to see. If you use the
3915 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3916 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3917 you may use them in debugging.
3920 This is the number that was used in the local label definition. So if the
3921 label is written @samp{55:} then the number is @samp{55}.
3924 This unusual character is included so you do not accidentally invent a symbol
3925 of the same name. The character has ASCII value of @samp{\002} (control-B).
3927 @item @emph{ordinal number}
3928 This is a serial number to keep the labels distinct. The first definition of
3929 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3930 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3931 the number @samp{1} and its 15th definition gets @samp{15} as well.
3934 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3935 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3937 @subheading Dollar Local Labels
3938 @cindex dollar local symbols
3940 On some targets @code{@value{AS}} also supports an even more local form of
3941 local labels called dollar labels. These labels go out of scope (i.e., they
3942 become undefined) as soon as a non-local label is defined. Thus they remain
3943 valid for only a small region of the input source code. Normal local labels,
3944 by contrast, remain in scope for the entire file, or until they are redefined
3945 by another occurrence of the same local label.
3947 Dollar labels are defined in exactly the same way as ordinary local labels,
3948 except that they have a dollar sign suffix to their numeric value, e.g.,
3951 They can also be distinguished from ordinary local labels by their transformed
3952 names which use ASCII character @samp{\001} (control-A) as the magic character
3953 to distinguish them from ordinary labels. For example, the fifth definition of
3954 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3957 @section The Special Dot Symbol
3959 @cindex dot (symbol)
3960 @cindex @code{.} (symbol)
3961 @cindex current address
3962 @cindex location counter
3963 The special symbol @samp{.} refers to the current address that
3964 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3965 .long .} defines @code{melvin} to contain its own address.
3966 Assigning a value to @code{.} is treated the same as a @code{.org}
3968 @ifclear no-space-dir
3969 Thus, the expression @samp{.=.+4} is the same as saying
3973 @node Symbol Attributes
3974 @section Symbol Attributes
3976 @cindex symbol attributes
3977 @cindex attributes, symbol
3978 Every symbol has, as well as its name, the attributes ``Value'' and
3979 ``Type''. Depending on output format, symbols can also have auxiliary
3982 The detailed definitions are in @file{a.out.h}.
3985 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3986 all these attributes, and probably won't warn you. This makes the
3987 symbol an externally defined symbol, which is generally what you
3991 * Symbol Value:: Value
3992 * Symbol Type:: Type
3995 * a.out Symbols:: Symbol Attributes: @code{a.out}
3999 * a.out Symbols:: Symbol Attributes: @code{a.out}
4002 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
4007 * COFF Symbols:: Symbol Attributes for COFF
4010 * SOM Symbols:: Symbol Attributes for SOM
4017 @cindex value of a symbol
4018 @cindex symbol value
4019 The value of a symbol is (usually) 32 bits. For a symbol which labels a
4020 location in the text, data, bss or absolute sections the value is the
4021 number of addresses from the start of that section to the label.
4022 Naturally for text, data and bss sections the value of a symbol changes
4023 as @code{@value{LD}} changes section base addresses during linking. Absolute
4024 symbols' values do not change during linking: that is why they are
4027 The value of an undefined symbol is treated in a special way. If it is
4028 0 then the symbol is not defined in this assembler source file, and
4029 @code{@value{LD}} tries to determine its value from other files linked into the
4030 same program. You make this kind of symbol simply by mentioning a symbol
4031 name without defining it. A non-zero value represents a @code{.comm}
4032 common declaration. The value is how much common storage to reserve, in
4033 bytes (addresses). The symbol refers to the first address of the
4039 @cindex type of a symbol
4041 The type attribute of a symbol contains relocation (section)
4042 information, any flag settings indicating that a symbol is external, and
4043 (optionally), other information for linkers and debuggers. The exact
4044 format depends on the object-code output format in use.
4049 @c The following avoids a "widow" subsection title. @group would be
4050 @c better if it were available outside examples.
4053 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
4055 @cindex @code{b.out} symbol attributes
4056 @cindex symbol attributes, @code{b.out}
4057 These symbol attributes appear only when @command{@value{AS}} is configured for
4058 one of the Berkeley-descended object output formats---@code{a.out} or
4064 @subsection Symbol Attributes: @code{a.out}
4066 @cindex @code{a.out} symbol attributes
4067 @cindex symbol attributes, @code{a.out}
4073 @subsection Symbol Attributes: @code{a.out}
4075 @cindex @code{a.out} symbol attributes
4076 @cindex symbol attributes, @code{a.out}
4080 * Symbol Desc:: Descriptor
4081 * Symbol Other:: Other
4085 @subsubsection Descriptor
4087 @cindex descriptor, of @code{a.out} symbol
4088 This is an arbitrary 16-bit value. You may establish a symbol's
4089 descriptor value by using a @code{.desc} statement
4090 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4091 @command{@value{AS}}.
4094 @subsubsection Other
4096 @cindex other attribute, of @code{a.out} symbol
4097 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4102 @subsection Symbol Attributes for COFF
4104 @cindex COFF symbol attributes
4105 @cindex symbol attributes, COFF
4107 The COFF format supports a multitude of auxiliary symbol attributes;
4108 like the primary symbol attributes, they are set between @code{.def} and
4109 @code{.endef} directives.
4111 @subsubsection Primary Attributes
4113 @cindex primary attributes, COFF symbols
4114 The symbol name is set with @code{.def}; the value and type,
4115 respectively, with @code{.val} and @code{.type}.
4117 @subsubsection Auxiliary Attributes
4119 @cindex auxiliary attributes, COFF symbols
4120 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4121 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4122 table information for COFF.
4127 @subsection Symbol Attributes for SOM
4129 @cindex SOM symbol attributes
4130 @cindex symbol attributes, SOM
4132 The SOM format for the HPPA supports a multitude of symbol attributes set with
4133 the @code{.EXPORT} and @code{.IMPORT} directives.
4135 The attributes are described in @cite{HP9000 Series 800 Assembly
4136 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4137 @code{EXPORT} assembler directive documentation.
4141 @chapter Expressions
4145 @cindex numeric values
4146 An @dfn{expression} specifies an address or numeric value.
4147 Whitespace may precede and/or follow an expression.
4149 The result of an expression must be an absolute number, or else an offset into
4150 a particular section. If an expression is not absolute, and there is not
4151 enough information when @command{@value{AS}} sees the expression to know its
4152 section, a second pass over the source program might be necessary to interpret
4153 the expression---but the second pass is currently not implemented.
4154 @command{@value{AS}} aborts with an error message in this situation.
4157 * Empty Exprs:: Empty Expressions
4158 * Integer Exprs:: Integer Expressions
4162 @section Empty Expressions
4164 @cindex empty expressions
4165 @cindex expressions, empty
4166 An empty expression has no value: it is just whitespace or null.
4167 Wherever an absolute expression is required, you may omit the
4168 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4169 is compatible with other assemblers.
4172 @section Integer Expressions
4174 @cindex integer expressions
4175 @cindex expressions, integer
4176 An @dfn{integer expression} is one or more @emph{arguments} delimited
4177 by @emph{operators}.
4180 * Arguments:: Arguments
4181 * Operators:: Operators
4182 * Prefix Ops:: Prefix Operators
4183 * Infix Ops:: Infix Operators
4187 @subsection Arguments
4189 @cindex expression arguments
4190 @cindex arguments in expressions
4191 @cindex operands in expressions
4192 @cindex arithmetic operands
4193 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4194 contexts arguments are sometimes called ``arithmetic operands''. In
4195 this manual, to avoid confusing them with the ``instruction operands'' of
4196 the machine language, we use the term ``argument'' to refer to parts of
4197 expressions only, reserving the word ``operand'' to refer only to machine
4198 instruction operands.
4200 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4201 @var{section} is one of text, data, bss, absolute,
4202 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4205 Numbers are usually integers.
4207 A number can be a flonum or bignum. In this case, you are warned
4208 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4209 these 32 bits are an integer. You may write integer-manipulating
4210 instructions that act on exotic constants, compatible with other
4213 @cindex subexpressions
4214 Subexpressions are a left parenthesis @samp{(} followed by an integer
4215 expression, followed by a right parenthesis @samp{)}; or a prefix
4216 operator followed by an argument.
4219 @subsection Operators
4221 @cindex operators, in expressions
4222 @cindex arithmetic functions
4223 @cindex functions, in expressions
4224 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4225 operators are followed by an argument. Infix operators appear
4226 between their arguments. Operators may be preceded and/or followed by
4230 @subsection Prefix Operator
4232 @cindex prefix operators
4233 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4234 one argument, which must be absolute.
4236 @c the tex/end tex stuff surrounding this small table is meant to make
4237 @c it align, on the printed page, with the similar table in the next
4238 @c section (which is inside an enumerate).
4240 \global\advance\leftskip by \itemindent
4245 @dfn{Negation}. Two's complement negation.
4247 @dfn{Complementation}. Bitwise not.
4251 \global\advance\leftskip by -\itemindent
4255 @subsection Infix Operators
4257 @cindex infix operators
4258 @cindex operators, permitted arguments
4259 @dfn{Infix operators} take two arguments, one on either side. Operators
4260 have precedence, but operations with equal precedence are performed left
4261 to right. Apart from @code{+} or @option{-}, both arguments must be
4262 absolute, and the result is absolute.
4265 @cindex operator precedence
4266 @cindex precedence of operators
4273 @dfn{Multiplication}.
4276 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4282 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4285 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4289 Intermediate precedence
4294 @dfn{Bitwise Inclusive Or}.
4300 @dfn{Bitwise Exclusive Or}.
4303 @dfn{Bitwise Or Not}.
4310 @cindex addition, permitted arguments
4311 @cindex plus, permitted arguments
4312 @cindex arguments for addition
4314 @dfn{Addition}. If either argument is absolute, the result has the section of
4315 the other argument. You may not add together arguments from different
4318 @cindex subtraction, permitted arguments
4319 @cindex minus, permitted arguments
4320 @cindex arguments for subtraction
4322 @dfn{Subtraction}. If the right argument is absolute, the
4323 result has the section of the left argument.
4324 If both arguments are in the same section, the result is absolute.
4325 You may not subtract arguments from different sections.
4326 @c FIXME is there still something useful to say about undefined - undefined ?
4328 @cindex comparison expressions
4329 @cindex expressions, comparison
4334 @dfn{Is Not Equal To}
4338 @dfn{Is Greater Than}
4340 @dfn{Is Greater Than Or Equal To}
4342 @dfn{Is Less Than Or Equal To}
4344 The comparison operators can be used as infix operators. A true results has a
4345 value of -1 whereas a false result has a value of 0. Note, these operators
4346 perform signed comparisons.
4349 @item Lowest Precedence
4358 These two logical operations can be used to combine the results of sub
4359 expressions. Note, unlike the comparison operators a true result returns a
4360 value of 1 but a false results does still return 0. Also note that the logical
4361 or operator has a slightly lower precedence than logical and.
4366 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4367 address; you can only have a defined section in one of the two arguments.
4370 @chapter Assembler Directives
4372 @cindex directives, machine independent
4373 @cindex pseudo-ops, machine independent
4374 @cindex machine independent directives
4375 All assembler directives have names that begin with a period (@samp{.}).
4376 The names are case insensitive for most targets, and usually written
4379 This chapter discusses directives that are available regardless of the
4380 target machine configuration for the @sc{gnu} assembler.
4382 Some machine configurations provide additional directives.
4383 @xref{Machine Dependencies}.
4386 @ifset machine-directives
4387 @xref{Machine Dependencies}, for additional directives.
4392 * Abort:: @code{.abort}
4394 * ABORT (COFF):: @code{.ABORT}
4397 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4398 * Altmacro:: @code{.altmacro}
4399 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4400 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4401 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4402 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4403 * Byte:: @code{.byte @var{expressions}}
4404 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4405 * Comm:: @code{.comm @var{symbol} , @var{length} }
4406 * Data:: @code{.data @var{subsection}}
4408 * Def:: @code{.def @var{name}}
4411 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4417 * Double:: @code{.double @var{flonums}}
4418 * Eject:: @code{.eject}
4419 * Else:: @code{.else}
4420 * Elseif:: @code{.elseif}
4423 * Endef:: @code{.endef}
4426 * Endfunc:: @code{.endfunc}
4427 * Endif:: @code{.endif}
4428 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4429 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4430 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4432 * Error:: @code{.error @var{string}}
4433 * Exitm:: @code{.exitm}
4434 * Extern:: @code{.extern}
4435 * Fail:: @code{.fail}
4436 * File:: @code{.file}
4437 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4438 * Float:: @code{.float @var{flonums}}
4439 * Func:: @code{.func}
4440 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4442 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4443 * Hidden:: @code{.hidden @var{names}}
4446 * hword:: @code{.hword @var{expressions}}
4447 * Ident:: @code{.ident}
4448 * If:: @code{.if @var{absolute expression}}
4449 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4450 * Include:: @code{.include "@var{file}"}
4451 * Int:: @code{.int @var{expressions}}
4453 * Internal:: @code{.internal @var{names}}
4456 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4457 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4458 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4459 * Lflags:: @code{.lflags}
4460 @ifclear no-line-dir
4461 * Line:: @code{.line @var{line-number}}
4464 * Linkonce:: @code{.linkonce [@var{type}]}
4465 * List:: @code{.list}
4466 * Ln:: @code{.ln @var{line-number}}
4467 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4468 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4470 * Local:: @code{.local @var{names}}
4473 * Long:: @code{.long @var{expressions}}
4475 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4478 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4479 * MRI:: @code{.mri @var{val}}
4480 * Noaltmacro:: @code{.noaltmacro}
4481 * Nolist:: @code{.nolist}
4482 * Nop:: @code{.nop @var{size}[, @var{control}]}
4483 * Octa:: @code{.octa @var{bignums}}
4484 * Offset:: @code{.offset @var{loc}}
4485 * Org:: @code{.org @var{new-lc}, @var{fill}}
4486 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4488 * PopSection:: @code{.popsection}
4489 * Previous:: @code{.previous}
4492 * Print:: @code{.print @var{string}}
4494 * Protected:: @code{.protected @var{names}}
4497 * Psize:: @code{.psize @var{lines}, @var{columns}}
4498 * Purgem:: @code{.purgem @var{name}}
4500 * PushSection:: @code{.pushsection @var{name}}
4503 * Quad:: @code{.quad @var{bignums}}
4504 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4505 * Rept:: @code{.rept @var{count}}
4506 * Sbttl:: @code{.sbttl "@var{subheading}"}
4508 * Scl:: @code{.scl @var{class}}
4511 * Section:: @code{.section @var{name}[, @var{flags}]}
4514 * Set:: @code{.set @var{symbol}, @var{expression}}
4515 * Short:: @code{.short @var{expressions}}
4516 * Single:: @code{.single @var{flonums}}
4518 * Size:: @code{.size [@var{name} , @var{expression}]}
4520 @ifclear no-space-dir
4521 * Skip:: @code{.skip @var{size} , @var{fill}}
4524 * Sleb128:: @code{.sleb128 @var{expressions}}
4525 @ifclear no-space-dir
4526 * Space:: @code{.space @var{size} , @var{fill}}
4529 * Stab:: @code{.stabd, .stabn, .stabs}
4532 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4533 * Struct:: @code{.struct @var{expression}}
4535 * SubSection:: @code{.subsection}
4536 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4540 * Tag:: @code{.tag @var{structname}}
4543 * Text:: @code{.text @var{subsection}}
4544 * Title:: @code{.title "@var{heading}"}
4546 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4549 * Uleb128:: @code{.uleb128 @var{expressions}}
4551 * Val:: @code{.val @var{addr}}
4555 * Version:: @code{.version "@var{string}"}
4556 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4557 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4560 * Warning:: @code{.warning @var{string}}
4561 * Weak:: @code{.weak @var{names}}
4562 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4563 * Word:: @code{.word @var{expressions}}
4564 @ifclear no-space-dir
4565 * Zero:: @code{.zero @var{size}}
4568 * 2byte:: @code{.2byte @var{expressions}}
4569 * 4byte:: @code{.4byte @var{expressions}}
4570 * 8byte:: @code{.8byte @var{bignums}}
4572 * Deprecated:: Deprecated Directives
4576 @section @code{.abort}
4578 @cindex @code{abort} directive
4579 @cindex stopping the assembly
4580 This directive stops the assembly immediately. It is for
4581 compatibility with other assemblers. The original idea was that the
4582 assembly language source would be piped into the assembler. If the sender
4583 of the source quit, it could use this directive tells @command{@value{AS}} to
4584 quit also. One day @code{.abort} will not be supported.
4588 @section @code{.ABORT} (COFF)
4590 @cindex @code{ABORT} directive
4591 When producing COFF output, @command{@value{AS}} accepts this directive as a
4592 synonym for @samp{.abort}.
4595 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4601 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4603 @cindex padding the location counter
4604 @cindex @code{align} directive
4605 Pad the location counter (in the current subsection) to a particular storage
4606 boundary. The first expression (which must be absolute) is the alignment
4607 required, as described below.
4609 The second expression (also absolute) gives the fill value to be stored in the
4610 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4611 padding bytes are normally zero. However, on most systems, if the section is
4612 marked as containing code and the fill value is omitted, the space is filled
4613 with no-op instructions.
4615 The third expression is also absolute, and is also optional. If it is present,
4616 it is the maximum number of bytes that should be skipped by this alignment
4617 directive. If doing the alignment would require skipping more bytes than the
4618 specified maximum, then the alignment is not done at all. You can omit the
4619 fill value (the second argument) entirely by simply using two commas after the
4620 required alignment; this can be useful if you want the alignment to be filled
4621 with no-op instructions when appropriate.
4623 The way the required alignment is specified varies from system to system.
4624 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4625 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4626 alignment request in bytes. For example @samp{.align 8} advances
4627 the location counter until it is a multiple of 8. If the location counter
4628 is already a multiple of 8, no change is needed. For the tic54x, the
4629 first expression is the alignment request in words.
4631 For other systems, including ppc, i386 using a.out format, arm and
4632 strongarm, it is the
4633 number of low-order zero bits the location counter must have after
4634 advancement. For example @samp{.align 3} advances the location
4635 counter until it a multiple of 8. If the location counter is already a
4636 multiple of 8, no change is needed.
4638 This inconsistency is due to the different behaviors of the various
4639 native assemblers for these systems which GAS must emulate.
4640 GAS also provides @code{.balign} and @code{.p2align} directives,
4641 described later, which have a consistent behavior across all
4642 architectures (but are specific to GAS).
4645 @section @code{.altmacro}
4646 Enable alternate macro mode, enabling:
4649 @item LOCAL @var{name} [ , @dots{} ]
4650 One additional directive, @code{LOCAL}, is available. It is used to
4651 generate a string replacement for each of the @var{name} arguments, and
4652 replace any instances of @var{name} in each macro expansion. The
4653 replacement string is unique in the assembly, and different for each
4654 separate macro expansion. @code{LOCAL} allows you to write macros that
4655 define symbols, without fear of conflict between separate macro expansions.
4657 @item String delimiters
4658 You can write strings delimited in these other ways besides
4659 @code{"@var{string}"}:
4662 @item '@var{string}'
4663 You can delimit strings with single-quote characters.
4665 @item <@var{string}>
4666 You can delimit strings with matching angle brackets.
4669 @item single-character string escape
4670 To include any single character literally in a string (even if the
4671 character would otherwise have some special meaning), you can prefix the
4672 character with @samp{!} (an exclamation mark). For example, you can
4673 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4675 @item Expression results as strings
4676 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4677 and use the result as a string.
4681 @section @code{.ascii "@var{string}"}@dots{}
4683 @cindex @code{ascii} directive
4684 @cindex string literals
4685 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4686 separated by commas. It assembles each string (with no automatic
4687 trailing zero byte) into consecutive addresses.
4690 @section @code{.asciz "@var{string}"}@dots{}
4692 @cindex @code{asciz} directive
4693 @cindex zero-terminated strings
4694 @cindex null-terminated strings
4695 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4696 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4699 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4701 @cindex padding the location counter given number of bytes
4702 @cindex @code{balign} directive
4703 Pad the location counter (in the current subsection) to a particular
4704 storage boundary. The first expression (which must be absolute) is the
4705 alignment request in bytes. For example @samp{.balign 8} advances
4706 the location counter until it is a multiple of 8. If the location counter
4707 is already a multiple of 8, no change is needed.
4709 The second expression (also absolute) gives the fill value to be stored in the
4710 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4711 padding bytes are normally zero. However, on most systems, if the section is
4712 marked as containing code and the fill value is omitted, the space is filled
4713 with no-op instructions.
4715 The third expression is also absolute, and is also optional. If it is present,
4716 it is the maximum number of bytes that should be skipped by this alignment
4717 directive. If doing the alignment would require skipping more bytes than the
4718 specified maximum, then the alignment is not done at all. You can omit the
4719 fill value (the second argument) entirely by simply using two commas after the
4720 required alignment; this can be useful if you want the alignment to be filled
4721 with no-op instructions when appropriate.
4723 @cindex @code{balignw} directive
4724 @cindex @code{balignl} directive
4725 The @code{.balignw} and @code{.balignl} directives are variants of the
4726 @code{.balign} directive. The @code{.balignw} directive treats the fill
4727 pattern as a two byte word value. The @code{.balignl} directives treats the
4728 fill pattern as a four byte longword value. For example, @code{.balignw
4729 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4730 filled in with the value 0x368d (the exact placement of the bytes depends upon
4731 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4734 @node Bundle directives
4735 @section Bundle directives
4736 @subsection @code{.bundle_align_mode @var{abs-expr}}
4737 @cindex @code{bundle_align_mode} directive
4739 @cindex instruction bundle
4740 @cindex aligned instruction bundle
4741 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4742 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4743 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4744 disabled (which is the default state). If the argument it not zero, it
4745 gives the size of an instruction bundle as a power of two (as for the
4746 @code{.p2align} directive, @pxref{P2align}).
4748 For some targets, it's an ABI requirement that no instruction may span a
4749 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4750 instructions that starts on an aligned boundary. For example, if
4751 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4752 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4753 effect, no single instruction may span a boundary between bundles. If an
4754 instruction would start too close to the end of a bundle for the length of
4755 that particular instruction to fit within the bundle, then the space at the
4756 end of that bundle is filled with no-op instructions so the instruction
4757 starts in the next bundle. As a corollary, it's an error if any single
4758 instruction's encoding is longer than the bundle size.
4760 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4761 @cindex @code{bundle_lock} directive
4762 @cindex @code{bundle_unlock} directive
4763 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4764 allow explicit control over instruction bundle padding. These directives
4765 are only valid when @code{.bundle_align_mode} has been used to enable
4766 aligned instruction bundle mode. It's an error if they appear when
4767 @code{.bundle_align_mode} has not been used at all, or when the last
4768 directive was @w{@code{.bundle_align_mode 0}}.
4770 @cindex bundle-locked
4771 For some targets, it's an ABI requirement that certain instructions may
4772 appear only as part of specified permissible sequences of multiple
4773 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4774 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4775 instruction sequence. For purposes of aligned instruction bundle mode, a
4776 sequence starting with @code{.bundle_lock} and ending with
4777 @code{.bundle_unlock} is treated as a single instruction. That is, the
4778 entire sequence must fit into a single bundle and may not span a bundle
4779 boundary. If necessary, no-op instructions will be inserted before the
4780 first instruction of the sequence so that the whole sequence starts on an
4781 aligned bundle boundary. It's an error if the sequence is longer than the
4784 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4785 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4786 nested. That is, a second @code{.bundle_lock} directive before the next
4787 @code{.bundle_unlock} directive has no effect except that it must be
4788 matched by another closing @code{.bundle_unlock} so that there is the
4789 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4792 @section @code{.byte @var{expressions}}
4794 @cindex @code{byte} directive
4795 @cindex integers, one byte
4796 @code{.byte} expects zero or more expressions, separated by commas.
4797 Each expression is assembled into the next byte.
4799 @node CFI directives
4800 @section CFI directives
4801 @subsection @code{.cfi_sections @var{section_list}}
4802 @cindex @code{cfi_sections} directive
4803 @code{.cfi_sections} may be used to specify whether CFI directives
4804 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4805 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4806 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4807 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4808 directive is not used is @code{.cfi_sections .eh_frame}.
4810 On targets that support compact unwinding tables these can be generated
4811 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4813 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4814 which is used by the @value{TIC6X} target.
4816 The @code{.cfi_sections} directive can be repeated, with the same or different
4817 arguments, provided that CFI generation has not yet started. Once CFI
4818 generation has started however the section list is fixed and any attempts to
4819 redefine it will result in an error.
4821 @subsection @code{.cfi_startproc [simple]}
4822 @cindex @code{cfi_startproc} directive
4823 @code{.cfi_startproc} is used at the beginning of each function that
4824 should have an entry in @code{.eh_frame}. It initializes some internal
4825 data structures. Don't forget to close the function by
4826 @code{.cfi_endproc}.
4828 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4829 it also emits some architecture dependent initial CFI instructions.
4831 @subsection @code{.cfi_endproc}
4832 @cindex @code{cfi_endproc} directive
4833 @code{.cfi_endproc} is used at the end of a function where it closes its
4834 unwind entry previously opened by
4835 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4837 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4838 @cindex @code{cfi_personality} directive
4839 @code{.cfi_personality} defines personality routine and its encoding.
4840 @var{encoding} must be a constant determining how the personality
4841 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4842 argument is not present, otherwise second argument should be
4843 a constant or a symbol name. When using indirect encodings,
4844 the symbol provided should be the location where personality
4845 can be loaded from, not the personality routine itself.
4846 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4847 no personality routine.
4849 @subsection @code{.cfi_personality_id @var{id}}
4850 @cindex @code{cfi_personality_id} directive
4851 @code{cfi_personality_id} defines a personality routine by its index as
4852 defined in a compact unwinding format.
4853 Only valid when generating compact EH frames (i.e.
4854 with @code{.cfi_sections eh_frame_entry}.
4856 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4857 @cindex @code{cfi_fde_data} directive
4858 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4859 used for the current function. These are emitted inline in the
4860 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4861 in the @code{.gnu.extab} section otherwise.
4862 Only valid when generating compact EH frames (i.e.
4863 with @code{.cfi_sections eh_frame_entry}.
4865 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4866 @code{.cfi_lsda} defines LSDA and its encoding.
4867 @var{encoding} must be a constant determining how the LSDA
4868 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4869 argument is not present, otherwise the second argument should be a constant
4870 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4871 meaning that no LSDA is present.
4873 @subsection @code{.cfi_inline_lsda} [@var{align}]
4874 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4875 switches to the corresponding @code{.gnu.extab} section.
4876 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4877 Only valid when generating compact EH frames (i.e.
4878 with @code{.cfi_sections eh_frame_entry}.
4880 The table header and unwinding opcodes will be generated at this point,
4881 so that they are immediately followed by the LSDA data. The symbol
4882 referenced by the @code{.cfi_lsda} directive should still be defined
4883 in case a fallback FDE based encoding is used. The LSDA data is terminated
4884 by a section directive.
4886 The optional @var{align} argument specifies the alignment required.
4887 The alignment is specified as a power of two, as with the
4888 @code{.p2align} directive.
4890 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4891 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4892 address from @var{register} and add @var{offset} to it}.
4894 @subsection @code{.cfi_def_cfa_register @var{register}}
4895 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4896 now on @var{register} will be used instead of the old one. Offset
4899 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4900 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4901 remains the same, but @var{offset} is new. Note that it is the
4902 absolute offset that will be added to a defined register to compute
4905 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4906 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4907 value that is added/subtracted from the previous offset.
4909 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4910 Previous value of @var{register} is saved at offset @var{offset} from
4913 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4914 Previous value of @var{register} is CFA + @var{offset}.
4916 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4917 Previous value of @var{register} is saved at offset @var{offset} from
4918 the current CFA register. This is transformed to @code{.cfi_offset}
4919 using the known displacement of the CFA register from the CFA.
4920 This is often easier to use, because the number will match the
4921 code it's annotating.
4923 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4924 Previous value of @var{register1} is saved in register @var{register2}.
4926 @subsection @code{.cfi_restore @var{register}}
4927 @code{.cfi_restore} says that the rule for @var{register} is now the
4928 same as it was at the beginning of the function, after all initial
4929 instruction added by @code{.cfi_startproc} were executed.
4931 @subsection @code{.cfi_undefined @var{register}}
4932 From now on the previous value of @var{register} can't be restored anymore.
4934 @subsection @code{.cfi_same_value @var{register}}
4935 Current value of @var{register} is the same like in the previous frame,
4936 i.e. no restoration needed.
4938 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4939 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4940 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4941 places them in the current row. This is useful for situations where you have
4942 multiple @code{.cfi_*} directives that need to be undone due to the control
4943 flow of the program. For example, we could have something like this (assuming
4944 the CFA is the value of @code{rbp}):
4954 .cfi_def_cfa %rsp, 8
4957 /* Do something else */
4960 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4961 to the instructions before @code{label}. This means we'd have to add multiple
4962 @code{.cfi} directives after @code{label} to recreate the original save
4963 locations of the registers, as well as setting the CFA back to the value of
4964 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4976 .cfi_def_cfa %rsp, 8
4980 /* Do something else */
4983 That way, the rules for the instructions after @code{label} will be the same
4984 as before the first @code{.cfi_restore} without having to use multiple
4985 @code{.cfi} directives.
4987 @subsection @code{.cfi_return_column @var{register}}
4988 Change return column @var{register}, i.e. the return address is either
4989 directly in @var{register} or can be accessed by rules for @var{register}.
4991 @subsection @code{.cfi_signal_frame}
4992 Mark current function as signal trampoline.
4994 @subsection @code{.cfi_window_save}
4995 SPARC register window has been saved.
4997 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4998 Allows the user to add arbitrary bytes to the unwind info. One
4999 might use this to add OS-specific CFI opcodes, or generic CFI
5000 opcodes that GAS does not yet support.
5002 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
5003 The current value of @var{register} is @var{label}. The value of @var{label}
5004 will be encoded in the output file according to @var{encoding}; see the
5005 description of @code{.cfi_personality} for details on this encoding.
5007 The usefulness of equating a register to a fixed label is probably
5008 limited to the return address register. Here, it can be useful to
5009 mark a code segment that has only one return address which is reached
5010 by a direct branch and no copy of the return address exists in memory
5011 or another register.
5014 @section @code{.comm @var{symbol} , @var{length} }
5016 @cindex @code{comm} directive
5017 @cindex symbol, common
5018 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
5019 common symbol in one object file may be merged with a defined or common symbol
5020 of the same name in another object file. If @code{@value{LD}} does not see a
5021 definition for the symbol--just one or more common symbols--then it will
5022 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
5023 absolute expression. If @code{@value{LD}} sees multiple common symbols with
5024 the same name, and they do not all have the same size, it will allocate space
5025 using the largest size.
5028 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
5029 an optional third argument. This is the desired alignment of the symbol,
5030 specified for ELF as a byte boundary (for example, an alignment of 16 means
5031 that the least significant 4 bits of the address should be zero), and for PE
5032 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
5033 boundary). The alignment must be an absolute expression, and it must be a
5034 power of two. If @code{@value{LD}} allocates uninitialized memory for the
5035 common symbol, it will use the alignment when placing the symbol. If no
5036 alignment is specified, @command{@value{AS}} will set the alignment to the
5037 largest power of two less than or equal to the size of the symbol, up to a
5038 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
5039 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
5040 @samp{--section-alignment} option; image file sections in PE are aligned to
5041 multiples of 4096, which is far too large an alignment for ordinary variables.
5042 It is rather the default alignment for (non-debug) sections within object
5043 (@samp{*.o}) files, which are less strictly aligned.}.
5047 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
5048 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
5052 @section @code{.data @var{subsection}}
5054 @cindex @code{data} directive
5055 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5056 end of the data subsection numbered @var{subsection} (which is an
5057 absolute expression). If @var{subsection} is omitted, it defaults
5062 @section @code{.def @var{name}}
5064 @cindex @code{def} directive
5065 @cindex COFF symbols, debugging
5066 @cindex debugging COFF symbols
5067 Begin defining debugging information for a symbol @var{name}; the
5068 definition extends until the @code{.endef} directive is encountered.
5071 This directive is only observed when @command{@value{AS}} is configured for COFF
5072 format output; when producing @code{b.out}, @samp{.def} is recognized,
5079 @section @code{.desc @var{symbol}, @var{abs-expression}}
5081 @cindex @code{desc} directive
5082 @cindex COFF symbol descriptor
5083 @cindex symbol descriptor, COFF
5084 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5085 to the low 16 bits of an absolute expression.
5088 The @samp{.desc} directive is not available when @command{@value{AS}} is
5089 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5090 object format. For the sake of compatibility, @command{@value{AS}} accepts
5091 it, but produces no output, when configured for COFF.
5097 @section @code{.dim}
5099 @cindex @code{dim} directive
5100 @cindex COFF auxiliary symbol information
5101 @cindex auxiliary symbol information, COFF
5102 This directive is generated by compilers to include auxiliary debugging
5103 information in the symbol table. It is only permitted inside
5104 @code{.def}/@code{.endef} pairs.
5107 @samp{.dim} is only meaningful when generating COFF format output; when
5108 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5114 @section @code{.double @var{flonums}}
5116 @cindex @code{double} directive
5117 @cindex floating point numbers (double)
5118 @code{.double} expects zero or more flonums, separated by commas. It
5119 assembles floating point numbers.
5121 The exact kind of floating point numbers emitted depends on how
5122 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5126 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5127 in @sc{ieee} format.
5132 @section @code{.eject}
5134 @cindex @code{eject} directive
5135 @cindex new page, in listings
5136 @cindex page, in listings
5137 @cindex listing control: new page
5138 Force a page break at this point, when generating assembly listings.
5141 @section @code{.else}
5143 @cindex @code{else} directive
5144 @code{.else} is part of the @command{@value{AS}} support for conditional
5145 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5146 of code to be assembled if the condition for the preceding @code{.if}
5150 @section @code{.elseif}
5152 @cindex @code{elseif} directive
5153 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5154 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5155 @code{.if} block that would otherwise fill the entire @code{.else} section.
5158 @section @code{.end}
5160 @cindex @code{end} directive
5161 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5162 process anything in the file past the @code{.end} directive.
5166 @section @code{.endef}
5168 @cindex @code{endef} directive
5169 This directive flags the end of a symbol definition begun with
5173 @samp{.endef} is only meaningful when generating COFF format output; if
5174 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
5175 directive but ignores it.
5180 @section @code{.endfunc}
5181 @cindex @code{endfunc} directive
5182 @code{.endfunc} marks the end of a function specified with @code{.func}.
5185 @section @code{.endif}
5187 @cindex @code{endif} directive
5188 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5189 it marks the end of a block of code that is only assembled
5190 conditionally. @xref{If,,@code{.if}}.
5193 @section @code{.equ @var{symbol}, @var{expression}}
5195 @cindex @code{equ} directive
5196 @cindex assigning values to symbols
5197 @cindex symbols, assigning values to
5198 This directive sets the value of @var{symbol} to @var{expression}.
5199 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5202 The syntax for @code{equ} on the HPPA is
5203 @samp{@var{symbol} .equ @var{expression}}.
5207 The syntax for @code{equ} on the Z80 is
5208 @samp{@var{symbol} equ @var{expression}}.
5209 On the Z80 it is an error if @var{symbol} is already defined,
5210 but the symbol is not protected from later redefinition.
5211 Compare @ref{Equiv}.
5215 @section @code{.equiv @var{symbol}, @var{expression}}
5216 @cindex @code{equiv} directive
5217 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5218 the assembler will signal an error if @var{symbol} is already defined. Note a
5219 symbol which has been referenced but not actually defined is considered to be
5222 Except for the contents of the error message, this is roughly equivalent to
5229 plus it protects the symbol from later redefinition.
5232 @section @code{.eqv @var{symbol}, @var{expression}}
5233 @cindex @code{eqv} directive
5234 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5235 evaluate the expression or any part of it immediately. Instead each time
5236 the resulting symbol is used in an expression, a snapshot of its current
5240 @section @code{.err}
5241 @cindex @code{err} directive
5242 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5243 message and, unless the @option{-Z} option was used, it will not generate an
5244 object file. This can be used to signal an error in conditionally compiled code.
5247 @section @code{.error "@var{string}"}
5248 @cindex error directive
5250 Similarly to @code{.err}, this directive emits an error, but you can specify a
5251 string that will be emitted as the error message. If you don't specify the
5252 message, it defaults to @code{".error directive invoked in source file"}.
5253 @xref{Errors, ,Error and Warning Messages}.
5256 .error "This code has not been assembled and tested."
5260 @section @code{.exitm}
5261 Exit early from the current macro definition. @xref{Macro}.
5264 @section @code{.extern}
5266 @cindex @code{extern} directive
5267 @code{.extern} is accepted in the source program---for compatibility
5268 with other assemblers---but it is ignored. @command{@value{AS}} treats
5269 all undefined symbols as external.
5272 @section @code{.fail @var{expression}}
5274 @cindex @code{fail} directive
5275 Generates an error or a warning. If the value of the @var{expression} is 500
5276 or more, @command{@value{AS}} will print a warning message. If the value is less
5277 than 500, @command{@value{AS}} will print an error message. The message will
5278 include the value of @var{expression}. This can occasionally be useful inside
5279 complex nested macros or conditional assembly.
5282 @section @code{.file}
5283 @cindex @code{file} directive
5285 @ifclear no-file-dir
5286 There are two different versions of the @code{.file} directive. Targets
5287 that support DWARF2 line number information use the DWARF2 version of
5288 @code{.file}. Other targets use the default version.
5290 @subheading Default Version
5292 @cindex logical file name
5293 @cindex file name, logical
5294 This version of the @code{.file} directive tells @command{@value{AS}} that we
5295 are about to start a new logical file. The syntax is:
5301 @var{string} is the new file name. In general, the filename is
5302 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5303 to specify an empty file name, you must give the quotes--@code{""}. This
5304 statement may go away in future: it is only recognized to be compatible with
5305 old @command{@value{AS}} programs.
5307 @subheading DWARF2 Version
5310 When emitting DWARF2 line number information, @code{.file} assigns filenames
5311 to the @code{.debug_line} file name table. The syntax is:
5314 .file @var{fileno} @var{filename}
5317 The @var{fileno} operand should be a unique positive integer to use as the
5318 index of the entry in the table. The @var{filename} operand is a C string
5321 The detail of filename indices is exposed to the user because the filename
5322 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5323 information, and thus the user must know the exact indices that table
5327 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5329 @cindex @code{fill} directive
5330 @cindex writing patterns in memory
5331 @cindex patterns, writing in memory
5332 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5333 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5334 may be zero or more. @var{Size} may be zero or more, but if it is
5335 more than 8, then it is deemed to have the value 8, compatible with
5336 other people's assemblers. The contents of each @var{repeat} bytes
5337 is taken from an 8-byte number. The highest order 4 bytes are
5338 zero. The lowest order 4 bytes are @var{value} rendered in the
5339 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5340 Each @var{size} bytes in a repetition is taken from the lowest order
5341 @var{size} bytes of this number. Again, this bizarre behavior is
5342 compatible with other people's assemblers.
5344 @var{size} and @var{value} are optional.
5345 If the second comma and @var{value} are absent, @var{value} is
5346 assumed zero. If the first comma and following tokens are absent,
5347 @var{size} is assumed to be 1.
5350 @section @code{.float @var{flonums}}
5352 @cindex floating point numbers (single)
5353 @cindex @code{float} directive
5354 This directive assembles zero or more flonums, separated by commas. It
5355 has the same effect as @code{.single}.
5357 The exact kind of floating point numbers emitted depends on how
5358 @command{@value{AS}} is configured.
5359 @xref{Machine Dependencies}.
5363 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5364 in @sc{ieee} format.
5369 @section @code{.func @var{name}[,@var{label}]}
5370 @cindex @code{func} directive
5371 @code{.func} emits debugging information to denote function @var{name}, and
5372 is ignored unless the file is assembled with debugging enabled.
5373 Only @samp{--gstabs[+]} is currently supported.
5374 @var{label} is the entry point of the function and if omitted @var{name}
5375 prepended with the @samp{leading char} is used.
5376 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5377 All functions are currently defined to have @code{void} return type.
5378 The function must be terminated with @code{.endfunc}.
5381 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5383 @cindex @code{global} directive
5384 @cindex symbol, making visible to linker
5385 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5386 @var{symbol} in your partial program, its value is made available to
5387 other partial programs that are linked with it. Otherwise,
5388 @var{symbol} takes its attributes from a symbol of the same name
5389 from another file linked into the same program.
5391 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5392 compatibility with other assemblers.
5395 On the HPPA, @code{.global} is not always enough to make it accessible to other
5396 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5397 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5402 @section @code{.gnu_attribute @var{tag},@var{value}}
5403 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5406 @section @code{.hidden @var{names}}
5408 @cindex @code{hidden} directive
5410 This is one of the ELF visibility directives. The other two are
5411 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5412 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5414 This directive overrides the named symbols default visibility (which is set by
5415 their binding: local, global or weak). The directive sets the visibility to
5416 @code{hidden} which means that the symbols are not visible to other components.
5417 Such symbols are always considered to be @code{protected} as well.
5421 @section @code{.hword @var{expressions}}
5423 @cindex @code{hword} directive
5424 @cindex integers, 16-bit
5425 @cindex numbers, 16-bit
5426 @cindex sixteen bit integers
5427 This expects zero or more @var{expressions}, and emits
5428 a 16 bit number for each.
5431 This directive is a synonym for @samp{.short}; depending on the target
5432 architecture, it may also be a synonym for @samp{.word}.
5436 This directive is a synonym for @samp{.short}.
5439 This directive is a synonym for both @samp{.short} and @samp{.word}.
5444 @section @code{.ident}
5446 @cindex @code{ident} directive
5448 This directive is used by some assemblers to place tags in object files. The
5449 behavior of this directive varies depending on the target. When using the
5450 a.out object file format, @command{@value{AS}} simply accepts the directive for
5451 source-file compatibility with existing assemblers, but does not emit anything
5452 for it. When using COFF, comments are emitted to the @code{.comment} or
5453 @code{.rdata} section, depending on the target. When using ELF, comments are
5454 emitted to the @code{.comment} section.
5457 @section @code{.if @var{absolute expression}}
5459 @cindex conditional assembly
5460 @cindex @code{if} directive
5461 @code{.if} marks the beginning of a section of code which is only
5462 considered part of the source program being assembled if the argument
5463 (which must be an @var{absolute expression}) is non-zero. The end of
5464 the conditional section of code must be marked by @code{.endif}
5465 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5466 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5467 If you have several conditions to check, @code{.elseif} may be used to avoid
5468 nesting blocks if/else within each subsequent @code{.else} block.
5470 The following variants of @code{.if} are also supported:
5472 @cindex @code{ifdef} directive
5473 @item .ifdef @var{symbol}
5474 Assembles the following section of code if the specified @var{symbol}
5475 has been defined. Note a symbol which has been referenced but not yet defined
5476 is considered to be undefined.
5478 @cindex @code{ifb} directive
5479 @item .ifb @var{text}
5480 Assembles the following section of code if the operand is blank (empty).
5482 @cindex @code{ifc} directive
5483 @item .ifc @var{string1},@var{string2}
5484 Assembles the following section of code if the two strings are the same. The
5485 strings may be optionally quoted with single quotes. If they are not quoted,
5486 the first string stops at the first comma, and the second string stops at the
5487 end of the line. Strings which contain whitespace should be quoted. The
5488 string comparison is case sensitive.
5490 @cindex @code{ifeq} directive
5491 @item .ifeq @var{absolute expression}
5492 Assembles the following section of code if the argument is zero.
5494 @cindex @code{ifeqs} directive
5495 @item .ifeqs @var{string1},@var{string2}
5496 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5498 @cindex @code{ifge} directive
5499 @item .ifge @var{absolute expression}
5500 Assembles the following section of code if the argument is greater than or
5503 @cindex @code{ifgt} directive
5504 @item .ifgt @var{absolute expression}
5505 Assembles the following section of code if the argument is greater than zero.
5507 @cindex @code{ifle} directive
5508 @item .ifle @var{absolute expression}
5509 Assembles the following section of code if the argument is less than or equal
5512 @cindex @code{iflt} directive
5513 @item .iflt @var{absolute expression}
5514 Assembles the following section of code if the argument is less than zero.
5516 @cindex @code{ifnb} directive
5517 @item .ifnb @var{text}
5518 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5519 following section of code if the operand is non-blank (non-empty).
5521 @cindex @code{ifnc} directive
5522 @item .ifnc @var{string1},@var{string2}.
5523 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5524 following section of code if the two strings are not the same.
5526 @cindex @code{ifndef} directive
5527 @cindex @code{ifnotdef} directive
5528 @item .ifndef @var{symbol}
5529 @itemx .ifnotdef @var{symbol}
5530 Assembles the following section of code if the specified @var{symbol}
5531 has not been defined. Both spelling variants are equivalent. Note a symbol
5532 which has been referenced but not yet defined is considered to be undefined.
5534 @cindex @code{ifne} directive
5535 @item .ifne @var{absolute expression}
5536 Assembles the following section of code if the argument is not equal to zero
5537 (in other words, this is equivalent to @code{.if}).
5539 @cindex @code{ifnes} directive
5540 @item .ifnes @var{string1},@var{string2}
5541 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5542 following section of code if the two strings are not the same.
5546 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5548 @cindex @code{incbin} directive
5549 @cindex binary files, including
5550 The @code{incbin} directive includes @var{file} verbatim at the current
5551 location. You can control the search paths used with the @samp{-I} command-line
5552 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5555 The @var{skip} argument skips a number of bytes from the start of the
5556 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5557 read. Note that the data is not aligned in any way, so it is the user's
5558 responsibility to make sure that proper alignment is provided both before and
5559 after the @code{incbin} directive.
5562 @section @code{.include "@var{file}"}
5564 @cindex @code{include} directive
5565 @cindex supporting files, including
5566 @cindex files, including
5567 This directive provides a way to include supporting files at specified
5568 points in your source program. The code from @var{file} is assembled as
5569 if it followed the point of the @code{.include}; when the end of the
5570 included file is reached, assembly of the original file continues. You
5571 can control the search paths used with the @samp{-I} command-line option
5572 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5576 @section @code{.int @var{expressions}}
5578 @cindex @code{int} directive
5579 @cindex integers, 32-bit
5580 Expect zero or more @var{expressions}, of any section, separated by commas.
5581 For each expression, emit a number that, at run time, is the value of that
5582 expression. The byte order and bit size of the number depends on what kind
5583 of target the assembly is for.
5587 On most forms of the H8/300, @code{.int} emits 16-bit
5588 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5595 @section @code{.internal @var{names}}
5597 @cindex @code{internal} directive
5599 This is one of the ELF visibility directives. The other two are
5600 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5601 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5603 This directive overrides the named symbols default visibility (which is set by
5604 their binding: local, global or weak). The directive sets the visibility to
5605 @code{internal} which means that the symbols are considered to be @code{hidden}
5606 (i.e., not visible to other components), and that some extra, processor specific
5607 processing must also be performed upon the symbols as well.
5611 @section @code{.irp @var{symbol},@var{values}}@dots{}
5613 @cindex @code{irp} directive
5614 Evaluate a sequence of statements assigning different values to @var{symbol}.
5615 The sequence of statements starts at the @code{.irp} directive, and is
5616 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5617 set to @var{value}, and the sequence of statements is assembled. If no
5618 @var{value} is listed, the sequence of statements is assembled once, with
5619 @var{symbol} set to the null string. To refer to @var{symbol} within the
5620 sequence of statements, use @var{\symbol}.
5622 For example, assembling
5630 is equivalent to assembling
5638 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5641 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5643 @cindex @code{irpc} directive
5644 Evaluate a sequence of statements assigning different values to @var{symbol}.
5645 The sequence of statements starts at the @code{.irpc} directive, and is
5646 terminated by an @code{.endr} directive. For each character in @var{value},
5647 @var{symbol} is set to the character, and the sequence of statements is
5648 assembled. If no @var{value} is listed, the sequence of statements is
5649 assembled once, with @var{symbol} set to the null string. To refer to
5650 @var{symbol} within the sequence of statements, use @var{\symbol}.
5652 For example, assembling
5660 is equivalent to assembling
5668 For some caveats with the spelling of @var{symbol}, see also the discussion
5672 @section @code{.lcomm @var{symbol} , @var{length}}
5674 @cindex @code{lcomm} directive
5675 @cindex local common symbols
5676 @cindex symbols, local common
5677 Reserve @var{length} (an absolute expression) bytes for a local common
5678 denoted by @var{symbol}. The section and value of @var{symbol} are
5679 those of the new local common. The addresses are allocated in the bss
5680 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5681 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5682 not visible to @code{@value{LD}}.
5685 Some targets permit a third argument to be used with @code{.lcomm}. This
5686 argument specifies the desired alignment of the symbol in the bss section.
5690 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5691 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5695 @section @code{.lflags}
5697 @cindex @code{lflags} directive (ignored)
5698 @command{@value{AS}} accepts this directive, for compatibility with other
5699 assemblers, but ignores it.
5701 @ifclear no-line-dir
5703 @section @code{.line @var{line-number}}
5705 @cindex @code{line} directive
5706 @cindex logical line number
5708 Change the logical line number. @var{line-number} must be an absolute
5709 expression. The next line has that logical line number. Therefore any other
5710 statements on the current line (after a statement separator character) are
5711 reported as on logical line number @var{line-number} @minus{} 1. One day
5712 @command{@value{AS}} will no longer support this directive: it is recognized only
5713 for compatibility with existing assembler programs.
5716 Even though this is a directive associated with the @code{a.out} or
5717 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5718 when producing COFF output, and treats @samp{.line} as though it
5719 were the COFF @samp{.ln} @emph{if} it is found outside a
5720 @code{.def}/@code{.endef} pair.
5722 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5723 used by compilers to generate auxiliary symbol information for
5728 @section @code{.linkonce [@var{type}]}
5730 @cindex @code{linkonce} directive
5731 @cindex common sections
5732 Mark the current section so that the linker only includes a single copy of it.
5733 This may be used to include the same section in several different object files,
5734 but ensure that the linker will only include it once in the final output file.
5735 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5736 Duplicate sections are detected based on the section name, so it should be
5739 This directive is only supported by a few object file formats; as of this
5740 writing, the only object file format which supports it is the Portable
5741 Executable format used on Windows NT.
5743 The @var{type} argument is optional. If specified, it must be one of the
5744 following strings. For example:
5748 Not all types may be supported on all object file formats.
5752 Silently discard duplicate sections. This is the default.
5755 Warn if there are duplicate sections, but still keep only one copy.
5758 Warn if any of the duplicates have different sizes.
5761 Warn if any of the duplicates do not have exactly the same contents.
5765 @section @code{.list}
5767 @cindex @code{list} directive
5768 @cindex listing control, turning on
5769 Control (in conjunction with the @code{.nolist} directive) whether or
5770 not assembly listings are generated. These two directives maintain an
5771 internal counter (which is zero initially). @code{.list} increments the
5772 counter, and @code{.nolist} decrements it. Assembly listings are
5773 generated whenever the counter is greater than zero.
5775 By default, listings are disabled. When you enable them (with the
5776 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5777 the initial value of the listing counter is one.
5780 @section @code{.ln @var{line-number}}
5782 @cindex @code{ln} directive
5783 @ifclear no-line-dir
5784 @samp{.ln} is a synonym for @samp{.line}.
5787 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5788 must be an absolute expression. The next line has that logical
5789 line number, so any other statements on the current line (after a
5790 statement separator character @code{;}) are reported as on logical
5791 line number @var{line-number} @minus{} 1.
5794 This directive is accepted, but ignored, when @command{@value{AS}} is
5795 configured for @code{b.out}; its effect is only associated with COFF
5801 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5802 @cindex @code{loc} directive
5803 When emitting DWARF2 line number information,
5804 the @code{.loc} directive will add a row to the @code{.debug_line} line
5805 number matrix corresponding to the immediately following assembly
5806 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5807 arguments will be applied to the @code{.debug_line} state machine before
5810 The @var{options} are a sequence of the following tokens in any order:
5814 This option will set the @code{basic_block} register in the
5815 @code{.debug_line} state machine to @code{true}.
5818 This option will set the @code{prologue_end} register in the
5819 @code{.debug_line} state machine to @code{true}.
5821 @item epilogue_begin
5822 This option will set the @code{epilogue_begin} register in the
5823 @code{.debug_line} state machine to @code{true}.
5825 @item is_stmt @var{value}
5826 This option will set the @code{is_stmt} register in the
5827 @code{.debug_line} state machine to @code{value}, which must be
5830 @item isa @var{value}
5831 This directive will set the @code{isa} register in the @code{.debug_line}
5832 state machine to @var{value}, which must be an unsigned integer.
5834 @item discriminator @var{value}
5835 This directive will set the @code{discriminator} register in the @code{.debug_line}
5836 state machine to @var{value}, which must be an unsigned integer.
5838 @item view @var{value}
5839 This option causes a row to be added to @code{.debug_line} in reference to the
5840 current address (which might not be the same as that of the following assembly
5841 instruction), and to associate @var{value} with the @code{view} register in the
5842 @code{.debug_line} state machine. If @var{value} is a label, both the
5843 @code{view} register and the label are set to the number of prior @code{.loc}
5844 directives at the same program location. If @var{value} is the literal
5845 @code{0}, the @code{view} register is set to zero, and the assembler asserts
5846 that there aren't any prior @code{.loc} directives at the same program
5847 location. If @var{value} is the literal @code{-0}, the assembler arrange for
5848 the @code{view} register to be reset in this row, even if there are prior
5849 @code{.loc} directives at the same program location.
5853 @node Loc_mark_labels
5854 @section @code{.loc_mark_labels @var{enable}}
5855 @cindex @code{loc_mark_labels} directive
5856 When emitting DWARF2 line number information,
5857 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5858 to the @code{.debug_line} line number matrix with the @code{basic_block}
5859 register in the state machine set whenever a code label is seen.
5860 The @var{enable} argument should be either 1 or 0, to enable or disable
5861 this function respectively.
5865 @section @code{.local @var{names}}
5867 @cindex @code{local} directive
5868 This directive, which is available for ELF targets, marks each symbol in
5869 the comma-separated list of @code{names} as a local symbol so that it
5870 will not be externally visible. If the symbols do not already exist,
5871 they will be created.
5873 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5874 accept an alignment argument, which is the case for most ELF targets,
5875 the @code{.local} directive can be used in combination with @code{.comm}
5876 (@pxref{Comm}) to define aligned local common data.
5880 @section @code{.long @var{expressions}}
5882 @cindex @code{long} directive
5883 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5886 @c no one seems to know what this is for or whether this description is
5887 @c what it really ought to do
5889 @section @code{.lsym @var{symbol}, @var{expression}}
5891 @cindex @code{lsym} directive
5892 @cindex symbol, not referenced in assembly
5893 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5894 the hash table, ensuring it cannot be referenced by name during the
5895 rest of the assembly. This sets the attributes of the symbol to be
5896 the same as the expression value:
5898 @var{other} = @var{descriptor} = 0
5899 @var{type} = @r{(section of @var{expression})}
5900 @var{value} = @var{expression}
5903 The new symbol is not flagged as external.
5907 @section @code{.macro}
5910 The commands @code{.macro} and @code{.endm} allow you to define macros that
5911 generate assembly output. For example, this definition specifies a macro
5912 @code{sum} that puts a sequence of numbers into memory:
5915 .macro sum from=0, to=5
5924 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5936 @item .macro @var{macname}
5937 @itemx .macro @var{macname} @var{macargs} @dots{}
5938 @cindex @code{macro} directive
5939 Begin the definition of a macro called @var{macname}. If your macro
5940 definition requires arguments, specify their names after the macro name,
5941 separated by commas or spaces. You can qualify the macro argument to
5942 indicate whether all invocations must specify a non-blank value (through
5943 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5944 (through @samp{:@code{vararg}}). You can supply a default value for any
5945 macro argument by following the name with @samp{=@var{deflt}}. You
5946 cannot define two macros with the same @var{macname} unless it has been
5947 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5948 definitions. For example, these are all valid @code{.macro} statements:
5952 Begin the definition of a macro called @code{comm}, which takes no
5955 @item .macro plus1 p, p1
5956 @itemx .macro plus1 p p1
5957 Either statement begins the definition of a macro called @code{plus1},
5958 which takes two arguments; within the macro definition, write
5959 @samp{\p} or @samp{\p1} to evaluate the arguments.
5961 @item .macro reserve_str p1=0 p2
5962 Begin the definition of a macro called @code{reserve_str}, with two
5963 arguments. The first argument has a default value, but not the second.
5964 After the definition is complete, you can call the macro either as
5965 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5966 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5967 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5968 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5970 @item .macro m p1:req, p2=0, p3:vararg
5971 Begin the definition of a macro called @code{m}, with at least three
5972 arguments. The first argument must always have a value specified, but
5973 not the second, which instead has a default value. The third formal
5974 will get assigned all remaining arguments specified at invocation time.
5976 When you call a macro, you can specify the argument values either by
5977 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5978 @samp{sum to=17, from=9}.
5982 Note that since each of the @var{macargs} can be an identifier exactly
5983 as any other one permitted by the target architecture, there may be
5984 occasional problems if the target hand-crafts special meanings to certain
5985 characters when they occur in a special position. For example, if the colon
5986 (@code{:}) is generally permitted to be part of a symbol name, but the
5987 architecture specific code special-cases it when occurring as the final
5988 character of a symbol (to denote a label), then the macro parameter
5989 replacement code will have no way of knowing that and consider the whole
5990 construct (including the colon) an identifier, and check only this
5991 identifier for being the subject to parameter substitution. So for example
5992 this macro definition:
6000 might not work as expected. Invoking @samp{label foo} might not create a label
6001 called @samp{foo} but instead just insert the text @samp{\l:} into the
6002 assembler source, probably generating an error about an unrecognised
6005 Similarly problems might occur with the period character (@samp{.})
6006 which is often allowed inside opcode names (and hence identifier names). So
6007 for example constructing a macro to build an opcode from a base name and a
6008 length specifier like this:
6011 .macro opcode base length
6016 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
6017 instruction but instead generate some kind of error as the assembler tries to
6018 interpret the text @samp{\base.\length}.
6020 There are several possible ways around this problem:
6023 @item Insert white space
6024 If it is possible to use white space characters then this is the simplest
6033 @item Use @samp{\()}
6034 The string @samp{\()} can be used to separate the end of a macro argument from
6035 the following text. eg:
6038 .macro opcode base length
6043 @item Use the alternate macro syntax mode
6044 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6045 used as a separator. eg:
6055 Note: this problem of correctly identifying string parameters to pseudo ops
6056 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6057 and @code{.irpc} (@pxref{Irpc}) as well.
6060 @cindex @code{endm} directive
6061 Mark the end of a macro definition.
6064 @cindex @code{exitm} directive
6065 Exit early from the current macro definition.
6067 @cindex number of macros executed
6068 @cindex macros, count executed
6070 @command{@value{AS}} maintains a counter of how many macros it has
6071 executed in this pseudo-variable; you can copy that number to your
6072 output with @samp{\@@}, but @emph{only within a macro definition}.
6074 @item LOCAL @var{name} [ , @dots{} ]
6075 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6076 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6077 @xref{Altmacro,,@code{.altmacro}}.
6081 @section @code{.mri @var{val}}
6083 @cindex @code{mri} directive
6084 @cindex MRI mode, temporarily
6085 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6086 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6087 affects code assembled until the next @code{.mri} directive, or until the end
6088 of the file. @xref{M, MRI mode, MRI mode}.
6091 @section @code{.noaltmacro}
6092 Disable alternate macro mode. @xref{Altmacro}.
6095 @section @code{.nolist}
6097 @cindex @code{nolist} directive
6098 @cindex listing control, turning off
6099 Control (in conjunction with the @code{.list} directive) whether or
6100 not assembly listings are generated. These two directives maintain an
6101 internal counter (which is zero initially). @code{.list} increments the
6102 counter, and @code{.nolist} decrements it. Assembly listings are
6103 generated whenever the counter is greater than zero.
6106 @section @code{.nop @var{size}[, @var{control}]}
6108 @cindex @code{nop} directive
6109 @cindex filling memory with no-op instructions
6110 This directive emits @var{size} bytes filled with no-op instructions.
6111 @var{size} is absolute expression, which must be a positve value.
6112 @var{control} controls how no-op instructions should be generated. If
6113 the comma and @var{control} are omitted, @var{control} is assumed to be
6116 Note: For Intel 80386 and AMD x86-64 targets, @var{control} specifies
6117 the size limit of a no-op instruction. The valid values of @var{control}
6118 are between 0 and 8 for 16-bit mode, between 0 and 10 for 32-bit mode,
6119 between 0 and 11 for 64-bit mode. When 0 is used, the no-op instruction
6120 size limit is set to the maximum supported size.
6123 @section @code{.octa @var{bignums}}
6125 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
6126 @cindex @code{octa} directive
6127 @cindex integer, 16-byte
6128 @cindex sixteen byte integer
6129 This directive expects zero or more bignums, separated by commas. For each
6130 bignum, it emits a 16-byte integer.
6132 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6133 hence @emph{octa}-word for 16 bytes.
6136 @section @code{.offset @var{loc}}
6138 @cindex @code{offset} directive
6139 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6140 be an absolute expression. This directive may be useful for defining
6141 symbols with absolute values. Do not confuse it with the @code{.org}
6145 @section @code{.org @var{new-lc} , @var{fill}}
6147 @cindex @code{org} directive
6148 @cindex location counter, advancing
6149 @cindex advancing location counter
6150 @cindex current address, advancing
6151 Advance the location counter of the current section to
6152 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6153 expression with the same section as the current subsection. That is,
6154 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6155 wrong section, the @code{.org} directive is ignored. To be compatible
6156 with former assemblers, if the section of @var{new-lc} is absolute,
6157 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6158 is the same as the current subsection.
6160 @code{.org} may only increase the location counter, or leave it
6161 unchanged; you cannot use @code{.org} to move the location counter
6164 @c double negative used below "not undefined" because this is a specific
6165 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6166 @c section. doc@cygnus.com 18feb91
6167 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6168 may not be undefined. If you really detest this restriction we eagerly await
6169 a chance to share your improved assembler.
6171 Beware that the origin is relative to the start of the section, not
6172 to the start of the subsection. This is compatible with other
6173 people's assemblers.
6175 When the location counter (of the current subsection) is advanced, the
6176 intervening bytes are filled with @var{fill} which should be an
6177 absolute expression. If the comma and @var{fill} are omitted,
6178 @var{fill} defaults to zero.
6181 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6183 @cindex padding the location counter given a power of two
6184 @cindex @code{p2align} directive
6185 Pad the location counter (in the current subsection) to a particular
6186 storage boundary. The first expression (which must be absolute) is the
6187 number of low-order zero bits the location counter must have after
6188 advancement. For example @samp{.p2align 3} advances the location
6189 counter until it a multiple of 8. If the location counter is already a
6190 multiple of 8, no change is needed.
6192 The second expression (also absolute) gives the fill value to be stored in the
6193 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6194 padding bytes are normally zero. However, on most systems, if the section is
6195 marked as containing code and the fill value is omitted, the space is filled
6196 with no-op instructions.
6198 The third expression is also absolute, and is also optional. If it is present,
6199 it is the maximum number of bytes that should be skipped by this alignment
6200 directive. If doing the alignment would require skipping more bytes than the
6201 specified maximum, then the alignment is not done at all. You can omit the
6202 fill value (the second argument) entirely by simply using two commas after the
6203 required alignment; this can be useful if you want the alignment to be filled
6204 with no-op instructions when appropriate.
6206 @cindex @code{p2alignw} directive
6207 @cindex @code{p2alignl} directive
6208 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6209 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6210 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6211 fill pattern as a four byte longword value. For example, @code{.p2alignw
6212 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6213 filled in with the value 0x368d (the exact placement of the bytes depends upon
6214 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6219 @section @code{.popsection}
6221 @cindex @code{popsection} directive
6222 @cindex Section Stack
6223 This is one of the ELF section stack manipulation directives. The others are
6224 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6225 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6228 This directive replaces the current section (and subsection) with the top
6229 section (and subsection) on the section stack. This section is popped off the
6235 @section @code{.previous}
6237 @cindex @code{previous} directive
6238 @cindex Section Stack
6239 This is one of the ELF section stack manipulation directives. The others are
6240 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6241 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6242 (@pxref{PopSection}).
6244 This directive swaps the current section (and subsection) with most recently
6245 referenced section/subsection pair prior to this one. Multiple
6246 @code{.previous} directives in a row will flip between two sections (and their
6247 subsections). For example:
6259 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6265 # Now in section A subsection 1
6269 # Now in section B subsection 0
6272 # Now in section B subsection 1
6275 # Now in section B subsection 0
6279 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6280 section B and 0x9abc into subsection 1 of section B.
6282 In terms of the section stack, this directive swaps the current section with
6283 the top section on the section stack.
6287 @section @code{.print @var{string}}
6289 @cindex @code{print} directive
6290 @command{@value{AS}} will print @var{string} on the standard output during
6291 assembly. You must put @var{string} in double quotes.
6295 @section @code{.protected @var{names}}
6297 @cindex @code{protected} directive
6299 This is one of the ELF visibility directives. The other two are
6300 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6302 This directive overrides the named symbols default visibility (which is set by
6303 their binding: local, global or weak). The directive sets the visibility to
6304 @code{protected} which means that any references to the symbols from within the
6305 components that defines them must be resolved to the definition in that
6306 component, even if a definition in another component would normally preempt
6311 @section @code{.psize @var{lines} , @var{columns}}
6313 @cindex @code{psize} directive
6314 @cindex listing control: paper size
6315 @cindex paper size, for listings
6316 Use this directive to declare the number of lines---and, optionally, the
6317 number of columns---to use for each page, when generating listings.
6319 If you do not use @code{.psize}, listings use a default line-count
6320 of 60. You may omit the comma and @var{columns} specification; the
6321 default width is 200 columns.
6323 @command{@value{AS}} generates formfeeds whenever the specified number of
6324 lines is exceeded (or whenever you explicitly request one, using
6327 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6328 those explicitly specified with @code{.eject}.
6331 @section @code{.purgem @var{name}}
6333 @cindex @code{purgem} directive
6334 Undefine the macro @var{name}, so that later uses of the string will not be
6335 expanded. @xref{Macro}.
6339 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6341 @cindex @code{pushsection} directive
6342 @cindex Section Stack
6343 This is one of the ELF section stack manipulation directives. The others are
6344 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6345 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6348 This directive pushes the current section (and subsection) onto the
6349 top of the section stack, and then replaces the current section and
6350 subsection with @code{name} and @code{subsection}. The optional
6351 @code{flags}, @code{type} and @code{arguments} are treated the same
6352 as in the @code{.section} (@pxref{Section}) directive.
6356 @section @code{.quad @var{bignums}}
6358 @cindex @code{quad} directive
6359 @code{.quad} expects zero or more bignums, separated by commas. For
6360 each bignum, it emits
6362 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6363 warning message; and just takes the lowest order 8 bytes of the bignum.
6364 @cindex eight-byte integer
6365 @cindex integer, 8-byte
6367 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6368 hence @emph{quad}-word for 8 bytes.
6371 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6372 warning message; and just takes the lowest order 16 bytes of the bignum.
6373 @cindex sixteen-byte integer
6374 @cindex integer, 16-byte
6378 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6380 @cindex @code{reloc} directive
6381 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6382 @var{expression}. If @var{offset} is a number, the relocation is generated in
6383 the current section. If @var{offset} is an expression that resolves to a
6384 symbol plus offset, the relocation is generated in the given symbol's section.
6385 @var{expression}, if present, must resolve to a symbol plus addend or to an
6386 absolute value, but note that not all targets support an addend. e.g. ELF REL
6387 targets such as i386 store an addend in the section contents rather than in the
6388 relocation. This low level interface does not support addends stored in the
6392 @section @code{.rept @var{count}}
6394 @cindex @code{rept} directive
6395 Repeat the sequence of lines between the @code{.rept} directive and the next
6396 @code{.endr} directive @var{count} times.
6398 For example, assembling
6406 is equivalent to assembling
6414 A count of zero is allowed, but nothing is generated. Negative counts are not
6415 allowed and if encountered will be treated as if they were zero.
6418 @section @code{.sbttl "@var{subheading}"}
6420 @cindex @code{sbttl} directive
6421 @cindex subtitles for listings
6422 @cindex listing control: subtitle
6423 Use @var{subheading} as the title (third line, immediately after the
6424 title line) when generating assembly listings.
6426 This directive affects subsequent pages, as well as the current page if
6427 it appears within ten lines of the top of a page.
6431 @section @code{.scl @var{class}}
6433 @cindex @code{scl} directive
6434 @cindex symbol storage class (COFF)
6435 @cindex COFF symbol storage class
6436 Set the storage-class value for a symbol. This directive may only be
6437 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6438 whether a symbol is static or external, or it may record further
6439 symbolic debugging information.
6442 The @samp{.scl} directive is primarily associated with COFF output; when
6443 configured to generate @code{b.out} output format, @command{@value{AS}}
6444 accepts this directive but ignores it.
6450 @section @code{.section @var{name}}
6452 @cindex named section
6453 Use the @code{.section} directive to assemble the following code into a section
6456 This directive is only supported for targets that actually support arbitrarily
6457 named sections; on @code{a.out} targets, for example, it is not accepted, even
6458 with a standard @code{a.out} section name.
6462 @c only print the extra heading if both COFF and ELF are set
6463 @subheading COFF Version
6466 @cindex @code{section} directive (COFF version)
6467 For COFF targets, the @code{.section} directive is used in one of the following
6471 .section @var{name}[, "@var{flags}"]
6472 .section @var{name}[, @var{subsection}]
6475 If the optional argument is quoted, it is taken as flags to use for the
6476 section. Each flag is a single character. The following flags are recognized:
6480 bss section (uninitialized data)
6482 section is not loaded
6488 exclude section from linking
6494 shared section (meaningful for PE targets)
6496 ignored. (For compatibility with the ELF version)
6498 section is not readable (meaningful for PE targets)
6500 single-digit power-of-two section alignment (GNU extension)
6503 If no flags are specified, the default flags depend upon the section name. If
6504 the section name is not recognized, the default will be for the section to be
6505 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6506 from the section, rather than adding them, so if they are used on their own it
6507 will be as if no flags had been specified at all.
6509 If the optional argument to the @code{.section} directive is not quoted, it is
6510 taken as a subsection number (@pxref{Sub-Sections}).
6515 @c only print the extra heading if both COFF and ELF are set
6516 @subheading ELF Version
6519 @cindex Section Stack
6520 This is one of the ELF section stack manipulation directives. The others are
6521 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6522 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6523 @code{.previous} (@pxref{Previous}).
6525 @cindex @code{section} directive (ELF version)
6526 For ELF targets, the @code{.section} directive is used like this:
6529 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6532 @anchor{Section Name Substitutions}
6533 @kindex --sectname-subst
6534 @cindex section name substitution
6535 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6536 argument may contain a substitution sequence. Only @code{%S} is supported
6537 at the moment, and substitutes the current section name. For example:
6540 .macro exception_code
6541 .section %S.exception
6542 [exception code here]
6557 The two @code{exception_code} invocations above would create the
6558 @code{.text.exception} and @code{.init.exception} sections respectively.
6559 This is useful e.g. to discriminate between ancillary sections that are
6560 tied to setup code to be discarded after use from ancillary sections that
6561 need to stay resident without having to define multiple @code{exception_code}
6562 macros just for that purpose.
6564 The optional @var{flags} argument is a quoted string which may contain any
6565 combination of the following characters:
6569 section is allocatable
6571 section is a GNU_MBIND section
6573 section is excluded from executable and shared library.
6577 section is executable
6579 section is mergeable
6581 section contains zero terminated strings
6583 section is a member of a section group
6585 section is used for thread-local-storage
6587 section is a member of the previously-current section's group, if any
6588 @item @code{<number>}
6589 a numeric value indicating the bits to be set in the ELF section header's flags
6590 field. Note - if one or more of the alphabetic characters described above is
6591 also included in the flags field, their bit values will be ORed into the
6593 @item @code{<target specific>}
6594 some targets extend this list with their own flag characters
6597 Note - once a section's flags have been set they cannot be changed. There are
6598 a few exceptions to this rule however. Processor and application specific
6599 flags can be added to an already defined section. The @code{.interp},
6600 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6601 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6602 section may have the executable (@code{x}) flag added.
6604 The optional @var{type} argument may contain one of the following constants:
6608 section contains data
6610 section does not contain data (i.e., section only occupies space)
6612 section contains data which is used by things other than the program
6614 section contains an array of pointers to init functions
6616 section contains an array of pointers to finish functions
6617 @item @@preinit_array
6618 section contains an array of pointers to pre-init functions
6619 @item @@@code{<number>}
6620 a numeric value to be set as the ELF section header's type field.
6621 @item @@@code{<target specific>}
6622 some targets extend this list with their own types
6625 Many targets only support the first three section types. The type may be
6626 enclosed in double quotes if necessary.
6628 Note on targets where the @code{@@} character is the start of a comment (eg
6629 ARM) then another character is used instead. For example the ARM port uses the
6632 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6633 special and have fixed types. Any attempt to declare them with a different
6634 type will generate an error from the assembler.
6636 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6637 be specified as well as an extra argument---@var{entsize}---like this:
6640 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6643 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6644 constants, each @var{entsize} octets long. Sections with both @code{M} and
6645 @code{S} must contain zero terminated strings where each character is
6646 @var{entsize} bytes long. The linker may remove duplicates within sections with
6647 the same name, same entity size and same flags. @var{entsize} must be an
6648 absolute expression. For sections with both @code{M} and @code{S}, a string
6649 which is a suffix of a larger string is considered a duplicate. Thus
6650 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6651 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6653 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6654 be present along with an additional field like this:
6657 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6660 The @var{GroupName} field specifies the name of the section group to which this
6661 particular section belongs. The optional linkage field can contain:
6665 indicates that only one copy of this section should be retained
6670 Note: if both the @var{M} and @var{G} flags are present then the fields for
6671 the Merge flag should come first, like this:
6674 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6677 If @var{flags} contains the @code{?} symbol then it may not also contain the
6678 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6679 present. Instead, @code{?} says to consider the section that's current before
6680 this directive. If that section used @code{G}, then the new section will use
6681 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6682 If not, then the @code{?} symbol has no effect.
6684 If no flags are specified, the default flags depend upon the section name. If
6685 the section name is not recognized, the default will be for the section to have
6686 none of the above flags: it will not be allocated in memory, nor writable, nor
6687 executable. The section will contain data.
6689 For ELF targets, the assembler supports another type of @code{.section}
6690 directive for compatibility with the Solaris assembler:
6693 .section "@var{name}"[, @var{flags}...]
6696 Note that the section name is quoted. There may be a sequence of comma
6701 section is allocatable
6705 section is executable
6707 section is excluded from executable and shared library.
6709 section is used for thread local storage
6712 This directive replaces the current section and subsection. See the
6713 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6714 some examples of how this directive and the other section stack directives
6720 @section @code{.set @var{symbol}, @var{expression}}
6722 @cindex @code{set} directive
6723 @cindex symbol value, setting
6724 Set the value of @var{symbol} to @var{expression}. This
6725 changes @var{symbol}'s value and type to conform to
6726 @var{expression}. If @var{symbol} was flagged as external, it remains
6727 flagged (@pxref{Symbol Attributes}).
6729 You may @code{.set} a symbol many times in the same assembly provided that the
6730 values given to the symbol are constants. Values that are based on expressions
6731 involving other symbols are allowed, but some targets may restrict this to only
6732 being done once per assembly. This is because those targets do not set the
6733 addresses of symbols at assembly time, but rather delay the assignment until a
6734 final link is performed. This allows the linker a chance to change the code in
6735 the files, changing the location of, and the relative distance between, various
6738 If you @code{.set} a global symbol, the value stored in the object
6739 file is the last value stored into it.
6742 On Z80 @code{set} is a real instruction, use
6743 @samp{@var{symbol} defl @var{expression}} instead.
6747 @section @code{.short @var{expressions}}
6749 @cindex @code{short} directive
6751 @code{.short} is normally the same as @samp{.word}.
6752 @xref{Word,,@code{.word}}.
6754 In some configurations, however, @code{.short} and @code{.word} generate
6755 numbers of different lengths. @xref{Machine Dependencies}.
6759 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6762 This expects zero or more @var{expressions}, and emits
6763 a 16 bit number for each.
6768 @section @code{.single @var{flonums}}
6770 @cindex @code{single} directive
6771 @cindex floating point numbers (single)
6772 This directive assembles zero or more flonums, separated by commas. It
6773 has the same effect as @code{.float}.
6775 The exact kind of floating point numbers emitted depends on how
6776 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6780 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6781 numbers in @sc{ieee} format.
6787 @section @code{.size}
6789 This directive is used to set the size associated with a symbol.
6793 @c only print the extra heading if both COFF and ELF are set
6794 @subheading COFF Version
6797 @cindex @code{size} directive (COFF version)
6798 For COFF targets, the @code{.size} directive is only permitted inside
6799 @code{.def}/@code{.endef} pairs. It is used like this:
6802 .size @var{expression}
6806 @samp{.size} is only meaningful when generating COFF format output; when
6807 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6814 @c only print the extra heading if both COFF and ELF are set
6815 @subheading ELF Version
6818 @cindex @code{size} directive (ELF version)
6819 For ELF targets, the @code{.size} directive is used like this:
6822 .size @var{name} , @var{expression}
6825 This directive sets the size associated with a symbol @var{name}.
6826 The size in bytes is computed from @var{expression} which can make use of label
6827 arithmetic. This directive is typically used to set the size of function
6832 @ifclear no-space-dir
6834 @section @code{.skip @var{size} , @var{fill}}
6836 @cindex @code{skip} directive
6837 @cindex filling memory
6838 This directive emits @var{size} bytes, each of value @var{fill}. Both
6839 @var{size} and @var{fill} are absolute expressions. If the comma and
6840 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6845 @section @code{.sleb128 @var{expressions}}
6847 @cindex @code{sleb128} directive
6848 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6849 compact, variable length representation of numbers used by the DWARF
6850 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6852 @ifclear no-space-dir
6854 @section @code{.space @var{size} , @var{fill}}
6856 @cindex @code{space} directive
6857 @cindex filling memory
6858 This directive emits @var{size} bytes, each of value @var{fill}. Both
6859 @var{size} and @var{fill} are absolute expressions. If the comma
6860 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6865 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6866 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6867 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6868 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6876 @section @code{.stabd, .stabn, .stabs}
6878 @cindex symbolic debuggers, information for
6879 @cindex @code{stab@var{x}} directives
6880 There are three directives that begin @samp{.stab}.
6881 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6882 The symbols are not entered in the @command{@value{AS}} hash table: they
6883 cannot be referenced elsewhere in the source file.
6884 Up to five fields are required:
6888 This is the symbol's name. It may contain any character except
6889 @samp{\000}, so is more general than ordinary symbol names. Some
6890 debuggers used to code arbitrarily complex structures into symbol names
6894 An absolute expression. The symbol's type is set to the low 8 bits of
6895 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6896 and debuggers choke on silly bit patterns.
6899 An absolute expression. The symbol's ``other'' attribute is set to the
6900 low 8 bits of this expression.
6903 An absolute expression. The symbol's descriptor is set to the low 16
6904 bits of this expression.
6907 An absolute expression which becomes the symbol's value.
6910 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6911 or @code{.stabs} statement, the symbol has probably already been created;
6912 you get a half-formed symbol in your object file. This is
6913 compatible with earlier assemblers!
6916 @cindex @code{stabd} directive
6917 @item .stabd @var{type} , @var{other} , @var{desc}
6919 The ``name'' of the symbol generated is not even an empty string.
6920 It is a null pointer, for compatibility. Older assemblers used a
6921 null pointer so they didn't waste space in object files with empty
6924 The symbol's value is set to the location counter,
6925 relocatably. When your program is linked, the value of this symbol
6926 is the address of the location counter when the @code{.stabd} was
6929 @cindex @code{stabn} directive
6930 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6931 The name of the symbol is set to the empty string @code{""}.
6933 @cindex @code{stabs} directive
6934 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6935 All five fields are specified.
6941 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6942 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6944 @cindex string, copying to object file
6945 @cindex string8, copying to object file
6946 @cindex string16, copying to object file
6947 @cindex string32, copying to object file
6948 @cindex string64, copying to object file
6949 @cindex @code{string} directive
6950 @cindex @code{string8} directive
6951 @cindex @code{string16} directive
6952 @cindex @code{string32} directive
6953 @cindex @code{string64} directive
6955 Copy the characters in @var{str} to the object file. You may specify more than
6956 one string to copy, separated by commas. Unless otherwise specified for a
6957 particular machine, the assembler marks the end of each string with a 0 byte.
6958 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6960 The variants @code{string16}, @code{string32} and @code{string64} differ from
6961 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6962 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6963 are stored in target endianness byte order.
6969 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6970 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6975 @section @code{.struct @var{expression}}
6977 @cindex @code{struct} directive
6978 Switch to the absolute section, and set the section offset to @var{expression},
6979 which must be an absolute expression. You might use this as follows:
6988 This would define the symbol @code{field1} to have the value 0, the symbol
6989 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6990 value 8. Assembly would be left in the absolute section, and you would need to
6991 use a @code{.section} directive of some sort to change to some other section
6992 before further assembly.
6996 @section @code{.subsection @var{name}}
6998 @cindex @code{subsection} directive
6999 @cindex Section Stack
7000 This is one of the ELF section stack manipulation directives. The others are
7001 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
7002 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
7005 This directive replaces the current subsection with @code{name}. The current
7006 section is not changed. The replaced subsection is put onto the section stack
7007 in place of the then current top of stack subsection.
7012 @section @code{.symver}
7013 @cindex @code{symver} directive
7014 @cindex symbol versioning
7015 @cindex versions of symbols
7016 Use the @code{.symver} directive to bind symbols to specific version nodes
7017 within a source file. This is only supported on ELF platforms, and is
7018 typically used when assembling files to be linked into a shared library.
7019 There are cases where it may make sense to use this in objects to be bound
7020 into an application itself so as to override a versioned symbol from a
7023 For ELF targets, the @code{.symver} directive can be used like this:
7025 .symver @var{name}, @var{name2@@nodename}
7027 If the symbol @var{name} is defined within the file
7028 being assembled, the @code{.symver} directive effectively creates a symbol
7029 alias with the name @var{name2@@nodename}, and in fact the main reason that we
7030 just don't try and create a regular alias is that the @var{@@} character isn't
7031 permitted in symbol names. The @var{name2} part of the name is the actual name
7032 of the symbol by which it will be externally referenced. The name @var{name}
7033 itself is merely a name of convenience that is used so that it is possible to
7034 have definitions for multiple versions of a function within a single source
7035 file, and so that the compiler can unambiguously know which version of a
7036 function is being mentioned. The @var{nodename} portion of the alias should be
7037 the name of a node specified in the version script supplied to the linker when
7038 building a shared library. If you are attempting to override a versioned
7039 symbol from a shared library, then @var{nodename} should correspond to the
7040 nodename of the symbol you are trying to override.
7042 If the symbol @var{name} is not defined within the file being assembled, all
7043 references to @var{name} will be changed to @var{name2@@nodename}. If no
7044 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
7047 Another usage of the @code{.symver} directive is:
7049 .symver @var{name}, @var{name2@@@@nodename}
7051 In this case, the symbol @var{name} must exist and be defined within
7052 the file being assembled. It is similar to @var{name2@@nodename}. The
7053 difference is @var{name2@@@@nodename} will also be used to resolve
7054 references to @var{name2} by the linker.
7056 The third usage of the @code{.symver} directive is:
7058 .symver @var{name}, @var{name2@@@@@@nodename}
7060 When @var{name} is not defined within the
7061 file being assembled, it is treated as @var{name2@@nodename}. When
7062 @var{name} is defined within the file being assembled, the symbol
7063 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7068 @section @code{.tag @var{structname}}
7070 @cindex COFF structure debugging
7071 @cindex structure debugging, COFF
7072 @cindex @code{tag} directive
7073 This directive is generated by compilers to include auxiliary debugging
7074 information in the symbol table. It is only permitted inside
7075 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7076 definitions in the symbol table with instances of those structures.
7079 @samp{.tag} is only used when generating COFF format output; when
7080 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
7086 @section @code{.text @var{subsection}}
7088 @cindex @code{text} directive
7089 Tells @command{@value{AS}} to assemble the following statements onto the end of
7090 the text subsection numbered @var{subsection}, which is an absolute
7091 expression. If @var{subsection} is omitted, subsection number zero
7095 @section @code{.title "@var{heading}"}
7097 @cindex @code{title} directive
7098 @cindex listing control: title line
7099 Use @var{heading} as the title (second line, immediately after the
7100 source file name and pagenumber) when generating assembly listings.
7102 This directive affects subsequent pages, as well as the current page if
7103 it appears within ten lines of the top of a page.
7107 @section @code{.type}
7109 This directive is used to set the type of a symbol.
7113 @c only print the extra heading if both COFF and ELF are set
7114 @subheading COFF Version
7117 @cindex COFF symbol type
7118 @cindex symbol type, COFF
7119 @cindex @code{type} directive (COFF version)
7120 For COFF targets, this directive is permitted only within
7121 @code{.def}/@code{.endef} pairs. It is used like this:
7127 This records the integer @var{int} as the type attribute of a symbol table
7131 @samp{.type} is associated only with COFF format output; when
7132 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
7133 directive but ignores it.
7139 @c only print the extra heading if both COFF and ELF are set
7140 @subheading ELF Version
7143 @cindex ELF symbol type
7144 @cindex symbol type, ELF
7145 @cindex @code{type} directive (ELF version)
7146 For ELF targets, the @code{.type} directive is used like this:
7149 .type @var{name} , @var{type description}
7152 This sets the type of symbol @var{name} to be either a
7153 function symbol or an object symbol. There are five different syntaxes
7154 supported for the @var{type description} field, in order to provide
7155 compatibility with various other assemblers.
7157 Because some of the characters used in these syntaxes (such as @samp{@@} and
7158 @samp{#}) are comment characters for some architectures, some of the syntaxes
7159 below do not work on all architectures. The first variant will be accepted by
7160 the GNU assembler on all architectures so that variant should be used for
7161 maximum portability, if you do not need to assemble your code with other
7164 The syntaxes supported are:
7167 .type <name> STT_<TYPE_IN_UPPER_CASE>
7168 .type <name>,#<type>
7169 .type <name>,@@<type>
7170 .type <name>,%<type>
7171 .type <name>,"<type>"
7174 The types supported are:
7179 Mark the symbol as being a function name.
7182 @itemx gnu_indirect_function
7183 Mark the symbol as an indirect function when evaluated during reloc
7184 processing. (This is only supported on assemblers targeting GNU systems).
7188 Mark the symbol as being a data object.
7192 Mark the symbol as being a thread-local data object.
7196 Mark the symbol as being a common data object.
7200 Does not mark the symbol in any way. It is supported just for completeness.
7202 @item gnu_unique_object
7203 Marks the symbol as being a globally unique data object. The dynamic linker
7204 will make sure that in the entire process there is just one symbol with this
7205 name and type in use. (This is only supported on assemblers targeting GNU
7210 Note: Some targets support extra types in addition to those listed above.
7216 @section @code{.uleb128 @var{expressions}}
7218 @cindex @code{uleb128} directive
7219 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7220 compact, variable length representation of numbers used by the DWARF
7221 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7225 @section @code{.val @var{addr}}
7227 @cindex @code{val} directive
7228 @cindex COFF value attribute
7229 @cindex value attribute, COFF
7230 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7231 records the address @var{addr} as the value attribute of a symbol table
7235 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
7236 configured for @code{b.out}, it accepts this directive but ignores it.
7242 @section @code{.version "@var{string}"}
7244 @cindex @code{version} directive
7245 This directive creates a @code{.note} section and places into it an ELF
7246 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7251 @section @code{.vtable_entry @var{table}, @var{offset}}
7253 @cindex @code{vtable_entry} directive
7254 This directive finds or creates a symbol @code{table} and creates a
7255 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7258 @section @code{.vtable_inherit @var{child}, @var{parent}}
7260 @cindex @code{vtable_inherit} directive
7261 This directive finds the symbol @code{child} and finds or creates the symbol
7262 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7263 parent whose addend is the value of the child symbol. As a special case the
7264 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7268 @section @code{.warning "@var{string}"}
7269 @cindex warning directive
7270 Similar to the directive @code{.error}
7271 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7274 @section @code{.weak @var{names}}
7276 @cindex @code{weak} directive
7277 This directive sets the weak attribute on the comma separated list of symbol
7278 @code{names}. If the symbols do not already exist, they will be created.
7280 On COFF targets other than PE, weak symbols are a GNU extension. This
7281 directive sets the weak attribute on the comma separated list of symbol
7282 @code{names}. If the symbols do not already exist, they will be created.
7284 On the PE target, weak symbols are supported natively as weak aliases.
7285 When a weak symbol is created that is not an alias, GAS creates an
7286 alternate symbol to hold the default value.
7289 @section @code{.weakref @var{alias}, @var{target}}
7291 @cindex @code{weakref} directive
7292 This directive creates an alias to the target symbol that enables the symbol to
7293 be referenced with weak-symbol semantics, but without actually making it weak.
7294 If direct references or definitions of the symbol are present, then the symbol
7295 will not be weak, but if all references to it are through weak references, the
7296 symbol will be marked as weak in the symbol table.
7298 The effect is equivalent to moving all references to the alias to a separate
7299 assembly source file, renaming the alias to the symbol in it, declaring the
7300 symbol as weak there, and running a reloadable link to merge the object files
7301 resulting from the assembly of the new source file and the old source file that
7302 had the references to the alias removed.
7304 The alias itself never makes to the symbol table, and is entirely handled
7305 within the assembler.
7308 @section @code{.word @var{expressions}}
7310 @cindex @code{word} directive
7311 This directive expects zero or more @var{expressions}, of any section,
7312 separated by commas.
7315 For each expression, @command{@value{AS}} emits a 32-bit number.
7318 For each expression, @command{@value{AS}} emits a 16-bit number.
7323 The size of the number emitted, and its byte order,
7324 depend on what target computer the assembly is for.
7327 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7328 @c happen---32-bit addressability, period; no long/short jumps.
7329 @ifset DIFF-TBL-KLUGE
7330 @cindex difference tables altered
7331 @cindex altered difference tables
7333 @emph{Warning: Special Treatment to support Compilers}
7337 Machines with a 32-bit address space, but that do less than 32-bit
7338 addressing, require the following special treatment. If the machine of
7339 interest to you does 32-bit addressing (or doesn't require it;
7340 @pxref{Machine Dependencies}), you can ignore this issue.
7343 In order to assemble compiler output into something that works,
7344 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7345 Directives of the form @samp{.word sym1-sym2} are often emitted by
7346 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7347 directive of the form @samp{.word sym1-sym2}, and the difference between
7348 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7349 creates a @dfn{secondary jump table}, immediately before the next label.
7350 This secondary jump table is preceded by a short-jump to the
7351 first byte after the secondary table. This short-jump prevents the flow
7352 of control from accidentally falling into the new table. Inside the
7353 table is a long-jump to @code{sym2}. The original @samp{.word}
7354 contains @code{sym1} minus the address of the long-jump to
7357 If there were several occurrences of @samp{.word sym1-sym2} before the
7358 secondary jump table, all of them are adjusted. If there was a
7359 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7360 long-jump to @code{sym4} is included in the secondary jump table,
7361 and the @code{.word} directives are adjusted to contain @code{sym3}
7362 minus the address of the long-jump to @code{sym4}; and so on, for as many
7363 entries in the original jump table as necessary.
7366 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7367 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7368 assembly language programmers.
7371 @c end DIFF-TBL-KLUGE
7373 @ifclear no-space-dir
7375 @section @code{.zero @var{size}}
7377 @cindex @code{zero} directive
7378 @cindex filling memory with zero bytes
7379 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7380 expression. This directive is actually an alias for the @samp{.skip} directive
7381 so in can take an optional second argument of the value to store in the bytes
7382 instead of zero. Using @samp{.zero} in this way would be confusing however.
7387 @section @code{.2byte @var{expression} [, @var{expression}]*}
7388 @cindex @code{2byte} directive
7389 @cindex two-byte integer
7390 @cindex integer, 2-byte
7392 This directive expects zero or more expressions, separated by commas. If there
7393 are no expressions then the directive does nothing. Otherwise each expression
7394 is evaluated in turn and placed in the next two bytes of the current output
7395 section, using the endian model of the target. If an expression will not fit
7396 in two bytes, a warning message is displayed and the least significant two
7397 bytes of the expression's value are used. If an expression cannot be evaluated
7398 at assembly time then relocations will be generated in order to compute the
7401 This directive does not apply any alignment before or after inserting the
7402 values. As a result of this, if relocations are generated, they may be
7403 different from those used for inserting values with a guaranteed alignment.
7405 This directive is only available for ELF targets,
7408 @section @code{.4byte @var{expression} [, @var{expression}]*}
7409 @cindex @code{4byte} directive
7410 @cindex four-byte integer
7411 @cindex integer, 4-byte
7413 Like the @option{.2byte} directive, except that it inserts unaligned, four byte
7414 long values into the output.
7417 @section @code{.8byte @var{expression} [, @var{expression}]*}
7418 @cindex @code{8byte} directive
7419 @cindex eight-byte integer
7420 @cindex integer, 8-byte
7422 Like the @option{.2byte} directive, except that it inserts unaligned, eight
7423 byte long bignum values into the output.
7428 @section Deprecated Directives
7430 @cindex deprecated directives
7431 @cindex obsolescent directives
7432 One day these directives won't work.
7433 They are included for compatibility with older assemblers.
7440 @node Object Attributes
7441 @chapter Object Attributes
7442 @cindex object attributes
7444 @command{@value{AS}} assembles source files written for a specific architecture
7445 into object files for that architecture. But not all object files are alike.
7446 Many architectures support incompatible variations. For instance, floating
7447 point arguments might be passed in floating point registers if the object file
7448 requires hardware floating point support---or floating point arguments might be
7449 passed in integer registers if the object file supports processors with no
7450 hardware floating point unit. Or, if two objects are built for different
7451 generations of the same architecture, the combination may require the
7452 newer generation at run-time.
7454 This information is useful during and after linking. At link time,
7455 @command{@value{LD}} can warn about incompatible object files. After link
7456 time, tools like @command{gdb} can use it to process the linked file
7459 Compatibility information is recorded as a series of object attributes. Each
7460 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7461 string, and indicates who sets the meaning of the tag. The tag is an integer,
7462 and indicates what property the attribute describes. The value may be a string
7463 or an integer, and indicates how the property affects this object. Missing
7464 attributes are the same as attributes with a zero value or empty string value.
7466 Object attributes were developed as part of the ABI for the ARM Architecture.
7467 The file format is documented in @cite{ELF for the ARM Architecture}.
7470 * GNU Object Attributes:: @sc{gnu} Object Attributes
7471 * Defining New Object Attributes:: Defining New Object Attributes
7474 @node GNU Object Attributes
7475 @section @sc{gnu} Object Attributes
7477 The @code{.gnu_attribute} directive records an object attribute
7478 with vendor @samp{gnu}.
7480 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7481 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7482 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7483 2} is set for architecture-independent attributes and clear for
7484 architecture-dependent ones.
7486 @subsection Common @sc{gnu} attributes
7488 These attributes are valid on all architectures.
7491 @item Tag_compatibility (32)
7492 The compatibility attribute takes an integer flag value and a vendor name. If
7493 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7494 then the file is only compatible with the named toolchain. If it is greater
7495 than 1, the file can only be processed by other toolchains under some private
7496 arrangement indicated by the flag value and the vendor name.
7499 @subsection MIPS Attributes
7502 @item Tag_GNU_MIPS_ABI_FP (4)
7503 The floating-point ABI used by this object file. The value will be:
7507 0 for files not affected by the floating-point ABI.
7509 1 for files using the hardware floating-point ABI with a standard
7510 double-precision FPU.
7512 2 for files using the hardware floating-point ABI with a single-precision FPU.
7514 3 for files using the software floating-point ABI.
7516 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7517 floating-point registers, 32-bit general-purpose registers and increased the
7518 number of callee-saved floating-point registers.
7520 5 for files using the hardware floating-point ABI with a double-precision FPU
7521 with either 32-bit or 64-bit floating-point registers and 32-bit
7522 general-purpose registers.
7524 6 for files using the hardware floating-point ABI with 64-bit floating-point
7525 registers and 32-bit general-purpose registers.
7527 7 for files using the hardware floating-point ABI with 64-bit floating-point
7528 registers, 32-bit general-purpose registers and a rule that forbids the
7529 direct use of odd-numbered single-precision floating-point registers.
7533 @subsection PowerPC Attributes
7536 @item Tag_GNU_Power_ABI_FP (4)
7537 The floating-point ABI used by this object file. The value will be:
7541 0 for files not affected by the floating-point ABI.
7543 1 for files using double-precision hardware floating-point ABI.
7545 2 for files using the software floating-point ABI.
7547 3 for files using single-precision hardware floating-point ABI.
7550 @item Tag_GNU_Power_ABI_Vector (8)
7551 The vector ABI used by this object file. The value will be:
7555 0 for files not affected by the vector ABI.
7557 1 for files using general purpose registers to pass vectors.
7559 2 for files using AltiVec registers to pass vectors.
7561 3 for files using SPE registers to pass vectors.
7565 @subsection IBM z Systems Attributes
7568 @item Tag_GNU_S390_ABI_Vector (8)
7569 The vector ABI used by this object file. The value will be:
7573 0 for files not affected by the vector ABI.
7575 1 for files using software vector ABI.
7577 2 for files using hardware vector ABI.
7581 @node Defining New Object Attributes
7582 @section Defining New Object Attributes
7584 If you want to define a new @sc{gnu} object attribute, here are the places you
7585 will need to modify. New attributes should be discussed on the @samp{binutils}
7590 This manual, which is the official register of attributes.
7592 The header for your architecture @file{include/elf}, to define the tag.
7594 The @file{bfd} support file for your architecture, to merge the attribute
7595 and issue any appropriate link warnings.
7597 Test cases in @file{ld/testsuite} for merging and link warnings.
7599 @file{binutils/readelf.c} to display your attribute.
7601 GCC, if you want the compiler to mark the attribute automatically.
7607 @node Machine Dependencies
7608 @chapter Machine Dependent Features
7610 @cindex machine dependencies
7611 The machine instruction sets are (almost by definition) different on
7612 each machine where @command{@value{AS}} runs. Floating point representations
7613 vary as well, and @command{@value{AS}} often supports a few additional
7614 directives or command-line options for compatibility with other
7615 assemblers on a particular platform. Finally, some versions of
7616 @command{@value{AS}} support special pseudo-instructions for branch
7619 This chapter discusses most of these differences, though it does not
7620 include details on any machine's instruction set. For details on that
7621 subject, see the hardware manufacturer's manual.
7625 * AArch64-Dependent:: AArch64 Dependent Features
7628 * Alpha-Dependent:: Alpha Dependent Features
7631 * ARC-Dependent:: ARC Dependent Features
7634 * ARM-Dependent:: ARM Dependent Features
7637 * AVR-Dependent:: AVR Dependent Features
7640 * Blackfin-Dependent:: Blackfin Dependent Features
7643 * CR16-Dependent:: CR16 Dependent Features
7646 * CRIS-Dependent:: CRIS Dependent Features
7649 * D10V-Dependent:: D10V Dependent Features
7652 * D30V-Dependent:: D30V Dependent Features
7655 * Epiphany-Dependent:: EPIPHANY Dependent Features
7658 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7661 * HPPA-Dependent:: HPPA Dependent Features
7664 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7667 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7670 * i860-Dependent:: Intel 80860 Dependent Features
7673 * i960-Dependent:: Intel 80960 Dependent Features
7676 * IA-64-Dependent:: Intel IA-64 Dependent Features
7679 * IP2K-Dependent:: IP2K Dependent Features
7682 * LM32-Dependent:: LM32 Dependent Features
7685 * M32C-Dependent:: M32C Dependent Features
7688 * M32R-Dependent:: M32R Dependent Features
7691 * M68K-Dependent:: M680x0 Dependent Features
7694 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7697 * Meta-Dependent :: Meta Dependent Features
7700 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7703 * MIPS-Dependent:: MIPS Dependent Features
7706 * MMIX-Dependent:: MMIX Dependent Features
7709 * MSP430-Dependent:: MSP430 Dependent Features
7712 * NDS32-Dependent:: Andes NDS32 Dependent Features
7715 * NiosII-Dependent:: Altera Nios II Dependent Features
7718 * NS32K-Dependent:: NS32K Dependent Features
7721 * PDP-11-Dependent:: PDP-11 Dependent Features
7724 * PJ-Dependent:: picoJava Dependent Features
7727 * PPC-Dependent:: PowerPC Dependent Features
7730 * PRU-Dependent:: PRU Dependent Features
7733 * RISC-V-Dependent:: RISC-V Dependent Features
7736 * RL78-Dependent:: RL78 Dependent Features
7739 * RX-Dependent:: RX Dependent Features
7742 * S/390-Dependent:: IBM S/390 Dependent Features
7745 * SCORE-Dependent:: SCORE Dependent Features
7748 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7749 * SH64-Dependent:: SuperH SH64 Dependent Features
7752 * Sparc-Dependent:: SPARC Dependent Features
7755 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7758 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7761 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7764 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7767 * V850-Dependent:: V850 Dependent Features
7770 * Vax-Dependent:: VAX Dependent Features
7773 * Visium-Dependent:: Visium Dependent Features
7776 * WebAssembly-Dependent:: WebAssembly Dependent Features
7779 * XGATE-Dependent:: XGATE Dependent Features
7782 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7785 * Xtensa-Dependent:: Xtensa Dependent Features
7788 * Z80-Dependent:: Z80 Dependent Features
7791 * Z8000-Dependent:: Z8000 Dependent Features
7798 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7799 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7800 @c peculiarity: to preserve cross-references, there must be a node called
7801 @c "Machine Dependencies". Hence the conditional nodenames in each
7802 @c major node below. Node defaulting in makeinfo requires adjacency of
7803 @c node and sectioning commands; hence the repetition of @chapter BLAH
7804 @c in both conditional blocks.
7807 @include c-aarch64.texi
7811 @include c-alpha.texi
7827 @include c-bfin.texi
7831 @include c-cr16.texi
7835 @include c-cris.texi
7840 @node Machine Dependencies
7841 @chapter Machine Dependent Features
7843 The machine instruction sets are different on each Renesas chip family,
7844 and there are also some syntax differences among the families. This
7845 chapter describes the specific @command{@value{AS}} features for each
7849 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7850 * SH-Dependent:: Renesas SH Dependent Features
7857 @include c-d10v.texi
7861 @include c-d30v.texi
7865 @include c-epiphany.texi
7869 @include c-h8300.texi
7873 @include c-hppa.texi
7877 @include c-i370.texi
7881 @include c-i386.texi
7885 @include c-i860.texi
7889 @include c-i960.texi
7893 @include c-ia64.texi
7897 @include c-ip2k.texi
7901 @include c-lm32.texi
7905 @include c-m32c.texi
7909 @include c-m32r.texi
7913 @include c-m68k.texi
7917 @include c-m68hc11.texi
7921 @include c-metag.texi
7925 @include c-microblaze.texi
7929 @include c-mips.texi
7933 @include c-mmix.texi
7937 @include c-msp430.texi
7941 @include c-nds32.texi
7945 @include c-nios2.texi
7949 @include c-ns32k.texi
7953 @include c-pdp11.texi
7969 @include c-riscv.texi
7973 @include c-rl78.texi
7981 @include c-s390.texi
7985 @include c-score.texi
7990 @include c-sh64.texi
7994 @include c-sparc.texi
7998 @include c-tic54x.texi
8002 @include c-tic6x.texi
8006 @include c-tilegx.texi
8010 @include c-tilepro.texi
8014 @include c-v850.texi
8022 @include c-visium.texi
8026 @include c-wasm32.texi
8030 @include c-xgate.texi
8034 @include c-xstormy16.texi
8038 @include c-xtensa.texi
8050 @c reverse effect of @down at top of generic Machine-Dep chapter
8054 @node Reporting Bugs
8055 @chapter Reporting Bugs
8056 @cindex bugs in assembler
8057 @cindex reporting bugs in assembler
8059 Your bug reports play an essential role in making @command{@value{AS}} reliable.
8061 Reporting a bug may help you by bringing a solution to your problem, or it may
8062 not. But in any case the principal function of a bug report is to help the
8063 entire community by making the next version of @command{@value{AS}} work better.
8064 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
8066 In order for a bug report to serve its purpose, you must include the
8067 information that enables us to fix the bug.
8070 * Bug Criteria:: Have you found a bug?
8071 * Bug Reporting:: How to report bugs
8075 @section Have You Found a Bug?
8076 @cindex bug criteria
8078 If you are not sure whether you have found a bug, here are some guidelines:
8081 @cindex fatal signal
8082 @cindex assembler crash
8083 @cindex crash of assembler
8085 If the assembler gets a fatal signal, for any input whatever, that is a
8086 @command{@value{AS}} bug. Reliable assemblers never crash.
8088 @cindex error on valid input
8090 If @command{@value{AS}} produces an error message for valid input, that is a bug.
8092 @cindex invalid input
8094 If @command{@value{AS}} does not produce an error message for invalid input, that
8095 is a bug. However, you should note that your idea of ``invalid input'' might
8096 be our idea of ``an extension'' or ``support for traditional practice''.
8099 If you are an experienced user of assemblers, your suggestions for improvement
8100 of @command{@value{AS}} are welcome in any case.
8104 @section How to Report Bugs
8106 @cindex assembler bugs, reporting
8108 A number of companies and individuals offer support for @sc{gnu} products. If
8109 you obtained @command{@value{AS}} from a support organization, we recommend you
8110 contact that organization first.
8112 You can find contact information for many support companies and
8113 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8117 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8121 The fundamental principle of reporting bugs usefully is this:
8122 @strong{report all the facts}. If you are not sure whether to state a
8123 fact or leave it out, state it!
8125 Often people omit facts because they think they know what causes the problem
8126 and assume that some details do not matter. Thus, you might assume that the
8127 name of a symbol you use in an example does not matter. Well, probably it does
8128 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8129 happens to fetch from the location where that name is stored in memory;
8130 perhaps, if the name were different, the contents of that location would fool
8131 the assembler into doing the right thing despite the bug. Play it safe and
8132 give a specific, complete example. That is the easiest thing for you to do,
8133 and the most helpful.
8135 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8136 it is new to us. Therefore, always write your bug reports on the assumption
8137 that the bug has not been reported previously.
8139 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8140 bell?'' This cannot help us fix a bug, so it is basically useless. We
8141 respond by asking for enough details to enable us to investigate.
8142 You might as well expedite matters by sending them to begin with.
8144 To enable us to fix the bug, you should include all these things:
8148 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8149 it with the @samp{--version} argument.
8151 Without this, we will not know whether there is any point in looking for
8152 the bug in the current version of @command{@value{AS}}.
8155 Any patches you may have applied to the @command{@value{AS}} source.
8158 The type of machine you are using, and the operating system name and
8162 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8166 The command arguments you gave the assembler to assemble your example and
8167 observe the bug. To guarantee you will not omit something important, list them
8168 all. A copy of the Makefile (or the output from make) is sufficient.
8170 If we were to try to guess the arguments, we would probably guess wrong
8171 and then we might not encounter the bug.
8174 A complete input file that will reproduce the bug. If the bug is observed when
8175 the assembler is invoked via a compiler, send the assembler source, not the
8176 high level language source. Most compilers will produce the assembler source
8177 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8178 the options @samp{-v --save-temps}; this will save the assembler source in a
8179 file with an extension of @file{.s}, and also show you exactly how
8180 @command{@value{AS}} is being run.
8183 A description of what behavior you observe that you believe is
8184 incorrect. For example, ``It gets a fatal signal.''
8186 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8187 will certainly notice it. But if the bug is incorrect output, we might not
8188 notice unless it is glaringly wrong. You might as well not give us a chance to
8191 Even if the problem you experience is a fatal signal, you should still say so
8192 explicitly. Suppose something strange is going on, such as, your copy of
8193 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8194 library on your system. (This has happened!) Your copy might crash and ours
8195 would not. If you told us to expect a crash, then when ours fails to crash, we
8196 would know that the bug was not happening for us. If you had not told us to
8197 expect a crash, then we would not be able to draw any conclusion from our
8201 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8202 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8203 option. Always send diffs from the old file to the new file. If you even
8204 discuss something in the @command{@value{AS}} source, refer to it by context, not
8207 The line numbers in our development sources will not match those in your
8208 sources. Your line numbers would convey no useful information to us.
8211 Here are some things that are not necessary:
8215 A description of the envelope of the bug.
8217 Often people who encounter a bug spend a lot of time investigating
8218 which changes to the input file will make the bug go away and which
8219 changes will not affect it.
8221 This is often time consuming and not very useful, because the way we
8222 will find the bug is by running a single example under the debugger
8223 with breakpoints, not by pure deduction from a series of examples.
8224 We recommend that you save your time for something else.
8226 Of course, if you can find a simpler example to report @emph{instead}
8227 of the original one, that is a convenience for us. Errors in the
8228 output will be easier to spot, running under the debugger will take
8229 less time, and so on.
8231 However, simplification is not vital; if you do not want to do this,
8232 report the bug anyway and send us the entire test case you used.
8235 A patch for the bug.
8237 A patch for the bug does help us if it is a good one. But do not omit
8238 the necessary information, such as the test case, on the assumption that
8239 a patch is all we need. We might see problems with your patch and decide
8240 to fix the problem another way, or we might not understand it at all.
8242 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8243 construct an example that will make the program follow a certain path through
8244 the code. If you do not send us the example, we will not be able to construct
8245 one, so we will not be able to verify that the bug is fixed.
8247 And if we cannot understand what bug you are trying to fix, or why your
8248 patch should be an improvement, we will not install it. A test case will
8249 help us to understand.
8252 A guess about what the bug is or what it depends on.
8254 Such guesses are usually wrong. Even we cannot guess right about such
8255 things without first using the debugger to find the facts.
8258 @node Acknowledgements
8259 @chapter Acknowledgements
8261 If you have contributed to GAS and your name isn't listed here,
8262 it is not meant as a slight. We just don't know about it. Send mail to the
8263 maintainer, and we'll correct the situation. Currently
8265 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8267 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8270 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8271 information and the 68k series machines, most of the preprocessing pass, and
8272 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8274 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8275 many bug fixes, including merging support for several processors, breaking GAS
8276 up to handle multiple object file format back ends (including heavy rewrite,
8277 testing, an integration of the coff and b.out back ends), adding configuration
8278 including heavy testing and verification of cross assemblers and file splits
8279 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8280 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8281 port (including considerable amounts of reverse engineering), a SPARC opcode
8282 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8283 assertions and made them work, much other reorganization, cleanup, and lint.
8285 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8286 in format-specific I/O modules.
8288 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8289 has done much work with it since.
8291 The Intel 80386 machine description was written by Eliot Dresselhaus.
8293 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8295 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8296 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8298 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8299 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8300 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8301 support a.out format.
8303 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8304 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8305 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8306 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8309 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8310 simplified the configuration of which versions accept which directives. He
8311 updated the 68k machine description so that Motorola's opcodes always produced
8312 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8313 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8314 cross-compilation support, and one bug in relaxation that took a week and
8315 required the proverbial one-bit fix.
8317 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8318 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8319 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8320 PowerPC assembler, and made a few other minor patches.
8322 Steve Chamberlain made GAS able to generate listings.
8324 Hewlett-Packard contributed support for the HP9000/300.
8326 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8327 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8328 formats). This work was supported by both the Center for Software Science at
8329 the University of Utah and Cygnus Support.
8331 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8332 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8333 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8334 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8335 and some initial 64-bit support).
8337 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8339 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8340 support for openVMS/Alpha.
8342 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8345 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8346 Inc.@: added support for Xtensa processors.
8348 Several engineers at Cygnus Support have also provided many small bug fixes and
8349 configuration enhancements.
8351 Jon Beniston added support for the Lattice Mico32 architecture.
8353 Many others have contributed large or small bugfixes and enhancements. If
8354 you have contributed significant work and are not mentioned on this list, and
8355 want to be, let us know. Some of the history has been lost; we are not
8356 intentionally leaving anyone out.
8358 @node GNU Free Documentation License
8359 @appendix GNU Free Documentation License
8363 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob