1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (c) 1991, 1992, 1993, 1994, 1995 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 @c defaults, config file may override:
17 @include asconfig.texi
19 @c common OR combinations of conditions
36 @set abnormal-separator
40 @settitle Using @value{AS}
43 @settitle Using @value{AS} (@value{TARGET})
45 @setchapternewpage odd
50 @c WARE! Some of the machine-dependent sections contain tables of machine
51 @c instructions. Except in multi-column format, these tables look silly.
52 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
53 @c the multi-col format is faked within @example sections.
55 @c Again unfortunately, the natural size that fits on a page, for these tables,
56 @c is different depending on whether or not smallbook is turned on.
57 @c This matters, because of order: text flow switches columns at each page
60 @c The format faked in this source works reasonably well for smallbook,
61 @c not well for the default large-page format. This manual expects that if you
62 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
63 @c tables in question. You can turn on one without the other at your
64 @c discretion, of course.
67 @c the insn tables look just as silly in info files regardless of smallbook,
68 @c might as well show 'em anyways.
74 * As: (as). The GNU assembler.
83 This file documents the GNU Assembler "@value{AS}".
85 Copyright (C) 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc.
87 Permission is granted to make and distribute verbatim copies of
88 this manual provided the copyright notice and this permission notice
89 are preserved on all copies.
92 Permission is granted to process this file through Tex and print the
93 results, provided the printed document carries copying permission
94 notice identical to this one except for the removal of this paragraph
95 (this paragraph not being relevant to the printed manual).
98 Permission is granted to copy and distribute modified versions of this manual
99 under the conditions for verbatim copying, provided that the entire resulting
100 derived work is distributed under the terms of a permission notice identical to
103 Permission is granted to copy and distribute translations of this manual
104 into another language, under the above conditions for modified versions.
108 @title Using @value{AS}
109 @subtitle The GNU Assembler
111 @subtitle for the @value{TARGET} family
114 @subtitle January 1994
117 The Free Software Foundation Inc. thanks The Nice Computer
118 Company of Australia for loaning Dean Elsner to write the
119 first (Vax) version of @code{as} for Project GNU.
120 The proprietors, management and staff of TNCCA thank FSF for
121 distracting the boss while they got some work
124 @author Dean Elsner, Jay Fenlason & friends
128 \hfill {\it Using {\tt @value{AS}}}\par
129 \hfill Edited by Roland Pesch for Cygnus Support\par
131 %"boxit" macro for figures:
132 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
133 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
134 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
135 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
136 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
139 @vskip 0pt plus 1filll
140 Copyright @copyright{} 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
142 Permission is granted to make and distribute verbatim copies of
143 this manual provided the copyright notice and this permission notice
144 are preserved on all copies.
146 Permission is granted to copy and distribute modified versions of this manual
147 under the conditions for verbatim copying, provided that the entire resulting
148 derived work is distributed under the terms of a permission notice identical to
151 Permission is granted to copy and distribute translations of this manual
152 into another language, under the above conditions for modified versions.
157 @top Using @value{AS}
159 This file is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
161 This version of the file describes @code{@value{AS}} configured to generate
162 code for @value{TARGET} architectures.
165 * Overview:: Overview
166 * Invoking:: Command-Line Options
168 * Sections:: Sections and Relocation
170 * Expressions:: Expressions
171 * Pseudo Ops:: Assembler Directives
172 * Machine Dependencies:: Machine Dependent Features
173 * Acknowledgements:: Who Did What
181 This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
183 This version of the manual describes @code{@value{AS}} configured to generate
184 code for @value{TARGET} architectures.
188 @cindex invocation summary
189 @cindex option summary
190 @cindex summary of options
191 Here is a brief summary of how to invoke @code{@value{AS}}. For details,
192 @pxref{Invoking,,Comand-Line Options}.
194 @c We don't use deffn and friends for the following because they seem
195 @c to be limited to one line for the header.
197 @value{AS} [ -a[dhlns][=file] ] [ -D ] [ -f ] [ --help ]
198 [ -I @var{dir} ] [ -J ] [ -K ] [ -L ] [ -o @var{objfile} ]
199 [ -R ] [ --statistics ] [ -v ] [ -version ] [ --version ]
200 [ -W ] [ -w ] [ -x ] [ -Z ]
202 @c am29k has no machine-dependent assembler options
204 @c start-sanitize-arc
206 [ -mbig-endian | -mlittle-endian ]
210 @c Hitachi family chips have no machine-dependent assembler options
213 @c HPPA has no machine-dependent assembler options (yet).
216 [ -Av6 | -Av7 | -Av8 | -Av9 | -Asparclite | -bump ]
219 @c Z8000 has no machine-dependent assembler options
222 @c see md_parse_option in tc-i960.c
223 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
227 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
230 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
231 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
232 [ --trap ] [ --break ]
233 [ --emulation=@var{name} ]
235 [ -- | @var{files} @dots{} ]
240 Turn on listings, in any of a variety of ways:
244 omit debugging directives
247 include high-level source
253 omit forms processing
259 set the name of the listing file
262 You may combine these options; for example, use @samp{-aln} for assembly
263 listing without forms processing. The @samp{=file} option, if used, must be
264 the last one. By itself, @samp{-a} defaults to @samp{-ahls}---that is, all
268 Ignored. This option is accepted for script compatibility with calls to
272 ``fast''---skip whitespace and comment preprocessing (assume source is
276 Print a summary of the command line options and exit.
279 Add directory @var{dir} to the search list for @code{.include} directives.
282 Don't warn about signed overflow.
285 @ifclear DIFF-TBL-KLUGE
286 This option is accepted but has no effect on the @value{TARGET} family.
288 @ifset DIFF-TBL-KLUGE
289 Issue warnings when difference tables altered for long displacements.
293 Keep (in the symbol table) local symbols, starting with @samp{L}.
295 @item -o @var{objfile}
296 Name the object-file output from @code{@value{AS}} @var{objfile}.
299 Fold the data section into the text section.
302 Print the maximum space (in bytes) and total time (in seconds) used by
307 Print the @code{as} version.
310 Print the @code{as} version and exit.
313 Suppress warning messages.
322 Generate an object file even after errors.
324 @item -- | @var{files} @dots{}
325 Standard input, or source files to assemble.
330 The following options are available when @value{AS} is configured for
335 @cindex ARC endianness
336 @cindex endianness, ARC
337 @cindex big endian output, ARC
339 Generate ``big endian'' format output.
341 @cindex little endian output, ARC
342 @item -mlittle-endian
343 Generate ``little endian'' format output.
349 The following options are available when @value{AS} is configured for the
350 Intel 80960 processor.
353 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
354 Specify which variant of the 960 architecture is the target.
357 Add code to collect statistics about branches taken.
360 Do not alter compare-and-branch instructions for long displacements;
367 The following options are available when @value{AS} is configured for the
368 Motorola 68000 series.
373 Shorten references to undefined symbols, to one word instead of two.
375 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040
376 @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32
377 Specify what processor in the 68000 family is the target. The default
378 is normally the 68020, but this can be changed at configuration time.
380 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
381 The target machine does (or does not) have a floating-point coprocessor.
382 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
383 the basic 68000 is not compatible with the 68881, a combination of the
384 two can be specified, since it's possible to do emulation of the
385 coprocessor instructions with the main processor.
387 @item -m68851 | -mno-68851
388 The target machine does (or does not) have a memory-management
389 unit coprocessor. The default is to assume an MMU for 68020 and up.
395 The following options are available when @code{@value{AS}} is configured
396 for the SPARC architecture:
399 @item -Av6 | -Av7 | -Av8 | -Av9 | -Asparclite
400 Explicitly select a variant of the SPARC architecture.
403 Warn when the assembler switches to another architecture.
408 The following options are available when @value{AS} is configured for
413 This option sets the largest size of an object that can be referenced
414 implicitly with the @code{gp} register. It is only accepted for targets that
415 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
417 @cindex MIPS endianness
418 @cindex endianness, MIPS
419 @cindex big endian output, MIPS
421 Generate ``big endian'' format output.
423 @cindex little endian output, MIPS
425 Generate ``little endian'' format output.
431 Generate code for a particular MIPS Instruction Set Architecture level.
432 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
433 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
438 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
439 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
440 instructions around accesses to the @samp{HI} and @samp{LO} registers.
441 @samp{-no-m4650} turns off this option.
443 @item -mcpu=@var{CPU}
444 Generate code for a particular MIPS cpu. This has little effect on the
445 assembler, but it is passed by @code{@value{GCC}}.
448 @item --emulation=@var{name}
449 This option causes @code{@value{AS}} to emulated @code{@value{AS}} configured
450 for some other target, in all respects, including output format (choosing
451 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
452 debugging information or store symbol table information, and default
453 endianness. The available configuration names are: @samp{mipsecoff},
454 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
455 @samp{mipsbelf}. The first two do not alter the default endianness from that
456 of the primary target for which the assembler was configured; the others change
457 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
458 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
459 selection in any case.
461 This option is currently supported only when the primary target
462 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
463 Furthermore, the primary target or others specified with
464 @samp{--enable-targets=@dots{}} at configuration time must include support for
465 the other format, if both are to be available. For example, the Irix 5
466 configuration includes support for both.
468 Eventually, this option will support more configurations, with more
469 fine-grained control over the assembler's behavior, and will be supported for
473 @code{@value{AS}} ignores this option. It is accepted for compatibility with
480 Control how to deal with multiplication overflow and division by zero.
481 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
482 (and only work for Instruction Set Architecture level 2 and higher);
483 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
489 * Manual:: Structure of this Manual
490 * GNU Assembler:: @value{AS}, the GNU Assembler
491 * Object Formats:: Object File Formats
492 * Command Line:: Command Line
493 * Input Files:: Input Files
494 * Object:: Output (Object) File
495 * Errors:: Error and Warning Messages
499 @section Structure of this Manual
501 @cindex manual, structure and purpose
502 This manual is intended to describe what you need to know to use
503 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
504 notation for symbols, constants, and expressions; the directives that
505 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
508 We also cover special features in the @value{TARGET}
509 configuration of @code{@value{AS}}, including assembler directives.
512 This manual also describes some of the machine-dependent features of
513 various flavors of the assembler.
516 @cindex machine instructions (not covered)
517 On the other hand, this manual is @emph{not} intended as an introduction
518 to programming in assembly language---let alone programming in general!
519 In a similar vein, we make no attempt to introduce the machine
520 architecture; we do @emph{not} describe the instruction set, standard
521 mnemonics, registers or addressing modes that are standard to a
522 particular architecture.
524 You may want to consult the manufacturer's
525 machine architecture manual for this information.
529 For information on the H8/300 machine instruction set, see @cite{H8/300
530 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
531 see @cite{H8/300H Series Programming Manual} (Hitachi).
534 For information on the H8/500 machine instruction set, see @cite{H8/500
535 Series Programming Manual} (Hitachi M21T001).
538 For information on the Hitachi SH machine instruction set, see
539 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
542 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
546 @c I think this is premature---pesch@cygnus.com, 17jan1991
548 Throughout this manual, we assume that you are running @dfn{GNU},
549 the portable operating system from the @dfn{Free Software
550 Foundation, Inc.}. This restricts our attention to certain kinds of
551 computer (in particular, the kinds of computers that @sc{gnu} can run on);
552 once this assumption is granted examples and definitions need less
555 @code{@value{AS}} is part of a team of programs that turn a high-level
556 human-readable series of instructions into a low-level
557 computer-readable series of instructions. Different versions of
558 @code{@value{AS}} are used for different kinds of computer.
561 @c There used to be a section "Terminology" here, which defined
562 @c "contents", "byte", "word", and "long". Defining "word" to any
563 @c particular size is confusing when the .word directive may generate 16
564 @c bits on one machine and 32 bits on another; in general, for the user
565 @c version of this manual, none of these terms seem essential to define.
566 @c They were used very little even in the former draft of the manual;
567 @c this draft makes an effort to avoid them (except in names of
571 @section @value{AS}, the GNU Assembler
573 @sc{gnu} @code{as} is really a family of assemblers.
575 This manual describes @code{@value{AS}}, a member of that family which is
576 configured for the @value{TARGET} architectures.
578 If you use (or have used) the @sc{gnu} assembler on one architecture, you
579 should find a fairly similar environment when you use it on another
580 architecture. Each version has much in common with the others,
581 including object file formats, most assembler directives (often called
582 @dfn{pseudo-ops}) and assembler syntax.@refill
584 @cindex purpose of @sc{gnu} @code{@value{AS}}
585 @code{@value{AS}} is primarily intended to assemble the output of the
586 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
587 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
588 assemble correctly everything that other assemblers for the same
589 machine would assemble.
591 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
594 @c This remark should appear in generic version of manual; assumption
595 @c here is that generic version sets M680x0.
596 This doesn't mean @code{@value{AS}} always uses the same syntax as another
597 assembler for the same architecture; for example, we know of several
598 incompatible versions of 680x0 assembly language syntax.
601 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
602 program in one pass of the source file. This has a subtle impact on the
603 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
606 @section Object File Formats
608 @cindex object file format
609 The @sc{gnu} assembler can be configured to produce several alternative
610 object file formats. For the most part, this does not affect how you
611 write assembly language programs; but directives for debugging symbols
612 are typically different in different file formats. @xref{Symbol
613 Attributes,,Symbol Attributes}.
616 On the @value{TARGET}, @code{@value{AS}} is configured to produce
617 @value{OBJ-NAME} format object files.
619 @c The following should exhaust all configs that set MULTI-OBJ, ideally
621 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
622 @code{a.out} or COFF format object files.
625 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
626 @code{b.out} or COFF format object files.
629 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
630 SOM or ELF format object files.
635 @section Command Line
637 @cindex command line conventions
638 After the program name @code{@value{AS}}, the command line may contain
639 options and file names. Options may appear in any order, and may be
640 before, after, or between file names. The order of file names is
643 @cindex standard input, as input file
645 @file{--} (two hyphens) by itself names the standard input file
646 explicitly, as one of the files for @code{@value{AS}} to assemble.
648 @cindex options, command line
649 Except for @samp{--} any command line argument that begins with a
650 hyphen (@samp{-}) is an option. Each option changes the behavior of
651 @code{@value{AS}}. No option changes the way another option works. An
652 option is a @samp{-} followed by one or more letters; the case of
653 the letter is important. All options are optional.
655 Some options expect exactly one file name to follow them. The file
656 name may either immediately follow the option's letter (compatible
657 with older assemblers) or it may be the next command argument (@sc{gnu}
658 standard). These two command lines are equivalent:
661 @value{AS} -o my-object-file.o mumble.s
662 @value{AS} -omy-object-file.o mumble.s
669 @cindex source program
671 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
672 describe the program input to one run of @code{@value{AS}}. The program may
673 be in one or more files; how the source is partitioned into files
674 doesn't change the meaning of the source.
676 @c I added "con" prefix to "catenation" just to prove I can overcome my
677 @c APL training... pesch@cygnus.com
678 The source program is a concatenation of the text in all the files, in the
681 Each time you run @code{@value{AS}} it assembles exactly one source
682 program. The source program is made up of one or more files.
683 (The standard input is also a file.)
685 You give @code{@value{AS}} a command line that has zero or more input file
686 names. The input files are read (from left file name to right). A
687 command line argument (in any position) that has no special meaning
688 is taken to be an input file name.
690 If you give @code{@value{AS}} no file names it attempts to read one input file
691 from the @code{@value{AS}} standard input, which is normally your terminal. You
692 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
695 Use @samp{--} if you need to explicitly name the standard input file
696 in your command line.
698 If the source is empty, @code{@value{AS}} produces a small, empty object
701 @subheading Filenames and Line-numbers
703 @cindex input file linenumbers
704 @cindex line numbers, in input files
705 There are two ways of locating a line in the input file (or files) and
706 either may be used in reporting error messages. One way refers to a line
707 number in a physical file; the other refers to a line number in a
708 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
710 @dfn{Physical files} are those files named in the command line given
711 to @code{@value{AS}}.
713 @dfn{Logical files} are simply names declared explicitly by assembler
714 directives; they bear no relation to physical files. Logical file names
715 help error messages reflect the original source file, when @code{@value{AS}}
716 source is itself synthesized from other files.
717 @xref{App-File,,@code{.app-file}}.
720 @section Output (Object) File
726 Every time you run @code{@value{AS}} it produces an output file, which is
727 your assembly language program translated into numbers. This file
728 is the object file. Its default name is
736 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
738 You can give it another name by using the @code{-o} option. Conventionally,
739 object file names end with @file{.o}. The default name is used for historical
740 reasons: older assemblers were capable of assembling self-contained programs
741 directly into a runnable program. (For some formats, this isn't currently
742 possible, but it can be done for the @code{a.out} format.)
746 The object file is meant for input to the linker @code{@value{LD}}. It contains
747 assembled program code, information to help @code{@value{LD}} integrate
748 the assembled program into a runnable file, and (optionally) symbolic
749 information for the debugger.
751 @c link above to some info file(s) like the description of a.out.
752 @c don't forget to describe GNU info as well as Unix lossage.
755 @section Error and Warning Messages
757 @cindex error messsages
758 @cindex warning messages
759 @cindex messages from @code{@value{AS}}
760 @code{@value{AS}} may write warnings and error messages to the standard error
761 file (usually your terminal). This should not happen when a compiler
762 runs @code{@value{AS}} automatically. Warnings report an assumption made so
763 that @code{@value{AS}} could keep assembling a flawed program; errors report a
764 grave problem that stops the assembly.
766 @cindex format of warning messages
767 Warning messages have the format
770 file_name:@b{NNN}:Warning Message Text
774 @cindex line numbers, in warnings/errors
775 (where @b{NNN} is a line number). If a logical file name has been given
776 (@pxref{App-File,,@code{.app-file}}) it is used for the filename,
777 otherwise the name of the current input file is used. If a logical line
780 (@pxref{Line,,@code{.line}})
784 (@pxref{Line,,@code{.line}})
787 (@pxref{Ln,,@code{.ln}})
790 then it is used to calculate the number printed,
791 otherwise the actual line in the current source file is printed. The
792 message text is intended to be self explanatory (in the grand Unix
795 @cindex format of error messages
796 Error messages have the format
798 file_name:@b{NNN}:FATAL:Error Message Text
800 The file name and line number are derived as for warning
801 messages. The actual message text may be rather less explanatory
802 because many of them aren't supposed to happen.
805 @chapter Command-Line Options
807 @cindex options, all versions of @code{@value{AS}}
808 This chapter describes command-line options available in @emph{all}
809 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
811 to the @value{TARGET}.
814 to particular machine architectures.
817 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2), you
818 can use the @samp{-Wa} option to pass arguments through to the
819 assembler. The assembler arguments must be separated from each other
820 (and the @samp{-Wa}) by commas. For example:
823 gcc -c -g -O -Wa,-alh,-L file.c
827 emits a listing to standard output with high-level
830 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
831 command-line options are automatically passed to the assembler by the compiler.
832 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
833 precisely what options it passes to each compilation pass, including the
837 * a:: -a[dhlns] enable listings
838 * D:: -D for compatibility
839 * f:: -f to work faster
840 * I:: -I for .include search path
841 @ifclear DIFF-TBL-KLUGE
842 * K:: -K for compatibility
844 @ifset DIFF-TBL-KLUGE
845 * K:: -K for difference tables
848 * L:: -L to retain local labels
849 * M:: -M or --mri to assemble in MRI compatibility mode
850 * o:: -o to name the object file
851 * R:: -R to join data and text sections
852 * statistics:: --statistics to see statistics about assembly
853 * v:: -v to announce version
854 * W:: -W to suppress warnings
855 * Z:: -Z to make object file even after errors
859 @section Enable Listings: @code{-a[dhlns]}
867 @cindex listings, enabling
868 @cindex assembly listings, enabling
870 These options enable listing output from the assembler. By itself,
871 @samp{-a} requests high-level, assembly, and symbols listing.
872 You can use other letters to select specific options for the list:
873 @samp{-ah} requests a high-level language listing,
874 @samp{-al} requests an output-program assembly listing, and
875 @samp{-as} requests a symbol table listing.
876 High-level listings require that a compiler debugging option like
877 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
880 Use the @samp{-ad} option to omit debugging directives from the
883 Once you have specified one of these options, you can further control
884 listing output and its appearance using the directives @code{.list},
885 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
887 The @samp{-an} option turns off all forms processing.
888 If you do not request listing output with one of the @samp{-a} options, the
889 listing-control directives have no effect.
891 The letters after @samp{-a} may be combined into one option,
892 @emph{e.g.}, @samp{-aln}.
898 This option has no effect whatsoever, but it is accepted to make it more
899 likely that scripts written for other assemblers also work with
903 @section Work Faster: @code{-f}
906 @cindex trusted compiler
907 @cindex faster processing (@code{-f})
908 @samp{-f} should only be used when assembling programs written by a
909 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
910 and comment preprocessing on
911 the input file(s) before assembling them. @xref{Preprocessing,
915 @emph{Warning:} if you use @samp{-f} when the files actually need to be
916 preprocessed (if they contain comments, for example), @code{@value{AS}} does
921 @section @code{.include} search path: @code{-I} @var{path}
923 @kindex -I @var{path}
924 @cindex paths for @code{.include}
925 @cindex search path for @code{.include}
926 @cindex @code{include} directive search path
927 Use this option to add a @var{path} to the list of directories
928 @code{@value{AS}} searches for files specified in @code{.include}
929 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
930 many times as necessary to include a variety of paths. The current
931 working directory is always searched first; after that, @code{@value{AS}}
932 searches any @samp{-I} directories in the same order as they were
933 specified (left to right) on the command line.
936 @section Difference Tables: @code{-K}
939 @ifclear DIFF-TBL-KLUGE
940 On the @value{TARGET} family, this option is allowed, but has no effect. It is
941 permitted for compatibility with the @sc{gnu} assembler on other platforms,
942 where it can be used to warn when the assembler alters the machine code
943 generated for @samp{.word} directives in difference tables. The @value{TARGET}
944 family does not have the addressing limitations that sometimes lead to this
945 alteration on other platforms.
948 @ifset DIFF-TBL-KLUGE
949 @cindex difference tables, warning
950 @cindex warning for altered difference tables
951 @code{@value{AS}} sometimes alters the code emitted for directives of the form
952 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
953 You can use the @samp{-K} option if you want a warning issued when this
958 @section Include Local Labels: @code{-L}
961 @cindex local labels, retaining in output
962 Labels beginning with @samp{L} (upper case only) are called @dfn{local
963 labels}. @xref{Symbol Names}. Normally you do not see such labels when
964 debugging, because they are intended for the use of programs (like
965 compilers) that compose assembler programs, not for your notice.
966 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
967 normally debug with them.
969 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
970 in the object file. Usually if you do this you also tell the linker
971 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
973 By default, a local label is any label beginning with @samp{L}, but each
974 target is allowed to redefine the local label prefix.
976 On the HPPA local labels begin with @samp{L$}.
978 @c start-sanitize-arc
980 On the ARC local labels begin with @samp{.L}.
985 @section Assemble in MRI Compatibility Mode: @code{-M}
988 @cindex MRI compatibility mode
989 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
990 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
991 compatible with the @code{ASM68K} assembler from Microtec Research. The exact
992 nature of the MRI syntax will not be documented here; see the MRI manuals for
993 more information. The purpose of this option is to permit assembling existing
994 MRI assembler code using @code{@value{AS}}.
996 The MRI compatibility is not complete. Certain operations of the MRI assembler
997 depend upon its object file format, and can not be supported using other object
998 file formats. Supporting these would require enhancing each object file format
999 individually. These are:
1002 @item global symbols in common section
1004 The MRI assembler supports common sections which are merged by the linker.
1005 Other object file formats do not support this. @code{@value{AS}} handles
1006 common sections by treating them as a single common symbol. It permits local
1007 symbols to be defined within a common section, but it can not support global
1008 symbols, since it has no way to describe them.
1010 @item complex relocations
1012 The MRI assembler supports relocations against a negated section address, and
1013 relocations which combine the start addresses of two or more sections. These
1014 are not support by other object file formats.
1016 @item @code{END} pseudo-op specifying start address
1018 The MRI @code{END} pseudo-op permits the specification of a start address.
1019 This is not supported by other object file formats. The start address may
1020 instead be specified using the @code{-e} option to the linker, or in a linker
1023 @item @code{IDNT} and @code{NAME} pseudo-ops
1025 The MRI @code{IDNT} and @code{NAME} pseudo-ops assign a module name to the
1026 output file. This is not supported by other object file formats.
1028 @item @code{ORG} pseudo-op
1030 The MRI @code{ORG} pseudo-op begins an absolute section at a given address.
1031 This differs from the usual @code{@value{AS}} @code{.org} pseudo-op, which
1032 changes the location within the current section. Absolute sections are not
1033 supported by other object file formats. The address of a section may be
1034 assigned within a linker script.
1037 There are some other features of the MRI assembler which are not supported by
1038 @code{@value{AS}}, typically either because they are difficult or because they
1039 seem of little consequence. Some of these may be supported in future releases.
1043 @item @code{.STARTOF.} and @code{.SIZEOF.} operators
1045 The @code{.STARTOF.} and @code{.SIZEOF.} operators are not supported. They
1046 require linker support.
1048 @item EBCDIC strings
1050 EBCDIC strings are not supported.
1052 @item packed binary coded decimal
1054 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1055 and @code{DCB.P} pseudo-ops are not supported.
1057 @item @code{FEQU} pseudo-op
1059 The @code{FEQU} pseudo-op is not supported.
1061 @item @code{NOOBJ} pseudo-op
1063 The @code{NOOBJ} pseudo-op is not supported.
1065 @item @code{OPT} branch control options
1067 The @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1068 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1069 relaxes all branches, whether forward or backward, to an appropriate size, so
1070 these options serve no purpose.
1072 @item @code{OPT} list control options
1074 The following @code{OPT} list control options are ignored: @code{C},
1075 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1076 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1078 @item other @code{OPT} options
1080 The following @code{OPT} options are ignored: @code{NEST}, @code{O},
1081 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1083 @item @code{OPT} @code{D} option is default
1085 The @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1086 @code{OPT NOD} may be used to turn it off.
1088 @item @code{XREF} pseudo-op.
1090 The @code{XREF} pseudo-op is ignored.
1094 Macros are not supported directly, but are supported by @code{gasp}.
1098 @section Name the Object File: @code{-o}
1101 @cindex naming object file
1102 @cindex object file name
1103 There is always one object file output when you run @code{@value{AS}}. By
1104 default it has the name
1107 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1121 You use this option (which takes exactly one filename) to give the
1122 object file a different name.
1124 Whatever the object file is called, @code{@value{AS}} overwrites any
1125 existing file of the same name.
1128 @section Join Data and Text Sections: @code{-R}
1131 @cindex data and text sections, joining
1132 @cindex text and data sections, joining
1133 @cindex joining text and data sections
1134 @cindex merging text and data sections
1135 @code{-R} tells @code{@value{AS}} to write the object file as if all
1136 data-section data lives in the text section. This is only done at
1137 the very last moment: your binary data are the same, but data
1138 section parts are relocated differently. The data section part of
1139 your object file is zero bytes long because all its bytes are
1140 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1142 When you specify @code{-R} it would be possible to generate shorter
1143 address displacements (because we do not have to cross between text and
1144 data section). We refrain from doing this simply for compatibility with
1145 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1148 When @code{@value{AS}} is configured for COFF output,
1149 this option is only useful if you use sections named @samp{.text} and
1154 @code{-R} is not supported for any of the HPPA targets. Using
1155 @code{-R} generates a warning from @code{@value{AS}}.
1159 @section Display Assembly Statistics: @code{--statistics}
1161 @kindex --statistics
1162 @cindex statistics, about assembly
1163 @cindex time, total for assembly
1164 @cindex space used, maximum for assembly
1165 Use @samp{--statistics} to display two statistics about the resources used by
1166 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1167 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1171 @section Announce Version: @code{-v}
1175 @cindex @code{@value{AS}} version
1176 @cindex version of @code{@value{AS}}
1177 You can find out what version of as is running by including the
1178 option @samp{-v} (which you can also spell as @samp{-version}) on the
1182 @section Suppress Warnings: @code{-W}
1185 @cindex suppressing warnings
1186 @cindex warnings, suppressing
1187 @code{@value{AS}} should never give a warning or error message when
1188 assembling compiler output. But programs written by people often
1189 cause @code{@value{AS}} to give a warning that a particular assumption was
1190 made. All such warnings are directed to the standard error file.
1191 If you use this option, no warnings are issued. This option only
1192 affects the warning messages: it does not change any particular of how
1193 @code{@value{AS}} assembles your file. Errors, which stop the assembly, are
1197 @section Generate Object File in Spite of Errors: @code{-Z}
1198 @cindex object file, after errors
1199 @cindex errors, continuing after
1200 After an error message, @code{@value{AS}} normally produces no output. If for
1201 some reason you are interested in object file output even after
1202 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1203 option. If there are any errors, @code{@value{AS}} continues anyways, and
1204 writes an object file after a final warning message of the form @samp{@var{n}
1205 errors, @var{m} warnings, generating bad object file.}
1210 @cindex machine-independent syntax
1211 @cindex syntax, machine-independent
1212 This chapter describes the machine-independent syntax allowed in a
1213 source file. @code{@value{AS}} syntax is similar to what many other
1214 assemblers use; it is inspired by the BSD 4.2
1219 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1223 * Preprocessing:: Preprocessing
1224 * Whitespace:: Whitespace
1225 * Comments:: Comments
1226 * Symbol Intro:: Symbols
1227 * Statements:: Statements
1228 * Constants:: Constants
1232 @section Preprocessing
1234 @cindex preprocessing
1235 The @code{@value{AS}} internal preprocessor:
1237 @cindex whitespace, removed by preprocessor
1239 adjusts and removes extra whitespace. It leaves one space or tab before
1240 the keywords on a line, and turns any other whitespace on the line into
1243 @cindex comments, removed by preprocessor
1245 removes all comments, replacing them with a single space, or an
1246 appropriate number of newlines.
1248 @cindex constants, converted by preprocessor
1250 converts character constants into the appropriate numeric values.
1253 It does not do macro processing, include file handling, or
1254 anything else you may get from your C compiler's preprocessor. You can
1255 do include file processing with the @code{.include} directive
1256 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1257 to get other ``CPP'' style preprocessing, by giving the input file a
1258 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1259 Output, gcc.info, Using GNU CC}.
1261 Excess whitespace, comments, and character constants
1262 cannot be used in the portions of the input text that are not
1265 @cindex turning preprocessing on and off
1266 @cindex preprocessing, turning on and off
1269 If the first line of an input file is @code{#NO_APP} or if you use the
1270 @samp{-f} option, whitespace and comments are not removed from the input file.
1271 Within an input file, you can ask for whitespace and comment removal in
1272 specific portions of the by putting a line that says @code{#APP} before the
1273 text that may contain whitespace or comments, and putting a line that says
1274 @code{#NO_APP} after this text. This feature is mainly intend to support
1275 @code{asm} statements in compilers whose output is otherwise free of comments
1282 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1283 Whitespace is used to separate symbols, and to make programs neater for
1284 people to read. Unless within character constants
1285 (@pxref{Characters,,Character Constants}), any whitespace means the same
1286 as exactly one space.
1292 There are two ways of rendering comments to @code{@value{AS}}. In both
1293 cases the comment is equivalent to one space.
1295 Anything from @samp{/*} through the next @samp{*/} is a comment.
1296 This means you may not nest these comments.
1300 The only way to include a newline ('\n') in a comment
1301 is to use this sort of comment.
1304 /* This sort of comment does not nest. */
1307 @cindex line comment character
1308 Anything from the @dfn{line comment} character to the next newline
1309 is considered a comment and is ignored. The line comment character is
1310 @c start-sanitize-arc
1312 @samp{;} on the ARC;
1316 @samp{#} on the Vax;
1319 @samp{#} on the i960;
1322 @samp{!} on the SPARC;
1325 @samp{|} on the 680x0;
1328 @samp{;} for the AMD 29K family;
1331 @samp{;} for the H8/300 family;
1334 @samp{!} for the H8/500 family;
1337 @samp{;} for the HPPA;
1340 @samp{!} for the Hitachi SH;
1343 @samp{!} for the Z8000;
1345 see @ref{Machine Dependencies}. @refill
1346 @c FIXME What about i386, m88k, i860?
1349 On some machines there are two different line comment characters. One
1350 character only begins a comment if it is the first non-whitespace character on
1351 a line, while the other always begins a comment.
1355 @cindex lines starting with @code{#}
1356 @cindex logical line numbers
1357 To be compatible with past assemblers, lines that begin with @samp{#} have a
1358 special interpretation. Following the @samp{#} should be an absolute
1359 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1360 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1361 new logical file name. The rest of the line, if any, should be whitespace.
1363 If the first non-whitespace characters on the line are not numeric,
1364 the line is ignored. (Just like a comment.)
1367 # This is an ordinary comment.
1368 # 42-6 "new_file_name" # New logical file name
1369 # This is logical line # 36.
1371 This feature is deprecated, and may disappear from future versions
1372 of @code{@value{AS}}.
1377 @cindex characters used in symbols
1378 @ifclear SPECIAL-SYMS
1379 A @dfn{symbol} is one or more characters chosen from the set of all
1380 letters (both upper and lower case), digits and the three characters
1386 A @dfn{symbol} is one or more characters chosen from the set of all
1387 letters (both upper and lower case), digits and the three characters
1388 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1394 On most machines, you can also use @code{$} in symbol names; exceptions
1395 are noted in @ref{Machine Dependencies}.
1397 No symbol may begin with a digit. Case is significant.
1398 There is no length limit: all characters are significant. Symbols are
1399 delimited by characters not in that set, or by the beginning of a file
1400 (since the source program must end with a newline, the end of a file is
1401 not a possible symbol delimiter). @xref{Symbols}.
1402 @cindex length of symbols
1407 @cindex statements, structure of
1408 @cindex line separator character
1409 @cindex statement separator character
1411 @ifclear abnormal-separator
1412 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1413 semicolon (@samp{;}). The newline or semicolon is considered part of
1414 the preceding statement. Newlines and semicolons within character
1415 constants are an exception: they do not end statements.
1417 @ifset abnormal-separator
1419 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1420 sign (@samp{@@}). The newline or at sign is considered part of the
1421 preceding statement. Newlines and at signs within character constants
1422 are an exception: they do not end statements.
1425 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1426 point (@samp{!}). The newline or exclamation point is considered part of the
1427 preceding statement. Newlines and exclamation points within character
1428 constants are an exception: they do not end statements.
1431 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1432 H8/300) a dollar sign (@samp{$}); or (for the
1435 (@samp{;}). The newline or separator character is considered part of
1436 the preceding statement. Newlines and separators within character
1437 constants are an exception: they do not end statements.
1442 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1443 separator character. (The line separator is usually @samp{;}, unless
1444 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1445 newline or separator character is considered part of the preceding
1446 statement. Newlines and separators within character constants are an
1447 exception: they do not end statements.
1450 @cindex newline, required at file end
1451 @cindex EOF, newline must precede
1452 It is an error to end any statement with end-of-file: the last
1453 character of any input file should be a newline.@refill
1455 @cindex continuing statements
1456 @cindex multi-line statements
1457 @cindex statement on multiple lines
1458 You may write a statement on more than one line if you put a
1459 backslash (@kbd{\}) immediately in front of any newlines within the
1460 statement. When @code{@value{AS}} reads a backslashed newline both
1461 characters are ignored. You can even put backslashed newlines in
1462 the middle of symbol names without changing the meaning of your
1465 An empty statement is allowed, and may include whitespace. It is ignored.
1467 @cindex instructions and directives
1468 @cindex directives and instructions
1469 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1470 @c @defn{} it in that case, as was done previously... pesch@cygnus.com,
1472 A statement begins with zero or more labels, optionally followed by a
1473 key symbol which determines what kind of statement it is. The key
1474 symbol determines the syntax of the rest of the statement. If the
1475 symbol begins with a dot @samp{.} then the statement is an assembler
1476 directive: typically valid for any computer. If the symbol begins with
1477 a letter the statement is an assembly language @dfn{instruction}: it
1478 assembles into a machine language instruction.
1480 Different versions of @code{@value{AS}} for different computers
1481 recognize different instructions. In fact, the same symbol may
1482 represent a different instruction in a different computer's assembly
1486 @cindex @code{:} (label)
1487 @cindex label (@code{:})
1488 A label is a symbol immediately followed by a colon (@code{:}).
1489 Whitespace before a label or after a colon is permitted, but you may not
1490 have whitespace between a label's symbol and its colon. @xref{Labels}.
1493 For HPPA targets, labels need not be immediately followed by a colon, but
1494 the definition of a label must begin in column zero. This also implies that
1495 only one label may be defined on each line.
1499 label: .directive followed by something
1500 another_label: # This is an empty statement.
1501 instruction operand_1, operand_2, @dots{}
1508 A constant is a number, written so that its value is known by
1509 inspection, without knowing any context. Like this:
1512 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1513 .ascii "Ring the bell\7" # A string constant.
1514 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1515 .float 0f-314159265358979323846264338327\
1516 95028841971.693993751E-40 # - pi, a flonum.
1521 * Characters:: Character Constants
1522 * Numbers:: Number Constants
1526 @subsection Character Constants
1528 @cindex character constants
1529 @cindex constants, character
1530 There are two kinds of character constants. A @dfn{character} stands
1531 for one character in one byte and its value may be used in
1532 numeric expressions. String constants (properly called string
1533 @emph{literals}) are potentially many bytes and their values may not be
1534 used in arithmetic expressions.
1538 * Chars:: Characters
1542 @subsubsection Strings
1544 @cindex string constants
1545 @cindex constants, string
1546 A @dfn{string} is written between double-quotes. It may contain
1547 double-quotes or null characters. The way to get special characters
1548 into a string is to @dfn{escape} these characters: precede them with
1549 a backslash @samp{\} character. For example @samp{\\} represents
1550 one backslash: the first @code{\} is an escape which tells
1551 @code{@value{AS}} to interpret the second character literally as a backslash
1552 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1553 escape character). The complete list of escapes follows.
1555 @cindex escape codes, character
1556 @cindex character escape codes
1559 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1562 @cindex @code{\b} (backspace character)
1563 @cindex backspace (@code{\b})
1564 Mnemonic for backspace; for ASCII this is octal code 010.
1567 @c Mnemonic for EOText; for ASCII this is octal code 004.
1570 @cindex @code{\f} (formfeed character)
1571 @cindex formfeed (@code{\f})
1572 Mnemonic for FormFeed; for ASCII this is octal code 014.
1575 @cindex @code{\n} (newline character)
1576 @cindex newline (@code{\n})
1577 Mnemonic for newline; for ASCII this is octal code 012.
1580 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1583 @cindex @code{\r} (carriage return character)
1584 @cindex carriage return (@code{\r})
1585 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1588 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1589 @c other assemblers.
1592 @cindex @code{\t} (tab)
1593 @cindex tab (@code{\t})
1594 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1597 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1598 @c @item \x @var{digit} @var{digit} @var{digit}
1599 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1601 @item \ @var{digit} @var{digit} @var{digit}
1602 @cindex @code{\@var{ddd}} (octal character code)
1603 @cindex octal character code (@code{\@var{ddd}})
1604 An octal character code. The numeric code is 3 octal digits.
1605 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1606 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1609 @item \@code{x} @var{hex-digit} @var{hex-digit}
1610 @cindex @code{\@var{xdd}} (hex character code)
1611 @cindex hex character code (@code{\@var{xdd}})
1612 A hex character code. The numeric code is 2 hexadecimal digits. Either
1613 upper or lower case @code{x} works.
1617 @cindex @code{\\} (@samp{\} character)
1618 @cindex backslash (@code{\\})
1619 Represents one @samp{\} character.
1622 @c Represents one @samp{'} (accent acute) character.
1623 @c This is needed in single character literals
1624 @c (@xref{Characters,,Character Constants}.) to represent
1628 @cindex @code{\"} (doublequote character)
1629 @cindex doublequote (@code{\"})
1630 Represents one @samp{"} character. Needed in strings to represent
1631 this character, because an unescaped @samp{"} would end the string.
1633 @item \ @var{anything-else}
1634 Any other character when escaped by @kbd{\} gives a warning, but
1635 assembles as if the @samp{\} was not present. The idea is that if
1636 you used an escape sequence you clearly didn't want the literal
1637 interpretation of the following character. However @code{@value{AS}} has no
1638 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
1639 code and warns you of the fact.
1642 Which characters are escapable, and what those escapes represent,
1643 varies widely among assemblers. The current set is what we think
1644 the BSD 4.2 assembler recognizes, and is a subset of what most C
1645 compilers recognize. If you are in doubt, do not use an escape
1649 @subsubsection Characters
1651 @cindex single character constant
1652 @cindex character, single
1653 @cindex constant, single character
1654 A single character may be written as a single quote immediately
1655 followed by that character. The same escapes apply to characters as
1656 to strings. So if you want to write the character backslash, you
1657 must write @kbd{'\\} where the first @code{\} escapes the second
1658 @code{\}. As you can see, the quote is an acute accent, not a
1659 grave accent. A newline
1661 @ifclear abnormal-separator
1662 (or semicolon @samp{;})
1664 @ifset abnormal-separator
1666 (or at sign @samp{@@})
1669 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
1675 immediately following an acute accent is taken as a literal character
1676 and does not count as the end of a statement. The value of a character
1677 constant in a numeric expression is the machine's byte-wide code for
1678 that character. @code{@value{AS}} assumes your character code is ASCII:
1679 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
1682 @subsection Number Constants
1684 @cindex constants, number
1685 @cindex number constants
1686 @code{@value{AS}} distinguishes three kinds of numbers according to how they
1687 are stored in the target machine. @emph{Integers} are numbers that
1688 would fit into an @code{int} in the C language. @emph{Bignums} are
1689 integers, but they are stored in more than 32 bits. @emph{Flonums}
1690 are floating point numbers, described below.
1693 * Integers:: Integers
1698 * Bit Fields:: Bit Fields
1704 @subsubsection Integers
1706 @cindex constants, integer
1708 @cindex binary integers
1709 @cindex integers, binary
1710 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
1711 the binary digits @samp{01}.
1713 @cindex octal integers
1714 @cindex integers, octal
1715 An octal integer is @samp{0} followed by zero or more of the octal
1716 digits (@samp{01234567}).
1718 @cindex decimal integers
1719 @cindex integers, decimal
1720 A decimal integer starts with a non-zero digit followed by zero or
1721 more digits (@samp{0123456789}).
1723 @cindex hexadecimal integers
1724 @cindex integers, hexadecimal
1725 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
1726 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
1728 Integers have the usual values. To denote a negative integer, use
1729 the prefix operator @samp{-} discussed under expressions
1730 (@pxref{Prefix Ops,,Prefix Operators}).
1733 @subsubsection Bignums
1736 @cindex constants, bignum
1737 A @dfn{bignum} has the same syntax and semantics as an integer
1738 except that the number (or its negative) takes more than 32 bits to
1739 represent in binary. The distinction is made because in some places
1740 integers are permitted while bignums are not.
1743 @subsubsection Flonums
1745 @cindex floating point numbers
1746 @cindex constants, floating point
1748 @cindex precision, floating point
1749 A @dfn{flonum} represents a floating point number. The translation is
1750 indirect: a decimal floating point number from the text is converted by
1751 @code{@value{AS}} to a generic binary floating point number of more than
1752 sufficient precision. This generic floating point number is converted
1753 to a particular computer's floating point format (or formats) by a
1754 portion of @code{@value{AS}} specialized to that computer.
1756 A flonum is written by writing (in order)
1761 (@samp{0} is optional on the HPPA.)
1765 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
1767 @kbd{e} is recommended. Case is not important.
1769 @c FIXME: verify if flonum syntax really this vague for most cases
1770 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
1771 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
1774 On the H8/300, H8/500,
1776 and AMD 29K architectures, the letter must be
1777 one of the letters @samp{DFPRSX} (in upper or lower case).
1779 @c start-sanitize-arc
1780 On the ARC, the letter one of the letters @samp{DFRS}
1781 (in upper or lower case).
1784 On the Intel 960 architecture, the letter must be
1785 one of the letters @samp{DFT} (in upper or lower case).
1787 On the HPPA architecture, the letter must be @samp{E} (upper case only).
1791 One of the letters @samp{DFPRSX} (in upper or lower case).
1793 @c start-sanitize-arc
1795 One of the letters @samp{DFRS} (in upper or lower case).
1799 One of the letters @samp{DFPRSX} (in upper or lower case).
1802 One of the letters @samp{DFT} (in upper or lower case).
1805 The letter @samp{E} (upper case only).
1810 An optional sign: either @samp{+} or @samp{-}.
1813 An optional @dfn{integer part}: zero or more decimal digits.
1816 An optional @dfn{fractional part}: @samp{.} followed by zero
1817 or more decimal digits.
1820 An optional exponent, consisting of:
1824 An @samp{E} or @samp{e}.
1825 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
1826 @c principle this can perfectly well be different on different targets.
1828 Optional sign: either @samp{+} or @samp{-}.
1830 One or more decimal digits.
1835 At least one of the integer part or the fractional part must be
1836 present. The floating point number has the usual base-10 value.
1838 @code{@value{AS}} does all processing using integers. Flonums are computed
1839 independently of any floating point hardware in the computer running
1844 @c Bit fields are written as a general facility but are also controlled
1845 @c by a conditional-compilation flag---which is as of now (21mar91)
1846 @c turned on only by the i960 config of GAS.
1848 @subsubsection Bit Fields
1851 @cindex constants, bit field
1852 You can also define numeric constants as @dfn{bit fields}.
1853 specify two numbers separated by a colon---
1855 @var{mask}:@var{value}
1858 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
1861 The resulting number is then packed
1863 @c this conditional paren in case bit fields turned on elsewhere than 960
1864 (in host-dependent byte order)
1866 into a field whose width depends on which assembler directive has the
1867 bit-field as its argument. Overflow (a result from the bitwise and
1868 requiring more binary digits to represent) is not an error; instead,
1869 more constants are generated, of the specified width, beginning with the
1870 least significant digits.@refill
1872 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
1873 @code{.short}, and @code{.word} accept bit-field arguments.
1878 @chapter Sections and Relocation
1883 * Secs Background:: Background
1884 * Ld Sections:: @value{LD} Sections
1885 * As Sections:: @value{AS} Internal Sections
1886 * Sub-Sections:: Sub-Sections
1890 @node Secs Background
1893 Roughly, a section is a range of addresses, with no gaps; all data
1894 ``in'' those addresses is treated the same for some particular purpose.
1895 For example there may be a ``read only'' section.
1897 @cindex linker, and assembler
1898 @cindex assembler, and linker
1899 The linker @code{@value{LD}} reads many object files (partial programs) and
1900 combines their contents to form a runnable program. When @code{@value{AS}}
1901 emits an object file, the partial program is assumed to start at address 0.
1902 @code{@value{LD}} assigns the final addresses for the partial program, so that
1903 different partial programs do not overlap. This is actually an
1904 oversimplification, but it suffices to explain how @code{@value{AS}} uses
1907 @code{@value{LD}} moves blocks of bytes of your program to their run-time
1908 addresses. These blocks slide to their run-time addresses as rigid
1909 units; their length does not change and neither does the order of bytes
1910 within them. Such a rigid unit is called a @emph{section}. Assigning
1911 run-time addresses to sections is called @dfn{relocation}. It includes
1912 the task of adjusting mentions of object-file addresses so they refer to
1913 the proper run-time addresses.
1915 For the H8/300 and H8/500,
1916 and for the Hitachi SH,
1917 @code{@value{AS}} pads sections if needed to
1918 ensure they end on a word (sixteen bit) boundary.
1921 @cindex standard @code{@value{AS}} sections
1922 An object file written by @code{@value{AS}} has at least three sections, any
1923 of which may be empty. These are named @dfn{text}, @dfn{data} and
1928 When it generates COFF output,
1930 @code{@value{AS}} can also generate whatever other named sections you specify
1931 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
1932 If you do not use any directives that place output in the @samp{.text}
1933 or @samp{.data} sections, these sections still exist, but are empty.
1938 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
1940 @code{@value{AS}} can also generate whatever other named sections you
1941 specify using the @samp{.space} and @samp{.subspace} directives. See
1942 @cite{HP9000 Series 800 Assembly Language Reference Manual}
1943 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
1944 assembler directives.
1947 Additionally, @code{@value{AS}} uses different names for the standard
1948 text, data, and bss sections when generating SOM output. Program text
1949 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
1950 BSS into @samp{$BSS$}.
1954 Within the object file, the text section starts at address @code{0}, the
1955 data section follows, and the bss section follows the data section.
1958 When generating either SOM or ELF output files on the HPPA, the text
1959 section starts at address @code{0}, the data section at address
1960 @code{0x4000000}, and the bss section follows the data section.
1963 To let @code{@value{LD}} know which data changes when the sections are
1964 relocated, and how to change that data, @code{@value{AS}} also writes to the
1965 object file details of the relocation needed. To perform relocation
1966 @code{@value{LD}} must know, each time an address in the object
1970 Where in the object file is the beginning of this reference to
1973 How long (in bytes) is this reference?
1975 Which section does the address refer to? What is the numeric value of
1977 (@var{address}) @minus{} (@var{start-address of section})?
1980 Is the reference to an address ``Program-Counter relative''?
1983 @cindex addresses, format of
1984 @cindex section-relative addressing
1985 In fact, every address @code{@value{AS}} ever uses is expressed as
1987 (@var{section}) + (@var{offset into section})
1990 Further, most expressions @code{@value{AS}} computes have this section-relative
1993 (For some object formats, such as SOM for the HPPA, some expressions are
1994 symbol-relative instead.)
1997 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
1998 @var{N} into section @var{secname}.''
2000 Apart from text, data and bss sections you need to know about the
2001 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2002 addresses in the absolute section remain unchanged. For example, address
2003 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2004 @code{@value{LD}}. Although the linker never arranges two partial programs'
2005 data sections with overlapping addresses after linking, @emph{by definition}
2006 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2007 part of a program is always the same address when the program is running as
2008 address @code{@{absolute@ 239@}} in any other part of the program.
2010 The idea of sections is extended to the @dfn{undefined} section. Any
2011 address whose section is unknown at assembly time is by definition
2012 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2013 Since numbers are always defined, the only way to generate an undefined
2014 address is to mention an undefined symbol. A reference to a named
2015 common block would be such a symbol: its value is unknown at assembly
2016 time so it has section @emph{undefined}.
2018 By analogy the word @emph{section} is used to describe groups of sections in
2019 the linked program. @code{@value{LD}} puts all partial programs' text
2020 sections in contiguous addresses in the linked program. It is
2021 customary to refer to the @emph{text section} of a program, meaning all
2022 the addresses of all partial programs' text sections. Likewise for
2023 data and bss sections.
2025 Some sections are manipulated by @code{@value{LD}}; others are invented for
2026 use of @code{@value{AS}} and have no meaning except during assembly.
2029 @section @value{LD} Sections
2030 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2035 @cindex named sections
2036 @cindex sections, named
2037 @item named sections
2040 @cindex text section
2041 @cindex data section
2045 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2046 separate but equal sections. Anything you can say of one section is
2049 When the program is running, however, it is
2050 customary for the text section to be unalterable. The
2051 text section is often shared among processes: it contains
2052 instructions, constants and the like. The data section of a running
2053 program is usually alterable: for example, C variables would be stored
2054 in the data section.
2059 This section contains zeroed bytes when your program begins running. It
2060 is used to hold unitialized variables or common storage. The length of
2061 each partial program's bss section is important, but because it starts
2062 out containing zeroed bytes there is no need to store explicit zero
2063 bytes in the object file. The bss section was invented to eliminate
2064 those explicit zeros from object files.
2066 @cindex absolute section
2067 @item absolute section
2068 Address 0 of this section is always ``relocated'' to runtime address 0.
2069 This is useful if you want to refer to an address that @code{@value{LD}} must
2070 not change when relocating. In this sense we speak of absolute
2071 addresses being ``unrelocatable'': they do not change during relocation.
2073 @cindex undefined section
2074 @item undefined section
2075 This ``section'' is a catch-all for address references to objects not in
2076 the preceding sections.
2077 @c FIXME: ref to some other doc on obj-file formats could go here.
2080 @cindex relocation example
2081 An idealized example of three relocatable sections follows.
2083 The example uses the traditional section names @samp{.text} and @samp{.data}.
2085 Memory addresses are on the horizontal axis.
2089 @c END TEXI2ROFF-KILL
2092 partial program # 1: |ttttt|dddd|00|
2099 partial program # 2: |TTT|DDD|000|
2102 +--+---+-----+--+----+---+-----+~~
2103 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2104 +--+---+-----+--+----+---+-----+~~
2106 addresses: 0 @dots{}
2113 \line{\it Partial program \#1: \hfil}
2114 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2115 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2117 \line{\it Partial program \#2: \hfil}
2118 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2119 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2121 \line{\it linked program: \hfil}
2122 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2123 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2124 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2125 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2127 \line{\it addresses: \hfil}
2131 @c END TEXI2ROFF-KILL
2134 @section @value{AS} Internal Sections
2136 @cindex internal @code{@value{AS}} sections
2137 @cindex sections in messages, internal
2138 These sections are meant only for the internal use of @code{@value{AS}}. They
2139 have no meaning at run-time. You do not really need to know about these
2140 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2141 warning messages, so it might be helpful to have an idea of their
2142 meanings to @code{@value{AS}}. These sections are used to permit the
2143 value of every expression in your assembly language program to be a
2144 section-relative address.
2147 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2148 @cindex assembler internal logic error
2149 An internal assembler logic error has been found. This means there is a
2150 bug in the assembler.
2153 @cindex expr (internal section)
2154 The assembler stores complex expression internally as combinations of
2155 symbols. When it needs to represent an expression as a symbol, it puts
2156 it in the expr section.
2158 @c FIXME item transfer[t] vector preload
2159 @c FIXME item transfer[t] vector postload
2160 @c FIXME item register
2164 @section Sub-Sections
2166 @cindex numbered subsections
2167 @cindex grouping data
2173 fall into two sections: text and data.
2175 You may have separate groups of
2177 data in named sections
2181 data in named sections
2187 that you want to end up near to each other in the object file, even though they
2188 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2189 use @dfn{subsections} for this purpose. Within each section, there can be
2190 numbered subsections with values from 0 to 8192. Objects assembled into the
2191 same subsection go into the object file together with other objects in the same
2192 subsection. For example, a compiler might want to store constants in the text
2193 section, but might not want to have them interspersed with the program being
2194 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2195 section of code being output, and a @samp{.text 1} before each group of
2196 constants being output.
2198 Subsections are optional. If you do not use subsections, everything
2199 goes in subsection number zero.
2202 Each subsection is zero-padded up to a multiple of four bytes.
2203 (Subsections may be padded a different amount on different flavors
2204 of @code{@value{AS}}.)
2208 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2209 boundary (two bytes).
2210 The same is true on the Hitachi SH.
2213 @c FIXME section padding (alignment)?
2214 @c Rich Pixley says padding here depends on target obj code format; that
2215 @c doesn't seem particularly useful to say without further elaboration,
2216 @c so for now I say nothing about it. If this is a generic BFD issue,
2217 @c these paragraphs might need to vanish from this manual, and be
2218 @c discussed in BFD chapter of binutils (or some such).
2221 On the AMD 29K family, no particular padding is added to section or
2222 subsection sizes; @value{AS} forces no alignment on this platform.
2226 Subsections appear in your object file in numeric order, lowest numbered
2227 to highest. (All this to be compatible with other people's assemblers.)
2228 The object file contains no representation of subsections; @code{@value{LD}} and
2229 other programs that manipulate object files see no trace of them.
2230 They just see all your text subsections as a text section, and all your
2231 data subsections as a data section.
2233 To specify which subsection you want subsequent statements assembled
2234 into, use a numeric argument to specify it, in a @samp{.text
2235 @var{expression}} or a @samp{.data @var{expression}} statement.
2238 When generating COFF output, you
2243 can also use an extra subsection
2244 argument with arbitrary named sections: @samp{.section @var{name},
2247 @var{Expression} should be an absolute expression.
2248 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2249 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2250 begins in @code{text 0}. For instance:
2252 .text 0 # The default subsection is text 0 anyway.
2253 .ascii "This lives in the first text subsection. *"
2255 .ascii "But this lives in the second text subsection."
2257 .ascii "This lives in the data section,"
2258 .ascii "in the first data subsection."
2260 .ascii "This lives in the first text section,"
2261 .ascii "immediately following the asterisk (*)."
2264 Each section has a @dfn{location counter} incremented by one for every byte
2265 assembled into that section. Because subsections are merely a convenience
2266 restricted to @code{@value{AS}} there is no concept of a subsection location
2267 counter. There is no way to directly manipulate a location counter---but the
2268 @code{.align} directive changes it, and any label definition captures its
2269 current value. The location counter of the section where statements are being
2270 assembled is said to be the @dfn{active} location counter.
2273 @section bss Section
2276 @cindex common variable storage
2277 The bss section is used for local common variable storage.
2278 You may allocate address space in the bss section, but you may
2279 not dictate data to load into it before your program executes. When
2280 your program starts running, all the contents of the bss
2281 section are zeroed bytes.
2283 Addresses in the bss section are allocated with special directives; you
2284 may not assemble anything directly into the bss section. Hence there
2285 are no bss subsections. @xref{Comm,,@code{.comm}},
2286 @pxref{Lcomm,,@code{.lcomm}}.
2292 Symbols are a central concept: the programmer uses symbols to name
2293 things, the linker uses symbols to link, and the debugger uses symbols
2297 @cindex debuggers, and symbol order
2298 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2299 the same order they were declared. This may break some debuggers.
2304 * Setting Symbols:: Giving Symbols Other Values
2305 * Symbol Names:: Symbol Names
2306 * Dot:: The Special Dot Symbol
2307 * Symbol Attributes:: Symbol Attributes
2314 A @dfn{label} is written as a symbol immediately followed by a colon
2315 @samp{:}. The symbol then represents the current value of the
2316 active location counter, and is, for example, a suitable instruction
2317 operand. You are warned if you use the same symbol to represent two
2318 different locations: the first definition overrides any other
2322 On the HPPA, the usual form for a label need not be immediately followed by a
2323 colon, but instead must start in column zero. Only one label may be defined on
2324 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2325 provides a special directive @code{.label} for defining labels more flexibly.
2328 @node Setting Symbols
2329 @section Giving Symbols Other Values
2331 @cindex assigning values to symbols
2332 @cindex symbol values, assigning
2333 A symbol can be given an arbitrary value by writing a symbol, followed
2334 by an equals sign @samp{=}, followed by an expression
2335 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2336 directive. @xref{Set,,@code{.set}}.
2339 @section Symbol Names
2341 @cindex symbol names
2342 @cindex names, symbol
2343 @ifclear SPECIAL-SYMS
2344 Symbol names begin with a letter or with one of @samp{._}. On most
2345 machines, you can also use @code{$} in symbol names; exceptions are
2346 noted in @ref{Machine Dependencies}. That character may be followed by any
2347 string of digits, letters, dollar signs (unless otherwise noted in
2348 @ref{Machine Dependencies}), and underscores.
2351 For the AMD 29K family, @samp{?} is also allowed in the
2352 body of a symbol name, though not at its beginning.
2357 Symbol names begin with a letter or with one of @samp{._}. On the
2359 H8/500, you can also use @code{$} in symbol names. That character may
2360 be followed by any string of digits, letters, dollar signs (save on the
2361 H8/300), and underscores.
2365 Case of letters is significant: @code{foo} is a different symbol name
2368 Each symbol has exactly one name. Each name in an assembly language program
2369 refers to exactly one symbol. You may use that symbol name any number of times
2372 @subheading Local Symbol Names
2374 @cindex local symbol names
2375 @cindex symbol names, local
2376 @cindex temporary symbol names
2377 @cindex symbol names, temporary
2378 Local symbols help compilers and programmers use names temporarily.
2379 There are ten local symbol names, which are re-used throughout the
2380 program. You may refer to them using the names @samp{0} @samp{1}
2381 @dots{} @samp{9}. To define a local symbol, write a label of the form
2382 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2383 recent previous definition of that symbol write @samp{@b{N}b}, using the
2384 same digit as when you defined the label. To refer to the next
2385 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2386 a choice of 10 forward references. The @samp{b} stands for
2387 ``backwards'' and the @samp{f} stands for ``forwards''.
2389 Local symbols are not emitted by the current @sc{gnu} C compiler.
2391 There is no restriction on how you can use these labels, but
2392 remember that at any point in the assembly you can refer to at most
2393 10 prior local labels and to at most 10 forward local labels.
2395 Local symbol names are only a notation device. They are immediately
2396 transformed into more conventional symbol names before the assembler
2397 uses them. The symbol names stored in the symbol table, appearing in
2398 error messages and optionally emitted to the object file have these
2403 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2404 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2405 used for symbols you are never intended to see. If you use the
2406 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2407 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2408 you may use them in debugging.
2411 If the label is written @samp{0:} then the digit is @samp{0}.
2412 If the label is written @samp{1:} then the digit is @samp{1}.
2413 And so on up through @samp{9:}.
2416 This unusual character is included so you do not accidentally invent
2417 a symbol of the same name. The character has ASCII value
2420 @item @emph{ordinal number}
2421 This is a serial number to keep the labels distinct. The first
2422 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2423 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2427 For instance, the first @code{1:} is named @code{L1@ctrl{A}1}, the 44th
2428 @code{3:} is named @code{L3@ctrl{A}44}.
2431 @section The Special Dot Symbol
2433 @cindex dot (symbol)
2434 @cindex @code{.} (symbol)
2435 @cindex current address
2436 @cindex location counter
2437 The special symbol @samp{.} refers to the current address that
2438 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2439 .long .} defines @code{melvin} to contain its own address.
2440 Assigning a value to @code{.} is treated the same as a @code{.org}
2441 directive. Thus, the expression @samp{.=.+4} is the same as saying
2442 @ifclear no-space-dir
2451 @node Symbol Attributes
2452 @section Symbol Attributes
2454 @cindex symbol attributes
2455 @cindex attributes, symbol
2456 Every symbol has, as well as its name, the attributes ``Value'' and
2457 ``Type''. Depending on output format, symbols can also have auxiliary
2460 The detailed definitions are in @file{a.out.h}.
2463 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2464 all these attributes, and probably won't warn you. This makes the
2465 symbol an externally defined symbol, which is generally what you
2469 * Symbol Value:: Value
2470 * Symbol Type:: Type
2473 * a.out Symbols:: Symbol Attributes: @code{a.out}
2477 * a.out Symbols:: Symbol Attributes: @code{a.out}
2480 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2485 * COFF Symbols:: Symbol Attributes for COFF
2488 * SOM Symbols:: Symbol Attributes for SOM
2495 @cindex value of a symbol
2496 @cindex symbol value
2497 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2498 location in the text, data, bss or absolute sections the value is the
2499 number of addresses from the start of that section to the label.
2500 Naturally for text, data and bss sections the value of a symbol changes
2501 as @code{@value{LD}} changes section base addresses during linking. Absolute
2502 symbols' values do not change during linking: that is why they are
2505 The value of an undefined symbol is treated in a special way. If it is
2506 0 then the symbol is not defined in this assembler source file, and
2507 @code{@value{LD}} tries to determine its value from other files linked into the
2508 same program. You make this kind of symbol simply by mentioning a symbol
2509 name without defining it. A non-zero value represents a @code{.comm}
2510 common declaration. The value is how much common storage to reserve, in
2511 bytes (addresses). The symbol refers to the first address of the
2517 @cindex type of a symbol
2519 The type attribute of a symbol contains relocation (section)
2520 information, any flag settings indicating that a symbol is external, and
2521 (optionally), other information for linkers and debuggers. The exact
2522 format depends on the object-code output format in use.
2527 @c The following avoids a "widow" subsection title. @group would be
2528 @c better if it were available outside examples.
2531 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2533 @cindex @code{b.out} symbol attributes
2534 @cindex symbol attributes, @code{b.out}
2535 These symbol attributes appear only when @code{@value{AS}} is configured for
2536 one of the Berkeley-descended object output formats---@code{a.out} or
2542 @subsection Symbol Attributes: @code{a.out}
2544 @cindex @code{a.out} symbol attributes
2545 @cindex symbol attributes, @code{a.out}
2551 @subsection Symbol Attributes: @code{a.out}
2553 @cindex @code{a.out} symbol attributes
2554 @cindex symbol attributes, @code{a.out}
2558 * Symbol Desc:: Descriptor
2559 * Symbol Other:: Other
2563 @subsubsection Descriptor
2565 @cindex descriptor, of @code{a.out} symbol
2566 This is an arbitrary 16-bit value. You may establish a symbol's
2567 descriptor value by using a @code{.desc} statement
2568 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2572 @subsubsection Other
2574 @cindex other attribute, of @code{a.out} symbol
2575 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2580 @subsection Symbol Attributes for COFF
2582 @cindex COFF symbol attributes
2583 @cindex symbol attributes, COFF
2585 The COFF format supports a multitude of auxiliary symbol attributes;
2586 like the primary symbol attributes, they are set between @code{.def} and
2587 @code{.endef} directives.
2589 @subsubsection Primary Attributes
2591 @cindex primary attributes, COFF symbols
2592 The symbol name is set with @code{.def}; the value and type,
2593 respectively, with @code{.val} and @code{.type}.
2595 @subsubsection Auxiliary Attributes
2597 @cindex auxiliary attributes, COFF symbols
2598 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2599 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2600 information for COFF.
2605 @subsection Symbol Attributes for SOM
2607 @cindex SOM symbol attributes
2608 @cindex symbol attributes, SOM
2610 The SOM format for the HPPA supports a multitude of symbol attributes set with
2611 the @code{.EXPORT} and @code{.IMPORT} directives.
2613 The attributes are described in @cite{HP9000 Series 800 Assembly
2614 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
2615 @code{EXPORT} assembler directive documentation.
2619 @chapter Expressions
2623 @cindex numeric values
2624 An @dfn{expression} specifies an address or numeric value.
2625 Whitespace may precede and/or follow an expression.
2627 The result of an expression must be an absolute number, or else an offset into
2628 a particular section. If an expression is not absolute, and there is not
2629 enough information when @code{@value{AS}} sees the expression to know its
2630 section, a second pass over the source program might be necessary to interpret
2631 the expression---but the second pass is currently not implemented.
2632 @code{@value{AS}} aborts with an error message in this situation.
2635 * Empty Exprs:: Empty Expressions
2636 * Integer Exprs:: Integer Expressions
2640 @section Empty Expressions
2642 @cindex empty expressions
2643 @cindex expressions, empty
2644 An empty expression has no value: it is just whitespace or null.
2645 Wherever an absolute expression is required, you may omit the
2646 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
2647 is compatible with other assemblers.
2650 @section Integer Expressions
2652 @cindex integer expressions
2653 @cindex expressions, integer
2654 An @dfn{integer expression} is one or more @emph{arguments} delimited
2655 by @emph{operators}.
2658 * Arguments:: Arguments
2659 * Operators:: Operators
2660 * Prefix Ops:: Prefix Operators
2661 * Infix Ops:: Infix Operators
2665 @subsection Arguments
2667 @cindex expression arguments
2668 @cindex arguments in expressions
2669 @cindex operands in expressions
2670 @cindex arithmetic operands
2671 @dfn{Arguments} are symbols, numbers or subexpressions. In other
2672 contexts arguments are sometimes called ``arithmetic operands''. In
2673 this manual, to avoid confusing them with the ``instruction operands'' of
2674 the machine language, we use the term ``argument'' to refer to parts of
2675 expressions only, reserving the word ``operand'' to refer only to machine
2676 instruction operands.
2678 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
2679 @var{section} is one of text, data, bss, absolute,
2680 or undefined. @var{NNN} is a signed, 2's complement 32 bit
2683 Numbers are usually integers.
2685 A number can be a flonum or bignum. In this case, you are warned
2686 that only the low order 32 bits are used, and @code{@value{AS}} pretends
2687 these 32 bits are an integer. You may write integer-manipulating
2688 instructions that act on exotic constants, compatible with other
2691 @cindex subexpressions
2692 Subexpressions are a left parenthesis @samp{(} followed by an integer
2693 expression, followed by a right parenthesis @samp{)}; or a prefix
2694 operator followed by an argument.
2697 @subsection Operators
2699 @cindex operators, in expressions
2700 @cindex arithmetic functions
2701 @cindex functions, in expressions
2702 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
2703 operators are followed by an argument. Infix operators appear
2704 between their arguments. Operators may be preceded and/or followed by
2708 @subsection Prefix Operator
2710 @cindex prefix operators
2711 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
2712 one argument, which must be absolute.
2714 @c the tex/end tex stuff surrounding this small table is meant to make
2715 @c it align, on the printed page, with the similar table in the next
2716 @c section (which is inside an enumerate).
2718 \global\advance\leftskip by \itemindent
2723 @dfn{Negation}. Two's complement negation.
2725 @dfn{Complementation}. Bitwise not.
2729 \global\advance\leftskip by -\itemindent
2733 @subsection Infix Operators
2735 @cindex infix operators
2736 @cindex operators, permitted arguments
2737 @dfn{Infix operators} take two arguments, one on either side. Operators
2738 have precedence, but operations with equal precedence are performed left
2739 to right. Apart from @code{+} or @code{-}, both arguments must be
2740 absolute, and the result is absolute.
2743 @cindex operator precedence
2744 @cindex precedence of operators
2751 @dfn{Multiplication}.
2754 @dfn{Division}. Truncation is the same as the C operator @samp{/}
2761 @dfn{Shift Left}. Same as the C operator @samp{<<}.
2765 @dfn{Shift Right}. Same as the C operator @samp{>>}.
2769 Intermediate precedence
2774 @dfn{Bitwise Inclusive Or}.
2780 @dfn{Bitwise Exclusive Or}.
2783 @dfn{Bitwise Or Not}.
2791 @cindex addition, permitted arguments
2792 @cindex plus, permitted arguments
2793 @cindex arguments for addition
2794 @dfn{Addition}. If either argument is absolute, the result has the section of
2795 the other argument. You may not add together arguments from different
2799 @cindex subtraction, permitted arguments
2800 @cindex minus, permitted arguments
2801 @cindex arguments for subtraction
2802 @dfn{Subtraction}. If the right argument is absolute, the
2803 result has the section of the left argument.
2804 If both arguments are in the same section, the result is absolute.
2805 You may not subtract arguments from different sections.
2806 @c FIXME is there still something useful to say about undefined - undefined ?
2810 In short, it's only meaningful to add or subtract the @emph{offsets} in an
2811 address; you can only have a defined section in one of the two arguments.
2814 @chapter Assembler Directives
2816 @cindex directives, machine independent
2817 @cindex pseudo-ops, machine independent
2818 @cindex machine independent directives
2819 All assembler directives have names that begin with a period (@samp{.}).
2820 The rest of the name is letters, usually in lower case.
2822 This chapter discusses directives that are available regardless of the
2823 target machine configuration for the @sc{gnu} assembler.
2825 Some machine configurations provide additional directives.
2826 @xref{Machine Dependencies}.
2829 @ifset machine-directives
2830 @xref{Machine Dependencies} for additional directives.
2835 * Abort:: @code{.abort}
2837 * ABORT:: @code{.ABORT}
2840 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
2841 * App-File:: @code{.app-file @var{string}}
2842 * Ascii:: @code{.ascii "@var{string}"}@dots{}
2843 * Asciz:: @code{.asciz "@var{string}"}@dots{}
2844 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
2845 * Byte:: @code{.byte @var{expressions}}
2846 * Comm:: @code{.comm @var{symbol} , @var{length} }
2847 * Data:: @code{.data @var{subsection}}
2849 * Def:: @code{.def @var{name}}
2852 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
2858 * Double:: @code{.double @var{flonums}}
2859 * Eject:: @code{.eject}
2860 * Else:: @code{.else}
2862 * Endef:: @code{.endef}
2865 * Endif:: @code{.endif}
2866 * Equ:: @code{.equ @var{symbol}, @var{expression}}
2867 * Extern:: @code{.extern}
2868 @ifclear no-file-dir
2869 * File:: @code{.file @var{string}}
2872 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
2873 * Float:: @code{.float @var{flonums}}
2874 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
2875 * hword:: @code{.hword @var{expressions}}
2876 * Ident:: @code{.ident}
2877 * If:: @code{.if @var{absolute expression}}
2878 * Include:: @code{.include "@var{file}"}
2879 * Int:: @code{.int @var{expressions}}
2880 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
2881 * Lflags:: @code{.lflags}
2882 @ifclear no-line-dir
2883 * Line:: @code{.line @var{line-number}}
2886 * Ln:: @code{.ln @var{line-number}}
2887 * List:: @code{.list}
2888 * Long:: @code{.long @var{expressions}}
2890 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
2893 * Nolist:: @code{.nolist}
2894 * Octa:: @code{.octa @var{bignums}}
2895 * Org:: @code{.org @var{new-lc} , @var{fill}}
2896 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
2897 * Psize:: @code{.psize @var{lines}, @var{columns}}
2898 * Quad:: @code{.quad @var{bignums}}
2899 * Sbttl:: @code{.sbttl "@var{subheading}"}
2901 * Scl:: @code{.scl @var{class}}
2904 * Section:: @code{.section @var{name}, @var{subsection}}
2907 * Set:: @code{.set @var{symbol}, @var{expression}}
2908 * Short:: @code{.short @var{expressions}}
2909 * Single:: @code{.single @var{flonums}}
2911 * Size:: @code{.size}
2914 * Space:: @code{.space @var{size} , @var{fill}}
2916 * Stab:: @code{.stabd, .stabn, .stabs}
2919 * String:: @code{.string "@var{str}"}
2921 * Tag:: @code{.tag @var{structname}}
2924 * Text:: @code{.text @var{subsection}}
2925 * Title:: @code{.title "@var{heading}"}
2927 * Type:: @code{.type @var{int}}
2928 * Val:: @code{.val @var{addr}}
2931 * Word:: @code{.word @var{expressions}}
2932 * Deprecated:: Deprecated Directives
2936 @section @code{.abort}
2938 @cindex @code{abort} directive
2939 @cindex stopping the assembly
2940 This directive stops the assembly immediately. It is for
2941 compatibility with other assemblers. The original idea was that the
2942 assembly language source would be piped into the assembler. If the sender
2943 of the source quit, it could use this directive tells @code{@value{AS}} to
2944 quit also. One day @code{.abort} will not be supported.
2948 @section @code{.ABORT}
2950 @cindex @code{ABORT} directive
2951 When producing COFF output, @code{@value{AS}} accepts this directive as a
2952 synonym for @samp{.abort}.
2955 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
2961 @section @code{.align @var{abs-expr} , @var{abs-expr}}
2963 @cindex padding the location counter
2964 @cindex @code{align} directive
2965 Pad the location counter (in the current subsection) to a particular
2966 storage boundary. The first expression (which must be absolute) is the
2967 alignment required, as described below.
2968 The second expression (also absolute) gives the value to be stored in
2969 the padding bytes. It (and the comma) may be omitted. If it is
2970 omitted, the padding bytes are zero.
2972 The way the required alignment is specified varies from system to system.
2973 For the a29k, HPPA, m86k, m88k, w65, sparc, and i386 using ELF format,
2974 the first expression is the
2975 alignment request in bytes. For example @samp{.align 8} advances
2976 the location counter until it is a multiple of 8. If the location counter
2977 is already a multiple of 8, no change is needed.
2979 For other systems, including the i386 using a.out format, it is the
2980 number of low-order zero bits the location counter must have after
2981 advancement. For example @samp{.align 3} advances the location
2982 counter until it a multiple of 8. If the location counter is already a
2983 multiple of 8, no change is needed.
2985 This inconsistency is due to the different behaviors of the various
2986 native assemblers for these systems which GAS must emulate.
2987 GAS also provides @code{.balign} and @code{.p2align} directives,
2988 described later, which have a consistent behavior across all
2989 architectures (but are specific to GAS).
2992 @section @code{.app-file @var{string}}
2994 @cindex logical file name
2995 @cindex file name, logical
2996 @cindex @code{app-file} directive
2998 @ifclear no-file-dir
2999 (which may also be spelled @samp{.file})
3001 tells @code{@value{AS}} that we are about to start a new
3002 logical file. @var{string} is the new file name. In general, the
3003 filename is recognized whether or not it is surrounded by quotes @samp{"};
3004 but if you wish to specify an empty file name is permitted,
3005 you must give the quotes--@code{""}. This statement may go away in
3006 future: it is only recognized to be compatible with old @code{@value{AS}}
3010 @section @code{.ascii "@var{string}"}@dots{}
3012 @cindex @code{ascii} directive
3013 @cindex string literals
3014 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3015 separated by commas. It assembles each string (with no automatic
3016 trailing zero byte) into consecutive addresses.
3019 @section @code{.asciz "@var{string}"}@dots{}
3021 @cindex @code{asciz} directive
3022 @cindex zero-terminated strings
3023 @cindex null-terminated strings
3024 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3025 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3028 @section @code{.balign @var{abs-expr} , @var{abs-expr}}
3030 @cindex padding the location counter given number of bytes
3031 @cindex @code{balign} directive
3032 Pad the location counter (in the current subsection) to a particular
3033 storage boundary. The first expression (which must be absolute) is the
3034 alignment request in bytes. For example @samp{.balign 8} advances
3035 the location counter until it is a multiple of 8. If the location counter
3036 is already a multiple of 8, no change is needed.
3038 The second expression (also absolute) gives the value to be stored in
3039 the padding bytes. It (and the comma) may be omitted. If it is
3040 omitted, the padding bytes are zero.
3043 @section @code{.byte @var{expressions}}
3045 @cindex @code{byte} directive
3046 @cindex integers, one byte
3047 @code{.byte} expects zero or more expressions, separated by commas.
3048 Each expression is assembled into the next byte.
3051 @section @code{.comm @var{symbol} , @var{length} }
3053 @cindex @code{comm} directive
3054 @cindex symbol, common
3055 @code{.comm} declares a named common area in the bss section. Normally
3056 @code{@value{LD}} reserves memory addresses for it during linking, so no partial
3057 program defines the location of the symbol. Use @code{.comm} to tell
3058 @code{@value{LD}} that it must be at least @var{length} bytes long. @code{@value{LD}}
3059 allocates space for each @code{.comm} symbol that is at least as
3060 long as the longest @code{.comm} request in any of the partial programs
3061 linked. @var{length} is an absolute expression.
3064 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3065 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3069 @section @code{.data @var{subsection}}
3071 @cindex @code{data} directive
3072 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3073 end of the data subsection numbered @var{subsection} (which is an
3074 absolute expression). If @var{subsection} is omitted, it defaults
3079 @section @code{.def @var{name}}
3081 @cindex @code{def} directive
3082 @cindex COFF symbols, debugging
3083 @cindex debugging COFF symbols
3084 Begin defining debugging information for a symbol @var{name}; the
3085 definition extends until the @code{.endef} directive is encountered.
3088 This directive is only observed when @code{@value{AS}} is configured for COFF
3089 format output; when producing @code{b.out}, @samp{.def} is recognized,
3096 @section @code{.desc @var{symbol}, @var{abs-expression}}
3098 @cindex @code{desc} directive
3099 @cindex COFF symbol descriptor
3100 @cindex symbol descriptor, COFF
3101 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3102 to the low 16 bits of an absolute expression.
3105 The @samp{.desc} directive is not available when @code{@value{AS}} is
3106 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3107 object format. For the sake of compatibility, @code{@value{AS}} accepts
3108 it, but produces no output, when configured for COFF.
3114 @section @code{.dim}
3116 @cindex @code{dim} directive
3117 @cindex COFF auxiliary symbol information
3118 @cindex auxiliary symbol information, COFF
3119 This directive is generated by compilers to include auxiliary debugging
3120 information in the symbol table. It is only permitted inside
3121 @code{.def}/@code{.endef} pairs.
3124 @samp{.dim} is only meaningful when generating COFF format output; when
3125 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3131 @section @code{.double @var{flonums}}
3133 @cindex @code{double} directive
3134 @cindex floating point numbers (double)
3135 @code{.double} expects zero or more flonums, separated by commas. It
3136 assembles floating point numbers.
3138 The exact kind of floating point numbers emitted depends on how
3139 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3143 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3144 in @sc{ieee} format.
3149 @section @code{.eject}
3151 @cindex @code{eject} directive
3152 @cindex new page, in listings
3153 @cindex page, in listings
3154 @cindex listing control: new page
3155 Force a page break at this point, when generating assembly listings.
3158 @section @code{.else}
3160 @cindex @code{else} directive
3161 @code{.else} is part of the @code{@value{AS}} support for conditional
3162 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3163 of code to be assembled if the condition for the preceding @code{.if}
3167 @node End, Endef, Else, Pseudo Ops
3168 @section @code{.end}
3170 @cindex @code{end} directive
3171 This doesn't do anything---but isn't an s_ignore, so I suspect it's
3172 meant to do something eventually (which is why it isn't documented here
3173 as "for compatibility with blah").
3178 @section @code{.endef}
3180 @cindex @code{endef} directive
3181 This directive flags the end of a symbol definition begun with
3185 @samp{.endef} is only meaningful when generating COFF format output; if
3186 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3187 directive but ignores it.
3192 @section @code{.endif}
3194 @cindex @code{endif} directive
3195 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3196 it marks the end of a block of code that is only assembled
3197 conditionally. @xref{If,,@code{.if}}.
3200 @section @code{.equ @var{symbol}, @var{expression}}
3202 @cindex @code{equ} directive
3203 @cindex assigning values to symbols
3204 @cindex symbols, assigning values to
3205 This directive sets the value of @var{symbol} to @var{expression}.
3206 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3209 The syntax for @code{equ} on the HPPA is
3210 @samp{@var{symbol} .equ @var{expression}}.
3214 @section @code{.extern}
3216 @cindex @code{extern} directive
3217 @code{.extern} is accepted in the source program---for compatibility
3218 with other assemblers---but it is ignored. @code{@value{AS}} treats
3219 all undefined symbols as external.
3221 @ifclear no-file-dir
3223 @section @code{.file @var{string}}
3225 @cindex @code{file} directive
3226 @cindex logical file name
3227 @cindex file name, logical
3228 @code{.file} (which may also be spelled @samp{.app-file}) tells
3229 @code{@value{AS}} that we are about to start a new logical file.
3230 @var{string} is the new file name. In general, the filename is
3231 recognized whether or not it is surrounded by quotes @samp{"}; but if
3232 you wish to specify an empty file name, you must give the
3233 quotes--@code{""}. This statement may go away in future: it is only
3234 recognized to be compatible with old @code{@value{AS}} programs.
3236 In some configurations of @code{@value{AS}}, @code{.file} has already been
3237 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3242 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3244 @cindex @code{fill} directive
3245 @cindex writing patterns in memory
3246 @cindex patterns, writing in memory
3247 @var{result}, @var{size} and @var{value} are absolute expressions.
3248 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3249 may be zero or more. @var{Size} may be zero or more, but if it is
3250 more than 8, then it is deemed to have the value 8, compatible with
3251 other people's assemblers. The contents of each @var{repeat} bytes
3252 is taken from an 8-byte number. The highest order 4 bytes are
3253 zero. The lowest order 4 bytes are @var{value} rendered in the
3254 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3255 Each @var{size} bytes in a repetition is taken from the lowest order
3256 @var{size} bytes of this number. Again, this bizarre behavior is
3257 compatible with other people's assemblers.
3259 @var{size} and @var{value} are optional.
3260 If the second comma and @var{value} are absent, @var{value} is
3261 assumed zero. If the first comma and following tokens are absent,
3262 @var{size} is assumed to be 1.
3265 @section @code{.float @var{flonums}}
3267 @cindex floating point numbers (single)
3268 @cindex @code{float} directive
3269 This directive assembles zero or more flonums, separated by commas. It
3270 has the same effect as @code{.single}.
3272 The exact kind of floating point numbers emitted depends on how
3273 @code{@value{AS}} is configured.
3274 @xref{Machine Dependencies}.
3278 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3279 in @sc{ieee} format.
3284 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3286 @cindex @code{global} directive
3287 @cindex symbol, making visible to linker
3288 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3289 @var{symbol} in your partial program, its value is made available to
3290 other partial programs that are linked with it. Otherwise,
3291 @var{symbol} takes its attributes from a symbol of the same name
3292 from another file linked into the same program.
3294 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3295 compatibility with other assemblers.
3298 On the HPPA, @code{.global} is not always enough to make it accessible to other
3299 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3300 @xref{HPPA Directives,, HPPA Assembler Directives}.
3304 @section @code{.hword @var{expressions}}
3306 @cindex @code{hword} directive
3307 @cindex integers, 16-bit
3308 @cindex numbers, 16-bit
3309 @cindex sixteen bit integers
3310 This expects zero or more @var{expressions}, and emits
3311 a 16 bit number for each.
3314 This directive is a synonym for @samp{.short}; depending on the target
3315 architecture, it may also be a synonym for @samp{.word}.
3319 This directive is a synonym for @samp{.short}.
3322 This directive is a synonym for both @samp{.short} and @samp{.word}.
3327 @section @code{.ident}
3329 @cindex @code{ident} directive
3330 This directive is used by some assemblers to place tags in object files.
3331 @code{@value{AS}} simply accepts the directive for source-file
3332 compatibility with such assemblers, but does not actually emit anything
3336 @section @code{.if @var{absolute expression}}
3338 @cindex conditional assembly
3339 @cindex @code{if} directive
3340 @code{.if} marks the beginning of a section of code which is only
3341 considered part of the source program being assembled if the argument
3342 (which must be an @var{absolute expression}) is non-zero. The end of
3343 the conditional section of code must be marked by @code{.endif}
3344 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3345 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}.
3347 The following variants of @code{.if} are also supported:
3349 @item .ifdef @var{symbol}
3350 @cindex @code{ifdef} directive
3351 Assembles the following section of code if the specified @var{symbol}
3356 @cindex @code{ifeqs} directive
3357 Not yet implemented.
3360 @item .ifndef @var{symbol}
3361 @itemx ifnotdef @var{symbol}
3362 @cindex @code{ifndef} directive
3363 @cindex @code{ifnotdef} directive
3364 Assembles the following section of code if the specified @var{symbol}
3365 has not been defined. Both spelling variants are equivalent.
3369 Not yet implemented.
3374 @section @code{.include "@var{file}"}
3376 @cindex @code{include} directive
3377 @cindex supporting files, including
3378 @cindex files, including
3379 This directive provides a way to include supporting files at specified
3380 points in your source program. The code from @var{file} is assembled as
3381 if it followed the point of the @code{.include}; when the end of the
3382 included file is reached, assembly of the original file continues. You
3383 can control the search paths used with the @samp{-I} command-line option
3384 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3388 @section @code{.int @var{expressions}}
3390 @cindex @code{int} directive
3391 @cindex integers, 32-bit
3392 Expect zero or more @var{expressions}, of any section, separated by commas.
3393 For each expression, emit a number that, at run time, is the value of that
3394 expression. The byte order and bit size of the number depends on what kind
3395 of target the assembly is for.
3399 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3400 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3406 @section @code{.lcomm @var{symbol} , @var{length}}
3408 @cindex @code{lcomm} directive
3409 @cindex local common symbols
3410 @cindex symbols, local common
3411 Reserve @var{length} (an absolute expression) bytes for a local common
3412 denoted by @var{symbol}. The section and value of @var{symbol} are
3413 those of the new local common. The addresses are allocated in the bss
3414 section, so that at run-time the bytes start off zeroed. @var{Symbol}
3415 is not declared global (@pxref{Global,,@code{.global}}), so is normally
3416 not visible to @code{@value{LD}}.
3419 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
3420 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
3424 @section @code{.lflags}
3426 @cindex @code{lflags} directive (ignored)
3427 @code{@value{AS}} accepts this directive, for compatibility with other
3428 assemblers, but ignores it.
3430 @ifclear no-line-dir
3432 @section @code{.line @var{line-number}}
3434 @cindex @code{line} directive
3438 @section @code{.ln @var{line-number}}
3440 @cindex @code{ln} directive
3442 @cindex logical line number
3444 Change the logical line number. @var{line-number} must be an absolute
3445 expression. The next line has that logical line number. Therefore any other
3446 statements on the current line (after a statement separator character) are
3447 reported as on logical line number @var{line-number} @minus{} 1. One day
3448 @code{@value{AS}} will no longer support this directive: it is recognized only
3449 for compatibility with existing assembler programs.
3453 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
3454 not available; use the synonym @code{.ln} in that context.
3459 @ifclear no-line-dir
3460 Even though this is a directive associated with the @code{a.out} or
3461 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
3462 when producing COFF output, and treats @samp{.line} as though it
3463 were the COFF @samp{.ln} @emph{if} it is found outside a
3464 @code{.def}/@code{.endef} pair.
3466 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
3467 used by compilers to generate auxiliary symbol information for
3472 @section @code{.ln @var{line-number}}
3474 @cindex @code{ln} directive
3475 @ifclear no-line-dir
3476 @samp{.ln} is a synonym for @samp{.line}.
3479 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
3480 must be an absolute expression. The next line has that logical
3481 line number, so any other statements on the current line (after a
3482 statement separator character @code{;}) are reported as on logical
3483 line number @var{line-number} @minus{} 1.
3486 This directive is accepted, but ignored, when @code{@value{AS}} is
3487 configured for @code{b.out}; its effect is only associated with COFF
3493 @section @code{.list}
3495 @cindex @code{list} directive
3496 @cindex listing control, turning on
3497 Control (in conjunction with the @code{.nolist} directive) whether or
3498 not assembly listings are generated. These two directives maintain an
3499 internal counter (which is zero initially). @code{.list} increments the
3500 counter, and @code{.nolist} decrements it. Assembly listings are
3501 generated whenever the counter is greater than zero.
3503 By default, listings are disabled. When you enable them (with the
3504 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
3505 the initial value of the listing counter is one.
3508 @section @code{.long @var{expressions}}
3510 @cindex @code{long} directive
3511 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
3514 @c no one seems to know what this is for or whether this description is
3515 @c what it really ought to do
3517 @section @code{.lsym @var{symbol}, @var{expression}}
3519 @cindex @code{lsym} directive
3520 @cindex symbol, not referenced in assembly
3521 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
3522 the hash table, ensuring it cannot be referenced by name during the
3523 rest of the assembly. This sets the attributes of the symbol to be
3524 the same as the expression value:
3526 @var{other} = @var{descriptor} = 0
3527 @var{type} = @r{(section of @var{expression})}
3528 @var{value} = @var{expression}
3531 The new symbol is not flagged as external.
3535 @section @code{.nolist}
3537 @cindex @code{nolist} directive
3538 @cindex listing control, turning off
3539 Control (in conjunction with the @code{.list} directive) whether or
3540 not assembly listings are generated. These two directives maintain an
3541 internal counter (which is zero initially). @code{.list} increments the
3542 counter, and @code{.nolist} decrements it. Assembly listings are
3543 generated whenever the counter is greater than zero.
3546 @section @code{.octa @var{bignums}}
3548 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
3549 @cindex @code{octa} directive
3550 @cindex integer, 16-byte
3551 @cindex sixteen byte integer
3552 This directive expects zero or more bignums, separated by commas. For each
3553 bignum, it emits a 16-byte integer.
3555 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
3556 hence @emph{octa}-word for 16 bytes.
3559 @section @code{.org @var{new-lc} , @var{fill}}
3561 @cindex @code{org} directive
3562 @cindex location counter, advancing
3563 @cindex advancing location counter
3564 @cindex current address, advancing
3565 Advance the location counter of the current section to
3566 @var{new-lc}. @var{new-lc} is either an absolute expression or an
3567 expression with the same section as the current subsection. That is,
3568 you can't use @code{.org} to cross sections: if @var{new-lc} has the
3569 wrong section, the @code{.org} directive is ignored. To be compatible
3570 with former assemblers, if the section of @var{new-lc} is absolute,
3571 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
3572 is the same as the current subsection.
3574 @code{.org} may only increase the location counter, or leave it
3575 unchanged; you cannot use @code{.org} to move the location counter
3578 @c double negative used below "not undefined" because this is a specific
3579 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
3580 @c section. pesch@cygnus.com 18feb91
3581 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
3582 may not be undefined. If you really detest this restriction we eagerly await
3583 a chance to share your improved assembler.
3585 Beware that the origin is relative to the start of the section, not
3586 to the start of the subsection. This is compatible with other
3587 people's assemblers.
3589 When the location counter (of the current subsection) is advanced, the
3590 intervening bytes are filled with @var{fill} which should be an
3591 absolute expression. If the comma and @var{fill} are omitted,
3592 @var{fill} defaults to zero.
3595 @section @code{.p2align @var{abs-expr} , @var{abs-expr}}
3597 @cindex padding the location counter given a power of two
3598 @cindex @code{p2align} directive
3599 Pad the location counter (in the current subsection) to a particular
3600 storage boundary. The first expression (which must be absolute) is the
3601 number of low-order zero bits the location counter must have after
3602 advancement. For example @samp{.p2align 3} advances the location
3603 counter until it a multiple of 8. If the location counter is already a
3604 multiple of 8, no change is needed.
3606 The second expression (also absolute) gives the value to be stored in
3607 the padding bytes. It (and the comma) may be omitted. If it is
3608 omitted, the padding bytes are zero.
3611 @section @code{.psize @var{lines} , @var{columns}}
3613 @cindex @code{psize} directive
3614 @cindex listing control: paper size
3615 @cindex paper size, for listings
3616 Use this directive to declare the number of lines---and, optionally, the
3617 number of columns---to use for each page, when generating listings.
3619 If you do not use @code{.psize}, listings use a default line-count
3620 of 60. You may omit the comma and @var{columns} specification; the
3621 default width is 200 columns.
3623 @code{@value{AS}} generates formfeeds whenever the specified number of
3624 lines is exceeded (or whenever you explicitly request one, using
3627 If you specify @var{lines} as @code{0}, no formfeeds are generated save
3628 those explicitly specified with @code{.eject}.
3631 @section @code{.quad @var{bignums}}
3633 @cindex @code{quad} directive
3634 @code{.quad} expects zero or more bignums, separated by commas. For
3635 each bignum, it emits
3637 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
3638 warning message; and just takes the lowest order 8 bytes of the bignum.
3639 @cindex eight-byte integer
3640 @cindex integer, 8-byte
3642 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
3643 hence @emph{quad}-word for 8 bytes.
3646 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
3647 warning message; and just takes the lowest order 16 bytes of the bignum.
3648 @cindex sixteen-byte integer
3649 @cindex integer, 16-byte
3653 @section @code{.sbttl "@var{subheading}"}
3655 @cindex @code{sbttl} directive
3656 @cindex subtitles for listings
3657 @cindex listing control: subtitle
3658 Use @var{subheading} as the title (third line, immediately after the
3659 title line) when generating assembly listings.
3661 This directive affects subsequent pages, as well as the current page if
3662 it appears within ten lines of the top of a page.
3666 @section @code{.scl @var{class}}
3668 @cindex @code{scl} directive
3669 @cindex symbol storage class (COFF)
3670 @cindex COFF symbol storage class
3671 Set the storage-class value for a symbol. This directive may only be
3672 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
3673 whether a symbol is static or external, or it may record further
3674 symbolic debugging information.
3677 The @samp{.scl} directive is primarily associated with COFF output; when
3678 configured to generate @code{b.out} output format, @code{@value{AS}}
3679 accepts this directive but ignores it.
3685 @section @code{.section @var{name}, @var{subsection}}
3687 @cindex @code{section} directive
3688 @cindex named section (COFF)
3689 @cindex COFF named section
3690 Assemble the following code into end of subsection numbered
3691 @var{subsection} in the COFF named section @var{name}. If you omit
3692 @var{subsection}, @code{@value{AS}} uses subsection number zero.
3693 @samp{.section .text} is equivalent to the @code{.text} directive;
3694 @samp{.section .data} is equivalent to the @code{.data} directive.
3696 This directive is only supported for targets that actually support arbitrarily
3697 named sections; on @code{a.out} targets, for example, it is not accepted, even
3698 with a standard @code{a.out} section name as its parameter.
3703 @section @code{.set @var{symbol}, @var{expression}}
3705 @cindex @code{set} directive
3706 @cindex symbol value, setting
3707 Set the value of @var{symbol} to @var{expression}. This
3708 changes @var{symbol}'s value and type to conform to
3709 @var{expression}. If @var{symbol} was flagged as external, it remains
3710 flagged. (@xref{Symbol Attributes}.)
3712 You may @code{.set} a symbol many times in the same assembly.
3714 If you @code{.set} a global symbol, the value stored in the object
3715 file is the last value stored into it.
3718 The syntax for @code{set} on the HPPA is
3719 @samp{@var{symbol} .set @var{expression}}.
3723 @section @code{.short @var{expressions}}
3725 @cindex @code{short} directive
3727 @code{.short} is normally the same as @samp{.word}.
3728 @xref{Word,,@code{.word}}.
3730 In some configurations, however, @code{.short} and @code{.word} generate
3731 numbers of different lengths; @pxref{Machine Dependencies}.
3735 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
3738 This expects zero or more @var{expressions}, and emits
3739 a 16 bit number for each.
3744 @section @code{.single @var{flonums}}
3746 @cindex @code{single} directive
3747 @cindex floating point numbers (single)
3748 This directive assembles zero or more flonums, separated by commas. It
3749 has the same effect as @code{.float}.
3751 The exact kind of floating point numbers emitted depends on how
3752 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3756 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
3757 numbers in @sc{ieee} format.
3763 @section @code{.size}
3765 @cindex @code{size} directive
3766 This directive is generated by compilers to include auxiliary debugging
3767 information in the symbol table. It is only permitted inside
3768 @code{.def}/@code{.endef} pairs.
3771 @samp{.size} is only meaningful when generating COFF format output; when
3772 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3777 @ifclear no-space-dir
3779 @section @code{.space @var{size} , @var{fill}}
3781 @cindex @code{space} directive
3782 @cindex filling memory
3783 This directive emits @var{size} bytes, each of value @var{fill}. Both
3784 @var{size} and @var{fill} are absolute expressions. If the comma
3785 and @var{fill} are omitted, @var{fill} is assumed to be zero.
3789 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
3790 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
3791 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
3792 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
3801 @section @code{.space}
3802 @cindex @code{space} directive
3804 On the AMD 29K, this directive is ignored; it is accepted for
3805 compatibility with other AMD 29K assemblers.
3808 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
3809 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
3815 @section @code{.stabd, .stabn, .stabs}
3817 @cindex symbolic debuggers, information for
3818 @cindex @code{stab@var{x}} directives
3819 There are three directives that begin @samp{.stab}.
3820 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
3821 The symbols are not entered in the @code{@value{AS}} hash table: they
3822 cannot be referenced elsewhere in the source file.
3823 Up to five fields are required:
3827 This is the symbol's name. It may contain any character except
3828 @samp{\000}, so is more general than ordinary symbol names. Some
3829 debuggers used to code arbitrarily complex structures into symbol names
3833 An absolute expression. The symbol's type is set to the low 8 bits of
3834 this expression. Any bit pattern is permitted, but @code{@value{LD}}
3835 and debuggers choke on silly bit patterns.
3838 An absolute expression. The symbol's ``other'' attribute is set to the
3839 low 8 bits of this expression.
3842 An absolute expression. The symbol's descriptor is set to the low 16
3843 bits of this expression.
3846 An absolute expression which becomes the symbol's value.
3849 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
3850 or @code{.stabs} statement, the symbol has probably already been created;
3851 you get a half-formed symbol in your object file. This is
3852 compatible with earlier assemblers!
3855 @cindex @code{stabd} directive
3856 @item .stabd @var{type} , @var{other} , @var{desc}
3858 The ``name'' of the symbol generated is not even an empty string.
3859 It is a null pointer, for compatibility. Older assemblers used a
3860 null pointer so they didn't waste space in object files with empty
3863 The symbol's value is set to the location counter,
3864 relocatably. When your program is linked, the value of this symbol
3865 is the address of the location counter when the @code{.stabd} was
3868 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
3869 @cindex @code{stabn} directive
3870 The name of the symbol is set to the empty string @code{""}.
3872 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
3873 @cindex @code{stabs} directive
3874 All five fields are specified.
3880 @section @code{.string} "@var{str}"
3882 @cindex string, copying to object file
3883 @cindex @code{string} directive
3885 Copy the characters in @var{str} to the object file. You may specify more than
3886 one string to copy, separated by commas. Unless otherwise specified for a
3887 particular machine, the assembler marks the end of each string with a 0 byte.
3888 You can use any of the escape sequences described in @ref{Strings,,Strings}.
3892 @section @code{.tag @var{structname}}
3894 @cindex COFF structure debugging
3895 @cindex structure debugging, COFF
3896 @cindex @code{tag} directive
3897 This directive is generated by compilers to include auxiliary debugging
3898 information in the symbol table. It is only permitted inside
3899 @code{.def}/@code{.endef} pairs. Tags are used to link structure
3900 definitions in the symbol table with instances of those structures.
3903 @samp{.tag} is only used when generating COFF format output; when
3904 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3910 @section @code{.text @var{subsection}}
3912 @cindex @code{text} directive
3913 Tells @code{@value{AS}} to assemble the following statements onto the end of
3914 the text subsection numbered @var{subsection}, which is an absolute
3915 expression. If @var{subsection} is omitted, subsection number zero
3919 @section @code{.title "@var{heading}"}
3921 @cindex @code{title} directive
3922 @cindex listing control: title line
3923 Use @var{heading} as the title (second line, immediately after the
3924 source file name and pagenumber) when generating assembly listings.
3926 This directive affects subsequent pages, as well as the current page if
3927 it appears within ten lines of the top of a page.
3931 @section @code{.type @var{int}}
3933 @cindex COFF symbol type
3934 @cindex symbol type, COFF
3935 @cindex @code{type} directive
3936 This directive, permitted only within @code{.def}/@code{.endef} pairs,
3937 records the integer @var{int} as the type attribute of a symbol table entry.
3940 @samp{.type} is associated only with COFF format output; when
3941 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
3942 directive but ignores it.
3948 @section @code{.val @var{addr}}
3950 @cindex @code{val} directive
3951 @cindex COFF value attribute
3952 @cindex value attribute, COFF
3953 This directive, permitted only within @code{.def}/@code{.endef} pairs,
3954 records the address @var{addr} as the value attribute of a symbol table
3958 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
3959 configured for @code{b.out}, it accepts this directive but ignores it.
3964 @section @code{.word @var{expressions}}
3966 @cindex @code{word} directive
3967 This directive expects zero or more @var{expressions}, of any section,
3968 separated by commas.
3971 For each expression, @code{@value{AS}} emits a 32-bit number.
3974 For each expression, @code{@value{AS}} emits a 16-bit number.
3979 The size of the number emitted, and its byte order,
3980 depend on what target computer the assembly is for.
3983 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
3984 @c happen---32-bit addressability, period; no long/short jumps.
3985 @ifset DIFF-TBL-KLUGE
3986 @cindex difference tables altered
3987 @cindex altered difference tables
3989 @emph{Warning: Special Treatment to support Compilers}
3993 Machines with a 32-bit address space, but that do less than 32-bit
3994 addressing, require the following special treatment. If the machine of
3995 interest to you does 32-bit addressing (or doesn't require it;
3996 @pxref{Machine Dependencies}), you can ignore this issue.
3999 In order to assemble compiler output into something that works,
4000 @code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
4001 Directives of the form @samp{.word sym1-sym2} are often emitted by
4002 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
4003 directive of the form @samp{.word sym1-sym2}, and the difference between
4004 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
4005 creates a @dfn{secondary jump table}, immediately before the next label.
4006 This secondary jump table is preceded by a short-jump to the
4007 first byte after the secondary table. This short-jump prevents the flow
4008 of control from accidentally falling into the new table. Inside the
4009 table is a long-jump to @code{sym2}. The original @samp{.word}
4010 contains @code{sym1} minus the address of the long-jump to
4013 If there were several occurrences of @samp{.word sym1-sym2} before the
4014 secondary jump table, all of them are adjusted. If there was a
4015 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
4016 long-jump to @code{sym4} is included in the secondary jump table,
4017 and the @code{.word} directives are adjusted to contain @code{sym3}
4018 minus the address of the long-jump to @code{sym4}; and so on, for as many
4019 entries in the original jump table as necessary.
4022 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
4023 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
4024 assembly language programmers.
4027 @c end DIFF-TBL-KLUGE
4030 @section Deprecated Directives
4032 @cindex deprecated directives
4033 @cindex obsolescent directives
4034 One day these directives won't work.
4035 They are included for compatibility with older assemblers.
4043 @node Machine Dependencies
4044 @chapter Machine Dependent Features
4046 @cindex machine dependencies
4047 The machine instruction sets are (almost by definition) different on
4048 each machine where @code{@value{AS}} runs. Floating point representations
4049 vary as well, and @code{@value{AS}} often supports a few additional
4050 directives or command-line options for compatibility with other
4051 assemblers on a particular platform. Finally, some versions of
4052 @code{@value{AS}} support special pseudo-instructions for branch
4055 This chapter discusses most of these differences, though it does not
4056 include details on any machine's instruction set. For details on that
4057 subject, see the hardware manufacturer's manual.
4060 @c start-sanitize-arc
4062 * ARC-Dependent:: ARC Dependent Features
4066 * Vax-Dependent:: VAX Dependent Features
4069 * AMD29K-Dependent:: AMD 29K Dependent Features
4072 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4075 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4078 * HPPA-Dependent:: HPPA Dependent Features
4081 * SH-Dependent:: Hitachi SH Dependent Features
4084 * i960-Dependent:: Intel 80960 Dependent Features
4087 * M68K-Dependent:: M680x0 Dependent Features
4090 * Sparc-Dependent:: SPARC Dependent Features
4093 * Z8000-Dependent:: Z8000 Dependent Features
4096 * MIPS-Dependent:: MIPS Dependent Features
4099 * i386-Dependent:: 80386 Dependent Features
4106 @c The following major nodes are *sections* in the GENERIC version, *chapters*
4107 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
4108 @c peculiarity: to preserve cross-references, there must be a node called
4109 @c "Machine Dependencies". Hence the conditional nodenames in each
4110 @c major node below. Node defaulting in makeinfo requires adjacency of
4111 @c node and sectioning commands; hence the repetition of @chapter BLAH
4112 @c in both conditional blocks.
4114 @c start-sanitize-arc
4119 @chapter ARC Dependent Features
4122 @node Machine Dependencies
4123 @chapter ARC Dependent Features
4128 * ARC-Opts:: Options
4129 * ARC-Float:: Floating Point
4130 * ARC-Directives:: Sparc Machine Directives
4136 @cindex options for ARC
4138 @cindex architectures, ARC
4139 @cindex ARC architectures
4140 The ARC chip family includes several successive levels (or other
4141 variants) of chip, using the same core instruction set, but including
4142 a few additional instructions at each level.
4144 By default, @code{@value{AS}} assumes the core instruction set (ARC
4145 base). The @code{.cpu} pseudo-op is used to select a different variant.
4148 @cindex @code{-mbig-endian} option (ARC)
4149 @cindex @code{-mlittle-endian} option (ARC)
4150 @cindex ARC big-endian output
4151 @cindex ARC little-endian output
4152 @cindex big-endian output, ARC
4153 @cindex little-endian output, ARC
4155 @itemx -mlittle-endian
4156 Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
4157 little-endian output at run time (unlike most other @sc{gnu} development
4158 tools, which must be configured for one or the other). Use
4159 @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
4164 @section Floating Point
4166 @cindex floating point, ARC (@sc{ieee})
4167 @cindex ARC floating point (@sc{ieee})
4168 The ARC cpu family currently does not have hardware floating point
4169 support. Software floating point support is provided by @code{GCC}
4170 and uses @sc{ieee} floating-point numbers.
4172 @node ARC-Directives
4173 @section ARC Machine Directives
4175 @cindex ARC machine directives
4176 @cindex machine directives, ARC
4177 The ARC version of @code{@value{AS}} supports the following additional
4182 @cindex @code{cpu} directive, SPARC
4183 This must be followed by the desired cpu. It must be one of
4184 @code{base}, @code{host}, @code{graphics}, or @code{audio}.
4196 @include c-a29k.texi
4201 @node Machine Dependencies
4202 @chapter Machine Dependent Features
4204 The machine instruction sets are different on each Hitachi chip family,
4205 and there are also some syntax differences among the families. This
4206 chapter describes the specific @code{@value{AS}} features for each
4210 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4211 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4212 * SH-Dependent:: Hitachi SH Dependent Features
4219 @include c-h8300.texi
4223 @include c-h8500.texi
4227 @include c-hppa.texi
4235 @include c-i960.texi
4239 @include c-m68k.texi
4243 @c FIXME! Stop ignoring when filled in.
4248 The 32x32 version of @code{@value{AS}} accepts a @samp{-m32032} option to
4249 specify thiat it is compiling for a 32032 processor, or a
4250 @samp{-m32532} to specify that it is compiling for a 32532 option.
4251 The default (if neither is specified) is chosen when the assembler
4255 I don't know anything about the 32x32 syntax assembled by
4256 @code{@value{AS}}. Someone who undersands the processor (I've never seen
4257 one) and the possible syntaxes should write this section.
4259 @section Floating Point
4260 The 32x32 uses @sc{ieee} floating point numbers, but @code{@value{AS}}
4261 only creates single or double precision values. I don't know if the
4262 32x32 understands extended precision numbers.
4264 @section 32x32 Machine Directives
4265 The 32x32 has no machine dependent directives.
4270 @include c-sparc.texi
4274 @include c-i386.texi
4282 @include c-mips.texi
4286 @c reverse effect of @down at top of generic Machine-Dep chapter
4290 @node Acknowledgements
4291 @chapter Acknowledgements
4293 If you have contributed to @code{@value{AS}} and your name isn't listed here,
4294 it is not meant as a slight. We just don't know about it. Send mail to the
4295 maintainer, and we'll correct the situation. Currently (January 1994), the
4296 maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
4298 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
4301 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
4302 information and the 68k series machines, most of the preprocessing pass, and
4303 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
4305 K. Richard Pixley maintained GAS for a while, adding various enhancements and
4306 many bug fixes, including merging support for several processors, breaking GAS
4307 up to handle multiple object file format back ends (including heavy rewrite,
4308 testing, an integration of the coff and b.out back ends), adding configuration
4309 including heavy testing and verification of cross assemblers and file splits
4310 and renaming, converted GAS to strictly ANSI C including full prototypes, added
4311 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
4312 port (including considerable amounts of reverse engineering), a SPARC opcode
4313 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
4314 assertions and made them work, much other reorganization, cleanup, and lint.
4316 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
4317 in format-specific I/O modules.
4319 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
4320 has done much work with it since.
4322 The Intel 80386 machine description was written by Eliot Dresselhaus.
4324 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
4326 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
4327 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
4329 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
4330 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
4331 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
4332 support a.out format.
4334 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
4335 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
4336 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
4337 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
4340 John Gilmore built the AMD 29000 support, added @code{.include} support, and
4341 simplified the configuration of which versions accept which directives. He
4342 updated the 68k machine description so that Motorola's opcodes always produced
4343 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
4344 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
4345 cross-compilation support, and one bug in relaxation that took a week and
4346 required the proverbial one-bit fix.
4348 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
4349 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
4350 added support for MIPS ECOFF and ELF targets, and made a few other minor
4353 Steve Chamberlain made @code{@value{AS}} able to generate listings.
4355 Hewlett-Packard contributed support for the HP9000/300.
4357 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
4358 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
4359 formats). This work was supported by both the Center for Software Science at
4360 the University of Utah and Cygnus Support.
4362 Support for ELF format files has been worked on by Mark Eichin of Cygnus
4363 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
4364 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
4365 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
4366 and some initial 64-bit support).
4368 Several engineers at Cygnus Support have also provided many small bug fixes and
4369 configuration enhancements.
4371 Many others have contributed large or small bugfixes and enhancements. If
4372 you have contributed significant work and are not mentioned on this list, and
4373 want to be, let us know. Some of the history has been lost; we are not
4374 intentionally leaving anyone out.