| \input texinfo @c -*-Texinfo-*- |
| @c Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 1998 |
| @c Free Software Foundation, Inc. |
| @c UPDATE!! On future updates-- |
| @c (1) check for new machine-dep cmdline options in |
| @c md_parse_option definitions in config/tc-*.c |
| @c (2) for platform-specific directives, examine md_pseudo_op |
| @c in config/tc-*.c |
| @c (3) for object-format specific directives, examine obj_pseudo_op |
| @c in config/obj-*.c |
| @c (4) portable directives in potable[] in read.c |
| @c %**start of header |
| @setfilename as.info |
| @c ---config--- |
| @c defaults, config file may override: |
| @set have-stabs |
| @c --- |
| @include asconfig.texi |
| @include gasver.texi |
| @c --- |
| @c common OR combinations of conditions |
| @ifset AOUT |
| @set aout-bout |
| @end ifset |
| @ifset ARM/Thumb |
| @set ARM |
| @end ifset |
| @ifset BOUT |
| @set aout-bout |
| @end ifset |
| @ifset H8/300 |
| @set H8 |
| @end ifset |
| @ifset H8/500 |
| @set H8 |
| @end ifset |
| @ifset SH |
| @set H8 |
| @end ifset |
| @ifset HPPA |
| @set abnormal-separator |
| @end ifset |
| @c ------------ |
| @ifset GENERIC |
| @settitle Using @value{AS} |
| @end ifset |
| @ifclear GENERIC |
| @settitle Using @value{AS} (@value{TARGET}) |
| @end ifclear |
| @setchapternewpage odd |
| @c %**end of header |
| |
| @c @smallbook |
| @c @set SMALL |
| @c WARE! Some of the machine-dependent sections contain tables of machine |
| @c instructions. Except in multi-column format, these tables look silly. |
| @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so |
| @c the multi-col format is faked within @example sections. |
| @c |
| @c Again unfortunately, the natural size that fits on a page, for these tables, |
| @c is different depending on whether or not smallbook is turned on. |
| @c This matters, because of order: text flow switches columns at each page |
| @c break. |
| @c |
| @c The format faked in this source works reasonably well for smallbook, |
| @c not well for the default large-page format. This manual expects that if you |
| @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the |
| @c tables in question. You can turn on one without the other at your |
| @c discretion, of course. |
| @ifinfo |
| @set SMALL |
| @c the insn tables look just as silly in info files regardless of smallbook, |
| @c might as well show 'em anyways. |
| @end ifinfo |
| |
| @ifinfo |
| @format |
| START-INFO-DIR-ENTRY |
| * As: (as). The GNU assembler. |
| END-INFO-DIR-ENTRY |
| @end format |
| @end ifinfo |
| |
| @finalout |
| @syncodeindex ky cp |
| |
| @ifinfo |
| This file documents the GNU Assembler "@value{AS}". |
| |
| Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc. |
| |
| Permission is granted to make and distribute verbatim copies of |
| this manual provided the copyright notice and this permission notice |
| are preserved on all copies. |
| |
| @ignore |
| Permission is granted to process this file through Tex and print the |
| results, provided the printed document carries copying permission |
| notice identical to this one except for the removal of this paragraph |
| (this paragraph not being relevant to the printed manual). |
| |
| @end ignore |
| Permission is granted to copy and distribute modified versions of this manual |
| under the conditions for verbatim copying, provided that the entire resulting |
| derived work is distributed under the terms of a permission notice identical to |
| this one. |
| |
| Permission is granted to copy and distribute translations of this manual |
| into another language, under the above conditions for modified versions. |
| @end ifinfo |
| |
| @titlepage |
| @title Using @value{AS} |
| @subtitle The @sc{gnu} Assembler |
| @ifclear GENERIC |
| @subtitle for the @value{TARGET} family |
| @end ifclear |
| @sp 1 |
| @subtitle Version @value{VERSION} |
| @sp 1 |
| @sp 13 |
| The Free Software Foundation Inc. thanks The Nice Computer |
| Company of Australia for loaning Dean Elsner to write the |
| first (Vax) version of @code{as} for Project @sc{gnu}. |
| The proprietors, management and staff of TNCCA thank FSF for |
| distracting the boss while they got some work |
| done. |
| @sp 3 |
| @author Dean Elsner, Jay Fenlason & friends |
| @page |
| @tex |
| {\parskip=0pt |
| \hfill {\it Using {\tt @value{AS}}}\par |
| \hfill Edited by Cygnus Support\par |
| } |
| %"boxit" macro for figures: |
| %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3) |
| \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt |
| \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil |
| #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline |
| \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box |
| @end tex |
| |
| @vskip 0pt plus 1filll |
| Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc. |
| |
| Permission is granted to make and distribute verbatim copies of |
| this manual provided the copyright notice and this permission notice |
| are preserved on all copies. |
| |
| Permission is granted to copy and distribute modified versions of this manual |
| under the conditions for verbatim copying, provided that the entire resulting |
| derived work is distributed under the terms of a permission notice identical to |
| this one. |
| |
| Permission is granted to copy and distribute translations of this manual |
| into another language, under the above conditions for modified versions. |
| @end titlepage |
| |
| @ifinfo |
| @node Top |
| @top Using @value{AS} |
| |
| This file is a user guide to the @sc{gnu} assembler @code{@value{AS}} version |
| @value{VERSION}. |
| @ifclear GENERIC |
| This version of the file describes @code{@value{AS}} configured to generate |
| code for @value{TARGET} architectures. |
| @end ifclear |
| @menu |
| * Overview:: Overview |
| * Invoking:: Command-Line Options |
| * Syntax:: Syntax |
| * Sections:: Sections and Relocation |
| * Symbols:: Symbols |
| * Expressions:: Expressions |
| * Pseudo Ops:: Assembler Directives |
| * Machine Dependencies:: Machine Dependent Features |
| * Reporting Bugs:: Reporting Bugs |
| * Acknowledgements:: Who Did What |
| * Index:: Index |
| @end menu |
| @end ifinfo |
| |
| @node Overview |
| @chapter Overview |
| @iftex |
| This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}. |
| @ifclear GENERIC |
| This version of the manual describes @code{@value{AS}} configured to generate |
| code for @value{TARGET} architectures. |
| @end ifclear |
| @end iftex |
| |
| @cindex invocation summary |
| @cindex option summary |
| @cindex summary of options |
| Here is a brief summary of how to invoke @code{@value{AS}}. For details, |
| @pxref{Invoking,,Comand-Line Options}. |
| |
| @c We don't use deffn and friends for the following because they seem |
| @c to be limited to one line for the header. |
| @smallexample |
| @value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ] |
| [ -f ] [ --gstabs ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ] |
| [ --keep-locals ] [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ] |
| [ -version ] [ --version ] [ -W ] [ -w ] [ -x ] [ -Z ] |
| @ifset A29K |
| @c am29k has no machine-dependent assembler options |
| @end ifset |
| @ifset ARC |
| [ -mbig-endian | -mlittle-endian ] |
| @end ifset |
| @ifset ARM |
| [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m[i]] ] |
| [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t ] |
| [ -mthumb | -mall ] |
| [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ] |
| [ -EB | -EL ] |
| [ -mapcs-32 | -mapcs-26 ] |
| @end ifset |
| @ifset D10V |
| [ -O ] |
| @end ifset |
| @ifset D30V |
| [ -O | -n | -N ] |
| @end ifset |
| @ifset H8 |
| @c Hitachi family chips have no machine-dependent assembler options |
| @end ifset |
| @ifset HPPA |
| @c HPPA has no machine-dependent assembler options (yet). |
| @end ifset |
| @ifset SPARC |
| @c The order here is important. See c-sparc.texi. |
| [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite |
| -Av8plus | -Av8plusa | -Av9 | -Av9a ] |
| [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ] |
| @end ifset |
| @ifset Z8000 |
| @c Z8000 has no machine-dependent assembler options |
| @end ifset |
| @ifset I960 |
| @c see md_parse_option in tc-i960.c |
| [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ] |
| [ -b ] [ -no-relax ] |
| @end ifset |
| @ifset M680X0 |
| [ -l ] [ -m68000 | -m68010 | -m68020 | ... ] |
| @end ifset |
| @ifset MCORE |
| [ -jsri2bsr ] [ -sifilter ] [ -relax ] |
| @end ifset |
| @ifset MIPS |
| [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ] |
| [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ] |
| [ --trap ] [ --break ] |
| [ --emulation=@var{name} ] |
| @end ifset |
| [ -- | @var{files} @dots{} ] |
| @end smallexample |
| |
| @table @code |
| @item -a[cdhlmns] |
| Turn on listings, in any of a variety of ways: |
| |
| @table @code |
| @item -ac |
| omit false conditionals |
| |
| @item -ad |
| omit debugging directives |
| |
| @item -ah |
| include high-level source |
| |
| @item -al |
| include assembly |
| |
| @item -am |
| include macro expansions |
| |
| @item -an |
| omit forms processing |
| |
| @item -as |
| include symbols |
| |
| @item =file |
| set the name of the listing file |
| @end table |
| |
| You may combine these options; for example, use @samp{-aln} for assembly |
| listing without forms processing. The @samp{=file} option, if used, must be |
| the last one. By itself, @samp{-a} defaults to @samp{-ahls}. |
| |
| @item -D |
| Ignored. This option is accepted for script compatibility with calls to |
| other assemblers. |
| |
| @item --defsym @var{sym}=@var{value} |
| Define the symbol @var{sym} to be @var{value} before assembling the input file. |
| @var{value} must be an integer constant. As in C, a leading @samp{0x} |
| indicates a hexadecimal value, and a leading @samp{0} indicates an octal value. |
| |
| @item -f |
| ``fast''---skip whitespace and comment preprocessing (assume source is |
| compiler output). |
| |
| @item --gstabs |
| Generate stabs debugging information for each assembler line. This |
| may help debugging assembler code, if the debugger can handle it. |
| |
| @item --help |
| Print a summary of the command line options and exit. |
| |
| @item -I @var{dir} |
| Add directory @var{dir} to the search list for @code{.include} directives. |
| |
| @item -J |
| Don't warn about signed overflow. |
| |
| @item -K |
| @ifclear DIFF-TBL-KLUGE |
| This option is accepted but has no effect on the @value{TARGET} family. |
| @end ifclear |
| @ifset DIFF-TBL-KLUGE |
| Issue warnings when difference tables altered for long displacements. |
| @end ifset |
| |
| @item -L |
| @itemx --keep-locals |
| Keep (in the symbol table) local symbols. On traditional a.out systems |
| these start with @samp{L}, but different systems have different local |
| label prefixes. |
| |
| @item -o @var{objfile} |
| Name the object-file output from @code{@value{AS}} @var{objfile}. |
| |
| @item -R |
| Fold the data section into the text section. |
| |
| @item --statistics |
| Print the maximum space (in bytes) and total time (in seconds) used by |
| assembly. |
| |
| @item --strip-local-absolute |
| Remove local absolute symbols from the outgoing symbol table. |
| |
| @item -v |
| @itemx -version |
| Print the @code{as} version. |
| |
| @item --version |
| Print the @code{as} version and exit. |
| |
| @item -W |
| Suppress warning messages. |
| |
| @item -w |
| Ignored. |
| |
| @item -x |
| Ignored. |
| |
| @item -Z |
| Generate an object file even after errors. |
| |
| @item -- | @var{files} @dots{} |
| Standard input, or source files to assemble. |
| |
| @end table |
| |
| @ifset ARC |
| The following options are available when @value{AS} is configured for |
| an ARC processor. |
| |
| @table @code |
| |
| @cindex ARC endianness |
| @cindex endianness, ARC |
| @cindex big endian output, ARC |
| @item -mbig-endian |
| Generate ``big endian'' format output. |
| |
| @cindex little endian output, ARC |
| @item -mlittle-endian |
| Generate ``little endian'' format output. |
| |
| @end table |
| @end ifset |
| |
| @ifset ARM |
| The following options are available when @value{AS} is configured for the ARM |
| processor family. |
| |
| @table @code |
| @item -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m] | -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t |
| Specify which variant of the ARM architecture is the target. |
| @item -mthumb | -mall |
| Enable or disable Thumb only instruction decoding. |
| @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu |
| Select which Floating Point architcture is the target. |
| @item -mapcs-32 | -mapcs-26 |
| Select which procedure calling convention is in use. |
| @item -EB | -EL |
| Select either big-endian (-EB) or little-endian (-EL) output. |
| @end table |
| @end ifset |
| |
| @ifset D10V |
| The following options are available when @value{AS} is configured for |
| a D10V processor. |
| @table @code |
| @cindex D10V optimization |
| @cindex optimization, D10V |
| @item -O |
| Optimize output by parallelizing instructions. |
| @end table |
| @end ifset |
| |
| @ifset D30V |
| The following options are available when @value{AS} is configured for a D30V |
| processor. |
| @table @code |
| @cindex D30V optimization |
| @cindex optimization, D30V |
| @item -O |
| Optimize output by parallelizing instructions. |
| |
| @cindex D30V nops |
| @item -n |
| Warn when nops are generated. |
| |
| @cindex D30V nops after 32-bit multiply |
| @item -N |
| Warn when a nop after a 32-bit multiply instruction is generated. |
| @end table |
| @end ifset |
| |
| @ifset I960 |
| The following options are available when @value{AS} is configured for the |
| Intel 80960 processor. |
| |
| @table @code |
| @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC |
| Specify which variant of the 960 architecture is the target. |
| |
| @item -b |
| Add code to collect statistics about branches taken. |
| |
| @item -no-relax |
| Do not alter compare-and-branch instructions for long displacements; |
| error if necessary. |
| |
| @end table |
| @end ifset |
| |
| |
| @ifset M680X0 |
| The following options are available when @value{AS} is configured for the |
| Motorola 68000 series. |
| |
| @table @code |
| |
| @item -l |
| Shorten references to undefined symbols, to one word instead of two. |
| |
| @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060 |
| @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200 |
| Specify what processor in the 68000 family is the target. The default |
| is normally the 68020, but this can be changed at configuration time. |
| |
| @item -m68881 | -m68882 | -mno-68881 | -mno-68882 |
| The target machine does (or does not) have a floating-point coprocessor. |
| The default is to assume a coprocessor for 68020, 68030, and cpu32. Although |
| the basic 68000 is not compatible with the 68881, a combination of the |
| two can be specified, since it's possible to do emulation of the |
| coprocessor instructions with the main processor. |
| |
| @item -m68851 | -mno-68851 |
| The target machine does (or does not) have a memory-management |
| unit coprocessor. The default is to assume an MMU for 68020 and up. |
| |
| @end table |
| @end ifset |
| |
| @ifset SPARC |
| The following options are available when @code{@value{AS}} is configured |
| for the SPARC architecture: |
| |
| @table @code |
| @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite |
| @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a |
| Explicitly select a variant of the SPARC architecture. |
| |
| @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment. |
| @samp{-Av9} and @samp{-Av9a} select a 64 bit environment. |
| |
| @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with |
| UltraSPARC extensions. |
| |
| @item -xarch=v8plus | -xarch=v8plusa |
| For compatibility with the Solaris v9 assembler. These options are |
| equivalent to -Av8plus and -Av8plusa, respectively. |
| |
| @item -bump |
| Warn when the assembler switches to another architecture. |
| @end table |
| @end ifset |
| |
| @ifset MIPS |
| The following options are available when @value{AS} is configured for |
| a MIPS processor. |
| |
| @table @code |
| @item -G @var{num} |
| This option sets the largest size of an object that can be referenced |
| implicitly with the @code{gp} register. It is only accepted for targets that |
| use ECOFF format, such as a DECstation running Ultrix. The default value is 8. |
| |
| @cindex MIPS endianness |
| @cindex endianness, MIPS |
| @cindex big endian output, MIPS |
| @item -EB |
| Generate ``big endian'' format output. |
| |
| @cindex little endian output, MIPS |
| @item -EL |
| Generate ``little endian'' format output. |
| |
| @cindex MIPS ISA |
| @item -mips1 |
| @itemx -mips2 |
| @itemx -mips3 |
| Generate code for a particular MIPS Instruction Set Architecture level. |
| @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors, |
| @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000} |
| processor. |
| |
| @item -m4650 |
| @itemx -no-m4650 |
| Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept |
| the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop} |
| instructions around accesses to the @samp{HI} and @samp{LO} registers. |
| @samp{-no-m4650} turns off this option. |
| |
| @item -mcpu=@var{CPU} |
| Generate code for a particular MIPS cpu. This has little effect on the |
| assembler, but it is passed by @code{@value{GCC}}. |
| |
| @cindex emulation |
| @item --emulation=@var{name} |
| This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured |
| for some other target, in all respects, including output format (choosing |
| between ELF and ECOFF only), handling of pseudo-opcodes which may generate |
| debugging information or store symbol table information, and default |
| endianness. The available configuration names are: @samp{mipsecoff}, |
| @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf}, |
| @samp{mipsbelf}. The first two do not alter the default endianness from that |
| of the primary target for which the assembler was configured; the others change |
| the default to little- or big-endian as indicated by the @samp{b} or @samp{l} |
| in the name. Using @samp{-EB} or @samp{-EL} will override the endianness |
| selection in any case. |
| |
| This option is currently supported only when the primary target |
| @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target. |
| Furthermore, the primary target or others specified with |
| @samp{--enable-targets=@dots{}} at configuration time must include support for |
| the other format, if both are to be available. For example, the Irix 5 |
| configuration includes support for both. |
| |
| Eventually, this option will support more configurations, with more |
| fine-grained control over the assembler's behavior, and will be supported for |
| more processors. |
| |
| @item -nocpp |
| @code{@value{AS}} ignores this option. It is accepted for compatibility with |
| the native tools. |
| |
| @need 900 |
| @item --trap |
| @itemx --no-trap |
| @itemx --break |
| @itemx --no-break |
| Control how to deal with multiplication overflow and division by zero. |
| @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception |
| (and only work for Instruction Set Architecture level 2 and higher); |
| @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a |
| break exception. |
| @end table |
| @end ifset |
| |
| @ifset MCORE |
| The following options are available when @value{AS} is configured for |
| an MCore processor. |
| |
| @table @code |
| @item -jsri2bsr |
| @itemx -nojsri2bsr |
| Enable or disable the JSRI to BSR transformation. By default this is enabled. |
| The command line option @samp{-nojsri2bsr} can be used to disable it. |
| |
| @item -sifilter |
| @itemx -nosifilter |
| Enable or disable the silicon filter behaviour. By default this is disabled. |
| The default can be overidden by the @samp{-sifilter} command line option. |
| |
| @item -relax |
| Alter jump instructions for long displacements. |
| |
| |
| @end table |
| @end ifset |
| |
| @menu |
| * Manual:: Structure of this Manual |
| * GNU Assembler:: The GNU Assembler |
| * Object Formats:: Object File Formats |
| * Command Line:: Command Line |
| * Input Files:: Input Files |
| * Object:: Output (Object) File |
| * Errors:: Error and Warning Messages |
| @end menu |
| |
| @node Manual |
| @section Structure of this Manual |
| |
| @cindex manual, structure and purpose |
| This manual is intended to describe what you need to know to use |
| @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including |
| notation for symbols, constants, and expressions; the directives that |
| @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}. |
| |
| @ifclear GENERIC |
| We also cover special features in the @value{TARGET} |
| configuration of @code{@value{AS}}, including assembler directives. |
| @end ifclear |
| @ifset GENERIC |
| This manual also describes some of the machine-dependent features of |
| various flavors of the assembler. |
| @end ifset |
| |
| @cindex machine instructions (not covered) |
| On the other hand, this manual is @emph{not} intended as an introduction |
| to programming in assembly language---let alone programming in general! |
| In a similar vein, we make no attempt to introduce the machine |
| architecture; we do @emph{not} describe the instruction set, standard |
| mnemonics, registers or addressing modes that are standard to a |
| particular architecture. |
| @ifset GENERIC |
| You may want to consult the manufacturer's |
| machine architecture manual for this information. |
| @end ifset |
| @ifclear GENERIC |
| @ifset H8/300 |
| For information on the H8/300 machine instruction set, see @cite{H8/300 |
| Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H, |
| see @cite{H8/300H Series Programming Manual} (Hitachi). |
| @end ifset |
| @ifset H8/500 |
| For information on the H8/500 machine instruction set, see @cite{H8/500 |
| Series Programming Manual} (Hitachi M21T001). |
| @end ifset |
| @ifset SH |
| For information on the Hitachi SH machine instruction set, see |
| @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.). |
| @end ifset |
| @ifset Z8000 |
| For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual} |
| @end ifset |
| @end ifclear |
| |
| @c I think this is premature---doc@cygnus.com, 17jan1991 |
| @ignore |
| Throughout this manual, we assume that you are running @dfn{GNU}, |
| the portable operating system from the @dfn{Free Software |
| Foundation, Inc.}. This restricts our attention to certain kinds of |
| computer (in particular, the kinds of computers that @sc{gnu} can run on); |
| once this assumption is granted examples and definitions need less |
| qualification. |
| |
| @code{@value{AS}} is part of a team of programs that turn a high-level |
| human-readable series of instructions into a low-level |
| computer-readable series of instructions. Different versions of |
| @code{@value{AS}} are used for different kinds of computer. |
| @end ignore |
| |
| @c There used to be a section "Terminology" here, which defined |
| @c "contents", "byte", "word", and "long". Defining "word" to any |
| @c particular size is confusing when the .word directive may generate 16 |
| @c bits on one machine and 32 bits on another; in general, for the user |
| @c version of this manual, none of these terms seem essential to define. |
| @c They were used very little even in the former draft of the manual; |
| @c this draft makes an effort to avoid them (except in names of |
| @c directives). |
| |
| @node GNU Assembler |
| @section The GNU Assembler |
| |
| @sc{gnu} @code{as} is really a family of assemblers. |
| @ifclear GENERIC |
| This manual describes @code{@value{AS}}, a member of that family which is |
| configured for the @value{TARGET} architectures. |
| @end ifclear |
| If you use (or have used) the @sc{gnu} assembler on one architecture, you |
| should find a fairly similar environment when you use it on another |
| architecture. Each version has much in common with the others, |
| including object file formats, most assembler directives (often called |
| @dfn{pseudo-ops}) and assembler syntax.@refill |
| |
| @cindex purpose of @sc{gnu} assembler |
| @code{@value{AS}} is primarily intended to assemble the output of the |
| @sc{gnu} C compiler @code{@value{GCC}} for use by the linker |
| @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}} |
| assemble correctly everything that other assemblers for the same |
| machine would assemble. |
| @ifset VAX |
| Any exceptions are documented explicitly (@pxref{Machine Dependencies}). |
| @end ifset |
| @ifset M680X0 |
| @c This remark should appear in generic version of manual; assumption |
| @c here is that generic version sets M680x0. |
| This doesn't mean @code{@value{AS}} always uses the same syntax as another |
| assembler for the same architecture; for example, we know of several |
| incompatible versions of 680x0 assembly language syntax. |
| @end ifset |
| |
| Unlike older assemblers, @code{@value{AS}} is designed to assemble a source |
| program in one pass of the source file. This has a subtle impact on the |
| @kbd{.org} directive (@pxref{Org,,@code{.org}}). |
| |
| @node Object Formats |
| @section Object File Formats |
| |
| @cindex object file format |
| The @sc{gnu} assembler can be configured to produce several alternative |
| object file formats. For the most part, this does not affect how you |
| write assembly language programs; but directives for debugging symbols |
| are typically different in different file formats. @xref{Symbol |
| Attributes,,Symbol Attributes}. |
| @ifclear GENERIC |
| @ifclear MULTI-OBJ |
| On the @value{TARGET}, @code{@value{AS}} is configured to produce |
| @value{OBJ-NAME} format object files. |
| @end ifclear |
| @c The following should exhaust all configs that set MULTI-OBJ, ideally |
| @ifset A29K |
| On the @value{TARGET}, @code{@value{AS}} can be configured to produce either |
| @code{a.out} or COFF format object files. |
| @end ifset |
| @ifset I960 |
| On the @value{TARGET}, @code{@value{AS}} can be configured to produce either |
| @code{b.out} or COFF format object files. |
| @end ifset |
| @ifset HPPA |
| On the @value{TARGET}, @code{@value{AS}} can be configured to produce either |
| SOM or ELF format object files. |
| @end ifset |
| @end ifclear |
| |
| @node Command Line |
| @section Command Line |
| |
| @cindex command line conventions |
| After the program name @code{@value{AS}}, the command line may contain |
| options and file names. Options may appear in any order, and may be |
| before, after, or between file names. The order of file names is |
| significant. |
| |
| @cindex standard input, as input file |
| @kindex -- |
| @file{--} (two hyphens) by itself names the standard input file |
| explicitly, as one of the files for @code{@value{AS}} to assemble. |
| |
| @cindex options, command line |
| Except for @samp{--} any command line argument that begins with a |
| hyphen (@samp{-}) is an option. Each option changes the behavior of |
| @code{@value{AS}}. No option changes the way another option works. An |
| option is a @samp{-} followed by one or more letters; the case of |
| the letter is important. All options are optional. |
| |
| Some options expect exactly one file name to follow them. The file |
| name may either immediately follow the option's letter (compatible |
| with older assemblers) or it may be the next command argument (@sc{gnu} |
| standard). These two command lines are equivalent: |
| |
| @smallexample |
| @value{AS} -o my-object-file.o mumble.s |
| @value{AS} -omy-object-file.o mumble.s |
| @end smallexample |
| |
| @node Input Files |
| @section Input Files |
| |
| @cindex input |
| @cindex source program |
| @cindex files, input |
| We use the phrase @dfn{source program}, abbreviated @dfn{source}, to |
| describe the program input to one run of @code{@value{AS}}. The program may |
| be in one or more files; how the source is partitioned into files |
| doesn't change the meaning of the source. |
| |
| @c I added "con" prefix to "catenation" just to prove I can overcome my |
| @c APL training... doc@cygnus.com |
| The source program is a concatenation of the text in all the files, in the |
| order specified. |
| |
| Each time you run @code{@value{AS}} it assembles exactly one source |
| program. The source program is made up of one or more files. |
| (The standard input is also a file.) |
| |
| You give @code{@value{AS}} a command line that has zero or more input file |
| names. The input files are read (from left file name to right). A |
| command line argument (in any position) that has no special meaning |
| is taken to be an input file name. |
| |
| If you give @code{@value{AS}} no file names it attempts to read one input file |
| from the @code{@value{AS}} standard input, which is normally your terminal. You |
| may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program |
| to assemble. |
| |
| Use @samp{--} if you need to explicitly name the standard input file |
| in your command line. |
| |
| If the source is empty, @code{@value{AS}} produces a small, empty object |
| file. |
| |
| @subheading Filenames and Line-numbers |
| |
| @cindex input file linenumbers |
| @cindex line numbers, in input files |
| There are two ways of locating a line in the input file (or files) and |
| either may be used in reporting error messages. One way refers to a line |
| number in a physical file; the other refers to a line number in a |
| ``logical'' file. @xref{Errors, ,Error and Warning Messages}. |
| |
| @dfn{Physical files} are those files named in the command line given |
| to @code{@value{AS}}. |
| |
| @dfn{Logical files} are simply names declared explicitly by assembler |
| directives; they bear no relation to physical files. Logical file names help |
| error messages reflect the original source file, when @code{@value{AS}} source |
| is itself synthesized from other files. @code{@value{AS}} understands the |
| @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also |
| @ref{File,,@code{.file}}. |
| |
| @node Object |
| @section Output (Object) File |
| |
| @cindex object file |
| @cindex output file |
| @kindex a.out |
| @kindex .o |
| Every time you run @code{@value{AS}} it produces an output file, which is |
| your assembly language program translated into numbers. This file |
| is the object file. Its default name is |
| @ifclear BOUT |
| @code{a.out}. |
| @end ifclear |
| @ifset BOUT |
| @ifset GENERIC |
| @code{a.out}, or |
| @end ifset |
| @code{b.out} when @code{@value{AS}} is configured for the Intel 80960. |
| @end ifset |
| You can give it another name by using the @code{-o} option. Conventionally, |
| object file names end with @file{.o}. The default name is used for historical |
| reasons: older assemblers were capable of assembling self-contained programs |
| directly into a runnable program. (For some formats, this isn't currently |
| possible, but it can be done for the @code{a.out} format.) |
| |
| @cindex linker |
| @kindex ld |
| The object file is meant for input to the linker @code{@value{LD}}. It contains |
| assembled program code, information to help @code{@value{LD}} integrate |
| the assembled program into a runnable file, and (optionally) symbolic |
| information for the debugger. |
| |
| @c link above to some info file(s) like the description of a.out. |
| @c don't forget to describe @sc{gnu} info as well as Unix lossage. |
| |
| @node Errors |
| @section Error and Warning Messages |
| |
| @cindex error messsages |
| @cindex warning messages |
| @cindex messages from assembler |
| @code{@value{AS}} may write warnings and error messages to the standard error |
| file (usually your terminal). This should not happen when a compiler |
| runs @code{@value{AS}} automatically. Warnings report an assumption made so |
| that @code{@value{AS}} could keep assembling a flawed program; errors report a |
| grave problem that stops the assembly. |
| |
| @cindex format of warning messages |
| Warning messages have the format |
| |
| @smallexample |
| file_name:@b{NNN}:Warning Message Text |
| @end smallexample |
| |
| @noindent |
| @cindex line numbers, in warnings/errors |
| (where @b{NNN} is a line number). If a logical file name has been given |
| (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of |
| the current input file is used. If a logical line number was given |
| @ifset GENERIC |
| (@pxref{Line,,@code{.line}}) |
| @end ifset |
| @ifclear GENERIC |
| @ifclear A29K |
| (@pxref{Line,,@code{.line}}) |
| @end ifclear |
| @ifset A29K |
| (@pxref{Ln,,@code{.ln}}) |
| @end ifset |
| @end ifclear |
| then it is used to calculate the number printed, |
| otherwise the actual line in the current source file is printed. The |
| message text is intended to be self explanatory (in the grand Unix |
| tradition). |
| |
| @cindex format of error messages |
| Error messages have the format |
| @smallexample |
| file_name:@b{NNN}:FATAL:Error Message Text |
| @end smallexample |
| The file name and line number are derived as for warning |
| messages. The actual message text may be rather less explanatory |
| because many of them aren't supposed to happen. |
| |
| @node Invoking |
| @chapter Command-Line Options |
| |
| @cindex options, all versions of assembler |
| This chapter describes command-line options available in @emph{all} |
| versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific |
| @ifclear GENERIC |
| to the @value{TARGET}. |
| @end ifclear |
| @ifset GENERIC |
| to particular machine architectures. |
| @end ifset |
| |
| If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2), |
| you can use the @samp{-Wa} option to pass arguments through to the assembler. |
| The assembler arguments must be separated from each other (and the @samp{-Wa}) |
| by commas. For example: |
| |
| @smallexample |
| gcc -c -g -O -Wa,-alh,-L file.c |
| @end smallexample |
| |
| @noindent |
| This passes two options to the assembler: @samp{-alh} (emit a listing to |
| standard output with with high-level and assembly source) and @samp{-L} (retain |
| local symbols in the symbol table). |
| |
| Usually you do not need to use this @samp{-Wa} mechanism, since many compiler |
| command-line options are automatically passed to the assembler by the compiler. |
| (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see |
| precisely what options it passes to each compilation pass, including the |
| assembler.) |
| |
| @menu |
| * a:: -a[cdhlns] enable listings |
| * D:: -D for compatibility |
| * f:: -f to work faster |
| * I:: -I for .include search path |
| @ifclear DIFF-TBL-KLUGE |
| * K:: -K for compatibility |
| @end ifclear |
| @ifset DIFF-TBL-KLUGE |
| * K:: -K for difference tables |
| @end ifset |
| |
| * L:: -L to retain local labels |
| * M:: -M or --mri to assemble in MRI compatibility mode |
| * MD:: --MD for dependency tracking |
| * o:: -o to name the object file |
| * R:: -R to join data and text sections |
| * statistics:: --statistics to see statistics about assembly |
| * traditional-format:: --traditional-format for compatible output |
| * v:: -v to announce version |
| * W:: -W to suppress warnings |
| * Z:: -Z to make object file even after errors |
| @end menu |
| |
| @node a |
| @section Enable Listings: @code{-a[cdhlns]} |
| |
| @kindex -a |
| @kindex -ac |
| @kindex -ad |
| @kindex -ah |
| @kindex -al |
| @kindex -an |
| @kindex -as |
| @cindex listings, enabling |
| @cindex assembly listings, enabling |
| |
| These options enable listing output from the assembler. By itself, |
| @samp{-a} requests high-level, assembly, and symbols listing. |
| You can use other letters to select specific options for the list: |
| @samp{-ah} requests a high-level language listing, |
| @samp{-al} requests an output-program assembly listing, and |
| @samp{-as} requests a symbol table listing. |
| High-level listings require that a compiler debugging option like |
| @samp{-g} be used, and that assembly listings (@samp{-al}) be requested |
| also. |
| |
| Use the @samp{-ac} option to omit false conditionals from a listing. Any lines |
| which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any |
| other conditional), or a true @code{.if} followed by an @code{.else}, will be |
| omitted from the listing. |
| |
| Use the @samp{-ad} option to omit debugging directives from the |
| listing. |
| |
| Once you have specified one of these options, you can further control |
| listing output and its appearance using the directives @code{.list}, |
| @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and |
| @code{.sbttl}. |
| The @samp{-an} option turns off all forms processing. |
| If you do not request listing output with one of the @samp{-a} options, the |
| listing-control directives have no effect. |
| |
| The letters after @samp{-a} may be combined into one option, |
| @emph{e.g.}, @samp{-aln}. |
| |
| @node D |
| @section @code{-D} |
| |
| @kindex -D |
| This option has no effect whatsoever, but it is accepted to make it more |
| likely that scripts written for other assemblers also work with |
| @code{@value{AS}}. |
| |
| @node f |
| @section Work Faster: @code{-f} |
| |
| @kindex -f |
| @cindex trusted compiler |
| @cindex faster processing (@code{-f}) |
| @samp{-f} should only be used when assembling programs written by a |
| (trusted) compiler. @samp{-f} stops the assembler from doing whitespace |
| and comment preprocessing on |
| the input file(s) before assembling them. @xref{Preprocessing, |
| ,Preprocessing}. |
| |
| @quotation |
| @emph{Warning:} if you use @samp{-f} when the files actually need to be |
| preprocessed (if they contain comments, for example), @code{@value{AS}} does |
| not work correctly. |
| @end quotation |
| |
| @node I |
| @section @code{.include} search path: @code{-I} @var{path} |
| |
| @kindex -I @var{path} |
| @cindex paths for @code{.include} |
| @cindex search path for @code{.include} |
| @cindex @code{include} directive search path |
| Use this option to add a @var{path} to the list of directories |
| @code{@value{AS}} searches for files specified in @code{.include} |
| directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as |
| many times as necessary to include a variety of paths. The current |
| working directory is always searched first; after that, @code{@value{AS}} |
| searches any @samp{-I} directories in the same order as they were |
| specified (left to right) on the command line. |
| |
| @node K |
| @section Difference Tables: @code{-K} |
| |
| @kindex -K |
| @ifclear DIFF-TBL-KLUGE |
| On the @value{TARGET} family, this option is allowed, but has no effect. It is |
| permitted for compatibility with the @sc{gnu} assembler on other platforms, |
| where it can be used to warn when the assembler alters the machine code |
| generated for @samp{.word} directives in difference tables. The @value{TARGET} |
| family does not have the addressing limitations that sometimes lead to this |
| alteration on other platforms. |
| @end ifclear |
| |
| @ifset DIFF-TBL-KLUGE |
| @cindex difference tables, warning |
| @cindex warning for altered difference tables |
| @code{@value{AS}} sometimes alters the code emitted for directives of the form |
| @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}. |
| You can use the @samp{-K} option if you want a warning issued when this |
| is done. |
| @end ifset |
| |
| @node L |
| @section Include Local Labels: @code{-L} |
| |
| @kindex -L |
| @cindex local labels, retaining in output |
| Labels beginning with @samp{L} (upper case only) are called @dfn{local |
| labels}. @xref{Symbol Names}. Normally you do not see such labels when |
| debugging, because they are intended for the use of programs (like |
| compilers) that compose assembler programs, not for your notice. |
| Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not |
| normally debug with them. |
| |
| This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols |
| in the object file. Usually if you do this you also tell the linker |
| @code{@value{LD}} to preserve symbols whose names begin with @samp{L}. |
| |
| By default, a local label is any label beginning with @samp{L}, but each |
| target is allowed to redefine the local label prefix. |
| @ifset HPPA |
| On the HPPA local labels begin with @samp{L$}. |
| @end ifset |
| @ifset ARM |
| @samp{;} for the ARM family; |
| @end ifset |
| |
| @node M |
| @section Assemble in MRI Compatibility Mode: @code{-M} |
| |
| @kindex -M |
| @cindex MRI compatibility mode |
| The @code{-M} or @code{--mri} option selects MRI compatibility mode. This |
| changes the syntax and pseudo-op handling of @code{@value{AS}} to make it |
| compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the |
| configured target) assembler from Microtec Research. The exact nature of the |
| MRI syntax will not be documented here; see the MRI manuals for more |
| information. Note in particular that the handling of macros and macro |
| arguments is somewhat different. The purpose of this option is to permit |
| assembling existing MRI assembler code using @code{@value{AS}}. |
| |
| The MRI compatibility is not complete. Certain operations of the MRI assembler |
| depend upon its object file format, and can not be supported using other object |
| file formats. Supporting these would require enhancing each object file format |
| individually. These are: |
| |
| @itemize @bullet |
| @item global symbols in common section |
| |
| The m68k MRI assembler supports common sections which are merged by the linker. |
| Other object file formats do not support this. @code{@value{AS}} handles |
| common sections by treating them as a single common symbol. It permits local |
| symbols to be defined within a common section, but it can not support global |
| symbols, since it has no way to describe them. |
| |
| @item complex relocations |
| |
| The MRI assemblers support relocations against a negated section address, and |
| relocations which combine the start addresses of two or more sections. These |
| are not support by other object file formats. |
| |
| @item @code{END} pseudo-op specifying start address |
| |
| The MRI @code{END} pseudo-op permits the specification of a start address. |
| This is not supported by other object file formats. The start address may |
| instead be specified using the @code{-e} option to the linker, or in a linker |
| script. |
| |
| @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops |
| |
| The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module |
| name to the output file. This is not supported by other object file formats. |
| |
| @item @code{ORG} pseudo-op |
| |
| The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given |
| address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op, |
| which changes the location within the current section. Absolute sections are |
| not supported by other object file formats. The address of a section may be |
| assigned within a linker script. |
| @end itemize |
| |
| There are some other features of the MRI assembler which are not supported by |
| @code{@value{AS}}, typically either because they are difficult or because they |
| seem of little consequence. Some of these may be supported in future releases. |
| |
| @itemize @bullet |
| |
| @item EBCDIC strings |
| |
| EBCDIC strings are not supported. |
| |
| @item packed binary coded decimal |
| |
| Packed binary coded decimal is not supported. This means that the @code{DC.P} |
| and @code{DCB.P} pseudo-ops are not supported. |
| |
| @item @code{FEQU} pseudo-op |
| |
| The m68k @code{FEQU} pseudo-op is not supported. |
| |
| @item @code{NOOBJ} pseudo-op |
| |
| The m68k @code{NOOBJ} pseudo-op is not supported. |
| |
| @item @code{OPT} branch control options |
| |
| The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB}, |
| @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically |
| relaxes all branches, whether forward or backward, to an appropriate size, so |
| these options serve no purpose. |
| |
| @item @code{OPT} list control options |
| |
| The following m68k @code{OPT} list control options are ignored: @code{C}, |
| @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M}, |
| @code{MEX}, @code{MC}, @code{MD}, @code{X}. |
| |
| @item other @code{OPT} options |
| |
| The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O}, |
| @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}. |
| |
| @item @code{OPT} @code{D} option is default |
| |
| The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler. |
| @code{OPT NOD} may be used to turn it off. |
| |
| @item @code{XREF} pseudo-op. |
| |
| The m68k @code{XREF} pseudo-op is ignored. |
| |
| @item @code{.debug} pseudo-op |
| |
| The i960 @code{.debug} pseudo-op is not supported. |
| |
| @item @code{.extended} pseudo-op |
| |
| The i960 @code{.extended} pseudo-op is not supported. |
| |
| @item @code{.list} pseudo-op. |
| |
| The various options of the i960 @code{.list} pseudo-op are not supported. |
| |
| @item @code{.optimize} pseudo-op |
| |
| The i960 @code{.optimize} pseudo-op is not supported. |
| |
| @item @code{.output} pseudo-op |
| |
| The i960 @code{.output} pseudo-op is not supported. |
| |
| @item @code{.setreal} pseudo-op |
| |
| The i960 @code{.setreal} pseudo-op is not supported. |
| |
| @end itemize |
| |
| @node MD |
| @section Dependency tracking: @code{--MD} |
| |
| @kindex --MD |
| @cindex dependency tracking |
| @cindex make rules |
| |
| @code{@value{AS}} can generate a dependency file for the file it creates. This |
| file consists of a single rule suitable for @code{make} describing the |
| dependencies of the main source file. |
| |
| The rule is written to the file named in its argument. |
| |
| This feature is used in the automatic updating of makefiles. |
| |
| @node o |
| @section Name the Object File: @code{-o} |
| |
| @kindex -o |
| @cindex naming object file |
| @cindex object file name |
| There is always one object file output when you run @code{@value{AS}}. By |
| default it has the name |
| @ifset GENERIC |
| @ifset I960 |
| @file{a.out} (or @file{b.out}, for Intel 960 targets only). |
| @end ifset |
| @ifclear I960 |
| @file{a.out}. |
| @end ifclear |
| @end ifset |
| @ifclear GENERIC |
| @ifset I960 |
| @file{b.out}. |
| @end ifset |
| @ifclear I960 |
| @file{a.out}. |
| @end ifclear |
| @end ifclear |
| You use this option (which takes exactly one filename) to give the |
| object file a different name. |
| |
| Whatever the object file is called, @code{@value{AS}} overwrites any |
| existing file of the same name. |
| |
| @node R |
| @section Join Data and Text Sections: @code{-R} |
| |
| @kindex -R |
| @cindex data and text sections, joining |
| @cindex text and data sections, joining |
| @cindex joining text and data sections |
| @cindex merging text and data sections |
| @code{-R} tells @code{@value{AS}} to write the object file as if all |
| data-section data lives in the text section. This is only done at |
| the very last moment: your binary data are the same, but data |
| section parts are relocated differently. The data section part of |
| your object file is zero bytes long because all its bytes are |
| appended to the text section. (@xref{Sections,,Sections and Relocation}.) |
| |
| When you specify @code{-R} it would be possible to generate shorter |
| address displacements (because we do not have to cross between text and |
| data section). We refrain from doing this simply for compatibility with |
| older versions of @code{@value{AS}}. In future, @code{-R} may work this way. |
| |
| @ifset COFF |
| When @code{@value{AS}} is configured for COFF output, |
| this option is only useful if you use sections named @samp{.text} and |
| @samp{.data}. |
| @end ifset |
| |
| @ifset HPPA |
| @code{-R} is not supported for any of the HPPA targets. Using |
| @code{-R} generates a warning from @code{@value{AS}}. |
| @end ifset |
| |
| @node statistics |
| @section Display Assembly Statistics: @code{--statistics} |
| |
| @kindex --statistics |
| @cindex statistics, about assembly |
| @cindex time, total for assembly |
| @cindex space used, maximum for assembly |
| Use @samp{--statistics} to display two statistics about the resources used by |
| @code{@value{AS}}: the maximum amount of space allocated during the assembly |
| (in bytes), and the total execution time taken for the assembly (in @sc{cpu} |
| seconds). |
| |
| @node traditional-format |
| @section Compatible output: @code{--traditional-format} |
| |
| @kindex --traditional-format |
| For some targets, the output of @code{@value{AS}} is different in some ways |
| from the output of some existing assembler. This switch requests |
| @code{@value{AS}} to use the traditional format instead. |
| |
| For example, it disables the exception frame optimizations which |
| @code{@value{AS}} normally does by default on @code{@value{GCC}} output. |
| |
| @node v |
| @section Announce Version: @code{-v} |
| |
| @kindex -v |
| @kindex -version |
| @cindex assembler version |
| @cindex version of assembler |
| You can find out what version of as is running by including the |
| option @samp{-v} (which you can also spell as @samp{-version}) on the |
| command line. |
| |
| @node W |
| @section Suppress Warnings: @code{-W} |
| |
| @kindex -W |
| @cindex suppressing warnings |
| @cindex warnings, suppressing |
| @code{@value{AS}} should never give a warning or error message when |
| assembling compiler output. But programs written by people often |
| cause @code{@value{AS}} to give a warning that a particular assumption was |
| made. All such warnings are directed to the standard error file. |
| If you use this option, no warnings are issued. This option only |
| affects the warning messages: it does not change any particular of how |
| @code{@value{AS}} assembles your file. Errors, which stop the assembly, are |
| still reported. |
| |
| @node Z |
| @section Generate Object File in Spite of Errors: @code{-Z} |
| @cindex object file, after errors |
| @cindex errors, continuing after |
| After an error message, @code{@value{AS}} normally produces no output. If for |
| some reason you are interested in object file output even after |
| @code{@value{AS}} gives an error message on your program, use the @samp{-Z} |
| option. If there are any errors, @code{@value{AS}} continues anyways, and |
| writes an object file after a final warning message of the form @samp{@var{n} |
| errors, @var{m} warnings, generating bad object file.} |
| |
| @node Syntax |
| @chapter Syntax |
| |
| @cindex machine-independent syntax |
| @cindex syntax, machine-independent |
| This chapter describes the machine-independent syntax allowed in a |
| source file. @code{@value{AS}} syntax is similar to what many other |
| assemblers use; it is inspired by the BSD 4.2 |
| @ifclear VAX |
| assembler. |
| @end ifclear |
| @ifset VAX |
| assembler, except that @code{@value{AS}} does not assemble Vax bit-fields. |
| @end ifset |
| |
| @menu |
| * Preprocessing:: Preprocessing |
| * Whitespace:: Whitespace |
| * Comments:: Comments |
| * Symbol Intro:: Symbols |
| * Statements:: Statements |
| * Constants:: Constants |
| @end menu |
| |
| @node Preprocessing |
| @section Preprocessing |
| |
| @cindex preprocessing |
| The @code{@value{AS}} internal preprocessor: |
| @itemize @bullet |
| @cindex whitespace, removed by preprocessor |
| @item |
| adjusts and removes extra whitespace. It leaves one space or tab before |
| the keywords on a line, and turns any other whitespace on the line into |
| a single space. |
| |
| @cindex comments, removed by preprocessor |
| @item |
| removes all comments, replacing them with a single space, or an |
| appropriate number of newlines. |
| |
| @cindex constants, converted by preprocessor |
| @item |
| converts character constants into the appropriate numeric values. |
| @end itemize |
| |
| It does not do macro processing, include file handling, or |
| anything else you may get from your C compiler's preprocessor. You can |
| do include file processing with the @code{.include} directive |
| (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver |
| to get other ``CPP'' style preprocessing, by giving the input file a |
| @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of |
| Output, gcc.info, Using GNU CC}. |
| |
| Excess whitespace, comments, and character constants |
| cannot be used in the portions of the input text that are not |
| preprocessed. |
| |
| @cindex turning preprocessing on and off |
| @cindex preprocessing, turning on and off |
| @kindex #NO_APP |
| @kindex #APP |
| If the first line of an input file is @code{#NO_APP} or if you use the |
| @samp{-f} option, whitespace and comments are not removed from the input file. |
| Within an input file, you can ask for whitespace and comment removal in |
| specific portions of the by putting a line that says @code{#APP} before the |
| text that may contain whitespace or comments, and putting a line that says |
| @code{#NO_APP} after this text. This feature is mainly intend to support |
| @code{asm} statements in compilers whose output is otherwise free of comments |
| and whitespace. |
| |
| @node Whitespace |
| @section Whitespace |
| |
| @cindex whitespace |
| @dfn{Whitespace} is one or more blanks or tabs, in any order. |
| Whitespace is used to separate symbols, and to make programs neater for |
| people to read. Unless within character constants |
| (@pxref{Characters,,Character Constants}), any whitespace means the same |
| as exactly one space. |
| |
| @node Comments |
| @section Comments |
| |
| @cindex comments |
| There are two ways of rendering comments to @code{@value{AS}}. In both |
| cases the comment is equivalent to one space. |
| |
| Anything from @samp{/*} through the next @samp{*/} is a comment. |
| This means you may not nest these comments. |
| |
| @smallexample |
| /* |
| The only way to include a newline ('\n') in a comment |
| is to use this sort of comment. |
| */ |
| |
| /* This sort of comment does not nest. */ |
| @end smallexample |
| |
| @cindex line comment character |
| Anything from the @dfn{line comment} character to the next newline |
| is considered a comment and is ignored. The line comment character is |
| @ifset A29K |
| @samp{;} for the AMD 29K family; |
| @end ifset |
| @ifset ARC |
| @samp{;} on the ARC; |
| @end ifset |
| @ifset H8/300 |
| @samp{;} for the H8/300 family; |
| @end ifset |
| @ifset H8/500 |
| @samp{!} for the H8/500 family; |
| @end ifset |
| @ifset HPPA |
| @samp{;} for the HPPA; |
| @end ifset |
| @ifset I960 |
| @samp{#} on the i960; |
| @end ifset |
| @ifset SH |
| @samp{!} for the Hitachi SH; |
| @end ifset |
| @ifset SPARC |
| @samp{!} on the SPARC; |
| @end ifset |
| @ifset M32R |
| @samp{#} on the m32r; |
| @end ifset |
| @ifset M680X0 |
| @samp{|} on the 680x0; |
| @end ifset |
| @ifset VAX |
| @samp{#} on the Vax; |
| @end ifset |
| @ifset Z8000 |
| @samp{!} for the Z8000; |
| @end ifset |
| @ifset V850 |
| @samp{#} on the V850; |
| @end ifset |
| see @ref{Machine Dependencies}. @refill |
| @c FIXME What about i386, m88k, i860? |
| |
| @ifset GENERIC |
| On some machines there are two different line comment characters. One |
| character only begins a comment if it is the first non-whitespace character on |
| a line, while the other always begins a comment. |
| @end ifset |
| |
| @ifset V850 |
| The V850 assembler also supports a double dash as starting a comment that |
| extends to the end of the line. |
| |
| @samp{--}; |
| @end ifset |
| |
| @kindex # |
| @cindex lines starting with @code{#} |
| @cindex logical line numbers |
| To be compatible with past assemblers, lines that begin with @samp{#} have a |
| special interpretation. Following the @samp{#} should be an absolute |
| expression (@pxref{Expressions}): the logical line number of the @emph{next} |
| line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a |
| new logical file name. The rest of the line, if any, should be whitespace. |
| |
| If the first non-whitespace characters on the line are not numeric, |
| the line is ignored. (Just like a comment.) |
| |
| @smallexample |
| # This is an ordinary comment. |
| # 42-6 "new_file_name" # New logical file name |
| # This is logical line # 36. |
| @end smallexample |
| This feature is deprecated, and may disappear from future versions |
| of @code{@value{AS}}. |
| |
| @node Symbol Intro |
| @section Symbols |
| |
| @cindex characters used in symbols |
| @ifclear SPECIAL-SYMS |
| A @dfn{symbol} is one or more characters chosen from the set of all |
| letters (both upper and lower case), digits and the three characters |
| @samp{_.$}. |
| @end ifclear |
| @ifset SPECIAL-SYMS |
| @ifclear GENERIC |
| @ifset H8 |
| A @dfn{symbol} is one or more characters chosen from the set of all |
| letters (both upper and lower case), digits and the three characters |
| @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in |
| symbol names.) |
| @end ifset |
| @end ifclear |
| @end ifset |
| @ifset GENERIC |
| On most machines, you can also use @code{$} in symbol names; exceptions |
| are noted in @ref{Machine Dependencies}. |
| @end ifset |
| No symbol may begin with a digit. Case is significant. |
| There is no length limit: all characters are significant. Symbols are |
| delimited by characters not in that set, or by the beginning of a file |
| (since the source program must end with a newline, the end of a file is |
| not a possible symbol delimiter). @xref{Symbols}. |
| @cindex length of symbols |
| |
| @node Statements |
| @section Statements |
| |
| @cindex statements, structure of |
| @cindex line separator character |
| @cindex statement separator character |
| @ifclear GENERIC |
| @ifclear abnormal-separator |
| A @dfn{statement} ends at a newline character (@samp{\n}) or at a |
| semicolon (@samp{;}). The newline or semicolon is considered part of |
| the preceding statement. Newlines and semicolons within character |
| constants are an exception: they do not end statements. |
| @end ifclear |
| @ifset abnormal-separator |
| @ifset A29K |
| A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at'' |
| sign (@samp{@@}). The newline or at sign is considered part of the |
| preceding statement. Newlines and at signs within character constants |
| are an exception: they do not end statements. |
| @end ifset |
| @ifset HPPA |
| A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation |
| point (@samp{!}). The newline or exclamation point is considered part of the |
| preceding statement. Newlines and exclamation points within character |
| constants are an exception: they do not end statements. |
| @end ifset |
| @ifset H8 |
| A @dfn{statement} ends at a newline character (@samp{\n}); or (for the |
| H8/300) a dollar sign (@samp{$}); or (for the |
| Hitachi-SH or the |
| H8/500) a semicolon |
| (@samp{;}). The newline or separator character is considered part of |
| the preceding statement. Newlines and separators within character |
| constants are an exception: they do not end statements. |
| @end ifset |
| @end ifset |
| @end ifclear |
| @ifset GENERIC |
| A @dfn{statement} ends at a newline character (@samp{\n}) or line |
| separator character. (The line separator is usually @samp{;}, unless |
| this conflicts with the comment character; @pxref{Machine Dependencies}.) The |
| newline or separator character is considered part of the preceding |
| statement. Newlines and separators within character constants are an |
| exception: they do not end statements. |
| @end ifset |
| |
| @cindex newline, required at file end |
| @cindex EOF, newline must precede |
| It is an error to end any statement with end-of-file: the last |
| character of any input file should be a newline.@refill |
| |
| An empty statement is allowed, and may include whitespace. It is ignored. |
| |
| @cindex instructions and directives |
| @cindex directives and instructions |
| @c "key symbol" is not used elsewhere in the document; seems pedantic to |
| @c @defn{} it in that case, as was done previously... doc@cygnus.com, |
| @c 13feb91. |
| A statement begins with zero or more labels, optionally followed by a |
| key symbol which determines what kind of statement it is. The key |
| symbol determines the syntax of the rest of the statement. If the |
| symbol begins with a dot @samp{.} then the statement is an assembler |
| directive: typically valid for any computer. If the symbol begins with |
| a letter the statement is an assembly language @dfn{instruction}: it |
| assembles into a machine language instruction. |
| @ifset GENERIC |
| Different versions of @code{@value{AS}} for different computers |
| recognize different instructions. In fact, the same symbol may |
| represent a different instruction in a different computer's assembly |
| language.@refill |
| @end ifset |
| |
| @cindex @code{:} (label) |
| @cindex label (@code{:}) |
| A label is a symbol immediately followed by a colon (@code{:}). |
| Whitespace before a label or after a colon is permitted, but you may not |
| have whitespace between a label's symbol and its colon. @xref{Labels}. |
| |
| @ifset HPPA |
| For HPPA targets, labels need not be immediately followed by a colon, but |
| the definition of a label must begin in column zero. This also implies that |
| only one label may be defined on each line. |
| @end ifset |
| |
| @smallexample |
| label: .directive followed by something |
| another_label: # This is an empty statement. |
| instruction operand_1, operand_2, @dots{} |
| @end smallexample |
| |
| @node Constants |
| @section Constants |
| |
| @cindex constants |
| A constant is a number, written so that its value is known by |
| inspection, without knowing any context. Like this: |
| @smallexample |
| @group |
| .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value. |
| .ascii "Ring the bell\7" # A string constant. |
| .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum. |
| .float 0f-314159265358979323846264338327\ |
| 95028841971.693993751E-40 # - pi, a flonum. |
| @end group |
| @end smallexample |
| |
| @menu |
| * Characters:: Character Constants |
| * Numbers:: Number Constants |
| @end menu |
| |
| @node Characters |
| @subsection Character Constants |
| |
| @cindex character constants |
| @cindex constants, character |
| There are two kinds of character constants. A @dfn{character} stands |
| for one character in one byte and its value may be used in |
| numeric expressions. String constants (properly called string |
| @emph{literals}) are potentially many bytes and their values may not be |
| used in arithmetic expressions. |
| |
| @menu |
| * Strings:: Strings |
| * Chars:: Characters |
| @end menu |
| |
| @node Strings |
| @subsubsection Strings |
| |
| @cindex string constants |
| @cindex constants, string |
| A @dfn{string} is written between double-quotes. It may contain |
| double-quotes or null characters. The way to get special characters |
| into a string is to @dfn{escape} these characters: precede them with |
| a backslash @samp{\} character. For example @samp{\\} represents |
| one backslash: the first @code{\} is an escape which tells |
| @code{@value{AS}} to interpret the second character literally as a backslash |
| (which prevents @code{@value{AS}} from recognizing the second @code{\} as an |
| escape character). The complete list of escapes follows. |
| |
| @cindex escape codes, character |
| @cindex character escape codes |
| @table @kbd |
| @c @item \a |
| @c Mnemonic for ACKnowledge; for ASCII this is octal code 007. |
| @c |
| @cindex @code{\b} (backspace character) |
| @cindex backspace (@code{\b}) |
| @item \b |
| Mnemonic for backspace; for ASCII this is octal code 010. |
| |
| @c @item \e |
| @c Mnemonic for EOText; for ASCII this is octal code 004. |
| @c |
| @cindex @code{\f} (formfeed character) |
| @cindex formfeed (@code{\f}) |
| @item \f |
| Mnemonic for FormFeed; for ASCII this is octal code 014. |
| |
| @cindex @code{\n} (newline character) |
| @cindex newline (@code{\n}) |
| @item \n |
| Mnemonic for newline; for ASCII this is octal code 012. |
| |
| @c @item \p |
| @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}. |
| @c |
| @cindex @code{\r} (carriage return character) |
| @cindex carriage return (@code{\r}) |
| @item \r |
| Mnemonic for carriage-Return; for ASCII this is octal code 015. |
| |
| @c @item \s |
| @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with |
| @c other assemblers. |
| @c |
| @cindex @code{\t} (tab) |
| @cindex tab (@code{\t}) |
| @item \t |
| Mnemonic for horizontal Tab; for ASCII this is octal code 011. |
| |
| @c @item \v |
| @c Mnemonic for Vertical tab; for ASCII this is octal code 013. |
| @c @item \x @var{digit} @var{digit} @var{digit} |
| @c A hexadecimal character code. The numeric code is 3 hexadecimal digits. |
| @c |
| @cindex @code{\@var{ddd}} (octal character code) |
| @cindex octal character code (@code{\@var{ddd}}) |
| @item \ @var{digit} @var{digit} @var{digit} |
| An octal character code. The numeric code is 3 octal digits. |
| For compatibility with other Unix systems, 8 and 9 are accepted as digits: |
| for example, @code{\008} has the value 010, and @code{\009} the value 011. |
| |
| @cindex @code{\@var{xd...}} (hex character code) |
| @cindex hex character code (@code{\@var{xd...}}) |
| @item \@code{x} @var{hex-digits...} |
| A hex character code. All trailing hex digits are combined. Either upper or |
| lower case @code{x} works. |
| |
| @cindex @code{\\} (@samp{\} character) |
| @cindex backslash (@code{\\}) |
| @item \\ |
| Represents one @samp{\} character. |
| |
| @c @item \' |
| @c Represents one @samp{'} (accent acute) character. |
| @c This is needed in single character literals |
| @c (@xref{Characters,,Character Constants}.) to represent |
| @c a @samp{'}. |
| @c |
| @cindex @code{\"} (doublequote character) |
| @cindex doublequote (@code{\"}) |
| @item \" |
| Represents one @samp{"} character. Needed in strings to represent |
| this character, because an unescaped @samp{"} would end the string. |
| |
| @item \ @var{anything-else} |
| Any other character when escaped by @kbd{\} gives a warning, but |
| assembles as if the @samp{\} was not present. The idea is that if |
| you used an escape sequence you clearly didn't want the literal |
| interpretation of the following character. However @code{@value{AS}} has no |
| other interpretation, so @code{@value{AS}} knows it is giving you the wrong |
| code and warns you of the fact. |
| @end table |
| |
| Which characters are escapable, and what those escapes represent, |
| varies widely among assemblers. The current set is what we think |
| the BSD 4.2 assembler recognizes, and is a subset of what most C |
| compilers recognize. If you are in doubt, do not use an escape |
| sequence. |
| |
| @node Chars |
| @subsubsection Characters |
| |
| @cindex single character constant |
| @cindex character, single |
| @cindex constant, single character |
| A single character may be written as a single quote immediately |
| followed by that character. The same escapes apply to characters as |
| to strings. So if you want to write the character backslash, you |
| must write @kbd{'\\} where the first @code{\} escapes the second |
| @code{\}. As you can see, the quote is an acute accent, not a |
| grave accent. A newline |
| @ifclear GENERIC |
| @ifclear abnormal-separator |
| (or semicolon @samp{;}) |
| @end ifclear |
| @ifset abnormal-separator |
| @ifset A29K |
| (or at sign @samp{@@}) |
| @end ifset |
| @ifset H8 |
| (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the |
| Hitachi SH or |
| H8/500) |
| @end ifset |
| @end ifset |
| @end ifclear |
| immediately following an acute accent is taken as a literal character |
| and does not count as the end of a statement. The value of a character |
| constant in a numeric expression is the machine's byte-wide code for |
| that character. @code{@value{AS}} assumes your character code is ASCII: |
| @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill |
| |
| @node Numbers |
| @subsection Number Constants |
| |
| @cindex constants, number |
| @cindex number constants |
| @code{@value{AS}} distinguishes three kinds of numbers according to how they |
| are stored in the target machine. @emph{Integers} are numbers that |
| would fit into an @code{int} in the C language. @emph{Bignums} are |
| integers, but they are stored in more than 32 bits. @emph{Flonums} |
| are floating point numbers, described below. |
| |
| @menu |
| * Integers:: Integers |
| * Bignums:: Bignums |
| * Flonums:: Flonums |
| @ifclear GENERIC |
| @ifset I960 |
| * Bit Fields:: Bit Fields |
| @end ifset |
| @end ifclear |
| @end menu |
| |
| @node Integers |
| @subsubsection Integers |
| @cindex integers |
| @cindex constants, integer |
| |
| @cindex binary integers |
| @cindex integers, binary |
| A binary integer is @samp{0b} or @samp{0B} followed by zero or more of |
| the binary digits @samp{01}. |
| |
| @cindex octal integers |
| @cindex integers, octal |
| An octal integer is @samp{0} followed by zero or more of the octal |
| digits (@samp{01234567}). |
| |
| @cindex decimal integers |
| @cindex integers, decimal |
| A decimal integer starts with a non-zero digit followed by zero or |
| more digits (@samp{0123456789}). |
| |
| @cindex hexadecimal integers |
| @cindex integers, hexadecimal |
| A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or |
| more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}. |
| |
| Integers have the usual values. To denote a negative integer, use |
| the prefix operator @samp{-} discussed under expressions |
| (@pxref{Prefix Ops,,Prefix Operators}). |
| |
| @node Bignums |
| @subsubsection Bignums |
| |
| @cindex bignums |
| @cindex constants, bignum |
| A @dfn{bignum} has the same syntax and semantics as an integer |
| except that the number (or its negative) takes more than 32 bits to |
| represent in binary. The distinction is made because in some places |
| integers are permitted while bignums are not. |
| |
| @node Flonums |
| @subsubsection Flonums |
| @cindex flonums |
| @cindex floating point numbers |
| @cindex constants, floating point |
| |
| @cindex precision, floating point |
| A @dfn{flonum} represents a floating point number. The translation is |
| indirect: a decimal floating point number from the text is converted by |
| @code{@value{AS}} to a generic binary floating point number of more than |
| sufficient precision. This generic floating point number is converted |
| to a particular computer's floating point format (or formats) by a |
| portion of @code{@value{AS}} specialized to that computer. |
| |
| A flonum is written by writing (in order) |
| @itemize @bullet |
| @item |
| The digit @samp{0}. |
| @ifset HPPA |
| (@samp{0} is optional on the HPPA.) |
| @end ifset |
| |
| @item |
| A letter, to tell @code{@value{AS}} the rest of the number is a flonum. |
| @ifset GENERIC |
| @kbd{e} is recommended. Case is not important. |
| @ignore |
| @c FIXME: verify if flonum syntax really this vague for most cases |
| (Any otherwise illegal letter works here, but that might be changed. Vax BSD |
| 4.2 assembler seems to allow any of @samp{defghDEFGH}.) |
| @end ignore |
| |
| On the H8/300, H8/500, |
| Hitachi SH, |
| and AMD 29K architectures, the letter must be |
| one of the letters @samp{DFPRSX} (in upper or lower case). |
| |
| On the ARC, the letter must be one of the letters @samp{DFRS} |
| (in upper or lower case). |
| |
| On the Intel 960 architecture, the letter must be |
| one of the letters @samp{DFT} (in upper or lower case). |
| |
| On the HPPA architecture, the letter must be @samp{E} (upper case only). |
| @end ifset |
| @ifclear GENERIC |
| @ifset A29K |
| One of the letters @samp{DFPRSX} (in upper or lower case). |
| @end ifset |
| @ifset ARC |
| One of the letters @samp{DFRS} (in upper or lower case). |
| @end ifset |
| @ifset H8 |
| One of the letters @samp{DFPRSX} (in upper or lower case). |
| @end ifset |
| @ifset HPPA |
| The letter @samp{E} (upper case only). |
| @end ifset |
| @ifset I960 |
| One of the letters @samp{DFT} (in upper or lower case). |
| @end ifset |
| @end ifclear |
| |
| @item |
| An optional sign: either @samp{+} or @samp{-}. |
| |
| @item |
| An optional @dfn{integer part}: zero or more decimal digits. |
| |
| @item |
| An optional @dfn{fractional part}: @samp{.} followed by zero |
| or more decimal digits. |
| |
| @item |
| An optional exponent, consisting of: |
| |
| @itemize @bullet |
| @item |
| An @samp{E} or @samp{e}. |
| @c I can't find a config where "EXP_CHARS" is other than 'eE', but in |
| @c principle this can perfectly well be different on different targets. |
| @item |
| Optional sign: either @samp{+} or @samp{-}. |
| @item |
| One or more decimal digits. |
| @end itemize |
| |
| @end itemize |
| |
| At least one of the integer part or the fractional part must be |
| present. The floating point number has the usual base-10 value. |
| |
| @code{@value{AS}} does all processing using integers. Flonums are computed |
| independently of any floating point hardware in the computer running |
| @code{@value{AS}}. |
| |
| @ifclear GENERIC |
| @ifset I960 |
| @c Bit fields are written as a general facility but are also controlled |
| @c by a conditional-compilation flag---which is as of now (21mar91) |
| @c turned on only by the i960 config of GAS. |
| @node Bit Fields |
| @subsubsection Bit Fields |
| |
| @cindex bit fields |
| @cindex constants, bit field |
| You can also define numeric constants as @dfn{bit fields}. |
| specify two numbers separated by a colon--- |
| @example |
| @var{mask}:@var{value} |
| @end example |
| @noindent |
| @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and |
| @var{value}. |
| |
| The resulting number is then packed |
| @ifset GENERIC |
| @c this conditional paren in case bit fields turned on elsewhere than 960 |
| (in host-dependent byte order) |
| @end ifset |
| into a field whose width depends on which assembler directive has the |
| bit-field as its argument. Overflow (a result from the bitwise and |
| requiring more binary digits to represent) is not an error; instead, |
| more constants are generated, of the specified width, beginning with the |
| least significant digits.@refill |
| |
| The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long}, |
| @code{.short}, and @code{.word} accept bit-field arguments. |
| @end ifset |
| @end ifclear |
| |
| @node Sections |
| @chapter Sections and Relocation |
| @cindex sections |
| @cindex relocation |
| |
| @menu |
| * Secs Background:: Background |
| * Ld Sections:: Linker Sections |
| * As Sections:: Assembler Internal Sections |
| * Sub-Sections:: Sub-Sections |
| * bss:: bss Section |
| @end menu |
| |
| @node Secs Background |
| @section Background |
| |
| Roughly, a section is a range of addresses, with no gaps; all data |
| ``in'' those addresses is treated the same for some particular purpose. |
| For example there may be a ``read only'' section. |
| |
| @cindex linker, and assembler |
| @cindex assembler, and linker |
| The linker @code{@value{LD}} reads many object files (partial programs) and |
| combines their contents to form a runnable program. When @code{@value{AS}} |
| emits an object file, the partial program is assumed to start at address 0. |
| @code{@value{LD}} assigns the final addresses for the partial program, so that |
| different partial programs do not overlap. This is actually an |
| oversimplification, but it suffices to explain how @code{@value{AS}} uses |
| sections. |
| |
| @code{@value{LD}} moves blocks of bytes of your program to their run-time |
| addresses. These blocks slide to their run-time addresses as rigid |
| units; their length does not change and neither does the order of bytes |
| within them. Such a rigid unit is called a @emph{section}. Assigning |
| run-time addresses to sections is called @dfn{relocation}. It includes |
| the task of adjusting mentions of object-file addresses so they refer to |
| the proper run-time addresses. |
| @ifset H8 |
| For the H8/300 and H8/500, |
| and for the Hitachi SH, |
| @code{@value{AS}} pads sections if needed to |
| ensure they end on a word (sixteen bit) boundary. |
| @end ifset |
| |
| @cindex standard assembler sections |
| An object file written by @code{@value{AS}} has at least three sections, any |
| of which may be empty. These are named @dfn{text}, @dfn{data} and |
| @dfn{bss} sections. |
| |
| @ifset COFF |
| @ifset GENERIC |
| When it generates COFF output, |
| @end ifset |
| @code{@value{AS}} can also generate whatever other named sections you specify |
| using the @samp{.section} directive (@pxref{Section,,@code{.section}}). |
| If you do not use any directives that place output in the @samp{.text} |
| or @samp{.data} sections, these sections still exist, but are empty. |
| @end ifset |
| |
| @ifset HPPA |
| @ifset GENERIC |
| When @code{@value{AS}} generates SOM or ELF output for the HPPA, |
| @end ifset |
| @code{@value{AS}} can also generate whatever other named sections you |
| specify using the @samp{.space} and @samp{.subspace} directives. See |
| @cite{HP9000 Series 800 Assembly Language Reference Manual} |
| (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace} |
| assembler directives. |
| |
| @ifset SOM |
| Additionally, @code{@value{AS}} uses different names for the standard |
| text, data, and bss sections when generating SOM output. Program text |
| is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and |
| BSS into @samp{$BSS$}. |
| @end ifset |
| @end ifset |
| |
| Within the object file, the text section starts at address @code{0}, the |
| data section follows, and the bss section follows the data section. |
| |
| @ifset HPPA |
| When generating either SOM or ELF output files on the HPPA, the text |
| section starts at address @code{0}, the data section at address |
| @code{0x4000000}, and the bss section follows the data section. |
| @end ifset |
| |
| To let @code{@value{LD}} know which data changes when the sections are |
| relocated, and how to change that data, @code{@value{AS}} also writes to the |
| object file details of the relocation needed. To perform relocation |
| @code{@value{LD}} must know, each time an address in the object |
| file is mentioned: |
| @itemize @bullet |
| @item |
| Where in the object file is the beginning of this reference to |
| an address? |
| @item |
| How long (in bytes) is this reference? |
| @item |
| Which section does the address refer to? What is the numeric value of |
| @display |
| (@var{address}) @minus{} (@var{start-address of section})? |
| @end display |
| @item |
| Is the reference to an address ``Program-Counter relative''? |
| @end itemize |
| |
| @cindex addresses, format of |
| @cindex section-relative addressing |
| In fact, every address @code{@value{AS}} ever uses is expressed as |
| @display |
| (@var{section}) + (@var{offset into section}) |
| @end display |
| @noindent |
| Further, most expressions @code{@value{AS}} computes have this section-relative |
| nature. |
| @ifset SOM |
| (For some object formats, such as SOM for the HPPA, some expressions are |
| symbol-relative instead.) |
| @end ifset |
| |
| In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset |
| @var{N} into section @var{secname}.'' |
| |
| Apart from text, data and bss sections you need to know about the |
| @dfn{absolute} section. When @code{@value{LD}} mixes partial programs, |
| addresses in the absolute section remain unchanged. For example, address |
| @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by |
| @code{@value{LD}}. Although the linker never arranges two partial programs' |
| data sections with overlapping addresses after linking, @emph{by definition} |
| their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one |
| part of a program is always the same address when the program is running as |
| address @code{@{absolute@ 239@}} in any other part of the program. |
| |
| The idea of sections is extended to the @dfn{undefined} section. Any |
| address whose section is unknown at assembly time is by definition |
| rendered @{undefined @var{U}@}---where @var{U} is filled in later. |
| Since numbers are always defined, the only way to generate an undefined |
| address is to mention an undefined symbol. A reference to a named |
| common block would be such a symbol: its value is unknown at assembly |
| time so it has section @emph{undefined}. |
| |
| By analogy the word @emph{section} is used to describe groups of sections in |
| the linked program. @code{@value{LD}} puts all partial programs' text |
| sections in contiguous addresses in the linked program. It is |
| customary to refer to the @emph{text section} of a program, meaning all |
| the addresses of all partial programs' text sections. Likewise for |
| data and bss sections. |
| |
| Some sections are manipulated by @code{@value{LD}}; others are invented for |
| use of @code{@value{AS}} and have no meaning except during assembly. |
| |
| @node Ld Sections |
| @section Linker Sections |
| @code{@value{LD}} deals with just four kinds of sections, summarized below. |
| |
| @table @strong |
| |
| @ifset COFF |
| @cindex named sections |
| @cindex sections, named |
| @item named sections |
| @end ifset |
| @ifset aout-bout |
| @cindex text section |
| @cindex data section |
| @itemx text section |
| @itemx data section |
| @end ifset |
| These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as |
| separate but equal sections. Anything you can say of one section is |
| true another. |
| @ifset aout-bout |
| When the program is running, however, it is |
| customary for the text section to be unalterable. The |
| text section is often shared among processes: it contains |
| instructions, constants and the like. The data section of a running |
| program is usually alterable: for example, C variables would be stored |
| in the data section. |
| @end ifset |
| |
| @cindex bss section |
| @item bss section |
| This section contains zeroed bytes when your program begins running. It |
| is used to hold unitialized variables or common storage. The length of |
| each partial program's bss section is important, but because it starts |
| out containing zeroed bytes there is no need to store explicit zero |
| bytes in the object file. The bss section was invented to eliminate |
| those explicit zeros from object files. |
| |
| @cindex absolute section |
| @item absolute section |
| Address 0 of this section is always ``relocated'' to runtime address 0. |
| This is useful if you want to refer to an address that @code{@value{LD}} must |
| not change when relocating. In this sense we speak of absolute |
| addresses being ``unrelocatable'': they do not change during relocation. |
| |
| @cindex undefined section |
| @item undefined section |
| This ``section'' is a catch-all for address references to objects not in |
| the preceding sections. |
| @c FIXME: ref to some other doc on obj-file formats could go here. |
| @end table |
| |
| @cindex relocation example |
| An idealized example of three relocatable sections follows. |
| @ifset COFF |
| The example uses the traditional section names @samp{.text} and @samp{.data}. |
| @end ifset |
| Memory addresses are on the horizontal axis. |
| |
| @c TEXI2ROFF-KILL |
| @ifinfo |
| @c END TEXI2ROFF-KILL |
| @smallexample |
| +-----+----+--+ |
| partial program # 1: |ttttt|dddd|00| |
| +-----+----+--+ |
| |
| text data bss |
| seg. seg. seg. |
| |
| +---+---+---+ |
| partial program # 2: |TTT|DDD|000| |
| +---+---+---+ |
| |
| +--+---+-----+--+----+---+-----+~~ |
| linked program: | |TTT|ttttt| |dddd|DDD|00000| |
| +--+---+-----+--+----+---+-----+~~ |
| |
| addresses: 0 @dots{} |
| @end smallexample |
| @c TEXI2ROFF-KILL |
| @end ifinfo |
| @need 5000 |
| @tex |
| |
| \line{\it Partial program \#1: \hfil} |
| \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil} |
| \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil} |
| |
| \line{\it Partial program \#2: \hfil} |
| \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil} |
| \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil} |
| |
| \line{\it linked program: \hfil} |
| \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil} |
| \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt |
| ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt |
| DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil} |
| |
| \line{\it addresses: \hfil} |
| \line{0\dots\hfil} |
| |
| @end tex |
| @c END TEXI2ROFF-KILL |
| |
| @node As Sections |
| @section Assembler Internal Sections |
| |
| @cindex internal assembler sections |
| @cindex sections in messages, internal |
| These sections are meant only for the internal use of @code{@value{AS}}. They |
| have no meaning at run-time. You do not really need to know about these |
| sections for most purposes; but they can be mentioned in @code{@value{AS}} |
| warning messages, so it might be helpful to have an idea of their |
| meanings to @code{@value{AS}}. These sections are used to permit the |
| value of every expression in your assembly language program to be a |
| section-relative address. |
| |
| @table @b |
| @cindex assembler internal logic error |
| @item ASSEMBLER-INTERNAL-LOGIC-ERROR! |
| An internal assembler logic error has been found. This means there is a |
| bug in the assembler. |
| |
| @cindex expr (internal section) |
| @item expr section |
| The assembler stores complex expression internally as combinations of |
| symbols. When it needs to represent an expression as a symbol, it puts |
| it in the expr section. |
| @c FIXME item debug |
| @c FIXME item transfer[t] vector preload |
| @c FIXME item transfer[t] vector postload |
| @c FIXME item register |
| @end table |
| |
| @node Sub-Sections |
| @section Sub-Sections |
| |
| @cindex numbered subsections |
| @cindex grouping data |
| @ifset aout-bout |
| Assembled bytes |
| @ifset COFF |
| conventionally |
| @end ifset |
| fall into two sections: text and data. |
| @end ifset |
| You may have separate groups of |
| @ifset GENERIC |
| data in named sections |
| @end ifset |
| @ifclear GENERIC |
| @ifclear aout-bout |
| data in named sections |
| @end ifclear |
| @ifset aout-bout |
| text or data |
| @end ifset |
| @end ifclear |
| that you want to end up near to each other in the object file, even though they |
| are not contiguous in the assembler source. @code{@value{AS}} allows you to |
| use @dfn{subsections} for this purpose. Within each section, there can be |
| numbered subsections with values from 0 to 8192. Objects assembled into the |
| same subsection go into the object file together with other objects in the same |
| subsection. For example, a compiler might want to store constants in the text |
| section, but might not want to have them interspersed with the program being |
| assembled. In this case, the compiler could issue a @samp{.text 0} before each |
| section of code being output, and a @samp{.text 1} before each group of |
| constants being output. |
| |
| Subsections are optional. If you do not use subsections, everything |
| goes in subsection number zero. |
| |
| @ifset GENERIC |
| Each subsection is zero-padded up to a multiple of four bytes. |
| (Subsections may be padded a different amount on different flavors |
| of @code{@value{AS}}.) |
| @end ifset |
| @ifclear GENERIC |
| @ifset H8 |
| On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word |
| boundary (two bytes). |
| The same is true on the Hitachi SH. |
| @end ifset |
| @ifset I960 |
| @c FIXME section padding (alignment)? |
| @c Rich Pixley says padding here depends on target obj code format; that |
| @c doesn't seem particularly useful to say without further elaboration, |
| @c so for now I say nothing about it. If this is a generic BFD issue, |
| @c these paragraphs might need to vanish from this manual, and be |
| @c discussed in BFD chapter of binutils (or some such). |
| @end ifset |
| @ifset A29K |
| On the AMD 29K family, no particular padding is added to section or |
| subsection sizes; @value{AS} forces no alignment on this platform. |
| @end ifset |
| @end ifclear |
| |
| Subsections appear in your object file in numeric order, lowest numbered |
| to highest. (All this to be compatible with other people's assemblers.) |
| The object file contains no representation of subsections; @code{@value{LD}} and |
| other programs that manipulate object files see no trace of them. |
| They just see all your text subsections as a text section, and all your |
| data subsections as a data section. |
| |
| To specify which subsection you want subsequent statements assembled |
| into, use a numeric argument to specify it, in a @samp{.text |
| @var{expression}} or a @samp{.data @var{expression}} statement. |
| @ifset COFF |
| @ifset GENERIC |
| When generating COFF output, you |
| @end ifset |
| @ifclear GENERIC |
| You |
| @end ifclear |
| can also use an extra subsection |
| argument with arbitrary named sections: @samp{.section @var{name}, |
| @var{expression}}. |
| @end ifset |
| @var{Expression} should be an absolute expression. |
| (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0} |
| is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly |
| begins in @code{text 0}. For instance: |
| @smallexample |
| .text 0 # The default subsection is text 0 anyway. |
| .ascii "This lives in the first text subsection. *" |
| .text 1 |
| .ascii "But this lives in the second text subsection." |
| .data 0 |
| .ascii "This lives in the data section," |
| .ascii "in the first data subsection." |
| .text 0 |
| .ascii "This lives in the first text section," |
| .ascii "immediately following the asterisk (*)." |
| @end smallexample |
| |
| Each section has a @dfn{location counter} incremented by one for every byte |
| assembled into that section. Because subsections are merely a convenience |
| restricted to @code{@value{AS}} there is no concept of a subsection location |
| counter. There is no way to directly manipulate a location counter---but the |
| @code{.align} directive changes it, and any label definition captures its |
| current value. The location counter of the section where statements are being |
| assembled is said to be the @dfn{active} location counter. |
| |
| @node bss |
| @section bss Section |
| |
| @cindex bss section |
| @cindex common variable storage |
| The bss section is used for local common variable storage. |
| You may allocate address space in the bss section, but you may |
| not dictate data to load into it before your program executes. When |
| your program starts running, all the contents of the bss |
| section are zeroed bytes. |
| |
| The @code{.lcomm} pseudo-op defines a symbol in the bss section; see |
| @ref{Lcomm,,@code{.lcomm}}. |
| |
| The @code{.comm} pseudo-op may be used to declare a common symbol, which is |
| another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}. |
| |
| @ifset GENERIC |
| When assembling for a target which supports multiple sections, such as ELF or |
| COFF, you may switch into the @code{.bss} section and define symbols as usual; |
| see @ref{Section,,@code{.section}}. You may only assemble zero values into the |
| section. Typically the section will only contain symbol definitions and |
| @code{.skip} directives (@pxref{Skip,,@code{.skip}}). |
| @end ifset |
| |
| @node Symbols |
| @chapter Symbols |
| |
| @cindex symbols |
| Symbols are a central concept: the programmer uses symbols to name |
| things, the linker uses symbols to link, and the debugger uses symbols |
| to debug. |
| |
| @quotation |
| @cindex debuggers, and symbol order |
| @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in |
| the same order they were declared. This may break some debuggers. |
| @end quotation |
| |
| @menu |
| * Labels:: Labels |
| * Setting Symbols:: Giving Symbols Other Values |
| * Symbol Names:: Symbol Names |
| * Dot:: The Special Dot Symbol |
| * Symbol Attributes:: Symbol Attributes |
| @end menu |
| |
| @node Labels |
| @section Labels |
| |
| @cindex labels |
| A @dfn{label} is written as a symbol immediately followed by a colon |
| @samp{:}. The symbol then represents the current value of the |
| active location counter, and is, for example, a suitable instruction |
| operand. You are warned if you use the same symbol to represent two |
| different locations: the first definition overrides any other |
| definitions. |
| |
| @ifset HPPA |
| On the HPPA, the usual form for a label need not be immediately followed by a |
| colon, but instead must start in column zero. Only one label may be defined on |
| a single line. To work around this, the HPPA version of @code{@value{AS}} also |
| provides a special directive @code{.label} for defining labels more flexibly. |
| @end ifset |
| |
| @node Setting Symbols |
| @section Giving Symbols Other Values |
| |
| @cindex assigning values to symbols |
| @cindex symbol values, assigning |
| A symbol can be given an arbitrary value by writing a symbol, followed |
| by an equals sign @samp{=}, followed by an expression |
| (@pxref{Expressions}). This is equivalent to using the @code{.set} |
| directive. @xref{Set,,@code{.set}}. |
| |
| @node Symbol Names |
| @section Symbol Names |
| |
| @cindex symbol names |
| @cindex names, symbol |
| @ifclear SPECIAL-SYMS |
| Symbol names begin with a letter or with one of @samp{._}. On most |
| machines, you can also use @code{$} in symbol names; exceptions are |
| noted in @ref{Machine Dependencies}. That character may be followed by any |
| string of digits, letters, dollar signs (unless otherwise noted in |
| @ref{Machine Dependencies}), and underscores. |
| @end ifclear |
| @ifset A29K |
| For the AMD 29K family, @samp{?} is also allowed in the |
| body of a symbol name, though not at its beginning. |
| @end ifset |
| |
| @ifset SPECIAL-SYMS |
| @ifset H8 |
| Symbol names begin with a letter or with one of @samp{._}. On the |
| Hitachi SH or the |
| H8/500, you can also use @code{$} in symbol names. That character may |
| be followed by any string of digits, letters, dollar signs (save on the |
| H8/300), and underscores. |
| @end ifset |
| @end ifset |
| |
| Case of letters is significant: @code{foo} is a different symbol name |
| than @code{Foo}. |
| |
| Each symbol has exactly one name. Each name in an assembly language program |
| refers to exactly one symbol. You may use that symbol name any number of times |
| in a program. |
| |
| @subheading Local Symbol Names |
| |
| @cindex local symbol names |
| @cindex symbol names, local |
| @cindex temporary symbol names |
| @cindex symbol names, temporary |
| Local symbols help compilers and programmers use names temporarily. |
| There are ten local symbol names, which are re-used throughout the |
| program. You may refer to them using the names @samp{0} @samp{1} |
| @dots{} @samp{9}. To define a local symbol, write a label of the form |
| @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most |
| recent previous definition of that symbol write @samp{@b{N}b}, using the |
| same digit as when you defined the label. To refer to the next |
| definition of a local label, write @samp{@b{N}f}---where @b{N} gives you |
| a choice of 10 forward references. The @samp{b} stands for |
| ``backwards'' and the @samp{f} stands for ``forwards''. |
| |
| Local symbols are not emitted by the current @sc{gnu} C compiler. |
| |
| There is no restriction on how you can use these labels, but |
| remember that at any point in the assembly you can refer to at most |
| 10 prior local labels and to at most 10 forward local labels. |
| |
| Local symbol names are only a notation device. They are immediately |
| transformed into more conventional symbol names before the assembler |
| uses them. The symbol names stored in the symbol table, appearing in |
| error messages and optionally emitted to the object file have these |
| parts: |
| |
| @table @code |
| @item L |
| All local labels begin with @samp{L}. Normally both @code{@value{AS}} and |
| @code{@value{LD}} forget symbols that start with @samp{L}. These labels are |
| used for symbols you are never intended to see. If you use the |
| @samp{-L} option then @code{@value{AS}} retains these symbols in the |
| object file. If you also instruct @code{@value{LD}} to retain these symbols, |
| you may use them in debugging. |
| |
| @item @var{digit} |
| If the label is written @samp{0:} then the digit is @samp{0}. |
| If the label is written @samp{1:} then the digit is @samp{1}. |
| And so on up through @samp{9:}. |
| |
| @item @kbd{C-A} |
| This unusual character is included so you do not accidentally invent |
| a symbol of the same name. The character has ASCII value |
| @samp{\001}. |
| |
| @item @emph{ordinal number} |
| This is a serial number to keep the labels distinct. The first |
| @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the |
| number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:} |
| through @samp{9:}. |
| @end table |
| |
| For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th |
| @code{3:} is named @code{L3@kbd{C-A}44}. |
| |
| @node Dot |
| @section The Special Dot Symbol |
| |
| @cindex dot (symbol) |
| @cindex @code{.} (symbol) |
| @cindex current address |
| @cindex location counter |
| The special symbol @samp{.} refers to the current address that |
| @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin: |
| .long .} defines @code{melvin} to contain its own address. |
| Assigning a value to @code{.} is treated the same as a @code{.org} |
| directive. Thus, the expression @samp{.=.+4} is the same as saying |
| @ifclear no-space-dir |
| @samp{.space 4}. |
| @end ifclear |
| @ifset no-space-dir |
| @ifset A29K |
| @samp{.block 4}. |
| @end ifset |
| @end ifset |
| |
| @node Symbol Attributes |
| @section Symbol Attributes |
| |
| @cindex symbol attributes |
| @cindex attributes, symbol |
| Every symbol has, as well as its name, the attributes ``Value'' and |
| ``Type''. Depending on output format, symbols can also have auxiliary |
| attributes. |
| @ifset INTERNALS |
| The detailed definitions are in @file{a.out.h}. |
| @end ifset |
| |
| If you use a symbol without defining it, @code{@value{AS}} assumes zero for |
| all these attributes, and probably won't warn you. This makes the |
| symbol an externally defined symbol, which is generally what you |
| would want. |
| |
| @menu |
| * Symbol Value:: Value |
| * Symbol Type:: Type |
| @ifset aout-bout |
| @ifset GENERIC |
| * a.out Symbols:: Symbol Attributes: @code{a.out} |
| @end ifset |
| @ifclear GENERIC |
| @ifclear BOUT |
| * a.out Symbols:: Symbol Attributes: @code{a.out} |
| @end ifclear |
| @ifset BOUT |
| * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out} |
| @end ifset |
| @end ifclear |
| @end ifset |
| @ifset COFF |
| * COFF Symbols:: Symbol Attributes for COFF |
| @end ifset |
| @ifset SOM |
| * SOM Symbols:: Symbol Attributes for SOM |
| @end ifset |
| @end menu |
| |
| @node Symbol Value |
| @subsection Value |
| |
| @cindex value of a symbol |
| @cindex symbol value |
| The value of a symbol is (usually) 32 bits. For a symbol which labels a |
| location in the text, data, bss or absolute sections the value is the |
| number of addresses from the start of that section to the label. |
| Naturally for text, data and bss sections the value of a symbol changes |
| as @code{@value{LD}} changes section base addresses during linking. Absolute |
| symbols' values do not change during linking: that is why they are |
| called absolute. |
| |
| The value of an undefined symbol is treated in a special way. If it is |
| 0 then the symbol is not defined in this assembler source file, and |
| @code{@value{LD}} tries to determine its value from other files linked into the |
| same program. You make this kind of symbol simply by mentioning a symbol |
| name without defining it. A non-zero value represents a @code{.comm} |
| common declaration. The value is how much common storage to reserve, in |
| bytes (addresses). The symbol refers to the first address of the |
| allocated storage. |
| |
| @node Symbol Type |
| @subsection Type |
| |
| @cindex type of a symbol |
| @cindex symbol type |
| The type attribute of a symbol contains relocation (section) |
| information, any flag settings indicating that a symbol is external, and |
| (optionally), other information for linkers and debuggers. The exact |
| format depends on the object-code output format in use. |
| |
| @ifset aout-bout |
| @ifclear GENERIC |
| @ifset BOUT |
| @c The following avoids a "widow" subsection title. @group would be |
| @c better if it were available outside examples. |
| @need 1000 |
| @node a.out Symbols |
| @subsection Symbol Attributes: @code{a.out}, @code{b.out} |
| |
| @cindex @code{b.out} symbol attributes |
| @cindex symbol attributes, @code{b.out} |
| These symbol attributes appear only when @code{@value{AS}} is configured for |
| one of the Berkeley-descended object output formats---@code{a.out} or |
| @code{b.out}. |
| |
| @end ifset |
| @ifclear BOUT |
| @node a.out Symbols |
| @subsection Symbol Attributes: @code{a.out} |
| |
| @cindex @code{a.out} symbol attributes |
| @cindex symbol attributes, @code{a.out} |
| |
| @end ifclear |
| @end ifclear |
| @ifset GENERIC |
| @node a.out Symbols |
| @subsection Symbol Attributes: @code{a.out} |
| |
| @cindex @code{a.out} symbol attributes |
| @cindex symbol attributes, @code{a.out} |
| |
| @end ifset |
| @menu |
| * Symbol Desc:: Descriptor |
| * Symbol Other:: Other |
| @end menu |
| |
| @node Symbol Desc |
| @subsubsection Descriptor |
| |
| @cindex descriptor, of @code{a.out} symbol |
| This is an arbitrary 16-bit value. You may establish a symbol's |
| descriptor value by using a @code{.desc} statement |
| (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to |
| @code{@value{AS}}. |
| |
| @node Symbol Other |
| @subsubsection Other |
| |
| @cindex other attribute, of @code{a.out} symbol |
| This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}. |
| @end ifset |
| |
| @ifset COFF |
| @node COFF Symbols |
| @subsection Symbol Attributes for COFF |
| |
| @cindex COFF symbol attributes |
| @cindex symbol attributes, COFF |
| |
| The COFF format supports a multitude of auxiliary symbol attributes; |
| like the primary symbol attributes, they are set between @code{.def} and |
| @code{.endef} directives. |
| |
| @subsubsection Primary Attributes |
| |
| @cindex primary attributes, COFF symbols |
| The symbol name is set with @code{.def}; the value and type, |
| respectively, with @code{.val} and @code{.type}. |
| |
| @subsubsection Auxiliary Attributes |
| |
| @cindex auxiliary attributes, COFF symbols |
| The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl}, |
| @code{.size}, and @code{.tag} can generate auxiliary symbol table |
| information for COFF. |
| @end ifset |
| |
| @ifset SOM |
| @node SOM Symbols |
| @subsection Symbol Attributes for SOM |
| |
| @cindex SOM symbol attributes |
| @cindex symbol attributes, SOM |
| |
| The SOM format for the HPPA supports a multitude of symbol attributes set with |
| the @code{.EXPORT} and @code{.IMPORT} directives. |
| |
| The attributes are described in @cite{HP9000 Series 800 Assembly |
| Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and |
| @code{EXPORT} assembler directive documentation. |
| @end ifset |
| |
| @node Expressions |
| @chapter Expressions |
| |
| @cindex expressions |
| @cindex addresses |
| @cindex numeric values |
| An @dfn{expression} specifies an address or numeric value. |
| Whitespace may precede and/or follow an expression. |
| |
| The result of an expression must be an absolute number, or else an offset into |
| a particular section. If an expression is not absolute, and there is not |
| enough information when @code{@value{AS}} sees the expression to know its |
| section, a second pass over the source program might be necessary to interpret |
| the expression---but the second pass is currently not implemented. |
| @code{@value{AS}} aborts with an error message in this situation. |
| |
| @menu |
| * Empty Exprs:: Empty Expressions |
| * Integer Exprs:: Integer Expressions |
| @end menu |
| |
| @node Empty Exprs |
| @section Empty Expressions |
| |
| @cindex empty expressions |
| @cindex expressions, empty |
| An empty expression has no value: it is just whitespace or null. |
| Wherever an absolute expression is required, you may omit the |
| expression, and @code{@value{AS}} assumes a value of (absolute) 0. This |
| is compatible with other assemblers. |
| |
| @node Integer Exprs |
| @section Integer Expressions |
| |
| @cindex integer expressions |
| @cindex expressions, integer |
| An @dfn{integer expression} is one or more @emph{arguments} delimited |
| by @emph{operators}. |
| |
| @menu |
| * Arguments:: Arguments |
| * Operators:: Operators |
| * Prefix Ops:: Prefix Operators |
| * Infix Ops:: Infix Operators |
| @end menu |
| |
| @node Arguments |
| @subsection Arguments |
| |
| @cindex expression arguments |
| @cindex arguments in expressions |
| @cindex operands in expressions |
| @cindex arithmetic operands |
| @dfn{Arguments} are symbols, numbers or subexpressions. In other |
| contexts arguments are sometimes called ``arithmetic operands''. In |
| this manual, to avoid confusing them with the ``instruction operands'' of |
| the machine language, we use the term ``argument'' to refer to parts of |
| expressions only, reserving the word ``operand'' to refer only to machine |
| instruction operands. |
| |
| Symbols are evaluated to yield @{@var{section} @var{NNN}@} where |
| @var{section} is one of text, data, bss, absolute, |
| or undefined. @var{NNN} is a signed, 2's complement 32 bit |
| integer. |
| |
| Numbers are usually integers. |
| |
| A number can be a flonum or bignum. In this case, you are warned |
| that only the low order 32 bits are used, and @code{@value{AS}} pretends |
| these 32 bits are an integer. You may write integer-manipulating |
| instructions that act on exotic constants, compatible with other |
| assemblers. |
| |
| @cindex subexpressions |
| Subexpressions are a left parenthesis @samp{(} followed by an integer |
| expression, followed by a right parenthesis @samp{)}; or a prefix |
| operator followed by an argument. |
| |
| @node Operators |
| @subsection Operators |
| |
| @cindex operators, in expressions |
| @cindex arithmetic functions |
| @cindex functions, in expressions |
| @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix |
| operators are followed by an argument. Infix operators appear |
| between their arguments. Operators may be preceded and/or followed by |
| whitespace. |
| |
| @node Prefix Ops |
| @subsection Prefix Operator |
| |
| @cindex prefix operators |
| @code{@value{AS}} has the following @dfn{prefix operators}. They each take |
| one argument, which must be absolute. |
| |
| @c the tex/end tex stuff surrounding this small table is meant to make |
| @c it align, on the printed page, with the similar table in the next |
| @c section (which is inside an enumerate). |
| @tex |
| \global\advance\leftskip by \itemindent |
| @end tex |
| |
| @table @code |
| @item - |
| @dfn{Negation}. Two's complement negation. |
| @item ~ |
| @dfn{Complementation}. Bitwise not. |
| @end table |
| |
| @tex |
| \global\advance\leftskip by -\itemindent |
| @end tex |
| |
| @node Infix Ops |
| @subsection Infix Operators |
| |
| @cindex infix operators |
| @cindex operators, permitted arguments |
| @dfn{Infix operators} take two arguments, one on either side. Operators |
| have precedence, but operations with equal precedence are performed left |
| to right. Apart from @code{+} or @code{-}, both arguments must be |
| absolute, and the result is absolute. |
| |
| @enumerate |
| @cindex operator precedence |
| @cindex precedence of operators |
| |
| @item |
| Highest Precedence |
| |
| @table @code |
| @item * |
| @dfn{Multiplication}. |
| |
| @item / |
| @dfn{Division}. Truncation is the same as the C operator @samp{/} |
| |
| @item % |
| @dfn{Remainder}. |
| |
| @item < |
| @itemx << |
| @dfn{Shift Left}. Same as the C operator @samp{<<}. |
| |
| @item > |
| @itemx >> |
| @dfn{Shift Right}. Same as the C operator @samp{>>}. |
| @end table |
| |
| @item |
| Intermediate precedence |
| |
| @table @code |
| @item | |
| |
| @dfn{Bitwise Inclusive Or}. |
| |
| @item & |
| @dfn{Bitwise And}. |
| |
| @item ^ |
| @dfn{Bitwise Exclusive Or}. |
| |
| @item ! |
| @dfn{Bitwise Or Not}. |
| @end table |
| |
| @item |
| Lowest Precedence |
| |
| @table @code |
| @cindex addition, permitted arguments |
| @cindex plus, permitted arguments |
| @cindex arguments for addition |
| @item + |
| @dfn{Addition}. If either argument is absolute, the result has the section of |
| the other argument. You may not add together arguments from different |
| sections. |
| |
| @cindex subtraction, permitted arguments |
| @cindex minus, permitted arguments |
| @cindex arguments for subtraction |
| @item - |
| @dfn{Subtraction}. If the right argument is absolute, the |
| result has the section of the left argument. |
| If both arguments are in the same section, the result is absolute. |
| You may not subtract arguments from different sections. |
| @c FIXME is there still something useful to say about undefined - undefined ? |
| @end table |
| @end enumerate |
| |
| In short, it's only meaningful to add or subtract the @emph{offsets} in an |
| address; you can only have a defined section in one of the two arguments. |
| |
| @node Pseudo Ops |
| @chapter Assembler Directives |
| |
| @cindex directives, machine independent |
| @cindex pseudo-ops, machine independent |
| @cindex machine independent directives |
| All assembler directives have names that begin with a period (@samp{.}). |
| The rest of the name is letters, usually in lower case. |
| |
| This chapter discusses directives that are available regardless of the |
| target machine configuration for the @sc{gnu} assembler. |
| @ifset GENERIC |
| Some machine configurations provide additional directives. |
| @xref{Machine Dependencies}. |
| @end ifset |
| @ifclear GENERIC |
| @ifset machine-directives |
| @xref{Machine Dependencies} for additional directives. |
| @end ifset |
| @end ifclear |
| |
| @menu |
| * Abort:: @code{.abort} |
| @ifset COFF |
| * ABORT:: @code{.ABORT} |
| @end ifset |
| |
| * Align:: @code{.align @var{abs-expr} , @var{abs-expr}} |
| * Ascii:: @code{.ascii "@var{string}"}@dots{} |
| * Asciz:: @code{.asciz "@var{string}"}@dots{} |
| * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}} |
| * Byte:: @code{.byte @var{expressions}} |
| * Comm:: @code{.comm @var{symbol} , @var{length} } |
| * Data:: @code{.data @var{subsection}} |
| @ifset COFF |
| * Def:: @code{.def @var{name}} |
| @end ifset |
| @ifset aout-bout |
| * Desc:: @code{.desc @var{symbol}, @var{abs-expression}} |
| @end ifset |
| @ifset COFF |
| * Dim:: @code{.dim} |
| @end ifset |
| |
| * Double:: @code{.double @var{flonums}} |
| * Eject:: @code{.eject} |
| * Else:: @code{.else} |
| * End:: @code{.end} |
| @ifset COFF |
| * Endef:: @code{.endef} |
| @end ifset |
| |
| * Endfunc:: @code{.endfunc} |
| * Endif:: @code{.endif} |
| * Equ:: @code{.equ @var{symbol}, @var{expression}} |
| * Equiv:: @code{.equiv @var{symbol}, @var{expression}} |
| * Err:: @code{.err} |
| * Exitm:: @code{.exitm} |
| * Extern:: @code{.extern} |
| * Fail:: @code{.fail} |
| @ifclear no-file-dir |
| * File:: @code{.file @var{string}} |
| @end ifclear |
| |
| * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}} |
| * Float:: @code{.float @var{flonums}} |
| * Func:: @code{.func} |
| * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}} |
| * hword:: @code{.hword @var{expressions}} |
| * Ident:: @code{.ident} |
| * If:: @code{.if @var{absolute expression}} |
| * Include:: @code{.include "@var{file}"} |
| * Int:: @code{.int @var{expressions}} |
| * Irp:: @code{.irp @var{symbol},@var{values}}@dots{} |
| * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{} |
| * Lcomm:: @code{.lcomm @var{symbol} , @var{length}} |
| * Lflags:: @code{.lflags} |
| @ifclear no-line-dir |
| * Line:: @code{.line @var{line-number}} |
| @end ifclear |
| |
| * Ln:: @code{.ln @var{line-number}} |
| * Linkonce:: @code{.linkonce [@var{type}]} |
| * List:: @code{.list} |
| * Long:: @code{.long @var{expressions}} |
| @ignore |
| * Lsym:: @code{.lsym @var{symbol}, @var{expression}} |
| @end ignore |
| |
| * Macro:: @code{.macro @var{name} @var{args}}@dots{} |
| * MRI:: @code{.mri @var{val}} |
| |
| * Nolist:: @code{.nolist} |
| * Octa:: @code{.octa @var{bignums}} |
| * Org:: @code{.org @var{new-lc} , @var{fill}} |
| * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}} |
| * Print:: @code{.print @var{string}} |
| * Psize:: @code{.psize @var{lines}, @var{columns}} |
| * Purgem:: @code{.purgem @var{name}} |
| * Quad:: @code{.quad @var{bignums}} |
| * Rept:: @code{.rept @var{count}} |
| * Sbttl:: @code{.sbttl "@var{subheading}"} |
| @ifset COFF |
| * Scl:: @code{.scl @var{class}} |
| * Section:: @code{.section @var{name}, @var{subsection}} |
| @end ifset |
| |
| * Set:: @code{.set @var{symbol}, @var{expression}} |
| * Short:: @code{.short @var{expressions}} |
| * Single:: @code{.single @var{flonums}} |
| @ifset COFF |
| * Size:: @code{.size} |
| @end ifset |
| |
| * Skip:: @code{.skip @var{size} , @var{fill}} |
| * Sleb128:: @code{.sleb128 @var{expressions}} |
| * Space:: @code{.space @var{size} , @var{fill}} |
| @ifset have-stabs |
| * Stab:: @code{.stabd, .stabn, .stabs} |
| @end ifset |
| |
| * String:: @code{.string "@var{str}"} |
| * Struct:: @code{.struct @var{expression}} |
| @ifset ELF |
| * Symver:: @code{.symver @var{name},@var{name2@@nodename}} |
| @end ifset |
| @ifset COFF |
| * Tag:: @code{.tag @var{structname}} |
| @end ifset |
| |
| * Text:: @code{.text @var{subsection}} |
| * Title:: @code{.title "@var{heading}"} |
| @ifset COFF |
| * Type:: @code{.type @var{int}} |
| * Val:: @code{.val @var{addr}} |
| @end ifset |
| |
| * Uleb128:: @code{.uleb128 @var{expressions}} |
| * Word:: @code{.word @var{expressions}} |
| * Deprecated:: Deprecated Directives |
| @end menu |
| |
| @node Abort |
| @section @code{.abort} |
| |
| @cindex @code{abort} directive |
| @cindex stopping the assembly |
| This directive stops the assembly immediately. It is for |
| compatibility with other assemblers. The original idea was that the |
| assembly language source would be piped into the assembler. If the sender |
| of the source quit, it could use this directive tells @code{@value{AS}} to |
| quit also. One day @code{.abort} will not be supported. |
| |
| @ifset COFF |
| @node ABORT |
| @section @code{.ABORT} |
| |
| @cindex @code{ABORT} directive |
| When producing COFF output, @code{@value{AS}} accepts this directive as a |
| synonym for @samp{.abort}. |
| |
| @ifset BOUT |
| When producing @code{b.out} output, @code{@value{AS}} accepts this directive, |
| but ignores it. |
| @end ifset |
| @end ifset |
| |
| @node Align |
| @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}} |
| |
| @cindex padding the location counter |
| @cindex @code{align} directive |
| Pad the location counter (in the current subsection) to a particular storage |
| boundary. The first expression (which must be absolute) is the alignment |
| required, as described below. |
| |
| The second expression (also absolute) gives the fill value to be stored in the |
| padding bytes. It (and the comma) may be omitted. If it is omitted, the |
| padding bytes are normally zero. However, on some systems, if the section is |
| marked as containing code and the fill value is omitted, the space is filled |
| with no-op instructions. |
| |
| The third expression is also absolute, and is also optional. If it is present, |
| it is the maximum number of bytes that should be skipped by this alignment |
| directive. If doing the alignment would require skipping more bytes than the |
| specified maximum, then the alignment is not done at all. You can omit the |
| fill value (the second argument) entirely by simply using two commas after the |
| required alignment; this can be useful if you want the alignment to be filled |
| with no-op instructions when appropriate. |
| |
| The way the required alignment is specified varies from system to system. |
| For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF |
| format, |
| the first expression is the |
| alignment request in bytes. For example @samp{.align 8} advances |
| the location counter until it is a multiple of 8. If the location counter |
| is already a multiple of 8, no change is needed. |
| |
| For other systems, including the i386 using a.out format, it is the |
| number of low-order zero bits the location counter must have after |
| advancement. For example @samp{.align 3} advances the location |
| counter until it a multiple of 8. If the location counter is already a |
| multiple of 8, no change is needed. |
| |
| This inconsistency is due to the different behaviors of the various |
| native assemblers for these systems which GAS must emulate. |
| GAS also provides @code{.balign} and @code{.p2align} directives, |
| described later, which have a consistent behavior across all |
| architectures (but are specific to GAS). |
| |
| @node Ascii |
| @section @code{.ascii "@var{string}"}@dots{} |
| |
| @cindex @code{ascii} directive |
| @cindex string literals |
| @code{.ascii} expects zero or more string literals (@pxref{Strings}) |
| separated by commas. It assembles each string (with no automatic |
| trailing zero byte) into consecutive addresses. |
| |
| @node Asciz |
| @section @code{.asciz "@var{string}"}@dots{} |
| |
| @cindex @code{asciz} directive |
| @cindex zero-terminated strings |
| @cindex null-terminated strings |
| @code{.asciz} is just like @code{.ascii}, but each string is followed by |
| a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''. |
| |
| @node Balign |
| @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}} |
| |
| @cindex padding the location counter given number of bytes |
| @cindex @code{balign} directive |
| Pad the location counter (in the current subsection) to a particular |
| storage boundary. The first expression (which must be absolute) is the |
| alignment request in bytes. For example @samp{.balign 8} advances |
| the location counter until it is a multiple of 8. If the location counter |
| is already a multiple of 8, no change is needed. |
| |
| The second expression (also absolute) gives the fill value to be stored in the |
| padding bytes. It (and the comma) may be omitted. If it is omitted, the |
| padding bytes are normally zero. However, on some systems, if the section is |
| marked as containing code and the fill value is omitted, the space is filled |
| with no-op instructions. |
| |
| The third expression is also absolute, and is also optional. If it is present, |
| it is the maximum number of bytes that should be skipped by this alignment |
| directive. If doing the alignment would require skipping more bytes than the |
| specified maximum, then the alignment is not done at all. You can omit the |
| fill value (the second argument) entirely by simply using two commas after the |
| required alignment; this can be useful if you want the alignment to be filled |
| with no-op instructions when appropriate. |
| |
| @cindex @code{balignw} directive |
| @cindex @code{balignl} directive |
| The @code{.balignw} and @code{.balignl} directives are variants of the |
| @code{.balign} directive. The @code{.balignw} directive treats the fill |
| pattern as a two byte word value. The @code{.balignl} directives treats the |
| fill pattern as a four byte longword value. For example, @code{.balignw |
| 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be |
| filled in with the value 0x368d (the exact placement of the bytes depends upon |
| the endianness of the processor). If it skips 1 or 3 bytes, the fill value is |
| undefined. |
| |
| @node Byte |
| @section @code{.byte @var{expressions}} |
| |
| @cindex @code{byte} directive |
| @cindex integers, one byte |
| @code{.byte} expects zero or more expressions, separated by commas. |
| Each expression is assembled into the next byte. |
| |
| @node Comm |
| @section @code{.comm @var{symbol} , @var{length} } |
| |
| @cindex @code{comm} directive |
| @cindex symbol, common |
| @code{.comm} declares a common symbol named @var{symbol}. When linking, a |
| common symbol in one object file may be merged with a defined or common symbol |
| of the same name in another object file. If @code{@value{LD}} does not see a |
| definition for the symbol--just one or more common symbols--then it will |
| allocate @var{length} bytes of uninitialized memory. @var{length} must be an |
| absolute expression. If @code{@value{LD}} sees multiple common symbols with |
| the same name, and they do not all have the same size, it will allocate space |
| using the largest size. |
| |
| @ifset ELF |
| When using ELF, the @code{.comm} directive takes an optional third argument. |
| This is the desired alignment of the symbol, specified as a byte boundary (for |
| example, an alignment of 16 means that the least significant 4 bits of the |
| address should be zero). The alignment must be an absolute expression, and it |
| must be a power of two. If @code{@value{LD}} allocates uninitialized memory |
| for the common symbol, it will use the alignment when placing the symbol. If |
| no alignment is specified, @code{@value{AS}} will set the alignment to the |
| largest power of two less than or equal to the size of the symbol, up to a |
| maximum of 16. |
| @end ifset |
| |
| @ifset HPPA |
| The syntax for @code{.comm} differs slightly on the HPPA. The syntax is |
| @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional. |
| @end ifset |
| |
| @node Data |
| @section @code{.data @var{subsection}} |
| |
| @cindex @code{data} directive |
| @code{.data} tells @code{@value{AS}} to assemble the following statements onto the |
| end of the data subsection numbered @var{subsection} (which is an |
| absolute expression). If @var{subsection} is omitted, it defaults |
| to zero. |
| |
| @ifset COFF |
| @node Def |
| @section @code{.def @var{name}} |
| |
| @cindex @code{def} directive |
| @cindex COFF symbols, debugging |
| @cindex debugging COFF symbols |
| Begin defining debugging information for a symbol @var{name}; the |
| definition extends until the @code{.endef} directive is encountered. |
| @ifset BOUT |
| |
| This directive is only observed when @code{@value{AS}} is configured for COFF |
| format output; when producing @code{b.out}, @samp{.def} is recognized, |
| but ignored. |
| @end ifset |
| @end ifset |
| |
| @ifset aout-bout |
| @node Desc |
| @section @code{.desc @var{symbol}, @var{abs-expression}} |
| |
| @cindex @code{desc} directive |
| @cindex COFF symbol descriptor |
| @cindex symbol descriptor, COFF |
| This directive sets the descriptor of the symbol (@pxref{Symbol Attributes}) |
| to the low 16 bits of an absolute expression. |
| |
| @ifset COFF |
| The @samp{.desc} directive is not available when @code{@value{AS}} is |
| configured for COFF output; it is only for @code{a.out} or @code{b.out} |
| object format. For the sake of compatibility, @code{@value{AS}} accepts |
| it, but produces no output, when configured for COFF. |
| @end ifset |
| @end ifset |
| |
| @ifset COFF |
| @node Dim |
| @section @code{.dim} |
| |
| @cindex @code{dim} directive |
| @cindex COFF auxiliary symbol information |
| @cindex auxiliary symbol information, COFF |
| This directive is generated by compilers to include auxiliary debugging |
| information in the symbol table. It is only permitted inside |
| @code{.def}/@code{.endef} pairs. |
| @ifset BOUT |
| |
| @samp{.dim} is only meaningful when generating COFF format output; when |
| @code{@value{AS}} is generating @code{b.out}, it accepts this directive but |
| ignores it. |
| @end ifset |
| @end ifset |
| |
| @node Double |
| @section @code{.double @var{flonums}} |
| |
| @cindex @code{double} directive |
| @cindex floating point numbers (double) |
| @code{.double} expects zero or more flonums, separated by commas. It |
| assembles floating point numbers. |
| @ifset GENERIC |
| The exact kind of floating point numbers emitted depends on how |
| @code{@value{AS}} is configured. @xref{Machine Dependencies}. |
| @end ifset |
| @ifclear GENERIC |
| @ifset IEEEFLOAT |
| On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers |
| in @sc{ieee} format. |
| @end ifset |
| @end ifclear |
| |
| @node Eject |
| @section @code{.eject} |
| |
| @cindex @code{eject} directive |
| @cindex new page, in listings |
| @cindex page, in listings |
| @cindex listing control: new page |
| Force a page break at this point, when generating assembly listings. |
| |
| @node Else |
| @section @code{.else} |
| |
| @cindex @code{else} directive |
| @code{.else} is part of the @code{@value{AS}} support for conditional |
| assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section |
| of code to be assembled if the condition for the preceding @code{.if} |
| was false. |
| |
| @node End |
| @section @code{.end} |
| |
| @cindex @code{end} directive |
| @code{.end} marks the end of the assembly file. @code{@value{AS}} does not |
| process anything in the file past the @code{.end} directive. |
| |
| @ifset COFF |
| @node Endef |
| @section @code{.endef} |
| |
| @cindex @code{endef} directive |
| This directive flags the end of a symbol definition begun with |
| @code{.def}. |
| @ifset BOUT |
| |
| @samp{.endef} is only meaningful when generating COFF format output; if |
| @code{@value{AS}} is configured to generate @code{b.out}, it accepts this |
| directive but ignores it. |
| @end ifset |
| @end ifset |
| |
| @node Endfunc |
| @section @code{.endfunc} |
| @cindex @code{endfunc} directive |
| @code{.endfunc} marks the end of a function specified with @code{.func}. |
| |
| @node Endif |
| @section @code{.endif} |
| |
| @cindex @code{endif} directive |
| @code{.endif} is part of the @code{@value{AS}} support for conditional assembly; |
| it marks the end of a block of code that is only assembled |
| conditionally. @xref{If,,@code{.if}}. |
| |
| @node Equ |
| @section @code{.equ @var{symbol}, @var{expression}} |
| |
| @cindex @code{equ} directive |
| @cindex assigning values to symbols |
| @cindex symbols, assigning values to |
| This directive sets the value of @var{symbol} to @var{expression}. |
| It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}. |
| |
| @ifset HPPA |
| The syntax for @code{equ} on the HPPA is |
| @samp{@var{symbol} .equ @var{expression}}. |
| @end ifset |
| |
| @node Equiv |
| @section @code{.equiv @var{symbol}, @var{expression}} |
| @cindex @code{equiv} directive |
| The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that |
| the assembler will signal an error if @var{symbol} is already defined. |
| |
| Except for the contents of the error message, this is roughly equivalent to |
| @smallexample |
| .ifdef SYM |
| .err |
| .endif |
| .equ SYM,VAL |
| @end smallexample |
| |
| @node Err |
| @section @code{.err} |
| @cindex @code{err} directive |
| If @code{@value{AS}} assembles a @code{.err} directive, it will print an error |
| message and, unless the @code{-Z} option was used, it will not generate an |
| object file. This can be used to signal error an conditionally compiled code. |
| |
| @node Exitm |
| @section @code{.exitm} |
| Exit early from the current macro definition. @xref{Macro}. |
| |
| @node Extern |
| @section @code{.extern} |
| |
| @cindex @code{extern} directive |
| @code{.extern} is accepted in the source program---for compatibility |
| with other assemblers---but it is ignored. @code{@value{AS}} treats |
| all undefined symbols as external. |
| |
| @node Fail |
| @section @code{.fail @var{expression}} |
| |
| @cindex @code{fail} directive |
| Generates an error or a warning. If the value of the @var{expression} is 500 |
| or more, @code{@value{AS}} will print a warning message. If the value is less |
| than 500, @code{@value{AS}} will print an error message. The message will |
| include the value of @var{expression}. This can occasionally be useful inside |
| complex nested macros or conditional assembly. |
| |
| @ifclear no-file-dir |
| @node File |
| @section @code{.file @var{string}} |
| |
| @cindex @code{file} directive |
| @cindex logical file name |
| @cindex file name, logical |
| @code{.file} tells @code{@value{AS}} that we are about to start a new logical |
| file. @var{string} is the new file name. In general, the filename is |
| recognized whether or not it is surrounded by quotes @samp{"}; but if you wish |
| to specify an empty file name, you must give the quotes--@code{""}. This |
| statement may go away in future: it is only recognized to be compatible with |
| old @code{@value{AS}} programs. |
| @ifset A29K |
| In some configurations of @code{@value{AS}}, @code{.file} has already been |
| removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}. |
| @end ifset |
| @end ifclear |
| |
| @node Fill |
| @section @code{.fill @var{repeat} , @var{size} , @var{value}} |
| |
| @cindex @code{fill} directive |
| @cindex writing patterns in memory |
| @cindex patterns, writing in memory |
| @var{result}, @var{size} and @var{value} are absolute expressions. |
| This emits @var{repeat} copies of @var{size} bytes. @var{Repeat} |
| may be zero or more. @var{Size} may be zero or more, but if it is |
| more than 8, then it is deemed to have the value 8, compatible with |
| other people's assemblers. The contents of each @var{repeat} bytes |
| is taken from an 8-byte number. The highest order 4 bytes are |
| zero. The lowest order 4 bytes are @var{value} rendered in the |
| byte-order of an integer on the computer @code{@value{AS}} is assembling for. |
| Each @var{size} bytes in a repetition is taken from the lowest order |
| @var{size} bytes of this number. Again, this bizarre behavior is |
| compatible with other people's assemblers. |
| |
| @var{size} and @var{value} are optional. |
| If the second comma and @var{value} are absent, @var{value} is |
| assumed zero. If the first comma and following tokens are absent, |
| @var{size} is assumed to be 1. |
| |
| @node Float |
| @section @code{.float @var{flonums}} |
| |
| @cindex floating point numbers (single) |
| @cindex @code{float} directive |
| This directive assembles zero or more flonums, separated by commas. It |
| has the same effect as @code{.single}. |
| @ifset GENERIC |
| The exact kind of floating point numbers emitted depends on how |
| @code{@value{AS}} is configured. |
| @xref{Machine Dependencies}. |
| @end ifset |
| @ifclear GENERIC |
| @ifset IEEEFLOAT |
| On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers |
| in @sc{ieee} format. |
| @end ifset |
| @end ifclear |
| |
| @node Func |
| @section @code{.func @var{name}[,@var{label}]} |
| @cindex @code{func} directive |
| @code{.func} emits debugging information to denote function @var{name}, and |
| is ignored unless the file is assembled with debugging enabled. |
| Only @samp{--gstabs} is currently supported. |
| @var{label} is the entry point of the function and if omitted @var{name} |
| prepended with the @samp{leading char} is used. |
| @samp{leading char} is usually @code{_} or nothing, depending on the target. |
| All functions are currently defined to have @code{void} return type. |
| The function must be terminated with @code{.endfunc}. |
| |
| @node Global |
| @section @code{.global @var{symbol}}, @code{.globl @var{symbol}} |
| |
| @cindex @code{global} directive |
| @cindex symbol, making visible to linker |
| @code{.global} makes the symbol visible to @code{@value{LD}}. If you define |
| @var{symbol} in your partial program, its value is made available to |
| other partial programs that are linked with it. Otherwise, |
| @var{symbol} takes its attributes from a symbol of the same name |
| from another file linked into the same program. |
| |
| Both spellings (@samp{.globl} and @samp{.global}) are accepted, for |
| compatibility with other assemblers. |
| |
| @ifset HPPA |
| On the HPPA, @code{.global} is not always enough to make it accessible to other |
| partial programs. You may need the HPPA-only @code{.EXPORT} directive as well. |
| @xref{HPPA Directives,, HPPA Assembler Directives}. |
| @end ifset |
| |
| @node hword |
| @section @code{.hword @var{expressions}} |
| |
| @cindex @code{hword} directive |
| @cindex integers, 16-bit |
| @cindex numbers, 16-bit |
| @cindex sixteen bit integers |
| This expects zero or more @var{expressions}, and emits |
| a 16 bit number for each. |
| |
| @ifset GENERIC |
| This directive is a synonym for @samp{.short}; depending on the target |
| architecture, it may also be a synonym for @samp{.word}. |
| @end ifset |
| @ifclear GENERIC |
| @ifset W32 |
| This directive is a synonym for @samp{.short}. |
| @end ifset |
| @ifset W16 |
| This directive is a synonym for both @samp{.short} and @samp{.word}. |
| @end ifset |
| @end ifclear |
| |
| @node Ident |
| @section @code{.ident} |
| |
| @cindex @code{ident} directive |
| This directive is used by some assemblers to place tags in object files. |
| @code{@value{AS}} simply accepts the directive for source-file |
| compatibility with such assemblers, but does not actually emit anything |
| for it. |
| |
| @node If |
| @section @code{.if @var{absolute expression}} |
| |
| @cindex conditional assembly |
| @cindex @code{if} directive |
| @code{.if} marks the beginning of a section of code which is only |
| considered part of the source program being assembled if the argument |
| (which must be an @var{absolute expression}) is non-zero. The end of |
| the conditional section of code must be marked by @code{.endif} |
| (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the |
| alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}). |
| |
| The following variants of @code{.if} are also supported: |
| @table @code |
| @cindex @code{ifdef} directive |
| @item .ifdef @var{symbol} |
| Assembles the following section of code if the specified @var{symbol} |
| has been defined. |
| |
| @cindex @code{ifc} directive |
| @item .ifc @var{string1},@var{string2} |
| Assembles the following section of code if the two strings are the same. The |
| strings may be optionally quoted with single quotes. If they are not quoted, |
| the first string stops at the first comma, and the second string stops at the |
| end of the line. Strings which contain whitespace should be quoted. The |
| string comparison is case sensitive. |
| |
| @cindex @code{ifeq} directive |
| @item .ifeq @var{absolute expression} |
| Assembles the following section of code if the argument is zero. |
| |
| @cindex @code{ifeqs} directive |
| @item .ifeqs @var{string1},@var{string2} |
| Another form of @code{.ifc}. The strings must be quoted using double quotes. |
| |
| @cindex @code{ifge} directive |
| @item .ifge @var{absolute expression} |
| Assembles the following section of code if the argument is greater than or |
| equal to zero. |
| |
| @cindex @code{ifgt} directive |
| @item .ifgt @var{absolute expression} |
| Assembles the following section of code if the argument is greater than zero. |
| |
| @cindex @code{ifle} directive |
| @item .ifle @var{absolute expression} |
| Assembles the following section of code if the argument is less than or equal |
| to zero. |
| |
| @cindex @code{iflt} directive |
| @item .iflt @var{absolute expression} |
| Assembles the following section of code if the argument is less than zero. |
| |
| @cindex @code{ifnc} directive |
| @item .ifnc @var{string1},@var{string2}. |
| Like @code{.ifc}, but the sense of the test is reversed: this assembles the |
| following section of code if the two strings are not the same. |
| |
| @cindex @code{ifndef} directive |
| @cindex @code{ifnotdef} directive |
| @item .ifndef @var{symbol} |
| @itemx .ifnotdef @var{symbol} |
| Assembles the following section of code if the specified @var{symbol} |
| has not been defined. Both spelling variants are equivalent. |
| |
| @cindex @code{ifne} directive |
| @item .ifne @var{absolute expression} |
| Assembles the following section of code if the argument is not equal to zero |
| (in other words, this is equivalent to @code{.if}). |
| |
| @cindex @code{ifnes} directive |
| @item .ifnes @var{string1},@var{string2} |
| Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the |
| following section of code if the two strings are not the same. |
| @end table |
| |
| @node Include |
| @section @code{.include "@var{file}"} |
| |
| @cindex @code{include} directive |
| @cindex supporting files, including |
| @cindex files, including |
| This directive provides a way to include supporting files at specified |
| points in your source program. The code from @var{file} is assembled as |
| if it followed the point of the @code{.include}; when the end of the |
| included file is reached, assembly of the original file continues. You |
| can control the search paths used with the @samp{-I} command-line option |
| (@pxref{Invoking,,Command-Line Options}). Quotation marks are required |
| around @var{file}. |
| |
| @node Int |
| @section @code{.int @var{expressions}} |
| |
| @cindex @code{int} directive |
| @cindex integers, 32-bit |
| Expect zero or more @var{expressions}, of any section, separated by commas. |
| For each expression, emit a number that, at run time, is the value of that |
| expression. The byte order and bit size of the number depends on what kind |
| of target the assembly is for. |
| |
| @ifclear GENERIC |
| @ifset H8 |
| On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit |
| integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits |
| 32-bit integers. |
| @end ifset |
| @end ifclear |
| |
| @node Irp |
| @section @code{.irp @var{symbol},@var{values}}@dots{} |
| |
| @cindex @code{irp} directive |
| Evaluate a sequence of statements assigning different values to @var{symbol}. |
| The sequence of statements starts at the @code{.irp} directive, and is |
| terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is |
| set to @var{value}, and the sequence of statements is assembled. If no |
| @var{value} is listed, the sequence of statements is assembled once, with |
| @var{symbol} set to the null string. To refer to @var{symbol} within the |
| sequence of statements, use @var{\symbol}. |
| |
| For example, assembling |
| |
| @example |
| .irp param,1,2,3 |
| move d\param,sp@@- |
| .endr |
| @end example |
| |
| is equivalent to assembling |
| |
| @example |
| move d1,sp@@- |
| move d2,sp@@- |
| move d3,sp@@- |
| @end example |
| |
| @node Irpc |
| @section @code{.irpc @var{symbol},@var{values}}@dots{} |
| |
| @cindex @code{irpc} directive |
| Evaluate a sequence of statements assigning different values to @var{symbol}. |
| The sequence of statements starts at the @code{.irpc} directive, and is |
| terminated by an @code{.endr} directive. For each character in @var{value}, |
| @var{symbol} is set to the character, and the sequence of statements is |
| assembled. If no @var{value} is listed, the sequence of statements is |
| assembled once, with @var{symbol} set to the null string. To refer to |
| @var{symbol} within the sequence of statements, use @var{\symbol}. |
| |
| For example, assembling |
| |
| @example |
| .irpc param,123 |
| move d\param,sp@@- |
| .endr |
| @end example |
| |
| is equivalent to assembling |
| |
| @example |
| move d1,sp@@- |
| move d2,sp@@- |
| move d3,sp@@- |
| @end example |
| |
| @node Lcomm |
| @section @code{.lcomm @var{symbol} , @var{length}} |
| |
| @cindex @code{lcomm} directive |
| @cindex local common symbols |
| @cindex symbols, local common |
| Reserve @var{length} (an absolute expression) bytes for a local common |
| denoted by @var{symbol}. The section and value of @var{symbol} are |
| those of the new local common. The addresses are allocated in the bss |
| section, so that at run-time the bytes start off zeroed. @var{Symbol} |
| is not declared global (@pxref{Global,,@code{.global}}), so is normally |
| not visible to @code{@value{LD}}. |
| |
| @ifset GENERIC |
| Some targets permit a third argument to be used with @code{.lcomm}. This |
| argument specifies the desired alignment of the symbol in the bss section. |
| @end ifset |
| |
| @ifset HPPA |
| The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is |
| @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional. |
| @end ifset |
| |
| @node Lflags |
| @section @code{.lflags} |
| |
| @cindex @code{lflags} directive (ignored) |
| @code{@value{AS}} accepts this directive, for compatibility with other |
| assemblers, but ignores it. |
| |
| @ifclear no-line-dir |
| @node Line |
| @section @code{.line @var{line-number}} |
| |
| @cindex @code{line} directive |
| @end ifclear |
| @ifset no-line-dir |
| @node Ln |
| @section @code{.ln @var{line-number}} |
| |
| @cindex @code{ln} directive |
| @end ifset |
| @cindex logical line number |
| @ifset aout-bout |
| Change the logical line number. @var{line-number} must be an absolute |
| expression. The next line has that logical line number. Therefore any other |
| statements on the current line (after a statement separator character) are |
| reported as on logical line number @var{line-number} @minus{} 1. One day |
| @code{@value{AS}} will no longer support this directive: it is recognized only |
| for compatibility with existing assembler programs. |
| |
| @ifset GENERIC |
| @ifset A29K |
| @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is |
| not available; use the synonym @code{.ln} in that context. |
| @end ifset |
| @end ifset |
| @end ifset |
| |
| @ifclear no-line-dir |
| Even though this is a directive associated with the @code{a.out} or |
| @code{b.out} object-code formats, @code{@value{AS}} still recognizes it |
| when producing COFF output, and treats @samp{.line} as though it |
| were the COFF @samp{.ln} @emph{if} it is found outside a |
| @code{.def}/@code{.endef} pair. |
| |
| Inside a @code{.def}, @samp{.line} is, instead, one of the directives |
| used by compilers to generate auxiliary symbol information for |
| debugging. |
| @end ifclear |
| |
| @node Linkonce |
| @section @code{.linkonce [@var{type}]} |
| @cindex COMDAT |
| @cindex @code{linkonce} directive |
| @cindex common sections |
| Mark the current section so that the linker only includes a single copy of it. |
| This may be used to include the same section in several different object files, |
| but ensure that the linker will only include it once in the final output file. |
| The @code{.linkonce} pseudo-op must be used for each instance of the section. |
| Duplicate sections are detected based on the section name, so it should be |
| unique. |
| |
| This directive is only supported by a few object file formats; as of this |
| writing, the only object file format which supports it is the Portable |
| Executable format used on Windows NT. |
| |
| The @var{type} argument is optional. If specified, it must be one of the |
| following strings. For example: |
| @smallexample |
| .linkonce same_size |
| @end smallexample |
| Not all types may be supported on all object file formats. |
| |
| @table @code |
| @item discard |
| Silently discard duplicate sections. This is the default. |
| |
| @item one_only |
| Warn if there are duplicate sections, but still keep only one copy. |
| |
| @item same_size |
| Warn if any of the duplicates have different sizes. |
| |
| @item same_contents |
| Warn if any of the duplicates do not have exactly the same contents. |
| @end table |
| |
| @node Ln |
| @section @code{.ln @var{line-number}} |
| |
| @cindex @code{ln} directive |
| @ifclear no-line-dir |
| @samp{.ln} is a synonym for @samp{.line}. |
| @end ifclear |
| @ifset no-line-dir |
| Tell @code{@value{AS}} to change the logical line number. @var{line-number} |
| must be an absolute expression. The next line has that logical |
| line number, so any other statements on the current line (after a |
| statement separator character @code{;}) are reported as on logical |
| line number @var{line-number} @minus{} 1. |
| @ifset BOUT |
| |
| This directive is accepted, but ignored, when @code{@value{AS}} is |
| configured for @code{b.out}; its effect is only associated with COFF |
| output format. |
| @end ifset |
| @end ifset |
| |
| @node MRI |
| @section @code{.mri @var{val}} |
| |
| @cindex @code{mri} directive |
| @cindex MRI mode, temporarily |
| If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If |
| @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change |
| affects code assembled until the next @code{.mri} directive, or until the end |
| of the file. @xref{M, MRI mode, MRI mode}. |
| |
| @node List |
| @section @code{.list} |
| |
| @cindex @code{list} directive |
| @cindex listing control, turning on |
| Control (in conjunction with the @code{.nolist} directive) whether or |
| not assembly listings are generated. These two directives maintain an |
| internal counter (which is zero initially). @code{.list} increments the |
| counter, and @code{.nolist} decrements it. Assembly listings are |
| generated whenever the counter is greater than zero. |
| |
| By default, listings are disabled. When you enable them (with the |
| @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}), |
| the initial value of the listing counter is one. |
| |
| @node Long |
| @section @code{.long @var{expressions}} |
| |
| @cindex @code{long} directive |
| @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}. |
| |
| @ignore |
| @c no one seems to know what this is for or whether this description is |
| @c what it really ought to do |
| @node Lsym |
| @section @code{.lsym @var{symbol}, @var{expression}} |
| |
| @cindex @code{lsym} directive |
| @cindex symbol, not referenced in assembly |
| @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in |
| the hash table, ensuring it cannot be referenced by name during the |
| rest of the assembly. This sets the attributes of the symbol to be |
| the same as the expression value: |
| @smallexample |
| @var{other} = @var{descriptor} = 0 |
| @var{type} = @r{(section of @var{expression})} |
| @var{value} = @var{expression} |
| @end smallexample |
| @noindent |
| The new symbol is not flagged as external. |
| @end ignore |
| |
| @node Macro |
| @section @code{.macro} |
| |
| @cindex macros |
| The commands @code{.macro} and @code{.endm} allow you to define macros that |
| generate assembly output. For example, this definition specifies a macro |
| @code{sum} that puts a sequence of numbers into memory: |
| |
| @example |
| .macro sum from=0, to=5 |
| .long \from |
| .if \to-\from |
| sum "(\from+1)",\to |
| .endif |
| .endm |
| @end example |
| |
| @noindent |
| With that definition, @samp{SUM 0,5} is equivalent to this assembly input: |
| |
| @example |
| .long 0 |
| .long 1 |
| .long 2 |
| .long 3 |
| .long 4 |
| .long 5 |
| @end example |
| |
| @ftable @code |
| @item .macro @var{macname} |
| @itemx .macro @var{macname} @var{macargs} @dots{} |
| @cindex @code{macro} directive |
| Begin the definition of a macro called @var{macname}. If your macro |
| definition requires arguments, specify their names after the macro name, |
| separated by commas or spaces. You can supply a default value for any |
| macro argument by following the name with @samp{=@var{deflt}}. For |
| example, these are all valid @code{.macro} statements: |
| |
| @table @code |
| @item .macro comm |
| Begin the definition of a macro called @code{comm}, which takes no |
| arguments. |
| |
| @item .macro plus1 p, p1 |
| @itemx .macro plus1 p p1 |
| Either statement begins the definition of a macro called @code{plus1}, |
| which takes two arguments; within the macro definition, write |
| @samp{\p} or @samp{\p1} to evaluate the arguments. |
| |
| @item .macro reserve_str p1=0 p2 |
| Begin the definition of a macro called @code{reserve_str}, with two |
| arguments. The first argument has a default value, but not the second. |
| After the definition is complete, you can call the macro either as |
| @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to |
| @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str |
| ,@var{b}} (with @samp{\p1} evaluating as the default, in this case |
| @samp{0}, and @samp{\p2} evaluating to @var{b}). |
| @end table |
| |
| When you call a macro, you can specify the argument values either by |
| position, or by keyword. For example, @samp{sum 9,17} is equivalent to |
| @samp{sum to=17, from=9}. |
| |
| @item .endm |
| @cindex @code{endm} directive |
| Mark the end of a macro definition. |
| |
| @item .exitm |
| @cindex @code{exitm} directive |
| Exit early from the current macro definition. |
| |
| @cindex number of macros executed |
| @cindex macros, count executed |
| @item \@@ |
| @code{@value{AS}} maintains a counter of how many macros it has |
| executed in this pseudo-variable; you can copy that number to your |
| output with @samp{\@@}, but @emph{only within a macro definition}. |
| |
| @ignore |
| @item LOCAL @var{name} [ , @dots{} ] |
| @emph{Warning: @code{LOCAL} is only available if you select ``alternate |
| macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,, |
| Alternate macro syntax}. |
| |
| Generate a string replacement for each of the @var{name} arguments, and |
| replace any instances of @var{name} in each macro expansion. The |
| replacement string is unique in the assembly, and different for each |
| separate macro expansion. @code{LOCAL} allows you to write macros that |
| define symbols, without fear of conflict between separate macro expansions. |
| @end ignore |
| @end ftable |
| |
| @node Nolist |
| @section @code{.nolist} |
| |
| @cindex @code{nolist} directive |
| @cindex listing control, turning off |
| Control (in conjunction with the @code{.list} directive) whether or |
| not assembly listings are generated. These two directives maintain an |
| internal counter (which is zero initially). @code{.list} increments the |
| counter, and @code{.nolist} decrements it. Assembly listings are |
| generated whenever the counter is greater than zero. |
| |
| @node Octa |
| @section @code{.octa @var{bignums}} |
| |
| @c FIXME: double size emitted for "octa" on i960, others? Or warn? |
| @cindex @code{octa} directive |
| @cindex integer, 16-byte |
| @cindex sixteen byte integer |
| This directive expects zero or more bignums, separated by commas. For each |
| bignum, it emits a 16-byte integer. |
| |
| The term ``octa'' comes from contexts in which a ``word'' is two bytes; |
| hence @emph{octa}-word for 16 bytes. |
| |
| @node Org |
| @section @code{.org @var{new-lc} , @var{fill}} |
| |
| @cindex @code{org} directive |
| @cindex location counter, advancing |
| @cindex advancing location counter |
| @cindex current address, advancing |
| Advance the location counter of the current section to |
| @var{new-lc}. @var{new-lc} is either an absolute expression or an |
| expression with the same section as the current subsection. That is, |
| you can't use @code{.org} to cross sections: if @var{new-lc} has the |
| wrong section, the @code{.org} directive is ignored. To be compatible |
| with former assemblers, if the section of @var{new-lc} is absolute, |
| @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc} |
| is the same as the current subsection. |
| |
| @code{.org} may only increase the location counter, or leave it |
| unchanged; you cannot use @code{.org} to move the location counter |
| backwards. |
| |
| @c double negative used below "not undefined" because this is a specific |
| @c reference to "undefined" (as SEG_UNKNOWN is called in this manual) |
| @c section. doc@cygnus.com 18feb91 |
| Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc} |
| may not be undefined. If you really detest this restriction we eagerly await |
| a chance to share your improved assembler. |
| |
| Beware that the origin is relative to the start of the section, not |
| to the start of the subsection. This is compatible with other |
| people's assemblers. |
| |
| When the location counter (of the current subsection) is advanced, the |
| intervening bytes are filled with @var{fill} which should be an |
| absolute expression. If the comma and @var{fill} are omitted, |
| @var{fill} defaults to zero. |
| |
| @node P2align |
| @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}} |
| |
| @cindex padding the location counter given a power of two |
| @cindex @code{p2align} directive |
| Pad the location counter (in the current subsection) to a particular |
| storage boundary. The first expression (which must be absolute) is the |
| number of low-order zero bits the location counter must have after |
| advancement. For example @samp{.p2align 3} advances the location |
| counter until it a multiple of 8. If the location counter is already a |
| multiple of 8, no change is needed. |
| |
| The second expression (also absolute) gives the fill value to be stored in the |
| padding bytes. It (and the comma) may be omitted. If it is omitted, the |
| padding bytes are normally zero. However, on some systems, if the section is |
| marked as containing code and the fill value is omitted, the space is filled |
| with no-op instructions. |
| |
| The third expression is also absolute, and is also optional. If it is present, |
| it is the maximum number of bytes that should be skipped by this alignment |
| directive. If doing the alignment would require skipping more bytes than the |
| specified maximum, then the alignment is not done at all. You can omit the |
| fill value (the second argument) entirely by simply using two commas after the |
| required alignment; this can be useful if you want the alignment to be filled |
| with no-op instructions when appropriate. |
| |
| @cindex @code{p2alignw} directive |
| @cindex @code{p2alignl} directive |
| The @code{.p2alignw} and @code{.p2alignl} directives are variants of the |
| @code{.p2align} directive. The @code{.p2alignw} directive treats the fill |
| pattern as a two byte word value. The @code{.p2alignl} directives treats the |
| fill pattern as a four byte longword value. For example, @code{.p2alignw |
| 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be |
| filled in with the value 0x368d (the exact placement of the bytes depends upon |
| the endianness of the processor). If it skips 1 or 3 bytes, the fill value is |
| undefined. |
| |
| @node Print |
| @section @code{.print @var{string}} |
| |
| @cindex @code{print} directive |
| @code{@value{AS}} will print @var{string} on the standard output during |
| assembly. You must put @var{string} in double quotes. |
| |
| @node Psize |
| @section @code{.psize @var{lines} , @var{columns}} |
| |
| @cindex @code{psize} directive |
| @cindex listing control: paper size |
| @cindex paper size, for listings |
| Use this directive to declare the number of lines---and, optionally, the |
| number of columns---to use for each page, when generating listings. |
| |
| If you do not use @code{.psize}, listings use a default line-count |
| of 60. You may omit the comma and @var{columns} specification; the |
| default width is 200 columns. |
| |
| @code{@value{AS}} generates formfeeds whenever the specified number of |
| lines is exceeded (or whenever you explicitly request one, using |
| @code{.eject}). |
| |
| If you specify @var{lines} as @code{0}, no formfeeds are generated save |
| those explicitly specified with @code{.eject}. |
| |
| @node Purgem |
| @section @code{.purgem @var{name}} |
| |
| @cindex @code{purgem} directive |
| Undefine the macro @var{name}, so that later uses of the string will not be |
| expanded. @xref{Macro}. |
| |
| @node Quad |
| @section @code{.quad @var{bignums}} |
| |
| @cindex @code{quad} directive |
| @code{.quad} expects zero or more bignums, separated by commas. For |
| each bignum, it emits |
| @ifclear bignum-16 |
| an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a |
| warning message; and just takes the lowest order 8 bytes of the bignum. |
| @cindex eight-byte integer |
| @cindex integer, 8-byte |
| |
| The term ``quad'' comes from contexts in which a ``word'' is two bytes; |
| hence @emph{quad}-word for 8 bytes. |
| @end ifclear |
| @ifset bignum-16 |
| a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a |
| warning message; and just takes the lowest order 16 bytes of the bignum. |
| @cindex sixteen-byte integer |
| @cindex integer, 16-byte |
| @end ifset |
| |
| @node Rept |
| @section @code{.rept @var{count}} |
| |
| @cindex @code{rept} directive |
| Repeat the sequence of lines between the @code{.rept} directive and the next |
| @code{.endr} directive @var{count} times. |
| |
| For example, assembling |
| |
| @example |
| .rept 3 |
| .long 0 |
| .endr |
| @end example |
| |
| is equivalent to assembling |
| |
| @example |
| .long 0 |
| .long 0 |
| .long 0 |
| @end example |
| |
| @node Sbttl |
| @section @code{.sbttl "@var{subheading}"} |
| |
| @cindex @code{sbttl} directive |
| @cindex subtitles for listings |
| @cindex listing control: subtitle |
| Use @var{subheading} as the title (third line, immediately after the |
| title line) when generating assembly listings. |
| |
| This directive affects subsequent pages, as well as the current page if |
| it appears within ten lines of the top of a page. |
| |
| @ifset COFF |
| @node Scl |
| @section @code{.scl @var{class}} |
| |
| @cindex @code{scl} directive |
| @cindex symbol storage class (COFF) |
| @cindex COFF symbol storage class |
| Set the storage-class value for a symbol. This directive may only be |
| used inside a @code{.def}/@code{.endef} pair. Storage class may flag |
| whether a symbol is static or external, or it may record further |
| symbolic debugging information. |
| @ifset BOUT |
| |
| The @samp{.scl} directive is primarily associated with COFF output; when |
| configured to generate @code{b.out} output format, @code{@value{AS}} |
| accepts this directive but ignores it. |
| @end ifset |
| @end ifset |
| |
| @node Section |
| @section @code{.section @var{name}} |
| |
| @cindex @code{section} directive |
| @cindex named section |
| Use the @code{.section} directive to assemble the following code into a section |
| named @var{name}. |
| |
| This directive is only supported for targets that actually support arbitrarily |
| named sections; on @code{a.out} targets, for example, it is not accepted, even |
| with a standard @code{a.out} section name. |
| |
| @ifset COFF |
| For COFF targets, the @code{.section} directive is used in one of the following |
| ways: |
| @smallexample |
| .section @var{name}[, "@var{flags}"] |
| .section @var{name}[, @var{subsegment}] |
| @end smallexample |
| |
| If the optional argument is quoted, it is taken as flags to use for the |
| section. Each flag is a single character. The following flags are recognized: |
| @table @code |
| @item b |
| bss section (uninitialized data) |
| @item n |
| section is not loaded |
| @item w |
| writable section |
| @item d |
| data section |
| @item r |
| read-only section |
| @item x |
| executable section |
| @end table |
| |
| If no flags are specified, the default flags depend upon the section name. If |
| the section name is not recognized, the default will be for the section to be |
| loaded and writable. |
| |
| If the optional argument to the @code{.section} directive is not quoted, it is |
| taken as a subsegment number (@pxref{Sub-Sections}). |
| @end ifset |
| |
| @ifset ELF |
| For ELF targets, the @code{.section} directive is used like this: |
| @smallexample |
| .section @var{name}[, "@var{flags}"[, @@@var{type}]] |
| @end smallexample |
| The optional @var{flags} argument is a quoted string which may contain any |
| combintion of the following characters: |
| @table @code |
| @item a |
| section is allocatable |
| @item w |
| section is writable |
| @item x |
| section is executable |
| @end table |
| |
| The optional @var{type} argument may contain one of the following constants: |
| @table @code |
| @item @@progbits |
| section contains data |
| @item @@nobits |
| section does not contain data (i.e., section only occupies space) |
| @end table |
| |
| If no flags are specified, the default flags depend upon the section name. If |
| the section name is not recognized, the default will be for the section to have |
| none of the above flags: it will not be allocated in memory, nor writable, nor |
| executable. The section will contain data. |
| |
| For ELF targets, the assembler supports another type of @code{.section} |
| directive for compatibility with the Solaris assembler: |
| @smallexample |
| .section "@var{name}"[, @var{flags}...] |
| @end smallexample |
| Note that the section name is quoted. There may be a sequence of comma |
| separated flags: |
| @table @code |
| @item #alloc |
| section is allocatable |
| @item #write |
| section is writable |
| @item #execinstr |
| section is executable |
| @end table |
| @end ifset |
| |
| @node Set |
| @section @code{.set @var{symbol}, @var{expression}} |
| |
| @cindex @code{set} directive |
| @cindex symbol value, setting |
| Set the value of @var{symbol} to @var{expression}. This |
| changes @var{symbol}'s value and type to conform to |
| @var{expression}. If @var{symbol} was flagged as external, it remains |
| flagged (@pxref{Symbol Attributes}). |
| |
| You may @code{.set} a symbol many times in the same assembly. |
| |
| If you @code{.set} a global symbol, the value stored in the object |
| file is the last value stored into it. |
| |
| @ifset HPPA |
| The syntax for @code{set} on the HPPA is |
| @samp{@var{symbol} .set @var{expression}}. |
| @end ifset |
| |
| @node Short |
| @section @code{.short @var{expressions}} |
| |
| @cindex @code{short} directive |
| @ifset GENERIC |
| @code{.short} is normally the same as @samp{.word}. |
| @xref{Word,,@code{.word}}. |
| |
| In some configurations, however, @code{.short} and @code{.word} generate |
| numbers of different lengths; @pxref{Machine Dependencies}. |
| @end ifset |
| @ifclear GENERIC |
| @ifset W16 |
| @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}. |
| @end ifset |
| @ifset W32 |
| This expects zero or more @var{expressions}, and emits |
| a 16 bit number for each. |
| @end ifset |
| @end ifclear |
| |
| @node Single |
| @section @code{.single @var{flonums}} |
| |
| @cindex @code{single} directive |
| @cindex floating point numbers (single) |
| This directive assembles zero or more flonums, separated by commas. It |
| has the same effect as @code{.float}. |
| @ifset GENERIC |
| The exact kind of floating point numbers emitted depends on how |
| @code{@value{AS}} is configured. @xref{Machine Dependencies}. |
| @end ifset |
| @ifclear GENERIC |
| @ifset IEEEFLOAT |
| On the @value{TARGET} family, @code{.single} emits 32-bit floating point |
| numbers in @sc{ieee} format. |
| @end ifset |
| @end ifclear |
| |
| @ifset COFF |
| @node Size |
| @section @code{.size} |
| |
| @cindex @code{size} directive |
| This directive is generated by compilers to include auxiliary debugging |
| information in the symbol table. It is only permitted inside |
| @code{.def}/@code{.endef} pairs. |
| @ifset BOUT |
| |
| @samp{.size} is only meaningful when generating COFF format output; when |
| @code{@value{AS}} is generating @code{b.out}, it accepts this directive but |
| ignores it. |
| @end ifset |
| @end ifset |
| |
| @node Sleb128 |
| @section @code{.sleb128 @var{expressions}} |
| |
| @cindex @code{sleb128} directive |
| @var{sleb128} stands for ``signed little endian base 128.'' This is a |
| compact, variable length representation of numbers used by the DWARF |
| symbolic debugging format. @xref{Uleb128,@code{.uleb128}}. |
| |
| @ifclear no-space-dir |
| @node Skip |
| @section @code{.skip @var{size} , @var{fill}} |
| |
| @cindex @code{skip} directive |
| @cindex filling memory |
| This directive emits @var{size} bytes, each of value @var{fill}. Both |
| @var{size} and @var{fill} are absolute expressions. If the comma and |
| @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as |
| @samp{.space}. |
| |
| @node Space |
| @section @code{.space @var{size} , @var{fill}} |
| |
| @cindex @code{space} directive |
| @cindex filling memory |
| This directive emits @var{size} bytes, each of value @var{fill}. Both |
| @var{size} and @var{fill} are absolute expressions. If the comma |
| and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same |
| as @samp{.skip}. |
| |
| @ifset HPPA |
| @quotation |
| @emph{Warning:} @code{.space} has a completely different meaning for HPPA |
| targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800 |
| Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the |
| @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives}, |
| for a summary. |
| @end quotation |
| @end ifset |
| @end ifclear |
| |
| @ifset A29K |
| @ifclear GENERIC |
| @node Space |
| @section @code{.space} |
| @cindex @code{space} directive |
| @end ifclear |
| On the AMD 29K, this directive is ignored; it is accepted for |
| compatibility with other AMD 29K assemblers. |
| |
| @quotation |
| @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive |
| @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}. |
| @end quotation |
| @end ifset |
| |
| @ifset have-stabs |
| @node Stab |
| @section @code{.stabd, .stabn, .stabs} |
| |
| @cindex symbolic debuggers, information for |
| @cindex @code{stab@var{x}} directives |
| There are three directives that begin @samp{.stab}. |
| All emit symbols (@pxref{Symbols}), for use by symbolic debuggers. |
| The symbols are not entered in the @code{@value{AS}} hash table: they |
| cannot be referenced elsewhere in the source file. |
| Up to five fields are required: |
| |
| @table @var |
| @item string |
| This is the symbol's name. It may contain any character except |
| @samp{\000}, so is more general than ordinary symbol names. Some |
| debuggers used to code arbitrarily complex structures into symbol names |
| using this field. |
| |
| @item type |
| An absolute expression. The symbol's type is set to the low 8 bits of |
| this expression. Any bit pattern is permitted, but @code{@value{LD}} |
| and debuggers choke on silly bit patterns. |
| |
| @item other |
| An absolute expression. The symbol's ``other'' attribute is set to the |
| low 8 bits of this expression. |
| |
| @item desc |
| An absolute expression. The symbol's descriptor is set to the low 16 |
| bits of this expression. |
| |
| @item value |
| An absolute expression which becomes the symbol's value. |
| @end table |
| |
| If a warning is detected while reading a @code{.stabd}, @code{.stabn}, |
| or @code{.stabs} statement, the symbol has probably already been created; |
| you get a half-formed symbol in your object file. This is |
| compatible with earlier assemblers! |
| |
| @table @code |
| @cindex @code{stabd} directive |
| @item .stabd @var{type} , @var{other} , @var{desc} |
| |
| The ``name'' of the symbol generated is not even an empty string. |
| It is a null pointer, for compatibility. Older assemblers used a |
| null pointer so they didn't waste space in object files with empty |
| strings. |
| |
| The symbol's value is set to the location counter, |
| relocatably. When your program is linked, the value of this symbol |
| is the address of the location counter when the @code{.stabd} was |
| assembled. |
| |
| @cindex @code{stabn} directive |
| @item .stabn @var{type} , @var{other} , @var{desc} , @var{value} |
| The name of the symbol is set to the empty string @code{""}. |
| |
| @cindex @code{stabs} directive |
| @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value} |
| All five fields are specified. |
| @end table |
| @end ifset |
| @c end have-stabs |
| |
| @node String |
| @section @code{.string} "@var{str}" |
| |
| @cindex string, copying to object file |
| @cindex @code{string} directive |
| |
| Copy the characters in @var{str} to the object file. You may specify more than |
| one string to copy, separated by commas. Unless otherwise specified for a |
| particular machine, the assembler marks the end of each string with a 0 byte. |
| You can use any of the escape sequences described in @ref{Strings,,Strings}. |
| |
| @node Struct |
| @section @code{.struct @var{expression}} |
| |
| @cindex @code{struct} directive |
| Switch to the absolute section, and set the section offset to @var{expression}, |
| which must be an absolute expression. You might use this as follows: |
| @smallexample |
| .struct 0 |
| field1: |
| .struct field1 + 4 |
| field2: |
| .struct field2 + 4 |
| field3: |
| @end smallexample |
| This would define the symbol @code{field1} to have the value 0, the symbol |
| @code{field2} to have the value 4, and the symbol @code{field3} to have the |
| value 8. Assembly would be left in the absolute section, and you would need to |
| use a @code{.section} directive of some sort to change to some other section |
| before further assembly. |
| |
| @ifset ELF |
| @node Symver |
| @section @code{.symver} |
| @cindex @code{symver} directive |
| @cindex symbol versioning |
| @cindex versions of symbols |
| Use the @code{.symver} directive to bind symbols to specific version nodes |
| within a source file. This is only supported on ELF platforms, and is |
| typically used when assembling files to be linked into a shared library. |
| There are cases where it may make sense to use this in objects to be bound |
| into an application itself so as to override a versioned symbol from a |
| shared library. |
| |
| For ELF targets, the @code{.symver} directive is used like this: |
| @smallexample |
| .symver @var{name}, @var{name2@@nodename} |
| @end smallexample |
| In this case, the symbol @var{name} must exist and be defined within the file |
| being assembled. The @code{.versym} directive effectively creates a symbol |
| alias with the name @var{name2@@nodename}, and in fact the main reason that we |
| just don't try and create a regular alias is that the @var{@@} character isn't |
| permitted in symbol names. The @var{name2} part of the name is the actual name |
| of the symbol by which it will be externally referenced. The name @var{name} |
| itself is merely a name of convenience that is used so that it is possible to |
| have definitions for multiple versions of a function within a single source |
| file, and so that the compiler can unambiguously know which version of a |
| function is being mentioned. The @var{nodename} portion of the alias should be |
| the name of a node specified in the version script supplied to the linker when |
| building a shared library. If you are attempting to override a versioned |
| symbol from a shared library, then @var{nodename} should correspond to the |
| nodename of the symbol you are trying to override. |
| @end ifset |
| |
| @ifset COFF |
| @node Tag |
| @section @code{.tag @var{structname}} |
| |
| @cindex COFF structure debugging |
| @cindex structure debugging, COFF |
| @cindex @code{tag} directive |
| This directive is generated by compilers to include auxiliary debugging |
| information in the symbol table. It is only permitted inside |
| @code{.def}/@code{.endef} pairs. Tags are used to link structure |
| definitions in the symbol table with instances of those structures. |
| @ifset BOUT |
| |
| @samp{.tag} is only used when generating COFF format output; when |
| @code{@value{AS}} is generating @code{b.out}, it accepts this directive but |
| ignores it. |
| @end ifset |
| @end ifset |
| |
| @node Text |
| @section @code{.text @var{subsection}} |
| |
| @cindex @code{text} directive |
| Tells @code{@value{AS}} to assemble the following statements onto the end of |
| the text subsection numbered @var{subsection}, which is an absolute |
| expression. If @var{subsection} is omitted, subsection number zero |
| is used. |
| |
| @node Title |
| @section @code{.title "@var{heading}"} |
| |
| @cindex @code{title} directive |
| @cindex listing control: title line |
| Use @var{heading} as the title (second line, immediately after the |
| source file name and pagenumber) when generating assembly listings. |
| |
| This directive affects subsequent pages, as well as the current page if |
| it appears within ten lines of the top of a page. |
| |
| @ifset COFF |
| @node Type |
| @section @code{.type @var{int}} |
| |
| @cindex COFF symbol type |
| @cindex symbol type, COFF |
| @cindex @code{type} directive |
| This directive, permitted only within @code{.def}/@code{.endef} pairs, |
| records the integer @var{int} as the type attribute of a symbol table entry. |
| @ifset BOUT |
| |
| @samp{.type} is associated only with COFF format output; when |
| @code{@value{AS}} is configured for @code{b.out} output, it accepts this |
| directive but ignores it. |
| @end ifset |
| @end ifset |
| |
| @ifset COFF |
| @node Val |
| @section @code{.val @var{addr}} |
| |
| @cindex @code{val} directive |
| @cindex COFF value attribute |
| @cindex value attribute, COFF |
| This directive, permitted only within @code{.def}/@code{.endef} pairs, |
| records the address @var{addr} as the value attribute of a symbol table |
| entry. |
| @ifset BOUT |
| |
| @samp{.val} is used only for COFF output; when @code{@value{AS}} is |
| configured for @code{b.out}, it accepts this directive but ignores it. |
| @end ifset |
| @end ifset |
| |
| @node Uleb128 |
| @section @code{.uleb128 @var{expressions}} |
| |
| @cindex @code{uleb128} directive |
| @var{uleb128} stands for ``unsigned little endian base 128.'' This is a |
| compact, variable length representation of numbers used by the DWARF |
| symbolic debugging format. @xref{Sleb128,@code{.sleb128}}. |
| |
| @node Word |
| @section @code{.word @var{expressions}} |
| |
| @cindex @code{word} directive |
| This directive expects zero or more @var{expressions}, of any section, |
| separated by commas. |
| @ifclear GENERIC |
| @ifset W32 |
| For each expression, @code{@value{AS}} emits a 32-bit number. |
| @end ifset |
| @ifset W16 |
| For each expression, @code{@value{AS}} emits a 16-bit number. |
| @end ifset |
| @end ifclear |
| @ifset GENERIC |
| |
| The size of the number emitted, and its byte order, |
| depend on what target computer the assembly is for. |
| @end ifset |
| |
| @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't |
| @c happen---32-bit addressability, period; no long/short jumps. |
| @ifset DIFF-TBL-KLUGE |
| @cindex difference tables altered |
| @cindex altered difference tables |
| @quotation |
| @emph{Warning: Special Treatment to support Compilers} |
| @end quotation |
| |
| @ifset GENERIC |
| Machines with a 32-bit address space, but that do less than 32-bit |
| addressing, require the following special treatment. If the machine of |
| interest to you does 32-bit addressing (or doesn't require it; |
| @pxref{Machine Dependencies}), you can ignore this issue. |
| |
| @end ifset |
| In order to assemble compiler output into something that works, |
| @code{@value{AS}} occasionlly does strange things to @samp{.word} directives. |
| Directives of the form @samp{.word sym1-sym2} are often emitted by |
| compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a |
| directive of the form @samp{.word sym1-sym2}, and the difference between |
| @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}} |
| creates a @dfn{secondary jump table}, immediately before the next label. |
| This secondary jump table is preceded by a short-jump to the |
| first byte after the secondary table. This short-jump prevents the flow |
| of control from accidentally falling into the new table. Inside the |
| table is a long-jump to @code{sym2}. The original @samp{.word} |
| contains @code{sym1} minus the address of the long-jump to |
| @code{sym2}. |
| |
| If there were several occurrences of @samp{.word sym1-sym2} before the |
| secondary jump table, all of them are adjusted. If there was a |
| @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a |
| long-jump to @code{sym4} is included in the secondary jump table, |
| and the @code{.word} directives are adjusted to contain @code{sym3} |
| minus the address of the long-jump to @code{sym4}; and so on, for as many |
| entries in the original jump table as necessary. |
| |
| @ifset INTERNALS |
| @emph{This feature may be disabled by compiling @code{@value{AS}} with the |
| @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse |
| assembly language programmers. |
| @end ifset |
| @end ifset |
| @c end DIFF-TBL-KLUGE |
| |
| @node Deprecated |
| @section Deprecated Directives |
| |
| @cindex deprecated directives |
| @cindex obsolescent directives |
| One day these directives won't work. |
| They are included for compatibility with older assemblers. |
| @table @t |
| @item .abort |
| @item .line |
| @end table |
| |
| @ifset GENERIC |
| @node Machine Dependencies |
| @chapter Machine Dependent Features |
| |
| @cindex machine dependencies |
| The machine instruction sets are (almost by definition) different on |
| each machine where @code{@value{AS}} runs. Floating point representations |
| vary as well, and @code{@value{AS}} often supports a few additional |
| directives or command-line options for compatibility with other |
| assemblers on a particular platform. Finally, some versions of |
| @code{@value{AS}} support special pseudo-instructions for branch |
| optimization. |
| |
| This chapter discusses most of these differences, though it does not |
| include details on any machine's instruction set. For details on that |
| subject, see the hardware manufacturer's manual. |
| |
| @menu |
| @ifset A29K |
| * AMD29K-Dependent:: AMD 29K Dependent Features |
| @end ifset |
| @ifset ARC |
| * ARC-Dependent:: ARC Dependent Features |
| @end ifset |
| @ifset ARM |
| * ARM-Dependent:: ARM Dependent Features |
| @end ifset |
| @ifset D10V |
| * D10V-Dependent:: D10V Dependent Features |
| @end ifset |
| @ifset D30V |
| * D30V-Dependent:: D30V Dependent Features |
| @end ifset |
| @ifset H8/300 |
| * H8/300-Dependent:: Hitachi H8/300 Dependent Features |
| @end ifset |
| @ifset H8/500 |
| * H8/500-Dependent:: Hitachi H8/500 Dependent Features |
| @end ifset |
| @ifset HPPA |
| * HPPA-Dependent:: HPPA Dependent Features |
| @end ifset |
| @ifset I80386 |
| * i386-Dependent:: Intel 80386 Dependent Features |
| @end ifset |
| @ifset I960 |
| * i960-Dependent:: Intel 80960 Dependent Features |
| @end ifset |
| @ifset M680X0 |
| * M68K-Dependent:: M680x0 Dependent Features |
| @end ifset |
| @ifset MIPS |
| * MIPS-Dependent:: MIPS Dependent Features |
| @end ifset |
| @ifset SH |
| * SH-Dependent:: Hitachi SH Dependent Features |
| @end ifset |
| @ifset SPARC |
| * Sparc-Dependent:: SPARC Dependent Features |
| @end ifset |
| @ifset V850 |
| * V850-Dependent:: V850 Dependent Features |
| @end ifset |
| @ifset Z8000 |
| * Z8000-Dependent:: Z8000 Dependent Features |
| @end ifset |
| @ifset VAX |
| * Vax-Dependent:: VAX Dependent Features |
| @end ifset |
| @end menu |
| |
| @lowersections |
| @end ifset |
| |
| @c The following major nodes are *sections* in the GENERIC version, *chapters* |
| @c in single-cpu versions. This is mainly achieved by @lowersections. There is a |
| @c peculiarity: to preserve cross-references, there must be a node called |
| @c "Machine Dependencies". Hence the conditional nodenames in each |
| @c major node below. Node defaulting in makeinfo requires adjacency of |
| @c node and sectioning commands; hence the repetition of @chapter BLAH |
| @c in both conditional blocks. |
| |
| @ifset ARC |
| @ifset GENERIC |
| @page |
| @node ARC-Dependent |
| @chapter ARC Dependent Features |
| @end ifset |
| @ifclear GENERIC |
| @node Machine Dependencies |
| @chapter ARC Dependent Features |
| @end ifclear |
| |
| @cindex ARC support |
| @menu |
| * ARC-Opts:: Options |
| * ARC-Float:: Floating Point |
| * ARC-Directives:: Sparc Machine Directives |
| @end menu |
| |
| @node ARC-Opts |
| @section Options |
| |
| @cindex options for ARC |
| @cindex ARC options |
| @cindex architectures, ARC |
| @cindex ARC architectures |
| The ARC chip family includes several successive levels (or other |
| variants) of chip, using the same core instruction set, but including |
| a few additional instructions at each level. |
| |
| By default, @code{@value{AS}} assumes the core instruction set (ARC |
| base). The @code{.cpu} pseudo-op is intended to be used to select |
| the variant. |
| |
| @table @code |
| @cindex @code{-mbig-endian} option (ARC) |
| @cindex @code{-mlittle-endian} option (ARC) |
| @cindex ARC big-endian output |
| @cindex ARC little-endian output |
| @cindex big-endian output, ARC |
| @cindex little-endian output, ARC |
| @item -mbig-endian |
| @itemx -mlittle-endian |
| Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or |
| little-endian output at run time (unlike most other @sc{gnu} development |
| tools, which must be configured for one or the other). Use |
| @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian} |
| for little-endian. |
| @end table |
| |
| @node ARC-Float |
| @section Floating Point |
| |
| @cindex floating point, ARC (@sc{ieee}) |
| @cindex ARC floating point (@sc{ieee}) |
| The ARC cpu family currently does not have hardware floating point |
| support. Software floating point support is provided by @code{GCC} |
| and uses @sc{ieee} floating-point numbers. |
| |
| @node ARC-Directives |
| @section ARC Machine Directives |
| |
| @cindex ARC machine directives |
| @cindex machine directives, ARC |
| The ARC version of @code{@value{AS}} supports the following additional |
| machine directives: |
| |
| @table @code |
| @item .cpu |
| @cindex @code{cpu} directive, SPARC |
| This must be followed by the desired cpu. |
| The ARC is intended to be customizable, @code{.cpu} is used to |
| select the desired variant [though currently there are none]. |
| |
| @end table |
| |
| @end ifset |
| |
| @ifset A29K |
| @include c-a29k.texi |
| @end ifset |
| |
| @ifset ARM |
| @include c-arm.texi |
| @end ifset |
| |
| @ifset Hitachi-all |
| @ifclear GENERIC |
| @node Machine Dependencies |
| @chapter Machine Dependent Features |
| |
| The machine instruction sets are different on each Hitachi chip family, |
| and there are also some syntax differences among the families. This |
| chapter describes the specific @code{@value{AS}} features for each |
| family. |
| |
| @menu |
| * H8/300-Dependent:: Hitachi H8/300 Dependent Features |
| * H8/500-Dependent:: Hitachi H8/500 Dependent Features |
| * SH-Dependent:: Hitachi SH Dependent Features |
| @end menu |
| @lowersections |
| @end ifclear |
| @end ifset |
| |
| @ifset D10V |
| @include c-d10v.texi |
| @end ifset |
| |
| @ifset D30V |
| @include c-d30v.texi |
| @end ifset |
| |
| @ifset H8/300 |
| @include c-h8300.texi |
| @end ifset |
| |
| @ifset H8/500 |
| @include c-h8500.texi |
| @end ifset |
| |
| @ifset HPPA |
| @include c-hppa.texi |
| @end ifset |
| |
| @ifset I80386 |
| @include c-i386.texi |
| @end ifset |
| |
| @ifset I960 |
| @include c-i960.texi |
| @end ifset |
| |
| |
| @ifset M680X0 |
| @include c-m68k.texi |
| @end ifset |
| |
| @ifset MIPS |
| @include c-mips.texi |
| @end ifset |
| |
| @ifset NS32K |
| @include c-ns32k.texi |
| @end ifset |
| |
| @ifset SH |
| @include c-sh.texi |
| @end ifset |
| |
| @ifset SPARC |
| @include c-sparc.texi |
| @end ifset |
| |
| @ifset Z8000 |
| @include c-z8k.texi |
| @end ifset |
| |
| @ifset VAX |
| @include c-vax.texi |
| @end ifset |
| |
| @ifset V850 |
| @include c-v850.texi |
| @end ifset |
| |
| @ifset GENERIC |
| @c reverse effect of @down at top of generic Machine-Dep chapter |
| @raisesections |
| @end ifset |
| |
| @node Reporting Bugs |
| @chapter Reporting Bugs |
| @cindex bugs in assembler |
| @cindex reporting bugs in assembler |
| |
| Your bug reports play an essential role in making @code{@value{AS}} reliable. |
| |
| Reporting a bug may help you by bringing a solution to your problem, or it may |
| not. But in any case the principal function of a bug report is to help the |
| entire community by making the next version of @code{@value{AS}} work better. |
| Bug reports are your contribution to the maintenance of @code{@value{AS}}. |
| |
| In order for a bug report to serve its purpose, you must include the |
| information that enables us to fix the bug. |
| |
| @menu |
| * Bug Criteria:: Have you found a bug? |
| * Bug Reporting:: How to report bugs |
| @end menu |
| |
| @node Bug Criteria |
| @section Have you found a bug? |
| @cindex bug criteria |
| |
| If you are not sure whether you have found a bug, here are some guidelines: |
| |
| @itemize @bullet |
| @cindex fatal signal |
| @cindex assembler crash |
| @cindex crash of assembler |
| @item |
| If the assembler gets a fatal signal, for any input whatever, that is a |
| @code{@value{AS}} bug. Reliable assemblers never crash. |
| |
| @cindex error on valid input |
| @item |
| If @code{@value{AS}} produces an error message for valid input, that is a bug. |
| |
| @cindex invalid input |
| @item |
| If @code{@value{AS}} does not produce an error message for invalid input, that |
| is a bug. However, you should note that your idea of ``invalid input'' might |
| be our idea of ``an extension'' or ``support for traditional practice''. |
| |
| @item |
| If you are an experienced user of assemblers, your suggestions for improvement |
| of @code{@value{AS}} are welcome in any case. |
| @end itemize |
| |
| @node Bug Reporting |
| @section How to report bugs |
| @cindex bug reports |
| @cindex assembler bugs, reporting |
| |
| A number of companies and individuals offer support for @sc{gnu} products. If |
| you obtained @code{@value{AS}} from a support organization, we recommend you |
| contact that organization first. |
| |
| You can find contact information for many support companies and |
| individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs |
| distribution. |
| |
| In any event, we also recommend that you send bug reports for @code{@value{AS}} |
| to @samp{bug-gnu-utils@@gnu.org}. |
| |
| The fundamental principle of reporting bugs usefully is this: |
| @strong{report all the facts}. If you are not sure whether to state a |
| fact or leave it out, state it! |
| |
| Often people omit facts because they think they know what causes the problem |
| and assume that some details do not matter. Thus, you might assume that the |
| name of a symbol you use in an example does not matter. Well, probably it does |
| not, but one cannot be sure. Perhaps the bug is a stray memory reference which |
| happens to fetch from the location where that name is stored in memory; |
| perhaps, if the name were different, the contents of that location would fool |
| the assembler into doing the right thing despite the bug. Play it safe and |
| give a specific, complete example. That is the easiest thing for you to do, |
| and the most helpful. |
| |
| Keep in mind that the purpose of a bug report is to enable us to fix the bug if |
| it is new to us. Therefore, always write your bug reports on the assumption |
| that the bug has not been reported previously. |
| |
| Sometimes people give a few sketchy facts and ask, ``Does this ring a |
| bell?'' Those bug reports are useless, and we urge everyone to |
| @emph{refuse to respond to them} except to chide the sender to report |
| bugs properly. |
| |
| To enable us to fix the bug, you should include all these things: |
| |
| @itemize @bullet |
| @item |
| The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start |
| it with the @samp{--version} argument. |
| |
| Without this, we will not know whether there is any point in looking for |
| the bug in the current version of @code{@value{AS}}. |
| |
| @item |
| Any patches you may have applied to the @code{@value{AS}} source. |
| |
| @item |
| The type of machine you are using, and the operating system name and |
| version number. |
| |
| @item |
| What compiler (and its version) was used to compile @code{@value{AS}}---e.g. |
| ``@code{gcc-2.7}''. |
| |
| @item |
| The command arguments you gave the assembler to assemble your example and |
| observe the bug. To guarantee you will not omit something important, list them |
| all. A copy of the Makefile (or the output from make) is sufficient. |
| |
| If we were to try to guess the arguments, we would probably guess wrong |
| and then we might not encounter the bug. |
| |
| @item |
| A complete input file that will reproduce the bug. If the bug is observed when |
| the assembler is invoked via a compiler, send the assembler source, not the |
| high level language source. Most compilers will produce the assembler source |
| when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use |
| the options @samp{-v --save-temps}; this will save the assembler source in a |
| file with an extension of @file{.s}, and also show you exactly how |
| @code{@value{AS}} is being run. |
| |
| @item |
| A description of what behavior you observe that you believe is |
| incorrect. For example, ``It gets a fatal signal.'' |
| |
| Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we |
| will certainly notice it. But if the bug is incorrect output, we might not |
| notice unless it is glaringly wrong. You might as well not give us a chance to |
| make a mistake. |
| |
| Even if the problem you experience is a fatal signal, you should still say so |
| explicitly. Suppose something strange is going on, such as, your copy of |
| @code{@value{AS}} is out of synch, or you have encountered a bug in the C |
| library on your system. (This has happened!) Your copy might crash and ours |
| would not. If you told us to expect a crash, then when ours fails to crash, we |
| would know that the bug was not happening for us. If you had not told us to |
| expect a crash, then we would not be able to draw any conclusion from our |
| observations. |
| |
| @item |
| If you wish to suggest changes to the @code{@value{AS}} source, send us context |
| diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p} |
| option. Always send diffs from the old file to the new file. If you even |
| discuss something in the @code{@value{AS}} source, refer to it by context, not |
| by line number. |
| |
| The line numbers in our development sources will not match those in your |
| sources. Your line numbers would convey no useful information to us. |
| @end itemize |
| |
| Here are some things that are not necessary: |
| |
| @itemize @bullet |
| @item |
| A description of the envelope of the bug. |
| |
| Often people who encounter a bug spend a lot of time investigating |
| which changes to the input file will make the bug go away and which |
| changes will not affect it. |
| |
| This is often time consuming and not very useful, because the way we |
| will find the bug is by running a single example under the debugger |
| with breakpoints, not by pure deduction from a series of examples. |
| We recommend that you save your time for something else. |
| |
| Of course, if you can find a simpler example to report @emph{instead} |
| of the original one, that is a convenience for us. Errors in the |
| output will be easier to spot, running under the debugger will take |
| less time, and so on. |
| |
| However, simplification is not vital; if you do not want to do this, |
| report the bug anyway and send us the entire test case you used. |
| |
| @item |
| A patch for the bug. |
| |
| A patch for the bug does help us if it is a good one. But do not omit |
| the necessary information, such as the test case, on the assumption that |
| a patch is all we need. We might see problems with your patch and decide |
| to fix the problem another way, or we might not understand it at all. |
| |
| Sometimes with a program as complicated as @code{@value{AS}} it is very hard to |
| construct an example that will make the program follow a certain path through |
| the code. If you do not send us the example, we will not be able to construct |
| one, so we will not be able to verify that the bug is fixed. |
| |
| And if we cannot understand what bug you are trying to fix, or why your |
| patch should be an improvement, we will not install it. A test case will |
| help us to understand. |
| |
| @item |
| A guess about what the bug is or what it depends on. |
| |
| Such guesses are usually wrong. Even we cannot guess right about such |
| things without first using the debugger to find the facts. |
| @end itemize |
| |
| @node Acknowledgements |
| @chapter Acknowledgements |
| |
| If you have contributed to @code{@value{AS}} and your name isn't listed here, |
| it is not meant as a slight. We just don't know about it. Send mail to the |
| maintainer, and we'll correct the situation. Currently |
| @c (January 1994), |
| the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}). |
| |
| Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any |
| more details?} |
| |
| Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug |
| information and the 68k series machines, most of the preprocessing pass, and |
| extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}. |
| |
| K. Richard Pixley maintained GAS for a while, adding various enhancements and |
| many bug fixes, including merging support for several processors, breaking GAS |
| up to handle multiple object file format back ends (including heavy rewrite, |
| testing, an integration of the coff and b.out back ends), adding configuration |
| including heavy testing and verification of cross assemblers and file splits |
| and renaming, converted GAS to strictly ANSI C including full prototypes, added |
| support for m680[34]0 and cpu32, did considerable work on i960 including a COFF |
| port (including considerable amounts of reverse engineering), a SPARC opcode |
| file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know'' |
| assertions and made them work, much other reorganization, cleanup, and lint. |
| |
| Ken Raeburn wrote the high-level BFD interface code to replace most of the code |
| in format-specific I/O modules. |
| |
| The original VMS support was contributed by David L. Kashtan. Eric Youngdale |
| has done much work with it since. |
| |
| The Intel 80386 machine description was written by Eliot Dresselhaus. |
| |
| Minh Tran-Le at IntelliCorp contributed some AIX 386 support. |
| |
| The Motorola 88k machine description was contributed by Devon Bowen of Buffalo |
| University and Torbjorn Granlund of the Swedish Institute of Computer Science. |
| |
| Keith Knowles at the Open Software Foundation wrote the original MIPS back end |
| (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support |
| (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to |
| support a.out format. |
| |
| Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k, |
| tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by |
| Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to |
| use BFD for some low-level operations, for use with the H8/300 and AMD 29k |
| targets. |
| |
| John Gilmore built the AMD 29000 support, added @code{.include} support, and |
| simplified the configuration of which versions accept which directives. He |
| updated the 68k machine description so that Motorola's opcodes always produced |
| fixed-size instructions (e.g. @code{jsr}), while synthetic instructions |
| remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested |
| cross-compilation support, and one bug in relaxation that took a week and |
| required the proverbial one-bit fix. |
| |
| Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the |
| 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix), |
| added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and |
| PowerPC assembler, and made a few other minor patches. |
| |
| Steve Chamberlain made @code{@value{AS}} able to generate listings. |
| |
| Hewlett-Packard contributed support for the HP9000/300. |
| |
| Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM) |
| along with a fairly extensive HPPA testsuite (for both SOM and ELF object |
| formats). This work was supported by both the Center for Software Science at |
| the University of Utah and Cygnus Support. |
| |
| Support for ELF format files has been worked on by Mark Eichin of Cygnus |
| Support (original, incomplete implementation for SPARC), Pete Hoogenboom and |
| Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open |
| Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc, |
| and some initial 64-bit support). |
| |
| Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD |
| support for openVMS/Alpha. |
| |
| Several engineers at Cygnus Support have also provided many small bug fixes and |
| configuration enhancements. |
| |
| Many others have contributed large or small bugfixes and enhancements. If |
| you have contributed significant work and are not mentioned on this list, and |
| want to be, let us know. Some of the history has been lost; we are not |
| intentionally leaving anyone out. |
| |
| @node Index |
| @unnumbered Index |
| |
| @printindex cp |
| |
| @contents |
| @bye |
| @c Local Variables: |
| @c fill-column: 79 |
| @c End: |