source: trunk/binutils/gas/doc/as.info-7@ 3294

This is as.info, produced by makeinfo version 4.3 from as.texinfo.

START-INFO-DIR-ENTRY
* As: (as).                     The GNU assembler.
* Gas: (as).                    The GNU assembler.
END-INFO-DIR-ENTRY

   This file documents the GNU Assembler "as".

   Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002
Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts.  A copy of the license is included in the section entitled "GNU
Free Documentation License".


File: as.info,  Node: callj-i960,  Next: Compare-and-branch-i960,  Up: Opcodes for i960

`callj'
.......

   You can write `callj' to have the assembler or the linker determine
the most appropriate form of subroutine call: `call', `bal', or
`calls'.  If the assembly source contains enough information--a
`.leafproc' or `.sysproc' directive defining the operand--then `as'
translates the `callj'; if not, it simply emits the `callj', leaving it
for the linker to resolve.


File: as.info,  Node: Compare-and-branch-i960,  Prev: callj-i960,  Up: Opcodes for i960

Compare-and-Branch
..................

   The 960 architectures provide combined Compare-and-Branch
instructions that permit you to store the branch target in the lower 13
bits of the instruction word itself.  However, if you specify a branch
target far enough away that its address won't fit in 13 bits, the
assembler can either issue an error, or convert your Compare-and-Branch
instruction into separate instructions to do the compare and the branch.

   Whether `as' gives an error or expands the instruction depends on
two choices you can make: whether you use the `-no-relax' option, and
whether you use a "Compare and Branch" instruction or a "Compare and
Jump" instruction.  The "Jump" instructions are _always_ expanded if
necessary; the "Branch" instructions are expanded when necessary
_unless_ you specify `-no-relax'--in which case `as' gives an error
instead.

   These are the Compare-and-Branch instructions, their "Jump" variants,
and the instruction pairs they may expand into:

             Compare and
          Branch      Jump       Expanded to
          ------    ------       ------------
             bbc                 chkbit; bno
             bbs                 chkbit; bo
          cmpibe    cmpije       cmpi; be
          cmpibg    cmpijg       cmpi; bg
         cmpibge   cmpijge       cmpi; bge
          cmpibl    cmpijl       cmpi; bl
         cmpible   cmpijle       cmpi; ble
         cmpibno   cmpijno       cmpi; bno
         cmpibne   cmpijne       cmpi; bne
          cmpibo    cmpijo       cmpi; bo
          cmpobe    cmpoje       cmpo; be
          cmpobg    cmpojg       cmpo; bg
         cmpobge   cmpojge       cmpo; bge
          cmpobl    cmpojl       cmpo; bl
         cmpoble   cmpojle       cmpo; ble
         cmpobne   cmpojne       cmpo; bne


File: as.info,  Node: IP2K-Dependent,  Next: M32R-Dependent,  Prev: i960-Dependent,  Up: Machine Dependencies

IP2K Dependent Features
=======================

* Menu:

* IP2K-Opts::                   IP2K Options


File: as.info,  Node: IP2K-Opts,  Up: IP2K-Dependent

IP2K Options
------------

   The Ubicom IP2K version of `as' has a few machine dependent options:

`-mip2022ext'
     `as' can assemble the extended IP2022 instructions, but it will
     only do so if this is specifically allowed via this command line
     option.

`-mip2022'
     This option restores the assembler's default behaviour of not
     permitting the extended IP2022 instructions to be assembled.


File: as.info,  Node: M32R-Dependent,  Next: M68K-Dependent,  Prev: IP2K-Dependent,  Up: Machine Dependencies

M32R Dependent Features
=======================

* Menu:

* M32R-Opts::                   M32R Options
* M32R-Warnings::               M32R Warnings


File: as.info,  Node: M32R-Opts,  Next: M32R-Warnings,  Up: M32R-Dependent

M32R Options
------------

   The Renease M32R version of `as' has a few machine dependent options:

`-m32rx'
     `as' can assemble code for several different members of the
     Renesas M32R family.  Normally the default is to assemble code for
     the M32R microprocessor.  This option may be used to change the
     default to the M32RX microprocessor, which adds some more
     instructions to the basic M32R instruction set, and some
     additional parameters to some of the original instructions.

`-m32r'
     This option can be used to restore the assembler's default
     behaviour of assembling for the M32R microprocessor.  This can be
     useful if the default has been changed by a previous command line
     option.

`-warn-explicit-parallel-conflicts'
     Instructs `as' to produce warning messages when questionable
     parallel instructions are encountered.  This option is enabled by
     default, but `gcc' disables it when it invokes `as' directly.
     Questionable instructions are those whoes behaviour would be
     different if they were executed sequentially.  For example the
     code fragment `mv r1, r2 || mv r3, r1' produces a different result
     from `mv r1, r2 \n mv r3, r1' since the former moves r1 into r3
     and then r2 into r1, whereas the later moves r2 into r1 and r3.

`-Wp'
     This is a shorter synonym for the
     _-warn-explicit-parallel-conflicts_ option.

`-no-warn-explicit-parallel-conflicts'
     Instructs `as' not to produce warning messages when questionable
     parallel instructions are encountered.

`-Wnp'
     This is a shorter synonym for the
     _-no-warn-explicit-parallel-conflicts_ option.


File: as.info,  Node: M32R-Warnings,  Prev: M32R-Opts,  Up: M32R-Dependent

M32R Warnings
-------------

   There are several warning and error messages that can be produced by
`as' which are specific to the M32R:

`output of 1st instruction is the same as an input to 2nd instruction - is this intentional ?'
     This message is only produced if warnings for explicit parallel
     conflicts have been enabled.  It indicates that the assembler has
     encountered a parallel instruction in which the destination
     register of the left hand instruction is used as an input register
     in the right hand instruction.  For example in this code fragment
     `mv r1, r2 || neg r3, r1' register r1 is the destination of the
     move instruction and the input to the neg instruction.

`output of 2nd instruction is the same as an input to 1st instruction - is this intentional ?'
     This message is only produced if warnings for explicit parallel
     conflicts have been enabled.  It indicates that the assembler has
     encountered a parallel instruction in which the destination
     register of the right hand instruction is used as an input
     register in the left hand instruction.  For example in this code
     fragment `mv r1, r2 || neg r2, r3' register r2 is the destination
     of the neg instruction and the input to the move instruction.

`instruction `...' is for the M32RX only'
     This message is produced when the assembler encounters an
     instruction which is only supported by the M32Rx processor, and
     the `-m32rx' command line flag has not been specified to allow
     assembly of such instructions.

`unknown instruction `...''
     This message is produced when the assembler encounters an
     instruction which it doe snot recognise.

`only the NOP instruction can be issued in parallel on the m32r'
     This message is produced when the assembler encounters a parallel
     instruction which does not involve a NOP instruction and the
     `-m32rx' command line flag has not been specified.  Only the M32Rx
     processor is able to execute two instructions in parallel.

`instruction `...' cannot be executed in parallel.'
     This message is produced when the assembler encounters a parallel
     instruction which is made up of one or two instructions which
     cannot be executed in parallel.

`Instructions share the same execution pipeline'
     This message is produced when the assembler encounters a parallel
     instruction whoes components both use the same execution pipeline.

`Instructions write to the same destination register.'
     This message is produced when the assembler encounters a parallel
     instruction where both components attempt to modify the same
     register.  For example these code fragments will produce this
     message: `mv r1, r2 || neg r1, r3' `jl r0 || mv r14, r1' `st r2,
     @-r1 || mv r1, r3' `mv r1, r2 || ld r0, @r1+' `cmp r1, r2 || addx
     r3, r4' (Both write to the condition bit)


File: as.info,  Node: M68K-Dependent,  Next: M68HC11-Dependent,  Prev: M32R-Dependent,  Up: Machine Dependencies

M680x0 Dependent Features
=========================

* Menu:

* M68K-Opts::                   M680x0 Options
* M68K-Syntax::                 Syntax
* M68K-Moto-Syntax::            Motorola Syntax
* M68K-Float::                  Floating Point
* M68K-Directives::             680x0 Machine Directives
* M68K-opcodes::                Opcodes


File: as.info,  Node: M68K-Opts,  Next: M68K-Syntax,  Up: M68K-Dependent

M680x0 Options
--------------

   The Motorola 680x0 version of `as' has a few machine dependent
options:

`-l'
     You can use the `-l' option to shorten the size of references to
     undefined symbols.  If you do not use the `-l' option, references
     to undefined symbols are wide enough for a full `long' (32 bits).
     (Since `as' cannot know where these symbols end up, `as' can only
     allocate space for the linker to fill in later.  Since `as' does
     not know how far away these symbols are, it allocates as much
     space as it can.)  If you use this option, the references are only
     one word wide (16 bits).  This may be useful if you want the
     object file to be as small as possible, and you know that the
     relevant symbols are always less than 17 bits away.

`--register-prefix-optional'
     For some configurations, especially those where the compiler
     normally does not prepend an underscore to the names of user
     variables, the assembler requires a `%' before any use of a
     register name.  This is intended to let the assembler distinguish
     between C variables and functions named `a0' through `a7', and so
     on.  The `%' is always accepted, but is not required for certain
     configurations, notably `sun3'.  The `--register-prefix-optional'
     option may be used to permit omitting the `%' even for
     configurations for which it is normally required.  If this is
     done, it will generally be impossible to refer to C variables and
     functions with the same names as register names.

`--bitwise-or'
     Normally the character `|' is treated as a comment character, which
     means that it can not be used in expressions.  The `--bitwise-or'
     option turns `|' into a normal character.  In this mode, you must
     either use C style comments, or start comments with a `#' character
     at the beginning of a line.

`--base-size-default-16  --base-size-default-32'
     If you use an addressing mode with a base register without
     specifying the size, `as' will normally use the full 32 bit value.
     For example, the addressing mode `%a0@(%d0)' is equivalent to
     `%a0@(%d0:l)'.  You may use the `--base-size-default-16' option to
     tell `as' to default to using the 16 bit value.  In this case,
     `%a0@(%d0)' is equivalent to `%a0@(%d0:w)'.  You may use the
     `--base-size-default-32' option to restore the default behaviour.

`--disp-size-default-16  --disp-size-default-32'
     If you use an addressing mode with a displacement, and the value
     of the displacement is not known, `as' will normally assume that
     the value is 32 bits.  For example, if the symbol `disp' has not
     been defined, `as' will assemble the addressing mode
     `%a0@(disp,%d0)' as though `disp' is a 32 bit value.  You may use
     the `--disp-size-default-16' option to tell `as' to instead assume
     that the displacement is 16 bits.  In this case, `as' will
     assemble `%a0@(disp,%d0)' as though `disp' is a 16 bit value.  You
     may use the `--disp-size-default-32' option to restore the default
     behaviour.

`--pcrel'
     Always keep branches PC-relative.  In the M680x0 architecture all
     branches are defined as PC-relative.  However, on some processors
     they are limited to word displacements maximum.  When `as' needs a
     long branch that is not available, it normally emits an absolute
     jump instead.  This option disables this substitution.  When this
     option is given and no long branches are available, only word
     branches will be emitted.  An error message will be generated if a
     word branch cannot reach its target.  This option has no effect on
     68020 and other processors that have long branches.  *note Branch
     Improvement: M68K-Branch..

`-m68000'
     `as' can assemble code for several different members of the
     Motorola 680x0 family.  The default depends upon how `as' was
     configured when it was built; normally, the default is to assemble
     code for the 68020 microprocessor.  The following options may be
     used to change the default.  These options control which
     instructions and addressing modes are permitted.  The members of
     the 680x0 family are very similar.  For detailed information about
     the differences, see the Motorola manuals.

    `-m68000'
    `-m68ec000'
    `-m68hc000'
    `-m68hc001'
    `-m68008'
    `-m68302'
    `-m68306'
    `-m68307'
    `-m68322'
    `-m68356'
          Assemble for the 68000. `-m68008', `-m68302', and so on are
          synonyms for `-m68000', since the chips are the same from the
          point of view of the assembler.

    `-m68010'
          Assemble for the 68010.

    `-m68020'
    `-m68ec020'
          Assemble for the 68020.  This is normally the default.

    `-m68030'
    `-m68ec030'
          Assemble for the 68030.

    `-m68040'
    `-m68ec040'
          Assemble for the 68040.

    `-m68060'
    `-m68ec060'
          Assemble for the 68060.

    `-mcpu32'
    `-m68330'
    `-m68331'
    `-m68332'
    `-m68333'
    `-m68334'
    `-m68336'
    `-m68340'
    `-m68341'
    `-m68349'
    `-m68360'
          Assemble for the CPU32 family of chips.

    `-m5200'
          Assemble for the ColdFire family of chips.

    `-m68881'
    `-m68882'
          Assemble 68881 floating point instructions.  This is the
          default for the 68020, 68030, and the CPU32.  The 68040 and
          68060 always support floating point instructions.

    `-mno-68881'
          Do not assemble 68881 floating point instructions.  This is
          the default for 68000 and the 68010.  The 68040 and 68060
          always support floating point instructions, even if this
          option is used.

    `-m68851'
          Assemble 68851 MMU instructions.  This is the default for the
          68020, 68030, and 68060.  The 68040 accepts a somewhat
          different set of MMU instructions; `-m68851' and `-m68040'
          should not be used together.

    `-mno-68851'
          Do not assemble 68851 MMU instructions.  This is the default
          for the 68000, 68010, and the CPU32.  The 68040 accepts a
          somewhat different set of MMU instructions.


File: as.info,  Node: M68K-Syntax,  Next: M68K-Moto-Syntax,  Prev: M68K-Opts,  Up: M68K-Dependent

Syntax
------

   This syntax for the Motorola 680x0 was developed at MIT.

   The 680x0 version of `as' uses instructions names and syntax
compatible with the Sun assembler.  Intervening periods are ignored;
for example, `movl' is equivalent to `mov.l'.

   In the following table APC stands for any of the address registers
(`%a0' through `%a7'), the program counter (`%pc'), the zero-address
relative to the program counter (`%zpc'), a suppressed address register
(`%za0' through `%za7'), or it may be omitted entirely.  The use of
SIZE means one of `w' or `l', and it may be omitted, along with the
leading colon, unless a scale is also specified.  The use of SCALE
means one of `1', `2', `4', or `8', and it may always be omitted along
with the leading colon.

   The following addressing modes are understood:
"Immediate"
     `#NUMBER'

"Data Register"
     `%d0' through `%d7'

"Address Register"
     `%a0' through `%a7'
     `%a7' is also known as `%sp', i.e. the Stack Pointer.  `%a6' is
     also known as `%fp', the Frame Pointer.

"Address Register Indirect"
     `%a0@' through `%a7@'

"Address Register Postincrement"
     `%a0@+' through `%a7@+'

"Address Register Predecrement"
     `%a0@-' through `%a7@-'

"Indirect Plus Offset"
     `APC@(NUMBER)'

"Index"
     `APC@(NUMBER,REGISTER:SIZE:SCALE)'

     The NUMBER may be omitted.

"Postindex"
     `APC@(NUMBER)@(ONUMBER,REGISTER:SIZE:SCALE)'

     The ONUMBER or the REGISTER, but not both, may be omitted.

"Preindex"
     `APC@(NUMBER,REGISTER:SIZE:SCALE)@(ONUMBER)'

     The NUMBER may be omitted.  Omitting the REGISTER produces the
     Postindex addressing mode.

"Absolute"
     `SYMBOL', or `DIGITS', optionally followed by `:b', `:w', or `:l'.


File: as.info,  Node: M68K-Moto-Syntax,  Next: M68K-Float,  Prev: M68K-Syntax,  Up: M68K-Dependent

Motorola Syntax
---------------

   The standard Motorola syntax for this chip differs from the syntax
already discussed (*note Syntax: M68K-Syntax.).  `as' can accept
Motorola syntax for operands, even if MIT syntax is used for other
operands in the same instruction.  The two kinds of syntax are fully
compatible.

   In the following table APC stands for any of the address registers
(`%a0' through `%a7'), the program counter (`%pc'), the zero-address
relative to the program counter (`%zpc'), or a suppressed address
register (`%za0' through `%za7').  The use of SIZE means one of `w' or
`l', and it may always be omitted along with the leading dot.  The use
of SCALE means one of `1', `2', `4', or `8', and it may always be
omitted along with the leading asterisk.

   The following additional addressing modes are understood:

"Address Register Indirect"
     `(%a0)' through `(%a7)'
     `%a7' is also known as `%sp', i.e. the Stack Pointer.  `%a6' is
     also known as `%fp', the Frame Pointer.

"Address Register Postincrement"
     `(%a0)+' through `(%a7)+'

"Address Register Predecrement"
     `-(%a0)' through `-(%a7)'

"Indirect Plus Offset"
     `NUMBER(%A0)' through `NUMBER(%A7)', or `NUMBER(%PC)'.

     The NUMBER may also appear within the parentheses, as in
     `(NUMBER,%A0)'.  When used with the PC, the NUMBER may be omitted
     (with an address register, omitting the NUMBER produces Address
     Register Indirect mode).

"Index"
     `NUMBER(APC,REGISTER.SIZE*SCALE)'

     The NUMBER may be omitted, or it may appear within the
     parentheses.  The APC may be omitted.  The REGISTER and the APC
     may appear in either order.  If both APC and REGISTER are address
     registers, and the SIZE and SCALE are omitted, then the first
     register is taken as the base register, and the second as the
     index register.

"Postindex"
     `([NUMBER,APC],REGISTER.SIZE*SCALE,ONUMBER)'

     The ONUMBER, or the REGISTER, or both, may be omitted.  Either the
     NUMBER or the APC may be omitted, but not both.

"Preindex"
     `([NUMBER,APC,REGISTER.SIZE*SCALE],ONUMBER)'

     The NUMBER, or the APC, or the REGISTER, or any two of them, may
     be omitted.  The ONUMBER may be omitted.  The REGISTER and the APC
     may appear in either order.  If both APC and REGISTER are address
     registers, and the SIZE and SCALE are omitted, then the first
     register is taken as the base register, and the second as the
     index register.


File: as.info,  Node: M68K-Float,  Next: M68K-Directives,  Prev: M68K-Moto-Syntax,  Up: M68K-Dependent

Floating Point
--------------

   Packed decimal (P) format floating literals are not supported.  Feel
free to add the code!

   The floating point formats generated by directives are these.

`.float'
     `Single' precision floating point constants.

`.double'
     `Double' precision floating point constants.

`.extend'
`.ldouble'
     `Extended' precision (`long double') floating point constants.


File: as.info,  Node: M68K-Directives,  Next: M68K-opcodes,  Prev: M68K-Float,  Up: M68K-Dependent

680x0 Machine Directives
------------------------

   In order to be compatible with the Sun assembler the 680x0 assembler
understands the following directives.

`.data1'
     This directive is identical to a `.data 1' directive.

`.data2'
     This directive is identical to a `.data 2' directive.

`.even'
     This directive is a special case of the `.align' directive; it
     aligns the output to an even byte boundary.

`.skip'
     This directive is identical to a `.space' directive.


File: as.info,  Node: M68K-opcodes,  Prev: M68K-Directives,  Up: M68K-Dependent

Opcodes
-------

* Menu:

* M68K-Branch::                 Branch Improvement
* M68K-Chars::                  Special Characters


File: as.info,  Node: M68K-Branch,  Next: M68K-Chars,  Up: M68K-opcodes

Branch Improvement
..................

   Certain pseudo opcodes are permitted for branch instructions.  They
expand to the shortest branch instruction that reach the target.
Generally these mnemonics are made by substituting `j' for `b' at the
start of a Motorola mnemonic.

   The following table summarizes the pseudo-operations.  A `*' flags
cases that are more fully described after the table:

               Displacement
               +------------------------------------------------------------
               |                68020           68000/10, not PC-relative OK
     Pseudo-Op |BYTE    WORD    LONG            ABSOLUTE LONG JUMP    **
               +------------------------------------------------------------
          jbsr |bsrs    bsrw    bsrl            jsr
           jra |bras    braw    bral            jmp
     *     jXX |bXXs    bXXw    bXXl            bNXs;jmp
     *    dbXX | N/A    dbXXw   dbXX;bras;bral  dbXX;bras;jmp
          fjXX | N/A    fbXXw   fbXXl            N/A
     
     XX: condition
     NX: negative of condition XX
                       `*'--see full description below
         `**'--this expansion mode is disallowed by `--pcrel'
`jbsr'
`jra'
     These are the simplest jump pseudo-operations; they always map to
     one particular machine instruction, depending on the displacement
     to the branch target.  This instruction will be a byte or word
     branch is that is sufficient.  Otherwise, a long branch will be
     emitted if available.  If no long branches are available and the
     `--pcrel' option is not given, an absolute long jump will be
     emitted instead.  If no long branches are available, the `--pcrel'
     option is given, and a word branch cannot reach the target, an
     error message is generated.

     In addition to standard branch operands, `as' allows these
     pseudo-operations to have all operands that are allowed for jsr
     and jmp, substituting these instructions if the operand given is
     not valid for a branch instruction.

`jXX'
     Here, `jXX' stands for an entire family of pseudo-operations,
     where XX is a conditional branch or condition-code test.  The full
     list of pseudo-ops in this family is:
           jhi   jls   jcc   jcs   jne   jeq   jvc
           jvs   jpl   jmi   jge   jlt   jgt   jle

     Usually, each of these pseudo-operations expands to a single branch
     instruction.  However, if a word branch is not sufficient, no long
     branches are available, and the `--pcrel' option is not given, `as'
     issues a longer code fragment in terms of NX, the opposite
     condition to XX.  For example, under these conditions:
              jXX foo
     gives
               bNXs oof
               jmp foo
           oof:

`dbXX'
     The full family of pseudo-operations covered here is
           dbhi   dbls   dbcc   dbcs   dbne   dbeq   dbvc
           dbvs   dbpl   dbmi   dbge   dblt   dbgt   dble
           dbf    dbra   dbt

     Motorola `dbXX' instructions allow word displacements only.  When
     a word displacement is sufficient, each of these pseudo-operations
     expands to the corresponding Motorola instruction.  When a word
     displacement is not sufficient and long branches are available,
     when the source reads `dbXX foo', `as' emits
               dbXX oo1
               bras oo2
           oo1:bral foo
           oo2:

     If, however, long branches are not available and the `--pcrel'
     option is not given, `as' emits
               dbXX oo1
               bras oo2
           oo1:jmp foo
           oo2:

`fjXX'
     This family includes
           fjne   fjeq   fjge   fjlt   fjgt   fjle   fjf
           fjt    fjgl   fjgle  fjnge  fjngl  fjngle fjngt
           fjnle  fjnlt  fjoge  fjogl  fjogt  fjole  fjolt
           fjor   fjseq  fjsf   fjsne  fjst   fjueq  fjuge
           fjugt  fjule  fjult  fjun

     Each of these pseudo-operations always expands to a single Motorola
     coprocessor branch instruction, word or long.  All Motorola
     coprocessor branch instructions allow both word and long
     displacements.


File: as.info,  Node: M68K-Chars,  Prev: M68K-Branch,  Up: M68K-opcodes

Special Characters
..................

The immediate character is `#' for Sun compatibility.  The line-comment
character is `|' (unless the `--bitwise-or' option is used).  If a `#'
appears at the beginning of a line, it is treated as a comment unless
it looks like `# line file', in which case it is treated normally.


File: as.info,  Node: M68HC11-Dependent,  Next: M88K-Dependent,  Prev: M68K-Dependent,  Up: Machine Dependencies

M68HC11 and M68HC12 Dependent Features
======================================

* Menu:

* M68HC11-Opts::                   M68HC11 and M68HC12 Options
* M68HC11-Syntax::                 Syntax
* M68HC11-Modifiers::              Symbolic Operand Modifiers
* M68HC11-Directives::             Assembler Directives
* M68HC11-Float::                  Floating Point
* M68HC11-opcodes::                Opcodes


File: as.info,  Node: M68HC11-Opts,  Next: M68HC11-Syntax,  Up: M68HC11-Dependent

M68HC11 and M68HC12 Options
---------------------------

   The Motorola 68HC11 and 68HC12 version of `as' have a few machine
dependent options.

`-m68hc11'
     This option switches the assembler in the M68HC11 mode. In this
     mode, the assembler only accepts 68HC11 operands and mnemonics. It
     produces code for the 68HC11.

`-m68hc12'
     This option switches the assembler in the M68HC12 mode. In this
     mode, the assembler also accepts 68HC12 operands and mnemonics. It
     produces code for the 68HC12. A few 68HC11 instructions are
     replaced by some 68HC12 instructions as recommended by Motorola
     specifications.

`-m68hcs12'
     This option switches the assembler in the M68HCS12 mode.  This
     mode is similar to `-m68hc12' but specifies to assemble for the
     68HCS12 series.  The only difference is on the assembling of the
     `movb' and `movw' instruction when a PC-relative operand is used.

`-mshort'
     This option controls the ABI and indicates to use a 16-bit integer
     ABI.  It has no effect on the assembled instructions.  This is the
     default.

`-mlong'
     This option controls the ABI and indicates to use a 32-bit integer
     ABI.

`-mshort-double'
     This option controls the ABI and indicates to use a 32-bit float
     ABI.  This is the default.

`-mlong-double'
     This option controls the ABI and indicates to use a 64-bit float
     ABI.

`--strict-direct-mode'
     You can use the `--strict-direct-mode' option to disable the
     automatic translation of direct page mode addressing into extended
     mode when the instruction does not support direct mode.  For
     example, the `clr' instruction does not support direct page mode
     addressing. When it is used with the direct page mode, `as' will
     ignore it and generate an absolute addressing.  This option
     prevents `as' from doing this, and the wrong usage of the direct
     page mode will raise an error.

`--short-branchs'
     The `--short-branchs' option turns off the translation of relative
     branches into absolute branches when the branch offset is out of
     range. By default `as' transforms the relative branch (`bsr',
     `bgt', `bge', `beq', `bne', `ble', `blt', `bhi', `bcc', `bls',
     `bcs', `bmi', `bvs', `bvs', `bra') into an absolute branch when
     the offset is out of the -128 .. 127 range.  In that case, the
     `bsr' instruction is translated into a `jsr', the `bra'
     instruction is translated into a `jmp' and the conditional branchs
     instructions are inverted and followed by a `jmp'. This option
     disables these translations and `as' will generate an error if a
     relative branch is out of range. This option does not affect the
     optimization associated to the `jbra', `jbsr' and `jbXX' pseudo
     opcodes.

`--force-long-branchs'
     The `--force-long-branchs' option forces the translation of
     relative branches into absolute branches. This option does not
     affect the optimization associated to the `jbra', `jbsr' and
     `jbXX' pseudo opcodes.

`--print-insn-syntax'
     You can use the `--print-insn-syntax' option to obtain the syntax
     description of the instruction when an error is detected.

`--print-opcodes'
     The `--print-opcodes' option prints the list of all the
     instructions with their syntax. The first item of each line
     represents the instruction name and the rest of the line indicates
     the possible operands for that instruction. The list is printed in
     alphabetical order. Once the list is printed `as' exits.

`--generate-example'
     The `--generate-example' option is similar to `--print-opcodes'
     but it generates an example for each instruction instead.


File: as.info,  Node: M68HC11-Syntax,  Next: M68HC11-Modifiers,  Prev: M68HC11-Opts,  Up: M68HC11-Dependent

Syntax
------

   In the M68HC11 syntax, the instruction name comes first and it may
be followed by one or several operands (up to three). Operands are
separated by comma (`,'). In the normal mode, `as' will complain if too
many operands are specified for a given instruction. In the MRI mode
(turned on with `-M' option), it will treat them as comments. Example:

     inx
     lda  #23
     bset 2,x #4
     brclr *bot #8 foo

   The following addressing modes are understood for 68HC11 and 68HC12:
"Immediate"
     `#NUMBER'

"Address Register"
     `NUMBER,X', `NUMBER,Y'

     The NUMBER may be omitted in which case 0 is assumed.

"Direct Addressing mode"
     `*SYMBOL', or `*DIGITS'

"Absolute"
     `SYMBOL', or `DIGITS'

   The M68HC12 has other more complex addressing modes. All of them are
supported and they are represented below:

"Constant Offset Indexed Addressing Mode"
     `NUMBER,REG'

     The NUMBER may be omitted in which case 0 is assumed.  The
     register can be either `X', `Y', `SP' or `PC'.  The assembler will
     use the smaller post-byte definition according to the constant
     value (5-bit constant offset, 9-bit constant offset or 16-bit
     constant offset).  If the constant is not known by the assembler
     it will use the 16-bit constant offset post-byte and the value
     will be resolved at link time.

"Offset Indexed Indirect"
     `[NUMBER,REG]'

     The register can be either `X', `Y', `SP' or `PC'.

"Auto Pre-Increment/Pre-Decrement/Post-Increment/Post-Decrement"
     `NUMBER,-REG' `NUMBER,+REG' `NUMBER,REG-' `NUMBER,REG+'

     The number must be in the range `-8'..`+8' and must not be 0.  The
     register can be either `X', `Y', `SP' or `PC'.

"Accumulator Offset"
     `ACC,REG'

     The accumulator register can be either `A', `B' or `D'.  The
     register can be either `X', `Y', `SP' or `PC'.

"Accumulator D offset indexed-indirect"
     `[D,REG]'

     The register can be either `X', `Y', `SP' or `PC'.

   For example:

     ldab 1024,sp
     ldd [10,x]
     orab 3,+x
     stab -2,y-
     ldx a,pc
     sty [d,sp]


File: as.info,  Node: M68HC11-Modifiers,  Next: M68HC11-Directives,  Prev: M68HC11-Syntax,  Up: M68HC11-Dependent

Symbolic Operand Modifiers
--------------------------

   The assembler supports several modifiers when using symbol addresses
in 68HC11 and 68HC12 instruction operands.  The general syntax is the
following:

     %modifier(symbol)

`%addr'
     This modifier indicates to the assembler and linker to use the
     16-bit physical address corresponding to the symbol.  This is
     intended to be used on memory window systems to map a symbol in
     the memory bank window.  If the symbol is in a memory expansion
     part, the physical address corresponds to the symbol address
     within the memory bank window.  If the symbol is not in a memory
     expansion part, this is the symbol address (using or not using the
     %addr modifier has no effect in that case).

`%page'
     This modifier indicates to use the memory page number corresponding
     to the symbol.  If the symbol is in a memory expansion part, its
     page number is computed by the linker as a number used to map the
     page containing the symbol in the memory bank window.  If the
     symbol is not in a memory expansion part, the page number is 0.

`%hi'
     This modifier indicates to use the 8-bit high part of the physical
     address of the symbol.

`%lo'
     This modifier indicates to use the 8-bit low part of the physical
     address of the symbol.

   For example a 68HC12 call to a function `foo_example' stored in
memory expansion part could be written as follows:

     call %addr(foo_example),%page(foo_example)

   and this is equivalent to

     call foo_example

   And for 68HC11 it could be written as follows:

     ldab #%page(foo_example)
     stab _page_switch
     jsr  %addr(foo_example)


File: as.info,  Node: M68HC11-Directives,  Next: M68HC11-Float,  Prev: M68HC11-Modifiers,  Up: M68HC11-Dependent

Assembler Directives
--------------------

   The 68HC11 and 68HC12 version of `as' have the following specific
assembler directives:

`.relax'
     The relax directive is used by the `GNU Compiler' to emit a
     specific relocation to mark a group of instructions for linker
     relaxation.  The sequence of instructions within the group must be
     known to the linker so that relaxation can be performed.

`.mode [mshort|mlong|mshort-double|mlong-double]'
     This directive specifies the ABI.  It overrides the `-mshort',
     `-mlong', `-mshort-double' and `-mlong-double' options.

`.far SYMBOL'
     This directive marks the symbol as a `far' symbol meaning that it
     uses a `call/rtc' calling convention as opposed to `jsr/rts'.
     During a final link, the linker will identify references to the
     `far' symbol and will verify the proper calling convention.

`.interrupt SYMBOL'
     This directive marks the symbol as an interrupt entry point.  This
     information is then used by the debugger to correctly unwind the
     frame across interrupts.

`.xrefb SYMBOL'
     This directive is defined for compatibility with the
     `Specification for Motorola 8 and 16-Bit Assembly Language Input
     Standard' and is ignored.


File: as.info,  Node: M68HC11-Float,  Next: M68HC11-opcodes,  Prev: M68HC11-Directives,  Up: M68HC11-Dependent

Floating Point
--------------

   Packed decimal (P) format floating literals are not supported.  Feel
free to add the code!

   The floating point formats generated by directives are these.

`.float'
     `Single' precision floating point constants.

`.double'
     `Double' precision floating point constants.

`.extend'
`.ldouble'
     `Extended' precision (`long double') floating point constants.


File: as.info,  Node: M68HC11-opcodes,  Prev: M68HC11-Float,  Up: M68HC11-Dependent

Opcodes
-------

* Menu:

* M68HC11-Branch::                 Branch Improvement


File: as.info,  Node: M68HC11-Branch,  Up: M68HC11-opcodes

Branch Improvement
..................

   Certain pseudo opcodes are permitted for branch instructions.  They
expand to the shortest branch instruction that reach the target.
Generally these mnemonics are made by prepending `j' to the start of
Motorola mnemonic. These pseudo opcodes are not affected by the
`--short-branchs' or `--force-long-branchs' options.

   The following table summarizes the pseudo-operations.

                             Displacement Width
          +-------------------------------------------------------------+
          |                     Options                                 |
          |    --short-branchs            --force-long-branchs          |
          +--------------------------+----------------------------------+
       Op |BYTE             WORD     | BYTE          WORD               |
          +--------------------------+----------------------------------+
      bsr | bsr <pc-rel>    <error>  |               jsr <abs>          |
      bra | bra <pc-rel>    <error>  |               jmp <abs>          |
     jbsr | bsr <pc-rel>   jsr <abs> | bsr <pc-rel>  jsr <abs>          |
     jbra | bra <pc-rel>   jmp <abs> | bra <pc-rel>  jmp <abs>          |
      bXX | bXX <pc-rel>    <error>  |               bNX +3; jmp <abs>  |
     jbXX | bXX <pc-rel>   bNX +3;   | bXX <pc-rel>  bNX +3; jmp <abs>  |
          |                jmp <abs> |                                  |
          +--------------------------+----------------------------------+
     XX: condition
     NX: negative of condition XX

`jbsr'
`jbra'
     These are the simplest jump pseudo-operations; they always map to
     one particular machine instruction, depending on the displacement
     to the branch target.

`jbXX'
     Here, `jbXX' stands for an entire family of pseudo-operations,
     where XX is a conditional branch or condition-code test.  The full
     list of pseudo-ops in this family is:
           jbcc   jbeq   jbge   jbgt   jbhi   jbvs   jbpl  jblo
           jbcs   jbne   jblt   jble   jbls   jbvc   jbmi

     For the cases of non-PC relative displacements and long
     displacements, `as' issues a longer code fragment in terms of NX,
     the opposite condition to XX.  For example, for the non-PC
     relative case:
              jbXX foo
     gives
               bNXs oof
               jmp foo
           oof:


File: as.info,  Node: M88K-Dependent,  Next: MIPS-Dependent,  Prev: M68HC11-Dependent,  Up: Machine Dependencies

Motorola M88K Dependent Features
================================

* Menu:

* M88K Directives::     M88K Machine Directives


File: as.info,  Node: M88K Directives,  Up: M88K-Dependent

M88K Machine Directives
-----------------------

   The M88K version of the assembler supports the following machine
directives:

`.align'
     This directive aligns the section program counter on the next
     4-byte boundary.

`.dfloat EXPR'
     This assembles a double precision (64-bit) floating point constant.

`.ffloat EXPR'
     This assembles a single precision (32-bit) floating point constant.

`.half EXPR'
     This directive assembles a half-word (16-bit) constant.

`.word EXPR'
     This assembles a word (32-bit) constant.

`.string "STR"'
     This directive behaves like the standard `.ascii' directive for
     copying STR into the object file.  The string is not terminated
     with a null byte.

`.set SYMBOL, VALUE'
     This directive creates a symbol named SYMBOL which is an alias for
     another symbol (possibly not yet defined).  This should not be
     confused with the mnemonic `set', which is a legitimate M88K
     instruction.

`.def SYMBOL, VALUE'
     This directive is synonymous with `.set' and is presumably provided
     for compatibility with other M88K assemblers.

`.bss SYMBOL, LENGTH, ALIGN'
     Reserve LENGTH bytes in the bss section for a local SYMBOL,
     aligned to the power of two specified by ALIGN.  LENGTH and ALIGN
     must be positive absolute expressions.  This directive differs
     from `.lcomm' only in that it permits you to specify an alignment.
     *Note `.lcomm': Lcomm.


File: as.info,  Node: MIPS-Dependent,  Next: MMIX-Dependent,  Prev: M88K-Dependent,  Up: Machine Dependencies

MIPS Dependent Features
=======================

   GNU `as' for MIPS architectures supports several different MIPS
processors, and MIPS ISA levels I through V, MIPS32, and MIPS64.  For
information about the MIPS instruction set, see `MIPS RISC
Architecture', by Kane and Heindrich (Prentice-Hall).  For an overview
of MIPS assembly conventions, see "Appendix D: Assembly Language
Programming" in the same work.

* Menu:

* MIPS Opts::           Assembler options
* MIPS Object::         ECOFF object code
* MIPS Stabs::          Directives for debugging information
* MIPS ISA::            Directives to override the ISA level
* MIPS autoextend::     Directives for extending MIPS 16 bit instructions
* MIPS insn::           Directive to mark data as an instruction
* MIPS option stack::   Directives to save and restore options
* MIPS ASE instruction generation overrides:: Directives to control
                        generation of MIPS ASE instructions


File: as.info,  Node: MIPS Opts,  Next: MIPS Object,  Up: MIPS-Dependent

Assembler options
-----------------

   The MIPS configurations of GNU `as' support these special options:

`-G NUM'
     This option sets the largest size of an object that can be
     referenced implicitly with the `gp' register.  It is only accepted
     for targets that use ECOFF format.  The default value is 8.

`-EB'
`-EL'
     Any MIPS configuration of `as' can select big-endian or
     little-endian output at run time (unlike the other GNU development
     tools, which must be configured for one or the other).  Use `-EB'
     to select big-endian output, and `-EL' for little-endian.

`-mips1'
`-mips2'
`-mips3'
`-mips4'
`-mips5'
`-mips32'
`-mips32r2'
`-mips64'
     Generate code for a particular MIPS Instruction Set Architecture
     level.  `-mips1' corresponds to the R2000 and R3000 processors,
     `-mips2' to the R6000 processor, `-mips3' to the R4000 processor,
     and `-mips4' to the R8000 and R10000 processors.  `-mips5',
     `-mips32', `-mips32r2', and `-mips64' correspond to generic MIPS
     V, MIPS32, MIPS32 RELEASE 2, and MIPS64 ISA processors,
     respectively.  You can also switch instruction sets during the
     assembly; see *Note Directives to override the ISA level: MIPS ISA.

`-mgp32'
`-mfp32'
     Some macros have different expansions for 32-bit and 64-bit
     registers.  The register sizes are normally inferred from the ISA
     and ABI, but these flags force a certain group of registers to be
     treated as 32 bits wide at all times.  `-mgp32' controls the size
     of general-purpose registers and `-mfp32' controls the size of
     floating-point registers.

     On some MIPS variants there is a 32-bit mode flag; when this flag
     is set, 64-bit instructions generate a trap.  Also, some 32-bit
     OSes only save the 32-bit registers on a context switch, so it is
     essential never to use the 64-bit registers.

`-mgp64'
     Assume that 64-bit general purpose registers are available.  This
     is provided in the interests of symmetry with -gp32.

`-mips16'
`-no-mips16'
     Generate code for the MIPS 16 processor.  This is equivalent to
     putting `.set mips16' at the start of the assembly file.
     `-no-mips16' turns off this option.

`-mips3d'
`-no-mips3d'
     Generate code for the MIPS-3D Application Specific Extension.
     This tells the assembler to accept MIPS-3D instructions.
     `-no-mips3d' turns off this option.

`-mdmx'
`-no-mdmx'
     Generate code for the MDMX Application Specific Extension.  This
     tells the assembler to accept MDMX instructions.  `-no-mdmx' turns
     off this option.

`-mfix7000'
`-mno-fix7000'
     Cause nops to be inserted if the read of the destination register
     of an mfhi or mflo instruction occurs in the following two
     instructions.

`-mfix-vr4122-bugs'
`-no-mfix-vr4122-bugs'
     Insert `nop' instructions to avoid errors in certain versions of
     the vr4122 core.  This option is intended to be used on
     GCC-generated code: it is not designed to catch errors in
     hand-written assembler code.

`-m4010'
`-no-m4010'
     Generate code for the LSI R4010 chip.  This tells the assembler to
     accept the R4010 specific instructions (`addciu', `ffc', etc.),
     and to not schedule `nop' instructions around accesses to the `HI'
     and `LO' registers.  `-no-m4010' turns off this option.

`-m4650'
`-no-m4650'
     Generate code for the MIPS R4650 chip.  This tells the assembler
     to accept the `mad' and `madu' instruction, and to not schedule
     `nop' instructions around accesses to the `HI' and `LO' registers.
     `-no-m4650' turns off this option.

`-m3900'
`-no-m3900'
`-m4100'
`-no-m4100'
     For each option `-mNNNN', generate code for the MIPS RNNNN chip.
     This tells the assembler to accept instructions specific to that
     chip, and to schedule for that chip's hazards.

`-march=CPU'
     Generate code for a particular MIPS cpu.  It is exactly equivalent
     to `-mCPU', except that there are more value of CPU understood.
     Valid CPU value are:

          2000, 3000, 3900, 4000, 4010, 4100, 4111, vr4120, vr4130,
          vr4181, 4300, 4400, 4600, 4650, 5000, rm5200, rm5230, rm5231,
          rm5261, rm5721, vr5400, vr5500, 6000, rm7000, 8000, 10000,
          12000, mips32-4k, sb1

`-mtune=CPU'
     Schedule and tune for a particular MIPS cpu.  Valid CPU values are
     identical to `-march=CPU'.

`-mabi=ABI'
     Record which ABI the source code uses.  The recognized arguments
     are: `32', `n32', `o64', `64' and `eabi'.

`-nocpp'
     This option is ignored.  It is accepted for command-line
     compatibility with other assemblers, which use it to turn off C
     style preprocessing.  With GNU `as', there is no need for
     `-nocpp', because the GNU assembler itself never runs the C
     preprocessor.

`--construct-floats'
`--no-construct-floats'
     The `--no-construct-floats' option disables the construction of
     double width floating point constants by loading the two halves of
     the value into the two single width floating point registers that
     make up the double width register.  This feature is useful if the
     processor support the FR bit in its status  register, and this bit
     is known (by the programmer) to be set.  This bit prevents the
     aliasing of the double width register by the single width
     registers.

     By default `--construct-floats' is selected, allowing construction
     of these floating point constants.

`--trap'
`--no-break'
     `as' automatically macro expands certain division and
     multiplication instructions to check for overflow and division by
     zero.  This option causes `as' to generate code to take a trap
     exception rather than a break exception when an error is detected.
     The trap instructions are only supported at Instruction Set
     Architecture level 2 and higher.

`--break'
`--no-trap'
     Generate code to take a break exception rather than a trap
     exception when an error is detected.  This is the default.

`-n'
     When this option is used, `as' will issue a warning every time it
     generates a nop instruction from a macro.


File: as.info,  Node: MIPS Object,  Next: MIPS Stabs,  Prev: MIPS Opts,  Up: MIPS-Dependent

MIPS ECOFF object code
----------------------

   Assembling for a MIPS ECOFF target supports some additional sections
besides the usual `.text', `.data' and `.bss'.  The additional sections
are `.rdata', used for read-only data, `.sdata', used for small data,
and `.sbss', used for small common objects.

   When assembling for ECOFF, the assembler uses the `$gp' (`$28')
register to form the address of a "small object".  Any object in the
`.sdata' or `.sbss' sections is considered "small" in this sense.  For
external objects, or for objects in the `.bss' section, you can use the
`gcc' `-G' option to control the size of objects addressed via `$gp';
the default value is 8, meaning that a reference to any object eight
bytes or smaller uses `$gp'.  Passing `-G 0' to `as' prevents it from
using the `$gp' register on the basis of object size (but the assembler
uses `$gp' for objects in `.sdata' or `sbss' in any case).  The size of
an object in the `.bss' section is set by the `.comm' or `.lcomm'
directive that defines it.  The size of an external object may be set
with the `.extern' directive.  For example, `.extern sym,4' declares
that the object at `sym' is 4 bytes in length, whie leaving `sym'
otherwise undefined.

   Using small ECOFF objects requires linker support, and assumes that
the `$gp' register is correctly initialized (normally done
automatically by the startup code).  MIPS ECOFF assembly code must not
modify the `$gp' register.


File: as.info,  Node: MIPS Stabs,  Next: MIPS ISA,  Prev: MIPS Object,  Up: MIPS-Dependent

Directives for debugging information
------------------------------------

   MIPS ECOFF `as' supports several directives used for generating
debugging information which are not support by traditional MIPS
assemblers.  These are `.def', `.endef', `.dim', `.file', `.scl',
`.size', `.tag', `.type', `.val', `.stabd', `.stabn', and `.stabs'.
The debugging information generated by the three `.stab' directives can
only be read by GDB, not by traditional MIPS debuggers (this
enhancement is required to fully support C++ debugging).  These
directives are primarily used by compilers, not assembly language
programmers!