c-m68k.texi

基于4个mips核的noc设计

@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000
@c Free Software Foundation, Inc.
@c This is part of the GAS manual.
@c For copying conditions, see the file as.texinfo.
@ifset GENERIC
@page
@node M68K-Dependent
@chapter M680x0 Dependent Features
@end ifset
@ifclear GENERIC
@node Machine Dependencies
@chapter M680x0 Dependent Features
@end ifclear

@cindex M680x0 support
@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
@end menu

@node M68K-Opts
@section M680x0 Options

@cindex options, M680x0
@cindex M680x0 options
The Motorola 680x0 version of @code{@value{AS}} has a few machine
dependent options:

@table @samp

@cindex @samp{-l} option, M680x0
@item -l
You can use the @samp{-l} option to shorten the size of references to undefined
symbols.  If you do not use the @samp{-l} option, references to undefined
symbols are wide enough for a full @code{long} (32 bits).  (Since
@code{@value{AS}} cannot know where these symbols end up, @code{@value{AS}} can
only allocate space for the linker to fill in later.  Since @code{@value{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.

@cindex @samp{--register-prefix-optional} option, M680x0
@item --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 @samp{%} before any use of a register name.  This
is intended to let the assembler distinguish between C variables and
functions named @samp{a0} through @samp{a7}, and so on.  The @samp{%} is
always accepted, but is not required for certain configurations, notably
@samp{sun3}.  The @samp{--register-prefix-optional} option may be used
to permit omitting the @samp{%} 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.

@cindex @samp{--bitwise-or} option, M680x0
@item --bitwise-or
Normally the character @samp{|} is treated as a comment character, which
means that it can not be used in expressions.  The @samp{--bitwise-or}
option turns @samp{|} into a normal character.  In this mode, you must
either use C style comments, or start comments with a @samp{#} character
at the beginning of a line.

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

@cindex @samp{--disp-size-default-16}
@cindex @samp{--disp-size-default-32}
@item --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, @code{@value{AS}} will normally assume that
the value is 32 bits.  For example, if the symbol @samp{disp} has not
been defined, @code{@value{AS}} will assemble the addressing mode
@samp{%a0@@(disp,%d0)} as though @samp{disp} is a 32 bit value.  You may
use the @samp{--disp-size-default-16} option to tell @code{@value{AS}}
to instead assume that the displacement is 16 bits.  In this case,
@code{@value{AS}} will assemble @samp{%a0@@(disp,%d0)} as though
@samp{disp} is a 16 bit value.  You may use the
@samp{--disp-size-default-32} option to restore the default behaviour.

@cindex @samp{--pcrel}
@item --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 @code{@value{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.
@pxref{M68K-Branch,,Branch Improvement}.

@cindex @samp{-m68000} and related options
@cindex architecture options, M680x0
@cindex M680x0 architecture options
@item -m68000
@code{@value{AS}} can assemble code for several different members of the
Motorola 680x0 family.  The default depends upon how @code{@value{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.

@table @samp
@item -m68000
@itemx -m68ec000
@itemx -m68hc000
@itemx -m68hc001
@itemx -m68008
@itemx -m68302
@itemx -m68306
@itemx -m68307
@itemx -m68322
@itemx -m68356
Assemble for the 68000. @samp{-m68008}, @samp{-m68302}, and so on are synonyms
for @samp{-m68000}, since the chips are the same from the point of view
of the assembler.

@item -m68010
Assemble for the 68010.

@item -m68020
@itemx -m68ec020
Assemble for the 68020.  This is normally the default.

@item -m68030
@itemx -m68ec030
Assemble for the 68030.

@item -m68040
@itemx -m68ec040
Assemble for the 68040.

@item -m68060
@itemx -m68ec060
Assemble for the 68060.

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

@item -m5200
Assemble for the ColdFire family of chips.

@item -m68881
@itemx -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.

@item -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.

@item -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; @samp{-m68851} and @samp{-m68040} should not be used
together.

@item -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.
@end table
@end table

@node M68K-Syntax
@section Syntax

@cindex @sc{mit}
This syntax for the Motorola 680x0 was developed at @sc{mit}.

@cindex M680x0 syntax
@cindex syntax, M680x0
@cindex M680x0 size modifiers
@cindex size modifiers, M680x0
The 680x0 version of @code{@value{AS}} uses instructions names and
syntax compatible with the Sun assembler.  Intervening periods are
ignored; for example, @samp{movl} is equivalent to @samp{mov.l}.

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

@cindex M680x0 addressing modes
@cindex addressing modes, M680x0
The following addressing modes are understood:
@table @dfn
@item Immediate
@samp{#@var{number}}

@item Data Register
@samp{%d0} through @samp{%d7}

@item Address Register
@samp{%a0} through @samp{%a7}@*
@samp{%a7} is also known as @samp{%sp}, i.e. the Stack Pointer.  @code{%a6}
is also known as @samp{%fp}, the Frame Pointer.

@item Address Register Indirect
@samp{%a0@@} through @samp{%a7@@}

@item Address Register Postincrement
@samp{%a0@@+} through @samp{%a7@@+}

@item Address Register Predecrement
@samp{%a0@@-} through @samp{%a7@@-}

@item Indirect Plus Offset
@samp{@var{apc}@@(@var{number})}

@item Index
@samp{@var{apc}@@(@var{number},@var{register}:@var{size}:@var{scale})}

The @var{number} may be omitted.

@item Postindex
@samp{@var{apc}@@(@var{number})@@(@var{onumber},@var{register}:@var{size}:@var{scale})}

The @var{onumber} or the @var{register}, but not both, may be omitted.

@item Preindex
@samp{@var{apc}@@(@var{number},@var{register}:@var{size}:@var{scale})@@(@var{onumber})}

The @var{number} may be omitted.  Omitting the @var{register} produces
the Postindex addressing mode.

@item Absolute
@samp{@var{symbol}}, or @samp{@var{digits}}, optionally followed by
@samp{:b}, @samp{:w}, or @samp{:l}.
@end table

@node M68K-Moto-Syntax
@section Motorola Syntax

@cindex Motorola syntax for the 680x0
@cindex alternate syntax for the 680x0

The standard Motorola syntax for this chip differs from the syntax
already discussed (@pxref{M68K-Syntax,,Syntax}).  @code{@value{AS}} can