as: M68K-Opts
9.21.1 M680x0 Options
---------------------
The Motorola 680x0 version of 'as' has a few machine dependent options:
'-march=ARCHITECTURE'
This option specifies a target architecture. The following
architectures are recognized: '68000', '68010', '68020', '68030',
'68040', '68060', 'cpu32', 'isaa', 'isaaplus', 'isab', 'isac' and
'cfv4e'.
'-mcpu=CPU'
This option specifies a target cpu. When used in conjunction with
the '-march' option, the cpu must be within the specified
architecture. Also, the generic features of the architecture are
used for instruction generation, rather than those of the specific
chip.
'-m[no-]68851'
'-m[no-]68881'
'-m[no-]div'
'-m[no-]usp'
'-m[no-]float'
'-m[no-]mac'
'-m[no-]emac'
Enable or disable various architecture specific features. If a
chip or architecture by default supports an option (for instance
'-march=isaaplus' includes the '-mdiv' option), explicitly
disabling the option will override the default.
'-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. 
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'
'-m5202'
'-m5204'
'-m5206'
'-m5206e'
'-m521x'
'-m5249'
'-m528x'
'-m5307'
'-m5407'
'-m547x'
'-m548x'
'-mcfv4'
'-mcfv4e'
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.
Info Catalog
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