as: M
2.9 Assemble in MRI Compatibility Mode: '-M'
============================================
The '-M' or '--mri' option selects MRI compatibility mode. This changes
the syntax and pseudo-op handling of 'as' to make it compatible with the
'ASM68K' 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 '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:
* 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. '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.
* 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.
* 'END' pseudo-op specifying start address
The MRI '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 '-e' option to the
linker, or in a linker script.
* 'IDNT', '.ident' and 'NAME' pseudo-ops
The MRI 'IDNT', '.ident' and 'NAME' pseudo-ops assign a module name
to the output file. This is not supported by other object file
formats.
* 'ORG' pseudo-op
The m68k MRI 'ORG' pseudo-op begins an absolute section at a given
address. This differs from the usual 'as' '.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.
There are some other features of the MRI assembler which are not
supported by 'as', typically either because they are difficult or
because they seem of little consequence. Some of these may be supported
in future releases.
* EBCDIC strings
EBCDIC strings are not supported.
* packed binary coded decimal
Packed binary coded decimal is not supported. This means that the
'DC.P' and 'DCB.P' pseudo-ops are not supported.
* 'FEQU' pseudo-op
The m68k 'FEQU' pseudo-op is not supported.
* 'NOOBJ' pseudo-op
The m68k 'NOOBJ' pseudo-op is not supported.
* 'OPT' branch control options
The m68k 'OPT' branch control options--'B', 'BRS', 'BRB', 'BRL',
and 'BRW'--are ignored. 'as' automatically relaxes all branches,
whether forward or backward, to an appropriate size, so these
options serve no purpose.
* 'OPT' list control options
The following m68k 'OPT' list control options are ignored: 'C',
'CEX', 'CL', 'CRE', 'E', 'G', 'I', 'M', 'MEX', 'MC', 'MD', 'X'.
* other 'OPT' options
The following m68k 'OPT' options are ignored: 'NEST', 'O', 'OLD',
'OP', 'P', 'PCO', 'PCR', 'PCS', 'R'.
* 'OPT' 'D' option is default
The m68k 'OPT' 'D' option is the default, unlike the MRI assembler.
'OPT NOD' may be used to turn it off.
* 'XREF' pseudo-op.
The m68k 'XREF' pseudo-op is ignored.
Info Catalog
as: listing
as: Invoking
as: MD