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 or the
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 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.
ENDpseudo-op specifying start address
ENDpseudo-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.
NAMEpseudo-ops assign a module name to the output file. This is not supported by other object file formats.
The m68k MRI
ORGpseudo-op begins an absolute section at a given address. This differs from the usual as
.orgpseudo-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
DCB.Ppseudo-ops are not supported.
FEQUpseudo-op is not supported.
NOOBJpseudo-op is not supported.
OPTbranch control options
OPTbranch control options—
BRW—are ignored. as automatically relaxes all branches, whether forward or backward, to an appropriate size, so these options serve no purpose.
OPTlist control options
The following m68k
OPTlist control options are ignored:
The following m68k
OPToptions are ignored:
Doption is default
Doption is the default, unlike the MRI assembler.
OPT NODmay be used to turn it off.
XREFpseudo-op is ignored.
.debugpseudo-op is not supported.
.extendedpseudo-op is not supported.
The various options of the i960
.listpseudo-op are not supported.
.optimizepseudo-op is not supported.
.outputpseudo-op is not supported.
.setrealpseudo-op is not supported.