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 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.
 
    * `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.
 
    * `.debug' pseudo-op
 
      The i960 `.debug' pseudo-op is not supported.
 
    * `.extended' pseudo-op
 
      The i960 `.extended' pseudo-op is not supported.
 
    * `.list' pseudo-op.
 
      The various options of the i960 `.list' pseudo-op are not
      supported.
 
    * `.optimize' pseudo-op
 
      The i960 `.optimize' pseudo-op is not supported.
 
    * `.output' pseudo-op
 
      The i960 `.output' pseudo-op is not supported.
 
    * `.setreal' pseudo-op
 
      The i960 `.setreal' pseudo-op is not supported.
 
 

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