Info: (as) MMIX-Expand

Info Catalog

as: MMIX-Opts

as: MMIX-Dependent

as: MMIX-Syntax

as: MMIX-Expand

 
 9.27.2 Instruction expansion
 ----------------------------
 
 When 'as' encounters an instruction with an operand that is either not
 known or does not fit the operand size of the instruction, 'as' (and
 'ld') will expand the instruction into a sequence of instructions
 semantically equivalent to the operand fitting the instruction.
 Expansion will take place for the following instructions:
 
 'GETA'
      Expands to a sequence of four instructions: 'SETL', 'INCML',
      'INCMH' and 'INCH'.  The operand must be a multiple of four.
 Conditional branches
      A branch instruction is turned into a branch with the complemented
      condition and prediction bit over five instructions; four
      instructions setting '$255' to the operand value, which like with
      'GETA' must be a multiple of four, and a final 'GO $255,$255,0'.
 'PUSHJ'
      Similar to expansion for conditional branches; four instructions
      set '$255' to the operand value, followed by a 'PUSHGO
      $255,$255,0'.
 'JMP'
      Similar to conditional branches and 'PUSHJ'.  The final instruction
      is 'GO $255,$255,0'.
 
    The linker 'ld' is expected to shrink these expansions for code
 assembled with '--relax' (though not currently implemented).