Re: Seeking suggestion

[Georg-Johann Lay]

Jamie Prescott schrieb:

Is there a reason why something like this would not work?
(define_insn "addsi3_nc"
  [(set (match_operand:SI 0 "fullreg_operand" "=r")
        (plus:SI (match_operand:SI 1 "fullreg_operand" "r")
                 (match_operand:SI 2 "fullreg_or_imm_operand" "rn")))]
  ""
  "..."
)

(define_expand "addsi3"
  [(set (match_operand:SI 0 "fullreg_operand" "=r")
        (plus:SI (match_operand:SI 1 "fullreg_operand" "r")
                 (match_operand:SI 2 "fullreg_or_imm_operand" "rn")))]
  ""
  {
    if (!TARGET_XXX2)
      emit_clobber(gen_rtx_REG(CCmode, CC_REGNUM));
    emit_insn(gen_addsi3_nc(operands[0], operands[1], operands[2]));
    DONE;
  }
)

That would limit to two instructions per basic insns, instead of the current 
three.
Thanks,

- Jamie

Maybe that works. But I would not include such stuff in one of my 
machine descriptions because addsi3_nc lies: Its effect on the machine 
differ from what it states algebraically in RTL. Therefore, you may get 
trouble in corner cases or when instructions are 
reordered/scheduled/combined/...

Georg-Johann