On Mon, Dec 08, 2014 at 09:44:44AM -0500, David Edelsohn wrote: > > -;; Discourage ai/addic because of carry but provide it in an alternative > > -;; allowing register zero as source. > > (define_insn "*add<mode>3_internal1" > > - [(set (match_operand:GPR 0 "gpc_reg_operand" "=r,r,?r,r") > > - (plus:GPR (match_operand:GPR 1 "gpc_reg_operand" "%r,b,r,b") > > - (match_operand:GPR 2 "add_operand" "r,I,I,L")))] > > + [(set (match_operand:GPR 0 "gpc_reg_operand" "=r,r,r") > > + (plus:GPR (match_operand:GPR 1 "gpc_reg_operand" "%r,b,b") > > + (match_operand:GPR 2 "add_operand" "r,I,L")))] > > "!DECIMAL_FLOAT_MODE_P (GET_MODE (operands[0])) && !DECIMAL_FLOAT_MODE_P > > (GET_MODE (operands[1]))" > > "@ > > add %0,%1,%2 > > addi %0,%1,%2 > > - addic %0,%1,%2 > > addis %0,%1,%v2" > > [(set_attr "type" "add")]) > > Why are you removing the alternative instead of clobbering XER[CA]?
I should have mentioned, sorry. We don't want to clobber CA on *every* add, and reload can generate more adds out of thin air. And CA is a fixed register. There may be a better way to do this, but I don't know it. Segher
