------- Comment #2 from tege-gcc at swox dot com 2007-12-13 10:52 ------- It does make sense to bluff somewhat about the costs of the few 3 operand instructions that we have:
lea mul const, regx, regy Exactly what cost to assign is not obvious. I think the nominal cost - epsilon is probably better than the nominal cost - 1 + epsilon. The latter is what Honza does. But teaching synth_mult about 2.5 operandness might be the best way to make constant multiplication code come out optimal. I'm not sure how to do that, though. Peeking at the constraints flags? :-) If I understand Honza right, he's trying to please reload more than synth_mult with his tweak. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34452
