On Thu, 17 May 2012 09:08:26 -0700, Richard Henderson wrote: > My question is, why are you generating compares in two different modes > early, before compare-elim runs? If you hadn't done that, your > redundant compare would already be eliminated. >
Good question. I tried to follow the example set by the rx port. I have two CC modes, the CCmode which says the compare clobbers all flags (cmp insn) and the NZmode which only clobbers the N and Z flags (tst insn). I select a specific mode for a compare during expand. Where can I do this otherwise? If I don't do it at expand time, it seems all the compare instructions end up being emitted as cmp's since GCC will never change the mode of compare itself and therefore the insn with a compare in CCmode will never match the test pattern which requires compare to have NZmode. -- PMatos
