On Wed, Nov 09, 2016 at 10:27:35PM +0100, Bernd Schmidt wrote: > On 11/09/2016 10:13 PM, Segher Boessenkool wrote: > > * simplify-rtx.c (simplify_binary_operation_1): Simplify > > (xor (and (xor A B) C) B) to (ior (and A C) (and B ~C)) and > > (xor (and (xor A B) C) B) to (ior (and A ~C) (and B C)) if C > > is a const_int. > > I think one of the xors should have A as the second operand.
The second, thanks for spotting it. > >+ /* If we have (xor (and (xor A B) C) A) with C a constant we can > >instead > >+ do (ior (and A ~C) (and B C)) which is a machine instruction on > >some > >+ machines, and also has shorter instruction path length. */ > >+ if (GET_CODE (op0) == AND > > Comments doesn't line up with the if/else on my monitor; could be email > damage but please check. I messed it up (had // comments first, whoops). > Other than that, I think it does qualify as a simplification (or at > least an improvement), so OK. Would be nice to check for it with a testcase. I'll do a PowerPC-specific testcase for all rl[wd]* next week. rl[wd]imi will show this xor-xor thing (half of all possible insns were not optimised before this patch). Is that enough? Segher
