2016-07-26 18:26 GMT+03:00 Jeff Law <l...@redhat.com>: > On 07/26/2016 03:57 AM, Ilya Enkovich wrote: >>> >>> >>> Ilya, what's the fundamental reason why we need to run >>> if-conversion again? Yes, I know you want to if-convert the >>> epilogue, but why? >>> >>> What are the consequences of not doing if-conversion on the >>> epilogue? Presumably we miss a vectorization opportunity on the >>> tail. But that may be a reasonable limitation to allow the >>> existing work to move forward while you go back and revamp things a >>> little. >> >> >> If we have some control-flow in a loop then we have to if-convert it >> for vectorizer. We need to preserve both versions: if-converted one >> for vectorizer and the original one to be used if vectorization >> fails. For epilogues we have similar situation and need two >> versions. I do it by running if-conversion on a copy of original >> loop. Note that it doesn't run full if-conversion pass. If-conversion >> is called for epilogue loop only. > > Right. So what I think Richi wants you to try is to use the if-converted > loop to construct the if-converted epilogue. It seems conceptually simple > and low cost -- the question is on the implementation side. I have no clue > how painful that would be.
Probably another part of if-conversion may be re-used to build required epilogue. I'll have a look. Thanks, Ilya > > jeff >
