[PATCH] D139275: [SimplifyCFG] `FoldBranchToCommonDest()`: deal with mismatched IV's in PHI's in common successor block

[Sam Tebbs via Phabricator via llvm-commits]

samtebbs added a comment.

Hi @lebedev.ri , after some more investigation it looks like the regressions are due to this patch breaking canonical loop form and therefore preventing optimisations later on in the pipeline. I don't think that the additional comparisons and selects that come from this transformation are ideal in all cases, either. I've attached a reproducer.F26309038: reprod.ll <https://reviews.llvm.org/F26309038>


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D139275/new/

https://reviews.llvm.org/D139275