[PATCH] D100329: [SimplifyCFG] Allow hoisting terminators only with HoistCommonInsts=false.

Tue Apr 13 02:37:29 PDT 2021

fhahn added a comment.

In D100329#2683985 <https://reviews.llvm.org/D100329#2683985>, @lebedev.ri wrote:

> Hmm, this seems pretty harmless.
> I do wonder if `FoldTwoEntryPHINode()` should be generalized, but until then this seems ok.
> Thank you.

Thanks! I checked the stats for loop-rotate for -O3 -flto on ARM64, and there were no changes, so it does not seem to work against the original goal of  D84108 <https://reviews.llvm.org/D84108>. I'm not sure how much work adjusting `FoldTwoEntryPHINode` would be and what the benefits would be. One advantage of doing it `HoistThenElseCodeToIf` is that if there are no PHIs, there are no extra instructions necessary at all. But if the successors have PHIs, it might make sense to limit it to cases where the phis can be folded.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D100329/new/

https://reviews.llvm.org/D100329