[PATCH] D143631: [LTO] Don't let InstCombine re-sink the vastly more expensive fdiv

Mon Feb 13 07:36:35 PST 2023

spatel added a comment.

In D143631#4119689 <https://reviews.llvm.org/D143631#4119689>, @craig.topper wrote:

> I've added another variation I encountered to D87479 <https://reviews.llvm.org/D87479>  which another run of LICM will not fix.

Would that case be fixed by disabling sinking in InstCombine? Maybe it's finally time to just drop sinking in InstCombine and deal with any fallout.

At least as a first check, compile-time sees a net improvement:
https://llvm-compile-time-tracker.com/compare.php?from=d87468e56c221555be7a1c1550036af5b7034896&to=a5691dd50d4098dec45571fcdfdc5403826a07de&stat=instructions:u

That change should also allow us to close a pile of longstanding InstCombine bugs caused by a conflict between iterative sinking and InstCombine's infinite-loop-threshold.

I get ~60 regression test failures with that patch, but regenerating the first 5 or so tests that I tried to update does not show any real regressions.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D143631/new/

https://reviews.llvm.org/D143631