[PATCH] D83926: [ValueTracking] Let isGuaranteedNotToBeUndefOrPoison use canCreateUndefOrPoison

Sun Jul 19 11:52:42 PDT 2020

nikic added a comment.

In D83926#2161062 <https://reviews.llvm.org/D83926#2161062>, @aqjune wrote:

> Since isGuaranteedNotToBeUndefOrPoison now traverses over many ops, there is 0.3% slowdown from ReleaseLTO-O3 in average on CTMark:
>  ...
>  The solution for this doesn't seem trivial. Fixing existing undef/poison-related bugs might introduce more calls to this function, which will bring more slowdown.
>  What would be the right direction to address this issue?

I'm not seeing any measurable impact from this change in terms of instructions retired: https://llvm-compile-time-tracker.com/compare.php?from=ef66e3d086308800d7947a385c2ae09d3f55a695&to=081c25553185740fde7d93d2a32ef4e87ae480aa&stat=instructions Most likely the difference you see is within noise for wall time measurements, which tends to be high.

Maybe it will become a problem in the future if this functions sees heavier usage, but I don't think compile-time is a big concern right now.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D83926/new/

https://reviews.llvm.org/D83926