[PATCH] D115526: [InstCombine] don't automatically drop poison-generating flags in SimplifyVectorDemandedElts

Mon Dec 13 05:48:15 PST 2021

spatel added a comment.

In D115526#3188491 <https://reviews.llvm.org/D115526#3188491>, @nikic wrote:

> LGTM. After looking a bit closer, I do think this is safe and independent of the shufflevector patches referenced above. We already convert non-demanded elements to poison, so converting them to poison through nowrap flags should be just fine.

Thanks! That's probably better than any of my attempts to put the reasoning into words.

References to preliminary steps in the path to cleaning this up:
https://llvm.org/PR43958
D70246 <https://reviews.llvm.org/D70246>

Let's give this a try and see if the theory holds up...

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D115526/new/

https://reviews.llvm.org/D115526