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

Fri Dec 10 08:36:28 PST 2021

spatel added reviewers: aqjune, hyeongyukim, regehr.
spatel added subscribers: hyeongyukim, aqjune, regehr.
spatel added a comment.

In D115526#3185635 <https://reviews.llvm.org/D115526#3185635>, @nikic wrote:

> It looks like the shufflevector poison change hasn't landed yet? D93818 <https://reviews.llvm.org/D93818> / D103874 <https://reviews.llvm.org/D103874>

Thanks for the reminder! ( cc @aqjune @hyeongyukim @regehr  )

I'm not sure what effect those patches would have here, so maybe we can add test examples to confirm that this doesn't break anything? 
All of the combinations of poison/undef that I tried in Alive2 with shuffles similar to the ones in the diffs here are shown as valid.

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https://reviews.llvm.org/D115526