[PATCH] D83440: [InstSimplify] Re-enable select ?, undef, X -> X transform when X is provably not poison

[Brooks Moses via Phabricator via llvm-commits]

brooksmoses added a comment.

I'd erroneously made this comment on the revision (where I think nobody will see it) rather than here, so copying it here:

A question about this: We got a couple of dozen MSAN warnings in the Google codebase from the revision that removed these -- I'm guessing that perhaps what happened was that the undef in question was a use-of-uninitialized-value, and this optimization was hiding the use so the MSAN checks didn't trigger. Is re-enabling this going to make those MSAN warnings go away again, re-hiding this undefined behavior?


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https://reviews.llvm.org/D83440