[PATCH] D135625: [instcombine] (extelt (inselt Vec, Value, Index), Index) -> Value

[Paul Walker via Phabricator via llvm-commits]

paulwalker-arm added a comment.

Sorry for the post commit question but I recall similar work being blocked when we wanted to say `extractelt(splat(x), idx) -> x` but the consensus was it could be an invalid transformation because if `idx` is out of range then the result is poison.  Does this transformation fall into the same trap whereby we're incorrectly removing a source of poison?  I'm not specifically seeking a revert I just want to play by the same set of rules because for scalable vectors there are several instances where we are being hampered by such poison preservation.


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https://reviews.llvm.org/D135625