[PATCH] D127119: [SLP]Fix undef handling in gather function.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added a comment.

In D127119#3564461 <https://reviews.llvm.org/D127119#3564461>, @hvdijk wrote:

> Comparing the changes to the tests in this diff to those in D127073 <https://reviews.llvm.org/D127073>, I am seeing a number of tests where we have more shufflevectors, and none where we have fewer. Are there improvements that are not as obvious to see?

Yes, there are. These extra shuffles caused by changes in performExtractsShuffleAction() and in IsIdenticalOrLessDefined lambda, these changes (they treat UndefMaskElem as possible poison) increase number of shuffles. Without them, there are less shuffles, these extra changes are required for correct handling of UndefMaskElem as posion.


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https://reviews.llvm.org/D127119