[PATCH] D107009: [WIP][X86] combineX86ShuffleChain(): canonicalize mask elts picking from splats

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added a comment.

combineX86ShuffleChain is very clear - its highest preference is: unary, then unary+permute, then binary, then binary+permute, then the various unary/unary+zero/binary variable shuffles.

These things tend to occur if some of the elements are constants/SM_SentinelUndef/SM_SentinelZero values and combineX86ShufflesRecursively gets stuck because it loses track of the sentinels at different recursion depths.

Do you have the shuffle masks that are being lowered to the blend / unpack cases?


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  https://reviews.llvm.org/D107009/new/

https://reviews.llvm.org/D107009