[PATCH] D87405: [X86][SSE] lowerShuffleAsDecomposedShuffleBlend - support decomposed unpacks for some vXi8/vXi16 cases

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: TellowKrinkle, craig.topper, spatel.
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Follow up to D86429 <https://reviews.llvm.org/D86429> to handle the remaining regressions.

This patch generalizes lowerShuffleAsDecomposedShuffleBlend to lowerShuffleAsDecomposedShuffleMerge, and attempts to use an UNPCKL shuffle mask instead of a blend for the cases where the inputs are coming from alternating vXi8/vXi16 sources. Technically they don't have to be alternating (just as long as they can fit into a lower lane half for the unpack) but I didn't find as many general cases and it needed a lot more of the function to be altered.

For vXi32/vXi64 cases this could still be beneficial but in most cases the existing permute+blend approach was better.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D87405

Files:
  llvm/lib/Target/X86/X86ISelLowering.cpp
  llvm/test/CodeGen/X86/vector-shuffle-128-v16.ll
  llvm/test/CodeGen/X86/vector-shuffle-256-v16.ll
  llvm/test/CodeGen/X86/vector-shuffle-256-v32.ll
  llvm/test/CodeGen/X86/vector-shuffle-512-v32.ll

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