[PATCH] D16683: [X86][SSE] Resolve target shuffle inputs to sentinels to permit more combines

[Simon Pilgrim via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: qcolombet, andreadb, spatel.
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The combineX86ShufflesRecursively only supports unary shuffles, but was missing the opportunity to combine binary shuffles with a zero / undef second input.

This patch resolves target shuffle inputs, converting the shuffle mask elements to SM_SentinelUndef/SM_SentinelZero where possible. It then resolves the updated mask to check if we have created a faux unary shuffle.

Additionally, we now attempt to recursively call combineX86ShufflesRecursively for all input operands (we used to just recurse for unary integer shuffles and unary unpacks) - it safely returns early if its not a target shuffle.

Repository:
  rL LLVM

http://reviews.llvm.org/D16683

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/pshufb-mask-comments.ll
  test/CodeGen/X86/vector-sext.ll
  test/CodeGen/X86/vector-zext.ll

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