[PATCH] D140811: [DAGCombiner][X86] `visitVECTOR_SHUFFLE()`: splats with a single non-undef element are not splats

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: RKSimon, pengfei.
lebedev.ri added a project: LLVM.
Herald added subscribers: ecnelises, hiraditya, nemanjai.
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lebedev.ri requested review of this revision.

This addresses a significant portion of regressions that would otherwise appear in D140677 <https://reviews.llvm.org/D140677>.

@RKSimon this seems obviously good in general overall,
but there are some dubious changes here, at mostly for SSE2:
we fail to simplify some and/andn masks,
and pull identical target-specific shuffles out of commutative opcodes.

Please can you indicate which of these should be dealt with?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D140811

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/AArch64/shuffles.ll
  llvm/test/CodeGen/PowerPC/v8i16_scalar_to_vector_shuffle.ll
  llvm/test/CodeGen/X86/haddsub-3.ll
  llvm/test/CodeGen/X86/haddsub-undef.ll
  llvm/test/CodeGen/X86/horizontal-sum.ll
  llvm/test/CodeGen/X86/phaddsub.ll
  llvm/test/CodeGen/X86/sse3.ll
  llvm/test/CodeGen/X86/vector-interleaved-store-i16-stride-7.ll
  llvm/test/CodeGen/X86/vector-interleaved-store-i32-stride-5.ll
  llvm/test/CodeGen/X86/vector-interleaved-store-i32-stride-7.ll
  llvm/test/CodeGen/X86/vector-interleaved-store-i64-stride-5.ll
  llvm/test/CodeGen/X86/vector-interleaved-store-i64-stride-7.ll
  llvm/test/CodeGen/X86/vector-narrow-binop.ll
  llvm/test/CodeGen/X86/vector-shuffle-128-v4.ll
  llvm/test/CodeGen/X86/vector-shuffle-combining-avx2.ll