[PATCH] D107572: [DAG] DAGCombiner::visitVECTOR_SHUFFLE - recognise chain of INSERT_SUBVECTOR patterns

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: RKSimon, craig.topper, spatel, efriedma, dmgreen, t.p.northover.
lebedev.ri added a project: LLVM.
Herald added subscribers: ecnelises, pengfei, hiraditya.
lebedev.ri requested review of this revision.

A logical extension to D107068 <https://reviews.llvm.org/D107068> - we don't strictly need to have
a single insertion into an otherwise-identity LHS.

While the general case of iteratively chopping off bits of a mask,
but keeping the shuffle result in obviously-bad codegen regressions,
the case where we reduce the entire shuffle into a seqnence of
subvector insertions, and drop said shuffle, seems promising.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107572

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/AArch64/arm64-neon-copy.ll
  llvm/test/CodeGen/X86/2012-04-26-sdglue.ll
  llvm/test/CodeGen/X86/avx-intrinsics-x86-upgrade.ll
  llvm/test/CodeGen/X86/avx-vperm2x128.ll
  llvm/test/CodeGen/X86/pr34592.ll
  llvm/test/CodeGen/X86/vector-shuffle-512-v16.ll

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