[all-commits] [llvm/llvm-project] 746084: [DAGCombiner] `combineShuffleOfSplatVal()`: don't ...

[Roman Lebedev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7460842fb2e4e9213cbd6c2ec928148bc3d2ebc5
      https://github.com/llvm/llvm-project/commit/7460842fb2e4e9213cbd6c2ec928148bc3d2ebc5
  Author: Roman Lebedev <lebedev.ri at gmail.com>
  Date:   2023-01-18 (Wed, 18 Jan 2023)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/X86/masked_store.ll

  Log Message:
  -----------
  [DAGCombiner] `combineShuffleOfSplatVal()`: don't assert that shuffle is non-undef

As per the test case from Steven Johnson in https://reviews.llvm.org/rGf8d9097168b7#1165311
we can indeed encounter such shuffles, that produce all-undef after folding,
before something else manages to optimize them away.