[all-commits] [llvm/llvm-project] 61a2d6: [DAG] foldShuffleOfConcatUndefs - ensure shuffles ...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 61a2d6bfe48cf3da4b95d1383bf866690287f8e8
      https://github.com/llvm/llvm-project/commit/61a2d6bfe48cf3da4b95d1383bf866690287f8e8
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2021-06-08 (Tue, 08 Jun 2021)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    A llvm/test/CodeGen/X86/pr50609.ll

  Log Message:
  -----------
  [DAG] foldShuffleOfConcatUndefs - ensure shuffles of upper (undef) subvector elements is undef (PR50609)

shuffle(concat(x,undef),concat(y,undef)) -> concat(shuffle(x,y),shuffle(x,y))

If the original shuffle references any of the upper (undef) subvector elements, ensure the split shuffle masks uses undef instead of an out-of-bounds value.

Fixes PR50609