[all-commits] [llvm/llvm-project] d2458b: [X86][SSE] combineX86ShufflesRecursively - bail if...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: d2458bcdc664a469c2198dcb65b94bcc445b1028
      https://github.com/llvm/llvm-project/commit/d2458bcdc664a469c2198dcb65b94bcc445b1028
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2021-07-16 (Fri, 16 Jul 2021)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/vector-shuffle-combining.ll

  Log Message:
  -----------
  [X86][SSE] combineX86ShufflesRecursively - bail if constant folding fails due to oneuse limits.

Fixes issue reported on D105827 where a single shuffle of a constant (with multiple uses) was caught in an infinite loop where one shuffle (UNPCKL) used an undef arg but then that got recombined to SHUFPS as the constant value had its own undef that confused matching.....