[all-commits] [llvm/llvm-project] ac8be2: [DAG] isSplatValue - don't attempt to merge any BI...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ac8be21365bc4a8897303d13161a0f5c7a511215
      https://github.com/llvm/llvm-project/commit/ac8be21365bc4a8897303d13161a0f5c7a511215
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2022-07-23 (Sat, 23 Jul 2022)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    M llvm/test/CodeGen/X86/fshl-splat-undef.ll
    M llvm/test/CodeGen/X86/vector-shuffle-combining.ll

  Log Message:
  -----------
  [DAG] isSplatValue - don't attempt to merge any BITCAST sub elements if they contain UNDEFs

We still haven't found a solution that correctly handles 'don't care' sub elements properly - given how close it is to the next release branch, I'm making this fail safe change and we can revisit this later if we can't find alternatives.

NOTE: This isn't a reversion of D128570 - it's the removal of undef handling across bitcasts entirely

Fixes #56520