[all-commits] [llvm/llvm-project] 72fd10: [X86] getTargetConstantBitsFromNode - don't suppor...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 72fd10adcbf8194a08141e38a95e11f4f1a8d7c2
      https://github.com/llvm/llvm-project/commit/72fd10adcbf8194a08141e38a95e11f4f1a8d7c2
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2024-01-28 (Sun, 28 Jan 2024)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp

  Log Message:
  -----------
  [X86] getTargetConstantBitsFromNode - don't support partial undefs by default.

Noticed by inspection - as undef bits are seen as zero, we could be matching in places where we require a zero but end up referencing an undef that could then get changed in a later fold.

Creating a test case has proven difficult as multi-use limits usually saves us, but really we shouldn't be allowing partial undefs for anything but constant folding.