[all-commits] [llvm/llvm-project] dd995a: [InstCombine] remove incorrect gep(x, undef) -> un...

[Nuno Lopes via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: dd995acedadfa27bca4e64f4cec4fa77c350adbe
      https://github.com/llvm/llvm-project/commit/dd995acedadfa27bca4e64f4cec4fa77c350adbe
  Author: Nuno Lopes <nuno.lopes at tecnico.ulisboa.pt>
  Date:   2022-01-30 (Sun, 30 Jan 2022)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
    M llvm/test/Transforms/InstCombine/vec_demanded_elts-inseltpoison.ll
    M llvm/test/Transforms/InstCombine/vec_demanded_elts.ll

  Log Message:
  -----------
  [InstCombine] remove incorrect gep(x, undef) -> undef optimization
gep(x, undef) carries the provenance of x, so we can't replace it with any
pointer like undef.
This leaves room for improvement for the poison case, but that's currently
not possible as the demanded bits API doesn't distinguish between undef &
poison bits.

Fixes #44790