[all-commits] [llvm/llvm-project] 478b22: [CGP] despeculateCountZeros - Don't create is-zero...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 478b22d95aee2b818008a7b92b8606175767d0de
      https://github.com/llvm/llvm-project/commit/478b22d95aee2b818008a7b92b8606175767d0de
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2021-07-24 (Sat, 24 Jul 2021)

  Changed paths:
    M llvm/lib/CodeGen/CodeGenPrepare.cpp
    M llvm/test/CodeGen/X86/clz.ll

  Log Message:
  -----------
  [CGP] despeculateCountZeros - Don't create is-zero branch if cttz/ctlz source is known non-zero

If value tracking can confirm that the cttz/ctlz source is known non-zero then we don't need to create a branch (which DAG will struggle to recover from).

Differential Revision: https://reviews.llvm.org/D106685