[all-commits] [llvm/llvm-project] 27b651: [InstCombine] cttz(zext(x)) -> zext(cttz(x)) if th...

[Dávid Bolvanský via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 27b651ca473ba33999888cc302efb5f856ec7cea
      https://github.com/llvm/llvm-project/commit/27b651ca473ba33999888cc302efb5f856ec7cea
  Author: Dávid Bolvanský <david.bolvansky at gmail.com>
  Date:   2021-05-03 (Mon, 03 May 2021)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
    M llvm/test/Transforms/InstCombine/cttz.ll

  Log Message:
  -----------
  [InstCombine] cttz(zext(x)) -> zext(cttz(x)) if the 'ZeroIsUndef' parameter is 'true' (PR50172)

Zext doesn't change the number of trailing zeros, so narrow cttz(zext(x)) -> zext(cttz(x)) if the 'ZeroIsUndef' parameter is 'true'.

Proofs:
https://alive2.llvm.org/ce/z/o2dnjY

Solves https://bugs.llvm.org/show_bug.cgi?id=50172

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D101582