[all-commits] [llvm/llvm-project] 6f149a: [InstCombine] Look through truncate to fold icmp w...

[chenglin.bi via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 6f149a17d4b1a254dd41a3b910021481c564a691
      https://github.com/llvm/llvm-project/commit/6f149a17d4b1a254dd41a3b910021481c564a691
  Author: chenglin.bi <chenglin.bi at linaro.org>
  Date:   2023-02-10 (Fri, 10 Feb 2023)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
    M llvm/lib/Transforms/InstCombine/InstCombineInternal.h
    M llvm/test/Transforms/InstCombine/cmp-intrinsic.ll

  Log Message:
  -----------
  [InstCombine] Look through truncate to fold icmp with intrinsics

The output of intrinsic functions like ctpop, cttz, ctlz have limited range from 0 to bitwidth. So if the truncate destination type can hold the source bitwidth size, we can just ignore the truncate and use the truncate src to do combination.

Alive2 proofs:
https://alive2.llvm.org/ce/z/9D_-qP

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D143368