[all-commits] [llvm/llvm-project] ffaaf2: [InstCombine] (rot X, ?) == 0/-1 --> X == 0/-1

[ZCBing via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ffaaf2498bda550beeedadb79060323b8d3b0188
      https://github.com/llvm/llvm-project/commit/ffaaf2498bda550beeedadb79060323b8d3b0188
  Author: Chenbing Zheng <Chenbing.Zheng at streamcomputing.com>
  Date:   2022-05-19 (Thu, 19 May 2022)

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

  Log Message:
  -----------
  [InstCombine] (rot X, ?) == 0/-1 --> X == 0/-1

In this patch we add a function foldICmpInstWithConstantAllowUndef
to fold integer comparisons with a constant operand: icmp Pred X, C
where X is some kind of instruction and C is AllowUndef.

We move this fold to the new function, so that it can solve undef elts in a vector.

Reviewed By: spatel, RKSimon

Differential Revision: https://reviews.llvm.org/D125220