[all-commits] [llvm/llvm-project] 7a6d6f: [InstCombine] improve folds for icmp with multiply...

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  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 7a6d6f0f7046f6ebcbf06eaf8f996d991a90e440
      https://github.com/llvm/llvm-project/commit/7a6d6f0f7046f6ebcbf06eaf8f996d991a90e440
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2020-09-07 (Mon, 07 Sep 2020)

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

  Log Message:
  -----------
  [InstCombine] improve folds for icmp with multiply operands (PR47432)

Check for no overflow along with an odd constant before
we lose information by converting to bitwise logic.

https://rise4fun.com/Alive/2Xl

  Pre: C1 != 0
  %mx = mul nsw i8 %x, C1
  %my = mul nsw i8 %y, C1
  %r = icmp eq i8 %mx, %my
  =>
  %r = icmp eq i8 %x, %y

  Name: nuw ne
  Pre: C1 != 0
  %mx = mul nuw i8 %x, C1
  %my = mul nuw i8 %y, C1
  %r = icmp ne i8 %mx, %my
  =>
  %r = icmp ne i8 %x, %y

  Name: odd ne
  Pre: C1 % 2 != 0
  %mx = mul i8 %x, C1
  %my = mul i8 %y, C1
  %r = icmp ne i8 %mx, %my
  =>
  %r = icmp ne i8 %x, %y