[all-commits] [llvm/llvm-project] 5a4c3f: [GlobalISel] Look through extends etc in CombinerH...

[Jessica Paquette via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 5a4c3f6b06f6f4045a4c18f41082561ddebc6775
      https://github.com/llvm/llvm-project/commit/5a4c3f6b06f6f4045a4c18f41082561ddebc6775
  Author: Jessica Paquette <jpaquette at apple.com>
  Date:   2020-06-15 (Mon, 15 Jun 2020)

  Changed paths:
    M llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
    M llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-trivial-arith.mir

  Log Message:
  -----------
  [GlobalISel] Look through extends etc in CombinerHelper::matchConstantOp

It's possible to end up with a zext or something in the way of a G_CONSTANT,
even pre-legalization. This can happen with memsets.

e.g.

https://godbolt.org/z/Bjc8cw

To make sure we can catch these cases, use `getConstantVRegValWithLookThrough`
instead of `mi_match`.

Differential Revision: https://reviews.llvm.org/D81875