[PATCH] D49097: [RegisterCoalescer] Another fix for subrange join unreachable

[Tim Renouf via Phabricator via llvm-commits]

tpr created this revision.
Herald added subscribers: llvm-commits, nhaehnle, qcolombet, MatzeB.

When checking for conflicts, two subreg values can be considered equal
if they are ultimately copies of the same register but one is undefined.

This is a simplified alternative to David's https://reviews.llvm.org/D35073 now that most of the
cases fixed by that are also fixed by Krzysztof's https://reviews.llvm.org/D48102.

Change-Id: I5c8c1a229237a46ae20d0dd18ee5121bfbfc5ad8


Repository:
  rL LLVM

https://reviews.llvm.org/D49097

Files:
  lib/CodeGen/RegisterCoalescer.cpp
  test/CodeGen/AMDGPU/coalescing-another-couldnt-join-subrange.mir

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