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

[Tim Renouf via Phabricator via llvm-commits]

tpr updated this revision to Diff 156150.
tpr added a comment.

[RegisterCoalescer] Another fix for subrange join unreachable

Summary:
The test shows a case where a use is not in a subrange because the
subreg is undefined at the use point, but, after a coalesce, the
subrange incorrectly still does not include the use even though the
subreg is now defined at that point. The incorrect live range causes a
"subrange join unreachable" assert on a later coalesce.

This commit ensures that a subrange is extended to all uses that can be
reached from a definition.

V2: Completely different fix, instead of working round the problem in
the later coalesce that actually asserted.


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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