[PATCH] D51574: [LiveRangeCalc] Fixed findReachingDefs bug

[Tim Renouf via Phabricator via llvm-commits]

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

findReachingDefs was incorrectly using its fast path of just blitting in
the live range extension when it did not see an undef itself but
encountered an undef live out of a predecessor block.

Now RegisterCoalescing calls extendToIndices (https://reviews.llvm.org/D49097), the bug was
causing an incorrect subrange which led to a "Couldn't join subrange!"
assert in a later coalesce.

Change-Id: I01c942b41ab5a145348289c8b221c45a2ec7200f


Repository:
  rL LLVM

https://reviews.llvm.org/D51574

Files:
  lib/CodeGen/LiveRangeCalc.cpp
  test/CodeGen/AMDGPU/regcoalescer-assert-from-incorrect-subrange-extension.mir

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