[PATCH] D127136: [RegisterCoalescer] Fix crash on early clobbered subreg operands.

[Daniil Fukalov via Phabricator via llvm-commits]

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The issue was with processing two subregs of the same reg are used in the same
instruction (e.g. inline asm): "def early-clobber" and other just "def".
Register coalescer ran in bad recursion if the early clobbered subreg is second
in the following sequence of COPYs.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D127136

Files:
  llvm/lib/CodeGen/RegisterCoalescer.cpp
  llvm/test/CodeGen/AMDGPU/coalescer-early-clobber-subreg.mir

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