[llvm] [AMDGPU] Add test for GCNRegPressure tracker bug (PR #73786)

[Valery Pykhtin via llvm-commits]

vpykhtin wrote:

I just realized that early-clobbers aren't processed correctly in the case when the same register used on LHS and RHS.

https://github.com/llvm/llvm-project/pull/73786