[llvm] [AMDGPU] Post-RA AGPR copy elimination pass (PR #153901)

[Shilei Tian via llvm-commits]

shiltian wrote:

> Should what this pass does be integrated in the AMDGPURewriteAGPRCopyMFMA pass instead of being its own thing?

IMHO it might be better.

https://github.com/llvm/llvm-project/pull/153901