[llvm] [AMDGPU][Scheduler] Support for rematerializing SGPRs and AGPRs (PR #140036)

[Lucas Ramirez via llvm-commits]

lucas-rami wrote:

This should be correct now. These RP excess calculations are a bit messy; my next PR will make things much more simple by using `GCNRegPressure` objects to track RP in regions showing excess pressure.

https://github.com/llvm/llvm-project/pull/140036