[llvm] [AMDGPU] Add AGPR pressure tracking (PR #214745)

[Romanov Vlad via llvm-commits]

romanovvlad wrote:

> > > Most of the changes are mechanical. It looks fine to me, but IIRC we have the AV super RC. How do we differentiate them here?
> > 
> > 
> > AFAIK, AV regs are tracked as part of VGPR regs (https://github.com/llvm/llvm-project/pull/214745/changes#diff-0cc602cd384aebd0894c4e02f293602abf32a93d143d90269b4eb4b20cfdc8bfL492), this patch doesn't change how they are handled.
> 
> They kind of should be treated together, but also not. The allocator can inflate VGPR/AGPR to AV and copy instead of spill. Treating AGPRs independently matters more for 908.

@arsenm Could you please clarify your recommendation? Or the patch is OK?

https://github.com/llvm/llvm-project/pull/214745