[llvm] [AMDGPU] RFC: Add and optionally use GCNIterativeRPTrackers (PR #88797)

[Valery Pykhtin via llvm-commits]

vpykhtin wrote:

Sorry but this is very hard to review. For example, you've moved getLiveRegMap to the new location and modified it at the same time.  Also, I start to think it wasn't a good idea to duplicate tracker's code because I cannot see the diffs. 

If I understood correctly, you can reuse gcn upward tracker in it's current state? You only need to introduce iterative downward tracker? 

https://github.com/llvm/llvm-project/pull/88797