[llvm] [WIP] AMDGPU: VGPR bank conflict avoidance hints (PR #192140)

[Joe Nash via llvm-commits]

Sisyph wrote:

This is an interesting idea. With this kind of hint, I think static analysis and runtime performance data would help to determine if the hint is useful. Since I have been looking at VOPD a lot recently, I'll mention that from the perspective of forming VOPD, we would like to have different banks used for a particular operand position (ie src0, src1) in nearby instructions. I wonder if it is fair to say we would like uniform sampling from each register bank both across operands and across instructions. 

https://github.com/llvm/llvm-project/pull/192140