[llvm] [AMDGPU] Skip register uses in AMDGPUResourceUsageAnalysis (PR #133242)

[Diana Picus via llvm-commits]

rovka wrote:

> So you would distinguish between:
> 
> * Shader reads v0 which was initialized by hardware. This counts as "used".
> * Shader reads an undefined value from v0 which was not initialized by hardware. This does not count as "used".
> 
> I guess we can do that. It just seems like extra effort in the compiler for (I claim) no tangible benefit.

So are we good with the patch as it is now? It currently reports v0 as used if the workitem-id-x isn't explicitly disabled. 

https://github.com/llvm/llvm-project/pull/133242