[llvm] [AMDGPU][SIInsertWaitcnts][NFC] Introduce Counter class (PR #190271)

[via llvm-commits]

vporpo wrote:

> I think we are asking is a stack of PRs, instead of some commits, nor a giant commit (we definitely don't want that). The advantage of a stack is, we can clearly see the path towards what you envision such that it is easier to see how these intermediate states play the role in the long run.

Stacked PRs can be very helpful for complicated interdependent patches. This patch series is very simple: we just introduce the Counter class one member function at a time by moving code from the pass to a member function. I have already shared the future state where the intermediate state is cleaned up, but if you still need to take a look at what each patch does, I pushed them (without squashing them this time) here: https://github.com/llvm/llvm-project/compare/main...vporpo:llvm-project:waitcnt_chain .

https://github.com/llvm/llvm-project/pull/190271