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

[via llvm-commits]

vporpo wrote:

> 1. Complete the design document.
> 2. Provide more PRs (not just commits) showing how this "temporary" change will be fixed.

1. There is nothing to add to the design document, it is complete. And by the way, introducing a class for the Counter should stand by itself without the need for a design document of any kind, it's a basic change. If you want to discuss implementation options about the Score class, this can be done later once we introduce the Score class, these are not relevant to the current Counter patch set.
2. I have already showed how these changes will proceed in the next several patches and the final state, both in the document and here: https://github.com/vporpo/llvm-project/commit/4f12ae1e2c69cb59f698127417910178fcf553c4 . I don't see the need to create a long PR set for such patches. They are just introducing the Counter class, one member function at a time, and they are easy to review with no complicated dependencies of any sort that would justify the need for a PR chain.

> I am not actually convinced by the need for making this small change right now, but I am willing to move on simply because it is taking too much energy. But this intermediate fix by itself is not okay.

Given that these patches need to remain small, some intermediate state is necessary and will be cleaned up in the follow-up patches. This is not uncommon and should not be a blocker.

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