[llvm] [AMDGPU] NFC: Provide RPTracker interface for external iterators (PR #93088)

[Jeffrey Byrnes via llvm-commits]

jrbyrnes wrote:

> I haven't found cases where advance or recede arecalled with ShouldTrackIt = false, and the semantics of the flag looks vague, can we avoid the flag?

Thanks for catching that, that was my mistake. We should be using the !ShouldTrackIt version during scheduling. I've corrected that in https://github.com/llvm/llvm-project/pull/93090 , and also corrected an issue with the way RP was calculated using the !ShouldTrackIt version.

I hope it is more clear why ShouldTrackIt is needed in the latest version. We cannot perform speculative RP queries (initCandidate) using the internal iterator, so we need a tracker which allows us to provide the NextMI. If we did not want to introduce a flag, we would need to implement a new tracker that doesn't use an internal iterator, as was done in https://github.com/llvm/llvm-project/pull/88797 

https://github.com/llvm/llvm-project/pull/93088