[llvm] [TableGen][SIInsertWaitcnts] use RegIntervals for AMDGPU (PR #174888)

[Nicolai Hähnle via llvm-commits]

https://github.com/nhaehnle commented:

Thank you! This looks like a real good step in the right direction. After this, some more of the structural changes we have downstream could already be upstreamed as well.

It is much more idiomatic in C++ to use half-open intervals, so I think we should do that here as well. Either way, consider adding a thin wrapper struct for the interval that implements `begin` and `end` so that foreach-loops can be used.

As for the TableGen change, I'd say the simple greedy approach here is fine for a first version.

https://github.com/llvm/llvm-project/pull/174888