[llvm] [NFCI][Analysis] Extract alloca slice analysis from SROA (PR #179593)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

I'm somewhat skeptical about this. I think this code is quite tightly coupled to SROA and much more sophisticated than what other code needs. The slice and partition distinction, plus concepts like splitability and split tails add a lot of complexity. SROA cares about handling things like overlapping accesses in a way other consumers mostly don't.

We have a much simpler variant of this as collectSRATypes() in GlobalOpt. I expect that is much closer to what is actually needed.

But generally, in this case I'd like to see how follow-on patches look like, to prove that this can indeed be used as intended.

https://github.com/llvm/llvm-project/pull/179593