[llvm] [SROA] Use SmallPtrSet for PromotableAllocas (PR #105809)

[Nikita Popov via llvm-commits]

nikic wrote:

Pretty sure this is going to cause non-determinism, e.g. because mem2reg will insert phi nodes in different order. You'd need a set container with stable order like SetVector -- though I think that one doesn't actually have efficient erase.

https://github.com/llvm/llvm-project/pull/105809