[llvm] [SROA] Improve select folding around casts (PR #222466)

[Daniel Donenfeld via llvm-commits]

daniel-donenfeld wrote:

@yxsamliu I have added a check for the volatile case, though I have not been able to fully validate that it works as expected. Can you share your reproducer? When I run the InferAddressSpacesPass, it also results in multiple addrspacecasts even with my latest change

https://github.com/llvm/llvm-project/pull/222466