[llvm] [PromoteMemToReg] Hoist removeIntrinsicUsers into a pre-pass before promotion (PR #224617)

[Marcin Radomski via llvm-commits]

dextero wrote:

Thanks for taking a look!

Code formatter check doesn't like new uses of deprecated `undef` in the tests, but I don't have a good idea on how to get rid of them - the code it's testing inserts `undef` stores after all. Removing the new tests would work I guess but is likely not the best idea :sweat_smile: I'd be grateful for any suggestions.

https://github.com/llvm/llvm-project/pull/224617