[llvm] [DSE] Remove MemoryPhis left trivial by deleted stores (PR #222867)

[Nikita Popov via llvm-commits]

nikic wrote:

It looks like this doesn't have any effect in practice: https://github.com/dtcxzyw/llvm-opt-benchmark-nightly/pull/1267

https://github.com/llvm/llvm-project/pull/222867