[llvm] [DebugInfo] Handle additional types of stores in assignment tracking (PR #129070)

[Jeremy Morse via llvm-commits]

https://github.com/jmorse commented:

Do we need a test covering the poison/undef path, i.e. an untagged unknown store to something where there's not a live dbg.value?

Can we use Ìnstruction::mayWriteToMemory` as the test for whether a store is unknown, or is that signing us up to too much maintenance? It might make sense if we allow any intrinsic that writes to memory to adopt this behaviour.

https://github.com/llvm/llvm-project/pull/129070