[llvm] [LiveDebugValues] Generalize approach to find stack units, NFC (PR #124862)

[Jeremy Morse via llvm-commits]

https://github.com/jmorse commented:

Being more general SGTM, and it's good to get isolated patches up first. I've got a couple of comments inline.

I wonder what the best way to test this is -- I suspect it can't be hit from x86 without great effort, and we have a bit of test coverage for that already. It would seem like overkill to enumerate these things in a unit test too. Thus, I think this can go in as a general performance improvement, but if there's more test coverage coming from AMDGPU in the future, that's reassuring too.

https://github.com/llvm/llvm-project/pull/124862