[llvm] [SCEVExpander] Do not reuse disjoint or (PR #80281)

[Nikita Popov via llvm-commits]

nikic wrote:

> Mostly to make sure I understand this properly, an alternate fix here would be to treat the or as needing it's poison generating flags dropped, and then mutate the or to an add in the same place we're dropping metadata right?

Yes, exactly.

https://github.com/llvm/llvm-project/pull/80281