[llvm] [PredicateInfo] Reserve adjacent LN_Last defs for the same phi use (PR #164577)

[Nikita Popov via llvm-commits]

nikic wrote:

Thanks. The fix looks right to me. I'd suggest adding a test to SCCP as well, to make sure this works end-to-end.

https://github.com/llvm/llvm-project/pull/164577