[llvm] [SCEV] Add PHI SCEV verification to ensure availability at loop entry (PR #127550)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Why doesn't the existing loop and block disposition verification catch this? isAvailableAtEntry is a combination of LoopInvariant and ProperlyDominatesBlock dispositions.

https://github.com/llvm/llvm-project/pull/127550