[llvm] [SCEV] Avoid recursion in PHI handling in more cases. (PR #215910)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

I'm not sure if the compile-time increase necessarily is an issue here, there are a few things we could do to somewhat offset the increase, e.g. https://github.com/llvm/llvm-project/pull/222915

https://github.com/llvm/llvm-project/pull/215910