[llvm] [VPlan] Simplify VPPhi with all-eq incoming (PR #190059)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

There is now a crash on rebase -- I thought Florian fixed the epilogue resume values, but there's apparently still a problem with fixScalarResumeValuesFromBypass. Marking as draft.

https://github.com/llvm/llvm-project/pull/190059