[llvm] [VPlan] Fold common edges away in convertPhisToBlends (PR #150368)

[Florian Hahn via llvm-commits]

fhahn wrote:

Hm, if we get the same benefits when doing it in simplifyBlends, that would probably be better for consistency and keeping the predication code simple.

https://github.com/llvm/llvm-project/pull/150368