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

[Mel Chen via llvm-commits]

https://github.com/Mel-Chen commented:

It looks correct to me. 
BTW, I don't have a particular preference, but I do have one question: as an optimization, should this be implemented in VPlanTransform::optimize?

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