[llvm] [VPlan] Be more careful with CSE in replicate regions. (PR #162110)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon commented:

> If we perform CSE on recipes inside a replicate region, we may end up with 2 VPPredInstPHIRecipes sharing the same operand.

Hm, this reminds me of our fix to the const-folder. I guess the cse and const-folder are more similar than I thought (also because I have a proposed patch to share getOpcode).

https://github.com/llvm/llvm-project/pull/162110