[llvm] StructurizeCFG: Optimize phi insertion during ssa reconstruction (PR #101301)

[via llvm-commits]

ruiling wrote:

> I have not yet looked at the code. But looking at the description, is this something that can be used in `CreateControlFlowHub()` as well?

Yes, there should be a way to improve the phi insertion in `CreateControlFlowHub()` (Like let different values sharing the same phi node). That needs some further investigation and it works quite different from what we have done here.

https://github.com/llvm/llvm-project/pull/101301