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

[Sameer Sahasrabuddhe via llvm-commits]

https://github.com/ssahasra commented:

I almost understand what is happening. Need to take a look at the tests one more time to convince myself that it actually works.

One very strong suggestion ... the "state" of this algorithm is all over the place. I think its worthwhile to consider making a single struct that contains all the information, with various methods that update its state. Kinda like a "locally designed" SSA updater. 

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