[llvm] [SSAUpdaterBulk] Add PHI simplification pass. (PR #132004)

[Nikita Popov via llvm-commits]

nikic wrote:

> Current implementation is incorrect: I cannot move new phis to the end because they can be used by existing phis if the user added 'variable' as incoming value for an existed phi.

Maybe I'm misunderstanding what you mean here, but phi's are all evaluated at the same time, not in order. If a phi refers to another phi, it always refers to the value of the phi at a previous cycle iteration.

https://github.com/llvm/llvm-project/pull/132004