[llvm] [LICM] Use DomTreeUpdater version of SplitBlockPredecessors, nfc (PR #107190)

[Nikita Popov via llvm-commits]

nikic wrote:

I can't say I'm particularly surprised. Manual DT updates are going to be faster than generic DTU updates, especially in pathological cases. We've observed similar things e.g. with DT updates during unrolling, and ended up replacing DTU with manual updates to address it.

TBH this makes me think that replacing existing uses of SplitBlockPredecessors directly updating DT with DTU is not something we should pursue.

https://github.com/llvm/llvm-project/pull/107190