[llvm] [LoopBoundSplit] Fix edge connections during transformation (PR #192106)

[Congzhe Cao via llvm-commits]

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CongzheUalberta wrote:

Thanks. Actually I moved one of the original `DT.changeImmediateDominator()` to right here because I think it makes sense to do the DT update right after the IR control flow change. Also added `DT.verify()` here to make the pass more robust. 

https://github.com/llvm/llvm-project/pull/192106