[llvm] [LoopUnroll] Remove redundant llvm.dbg instructions after blocks (PR #89069)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Thanks for the update! The change isn't really specific to LoopUnroll, but any code that uses `MergeBlockIntoPredecessor`; could you update the title and also update the PR descriptions .

Please also include `Fixes https://github.com/llvm/llvm-project/issues/89073` at the end of the PR description, so the issue gets auto-closed when the PR is merged.

Please also add a loop-unroll test based on the issue.

https://github.com/llvm/llvm-project/pull/89069