[llvm] [DebugInfo][LoopStrengthReduce] Fix missing debug location updates (PR #97519)

[Jeremy Morse via llvm-commits]

https://github.com/jmorse approved this pull request.

Patch LGTM, @OCHyams @SLTozer have reviewed more of these, are there any more concerns than out-of-place source locations and potential loss of coverage?

Instructions inheriting the adjacent source location is technically part of LLVMs design, I think the difficulty is that it works well 99.9% of the time, but occasionally you need more finesse when picking them. The current solution is just a very good approximation of ideal source location placement (as far as I'm aware).

https://github.com/llvm/llvm-project/pull/97519