[llvm] [DebugInfo][RemoveDIs] Have LICM insert at iterator positions (PR #73671)

[Orlando Cazalet-Hyams via llvm-commits]

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

That lines up with my understanding, but not seeing it written down anywhere had my second guessing myself.

I've traversed the ilist node / iterator code to fully remind myself and am confident to LGTM this.

https://github.com/llvm/llvm-project/pull/73671