[llvm-branch-commits] [flang] [flang][OpenMP] Reject END DO on construct that crosses label-DO (PR #169714)

[Tom Eccles via llvm-branch-commits]

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

LGTM.

I found the CanonicalizeIfMatch function pretty difficult to reason about, but that wasn't added in this commit and it might just be me so it can stay how it is. From the tests included in the PR and my own manual testing I am satisfied that this does do the right thing.

https://github.com/llvm/llvm-project/pull/169714