[flang] [llvm] [flang][OpenMP] Use StylizedInstance in converted clauses (PR #171907)

[Kareem Ergawy via llvm-commits]

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

LGTM! Thanks for this well-thought clean-up. Separating parser stuff from MLIR lowering makes perfect sense.

https://github.com/llvm/llvm-project/pull/171907