[flang][OpenMP] Implement lastprivate with collapse (#99500)
This patch enables the lastprivate clause to be used in the presence of
the collapse clause.
Note: the way we currently implement lastprivate means that this adds a
large number of compare instructions to the end of every iteration of
the loop. This is a clearly non-optimal thing to do, but lastprivate in
general will need re-implementing to prevent this. This is planned as
part of the delayed privatization work. This current implementation is
just a stop-gap measure as generating sub-optimal but working code is
better than crashing out.
llvm-project
4b9fab59 - [flang][OpenMP] Implement lastprivate with collapse (#99500)
