[clang] [flang] [llvm] [openmp] [OpenMP][Offload] Add offload runtime support for dyn_groupprivate clause (PR #152831)

[Kevin Sala Penades via llvm-commits]

kevinsala wrote:

PR updated to follow the latest version accepted by the OpenMP committee. It also adds a performance fix when returning the pointer in `omp_get_dyn_gprivate_nofb_ptr`.

New reviews are appreciated! @adurang @mjklemm @arsenm

https://github.com/llvm/llvm-project/pull/152831