[mlir] [flang] [llvm] [flang][mlir][OpenMP] Add support for COPYPRIVATE (PR #73128)

[Leandro Lupori via llvm-commits]

luporl wrote:

A few notes about this last commit:

- I have implemented COPYPRIVATE support for HLFIR only. Do we also need to support it in FIR mode?

- I have written only a basic test for now, covering simple scalars and arrays. My plan is to add more tests, but I wanted to get some feedback first, to avoid having to rewrite the tests too much.

- There is one thing that I've noticed a bit late. The `__kmpc_copyprivate` function uses 2 barriers, which may impact the performance of COPYPRIVATE with multiple variables. Combining the updates of all variables to use a single `__kmpc_copyprivate` call is not straightforward.

https://github.com/llvm/llvm-project/pull/73128