[libcxx-commits] [libcxx] [libcxxabi] Adding Separate OpenMP Offloading Backend to `libcxx/include/__algorithm/pstl_backends` (PR #66968)

[Anton Rydahl via libcxx-commits]

AntonRydahl wrote:

I think I have addressed everything we talked about in the live code reviews, with the following exceptions:

1. There is a dependency on https://github.com/llvm/llvm-project/pull/68642 which we want to use to check whether a user-provided binary operator "desugars" to a supported reduction operator. I think that PR is ready to land, though.

2. There is a dependency on this issue: https://github.com/llvm/llvm-project/issues/70718. A workaround for now is to keep the files like any_of.h and sort.h. Ideally, we should not need those files, but there is a problem with `_LIBCPP_PSTL_CUSTOMIZATION_POINT`. On the other hand, we should implement offloading versions of `std::sort` and `std::any_of` at some point and then this bullet is less of a concern.

3. I was forced to add include and link paths to `omp.h` and `libomptarget.a` in the tests to make sure that the LLVM versions were used rather than the system ones. It would be more elegant if we could omit those. 

https://github.com/llvm/llvm-project/pull/66968