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

[Louis Dionne via cfe-commits]

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@@ -0,0 +1,220 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_PSTL_BACKENDS_OPENMP_BACKEND_OMP_OFFLOAD_H
+#define _LIBCPP___ALGORITHM_PSTL_BACKENDS_OPENMP_BACKEND_OMP_OFFLOAD_H
+
+#include <__algorithm/unwrap_iter.h>
+#include <__assert>
+#include <__config>
+#include <__functional/operations.h>
+#include <__iterator/iterator_traits.h>
+#include <__iterator/wrap_iter.h>
+#include <__memory/addressof.h>
+#include <__memory/pointer_traits.h>
+#include <__type_traits/is_pointer.h>
+#include <__type_traits/is_same.h>
+#include <__utility/empty.h>
+#include <__utility/move.h>
+#include <cstddef>
+#include <optional>
+
+// is_same
+
+// __libcpp_is_contiguous_iterator
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace __par_backend {
+inline namespace __omp_gpu_backend {
+
+//===----------------------------------------------------------------------===//
+// Functions for eaxtracting the pase pointers
+//===----------------------------------------------------------------------===//
+
+// In the general case we do not need to extract it. This is for instance the
+// case for pointers.
+template <typename _Tp>
+_LIBCPP_HIDE_FROM_ABI inline auto __omp_extract_base_ptr(_Tp p) noexcept {
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ldionne wrote:

Non-blocking, but I would consider introducing this function only in the future when it is useful for non-contiguous iterators. For now it seems to be just adding a bit of complexity.

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