1 files changed, 97 insertions, 0 deletions
diff --git a/contrib/llvm-project/libcxx/include/__pstl/internal/execution_impl.h b/contrib/llvm-project/libcxx/include/__pstl/internal/execution_impl.h
new file mode 100644
index 000000000000..c3a7405d393f
--- /dev/null
+++ b/contrib/llvm-project/libcxx/include/__pstl/internal/execution_impl.h
@@ -0,0 +1,97 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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 _PSTL_EXECUTION_IMPL_H
+#define _PSTL_EXECUTION_IMPL_H
+
+#include <__config>
+#include <__iterator/iterator_traits.h>
+#include <__type_traits/conditional.h>
+#include <__type_traits/conjunction.h>
+#include <__type_traits/decay.h>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_base_of.h>
+
+#include <__pstl/internal/execution_defs.h>
+
+#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+namespace __pstl {
+namespace __internal {
+
+template <typename _IteratorTag, typename... _IteratorTypes>
+using __are_iterators_of = std::conjunction<
+    std::is_base_of<_IteratorTag, typename std::iterator_traits<std::decay_t<_IteratorTypes>>::iterator_category>...>;
+
+template <typename... _IteratorTypes>
+using __are_random_access_iterators = __are_iterators_of<std::random_access_iterator_tag, _IteratorTypes...>;
+
+struct __serial_backend_tag {};
+struct __tbb_backend_tag {};
+struct __openmp_backend_tag {};
+
+#  if defined(_PSTL_PAR_BACKEND_TBB)
+using __par_backend_tag = __tbb_backend_tag;
+#  elif defined(_PSTL_PAR_BACKEND_OPENMP)
+using __par_backend_tag = __openmp_backend_tag;
+#  elif defined(_PSTL_PAR_BACKEND_SERIAL)
+using __par_backend_tag = __serial_backend_tag;
+#  else
+#    error "A parallel backend must be specified";
+#  endif
+
+template <class _IsVector>
+struct __serial_tag {
+  using __is_vector = _IsVector;
+};
+
+template <class _IsVector>
+struct __parallel_tag {
+  using __is_vector = _IsVector;
+  // backend tag can be change depending on
+  // TBB availability in the environment
+  using __backend_tag = __par_backend_tag;
+};
+
+template <class _IsVector, class... _IteratorTypes>
+using __tag_type =
+    typename std::conditional<__internal::__are_random_access_iterators<_IteratorTypes...>::value,
+                              __parallel_tag<_IsVector>,
+                              __serial_tag<_IsVector>>::type;
+
+template <class... _IteratorTypes>
+_LIBCPP_HIDE_FROM_ABI __serial_tag</*_IsVector = */ std::false_type>
+__select_backend(__pstl::execution::sequenced_policy, _IteratorTypes&&...) {
+  return {};
+}
+
+template <class... _IteratorTypes>
+_LIBCPP_HIDE_FROM_ABI __serial_tag<__internal::__are_random_access_iterators<_IteratorTypes...>>
+__select_backend(__pstl::execution::unsequenced_policy, _IteratorTypes&&...) {
+  return {};
+}
+
+template <class... _IteratorTypes>
+_LIBCPP_HIDE_FROM_ABI __tag_type</*_IsVector = */ std::false_type, _IteratorTypes...>
+__select_backend(__pstl::execution::parallel_policy, _IteratorTypes&&...) {
+  return {};
+}
+
+template <class... _IteratorTypes>
+_LIBCPP_HIDE_FROM_ABI __tag_type<__internal::__are_random_access_iterators<_IteratorTypes...>, _IteratorTypes...>
+__select_backend(__pstl::execution::parallel_unsequenced_policy, _IteratorTypes&&...) {
+  return {};
+}
+
+} // namespace __internal
+} // namespace __pstl
+
+#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
+
+#endif /* _PSTL_EXECUTION_IMPL_H */