1//===----------------------------------------------------------------------===//
 2//
 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 4// See https://llvm.org/LICENSE.txt for license information.
 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 6//
 7//===----------------------------------------------------------------------===//
 8
 9#ifndef _LIBCPP___PSTL_CPU_ALGOS_MERGE_H
10#define _LIBCPP___PSTL_CPU_ALGOS_MERGE_H
11
12#include <__algorithm/merge.h>
13#include <__assert>
14#include <__config>
15#include <__iterator/concepts.h>
16#include <__pstl/backend_fwd.h>
17#include <__pstl/cpu_algos/cpu_traits.h>
18#include <__type_traits/is_execution_policy.h>
19#include <__utility/move.h>
20#include <optional>
21
22#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
23#  pragma GCC system_header
24#endif
25
26_LIBCPP_PUSH_MACROS
27#include <__undef_macros>
28
29#if _LIBCPP_STD_VER >= 17
30
31_LIBCPP_BEGIN_NAMESPACE_STD
32namespace __pstl {
33
34template <class _Backend, class _RawExecutionPolicy>
35struct __cpu_parallel_merge {
36  template <class _Policy, class _ForwardIterator1, class _ForwardIterator2, class _ForwardOutIterator, class _Comp>
37  _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator> operator()(
38      _Policy&& __policy,
39      _ForwardIterator1 __first1,
40      _ForwardIterator1 __last1,
41      _ForwardIterator2 __first2,
42      _ForwardIterator2 __last2,
43      _ForwardOutIterator __result,
44      _Comp __comp) const noexcept {
45    if constexpr (__is_parallel_execution_policy_v<_RawExecutionPolicy> &&
46                  __has_random_access_iterator_category_or_concept<_ForwardIterator1>::value &&
47                  __has_random_access_iterator_category_or_concept<_ForwardIterator2>::value &&
48                  __has_random_access_iterator_category_or_concept<_ForwardOutIterator>::value) {
49      auto __res = __cpu_traits<_Backend>::__merge(
50          __first1,
51          __last1,
52          __first2,
53          __last2,
54          __result,
55          __comp,
56          [&__policy](_ForwardIterator1 __g_first1,
57                      _ForwardIterator1 __g_last1,
58                      _ForwardIterator2 __g_first2,
59                      _ForwardIterator2 __g_last2,
60                      _ForwardOutIterator __g_result,
61                      _Comp __g_comp) {
62            using _MergeUnseq             = __pstl::__merge<_Backend, __remove_parallel_policy_t<_RawExecutionPolicy>>;
63            [[maybe_unused]] auto __g_res = _MergeUnseq()(
64                std::__remove_parallel_policy(__policy),
65                std::move(__g_first1),
66                std::move(__g_last1),
67                std::move(__g_first2),
68                std::move(__g_last2),
69                std::move(__g_result),
70                std::move(__g_comp));
71            _LIBCPP_ASSERT_INTERNAL(__g_res, "unsed/sed should never try to allocate!");
72          });
73      if (!__res)
74        return nullopt;
75      return __result + (__last1 - __first1) + (__last2 - __first2);
76    } else {
77      return std::merge(__first1, __last1, __first2, __last2, __result, __comp);
78    }
79  }
80};
81
82} // namespace __pstl
83_LIBCPP_END_NAMESPACE_STD
84
85#endif // _LIBCPP_STD_VER >= 17
86
87_LIBCPP_POP_MACROS
88
89#endif // _LIBCPP___PSTL_CPU_ALGOS_MERGE_H