xref: /freebsd/contrib/llvm-project/libcxx/include/__pstl/cpu_algos/merge.h (revision 0fca6ea1d4eea4c934cfff25ac9ee8ad6fe95583)
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 _LIBCPP_BEGIN_NAMESPACE_STD
30 namespace __pstl {
31 
32 template <class _Backend, class _RawExecutionPolicy>
33 struct __cpu_parallel_merge {
34   template <class _Policy, class _ForwardIterator1, class _ForwardIterator2, class _ForwardOutIterator, class _Comp>
operator__cpu_parallel_merge35   _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator> operator()(
36       _Policy&& __policy,
37       _ForwardIterator1 __first1,
38       _ForwardIterator1 __last1,
39       _ForwardIterator2 __first2,
40       _ForwardIterator2 __last2,
41       _ForwardOutIterator __result,
42       _Comp __comp) const noexcept {
43     if constexpr (__is_parallel_execution_policy_v<_RawExecutionPolicy> &&
44                   __has_random_access_iterator_category_or_concept<_ForwardIterator1>::value &&
45                   __has_random_access_iterator_category_or_concept<_ForwardIterator2>::value &&
46                   __has_random_access_iterator_category_or_concept<_ForwardOutIterator>::value) {
47       auto __res = __cpu_traits<_Backend>::__merge(
48           __first1,
49           __last1,
50           __first2,
51           __last2,
52           __result,
53           __comp,
54           [&__policy](_ForwardIterator1 __g_first1,
55                       _ForwardIterator1 __g_last1,
56                       _ForwardIterator2 __g_first2,
57                       _ForwardIterator2 __g_last2,
58                       _ForwardOutIterator __g_result,
59                       _Comp __g_comp) {
60             using _MergeUnseq             = __pstl::__merge<_Backend, __remove_parallel_policy_t<_RawExecutionPolicy>>;
61             [[maybe_unused]] auto __g_res = _MergeUnseq()(
62                 std::__remove_parallel_policy(__policy),
63                 std::move(__g_first1),
64                 std::move(__g_last1),
65                 std::move(__g_first2),
66                 std::move(__g_last2),
67                 std::move(__g_result),
68                 std::move(__g_comp));
69             _LIBCPP_ASSERT_INTERNAL(__g_res, "unsed/sed should never try to allocate!");
70           });
71       if (!__res)
72         return nullopt;
73       return __result + (__last1 - __first1) + (__last2 - __first2);
74     } else {
75       return std::merge(__first1, __last1, __first2, __last2, __result, __comp);
76     }
77   }
78 };
79 
80 } // namespace __pstl
81 _LIBCPP_END_NAMESPACE_STD
82 
83 _LIBCPP_POP_MACROS
84 
85 #endif // _LIBCPP___PSTL_CPU_ALGOS_MERGE_H
86