libcxx/include/__algorithm/pstl_backends/cpu_backends/merge.h

   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___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_MERGE_H
  10 #define _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_MERGE_H
  11
  12 #include <__algorithm/merge.h>
  13 #include <__algorithm/pstl_backends/cpu_backends/backend.h>
  14 #include <__config>
  15 #include <__iterator/concepts.h>
  16 #include <__type_traits/is_execution_policy.h>
  17 #include <__utility/move.h>
  18 #include <optional>
  19
  20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  21 #  pragma GCC system_header
  22 #endif
  23
  24 #if !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
  25
  26 _LIBCPP_PUSH_MACROS
  27 #  include <__undef_macros>
  28
  29 _LIBCPP_BEGIN_NAMESPACE_STD
  30
  31 template <class _ExecutionPolicy,
  32           class _ForwardIterator1,
  33           class _ForwardIterator2,
  34           class _ForwardOutIterator,
  35           class _Comp>
  36 _LIBCPP_HIDE_FROM_ABI optional<_ForwardOutIterator> __pstl_merge(
  37     __cpu_backend_tag,
  38     _ForwardIterator1 __first1,
  39     _ForwardIterator1 __last1,
  40     _ForwardIterator2 __first2,
  41     _ForwardIterator2 __last2,
  42     _ForwardOutIterator __result,
  43     _Comp __comp) {
  44   if constexpr (__is_parallel_execution_policy_v<_ExecutionPolicy> &&
  45                 __has_random_access_iterator_category_or_concept<_ForwardIterator1>::value &&
  46                 __has_random_access_iterator_category_or_concept<_ForwardIterator2>::value &&
  47                 __has_random_access_iterator_category_or_concept<_ForwardOutIterator>::value) {
  48     auto __res = __par_backend::__parallel_merge(
  49         __first1,
  50         __last1,
  51         __first2,
  52         __last2,
  53         __result,
  54         __comp,
  55         [](_ForwardIterator1 __g_first1,
  56            _ForwardIterator1 __g_last1,
  57            _ForwardIterator2 __g_first2,
  58            _ForwardIterator2 __g_last2,
  59            _ForwardOutIterator __g_result,
  60            _Comp __g_comp) {
  61           [[maybe_unused]] auto __g_res = std::__pstl_merge<__remove_parallel_policy_t<_ExecutionPolicy>>(
  62               __cpu_backend_tag{},
  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 _LIBCPP_END_NAMESPACE_STD
  80
  81 _LIBCPP_POP_MACROS
  82
  83 #endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_PSTL) && _LIBCPP_STD_VER >= 17
  84
  85 #endif // _LIBCPP___ALGORITHM_PSTL_BACKENDS_CPU_BACKENDS_MERGE_H