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_DISPATCH_H
10#define _LIBCPP___PSTL_DISPATCH_H
11
12#include <__config>
13#include <__pstl/backend_fwd.h>
14#include <__type_traits/conditional.h>
15#include <__type_traits/enable_if.h>
16#include <__type_traits/integral_constant.h>
17#include <__type_traits/type_identity.h>
18
19#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
20# pragma GCC system_header
21#endif
22
23_LIBCPP_PUSH_MACROS
24#include <__undef_macros>
25
26#if _LIBCPP_STD_VER >= 17
27
28_LIBCPP_BEGIN_NAMESPACE_STD
29namespace __pstl {
30
31template <template <class, class> class _Algorithm, class _Backend, class _ExecutionPolicy, class = void>
32constexpr bool __is_implemented_v = false;
33
34template <template <class, class> class _Algorithm, class _Backend, class _ExecutionPolicy>
35constexpr bool __is_implemented_v<_Algorithm,
36 _Backend,
37 _ExecutionPolicy,
38 __enable_if_t<sizeof(_Algorithm<_Backend, _ExecutionPolicy>)>> = true;
39
40// Helpful to provide better error messages. This will show the algorithm and the execution policy
41// in the compiler diagnostic.
42template <template <class, class> class _Algorithm, class _ExecutionPolicy>
43constexpr bool __cant_find_backend_for = false;
44
45template <template <class, class> class _Algorithm, class _BackendConfiguration, class _ExecutionPolicy>
46struct __find_first_implemented;
47
48template <template <class, class> class _Algorithm, class _ExecutionPolicy>
49struct __find_first_implemented<_Algorithm, __backend_configuration<>, _ExecutionPolicy> {
50 static_assert(__cant_find_backend_for<_Algorithm, _ExecutionPolicy>,
51 "Could not find a PSTL backend for the given algorithm and execution policy");
52};
53
54template <template <class, class> class _Algorithm, class _B1, class... _Bn, class _ExecutionPolicy>
55struct __find_first_implemented<_Algorithm, __backend_configuration<_B1, _Bn...>, _ExecutionPolicy>
56 : _If<__is_implemented_v<_Algorithm, _B1, _ExecutionPolicy>,
57 __type_identity<_Algorithm<_B1, _ExecutionPolicy>>,
58 __find_first_implemented<_Algorithm, __backend_configuration<_Bn...>, _ExecutionPolicy> > {};
59
60template <template <class, class> class _Algorithm, class _BackendConfiguration, class _ExecutionPolicy>
61using __dispatch _LIBCPP_NODEBUG =
62 typename __find_first_implemented<_Algorithm, _BackendConfiguration, _ExecutionPolicy>::type;
63
64} // namespace __pstl
65_LIBCPP_END_NAMESPACE_STD
66
67#endif // _LIBCPP_STD_VER >= 17
68
69_LIBCPP_POP_MACROS
70
71#endif // _LIBCPP___PSTL_DISPATCH_H
72