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_LIBCPP_BEGIN_NAMESPACE_STD
27namespace __pstl {
28
29template <template <class, class> class _Algorithm, class _Backend, class _ExecutionPolicy, class = void>
30constexpr bool __is_implemented_v = false;
31
32template <template <class, class> class _Algorithm, class _Backend, class _ExecutionPolicy>
33constexpr bool __is_implemented_v<_Algorithm,
34 _Backend,
35 _ExecutionPolicy,
36 __enable_if_t<sizeof(_Algorithm<_Backend, _ExecutionPolicy>)>> = true;
37
38// Helpful to provide better error messages. This will show the algorithm and the execution policy
39// in the compiler diagnostic.
40template <template <class, class> class _Algorithm, class _ExecutionPolicy>
41constexpr bool __cant_find_backend_for = false;
42
43template <template <class, class> class _Algorithm, class _BackendConfiguration, class _ExecutionPolicy>
44struct __find_first_implemented;
45
46template <template <class, class> class _Algorithm, class _ExecutionPolicy>
47struct __find_first_implemented<_Algorithm, __backend_configuration<>, _ExecutionPolicy> {
48 static_assert(__cant_find_backend_for<_Algorithm, _ExecutionPolicy>,
49 "Could not find a PSTL backend for the given algorithm and execution policy");
50};
51
52template <template <class, class> class _Algorithm, class _B1, class... _Bn, class _ExecutionPolicy>
53struct __find_first_implemented<_Algorithm, __backend_configuration<_B1, _Bn...>, _ExecutionPolicy>
54 : _If<__is_implemented_v<_Algorithm, _B1, _ExecutionPolicy>,
55 __type_identity<_Algorithm<_B1, _ExecutionPolicy>>,
56 __find_first_implemented<_Algorithm, __backend_configuration<_Bn...>, _ExecutionPolicy> > {};
57
58template <template <class, class> class _Algorithm, class _BackendConfiguration, class _ExecutionPolicy>
59using __dispatch = typename __find_first_implemented<_Algorithm, _BackendConfiguration, _ExecutionPolicy>::type;
60
61} // namespace __pstl
62_LIBCPP_END_NAMESPACE_STD
63
64_LIBCPP_POP_MACROS
65
66#endif // _LIBCPP___PSTL_DISPATCH_H
67