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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_COPY_MOVE_COMMON_H
10 : #define _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
11 :
12 : #include <__algorithm/iterator_operations.h>
13 : #include <__algorithm/unwrap_iter.h>
14 : #include <__algorithm/unwrap_range.h>
15 : #include <__config>
16 : #include <__iterator/iterator_traits.h>
17 : #include <__memory/pointer_traits.h>
18 : #include <__type_traits/enable_if.h>
19 : #include <__type_traits/is_always_bitcastable.h>
20 : #include <__type_traits/is_constant_evaluated.h>
21 : #include <__type_traits/is_copy_constructible.h>
22 : #include <__type_traits/is_trivially_assignable.h>
23 : #include <__type_traits/is_trivially_copyable.h>
24 : #include <__type_traits/is_volatile.h>
25 : #include <__utility/move.h>
26 : #include <__utility/pair.h>
27 : #include <cstddef>
28 :
29 : #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
30 : # pragma GCC system_header
31 : #endif
32 :
33 : _LIBCPP_BEGIN_NAMESPACE_STD
34 :
35 : // Type traits.
36 :
37 : template <class _From, class _To>
38 : struct __can_lower_copy_assignment_to_memmove {
39 : static const bool value =
40 : // If the types are always bitcastable, it's valid to do a bitwise copy between them.
41 : __is_always_bitcastable<_From, _To>::value &&
42 : // Reject conversions that wouldn't be performed by the regular built-in assignment (e.g. between arrays).
43 : is_trivially_assignable<_To&, const _From&>::value &&
44 : // `memmove` doesn't accept `volatile` pointers, make sure the optimization SFINAEs away in that case.
45 : !is_volatile<_From>::value &&
46 : !is_volatile<_To>::value;
47 : };
48 :
49 : template <class _From, class _To>
50 : struct __can_lower_move_assignment_to_memmove {
51 : static const bool value =
52 : __is_always_bitcastable<_From, _To>::value &&
53 : is_trivially_assignable<_To&, _From&&>::value &&
54 : !is_volatile<_From>::value &&
55 : !is_volatile<_To>::value;
56 : };
57 :
58 : // `memmove` algorithms implementation.
59 :
60 : template <class _In, class _Out>
61 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
62 0 : __copy_trivial_impl(_In* __first, _In* __last, _Out* __result) {
63 0 : const size_t __n = static_cast<size_t>(__last - __first);
64 0 : ::__builtin_memmove(__result, __first, __n * sizeof(_Out));
65 :
66 0 : return std::make_pair(__last, __result + __n);
67 : }
68 :
69 : template <class _In, class _Out>
70 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
71 0 : __copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __result) {
72 0 : const size_t __n = static_cast<size_t>(__last - __first);
73 0 : __result -= __n;
74 :
75 0 : ::__builtin_memmove(__result, __first, __n * sizeof(_Out));
76 :
77 0 : return std::make_pair(__last, __result);
78 : }
79 :
80 : // Iterator unwrapping and dispatching to the correct overload.
81 :
82 : template <class _F1, class _F2>
83 : struct __overload : _F1, _F2 {
84 : using _F1::operator();
85 : using _F2::operator();
86 : };
87 :
88 : template <class _InIter, class _Sent, class _OutIter, class = void>
89 : struct __can_rewrap : false_type {};
90 :
91 : template <class _InIter, class _Sent, class _OutIter>
92 : struct __can_rewrap<_InIter,
93 : _Sent,
94 : _OutIter,
95 : // Note that sentinels are always copy-constructible.
96 : __enable_if_t< is_copy_constructible<_InIter>::value &&
97 : is_copy_constructible<_OutIter>::value > > : true_type {};
98 :
99 : template <class _Algorithm,
100 : class _InIter,
101 : class _Sent,
102 : class _OutIter,
103 : __enable_if_t<__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
104 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
105 2462 : __unwrap_and_dispatch(_InIter __first, _Sent __last, _OutIter __out_first) {
106 2462 : auto __range = std::__unwrap_range(__first, std::move(__last));
107 2462 : auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first));
108 4924 : return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)),
109 2462 : std::__rewrap_iter(std::move(__out_first), std::move(__result.second)));
110 : }
111 :
112 : template <class _Algorithm,
113 : class _InIter,
114 : class _Sent,
115 : class _OutIter,
116 : __enable_if_t<!__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
117 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
118 : __unwrap_and_dispatch(_InIter __first, _Sent __last, _OutIter __out_first) {
119 : return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
120 : }
121 :
122 : template <class _IterOps, class _InValue, class _OutIter, class = void>
123 : struct __can_copy_without_conversion : false_type {};
124 :
125 : template <class _IterOps, class _InValue, class _OutIter>
126 : struct __can_copy_without_conversion<
127 : _IterOps,
128 : _InValue,
129 : _OutIter,
130 : __enable_if_t<is_same<_InValue, typename _IterOps::template __value_type<_OutIter> >::value> > : true_type {};
131 :
132 : template <class _AlgPolicy,
133 : class _NaiveAlgorithm,
134 : class _OptimizedAlgorithm,
135 : class _InIter,
136 : class _Sent,
137 : class _OutIter>
138 : _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
139 2462 : __dispatch_copy_or_move(_InIter __first, _Sent __last, _OutIter __out_first) {
140 : #ifdef _LIBCPP_COMPILER_GCC
141 : // GCC doesn't support `__builtin_memmove` during constant evaluation.
142 : if (__libcpp_is_constant_evaluated()) {
143 : return std::__unwrap_and_dispatch<_NaiveAlgorithm>(std::move(__first), std::move(__last), std::move(__out_first));
144 : }
145 : #else
146 : // In Clang, `__builtin_memmove` only supports fully trivially copyable types (just having trivial copy assignment is
147 : // insufficient). Also, conversions are not supported.
148 2462 : if (__libcpp_is_constant_evaluated()) {
149 : using _InValue = typename _IterOps<_AlgPolicy>::template __value_type<_InIter>;
150 : if (!is_trivially_copyable<_InValue>::value ||
151 : !__can_copy_without_conversion<_IterOps<_AlgPolicy>, _InValue, _OutIter>::value) {
152 0 : return std::__unwrap_and_dispatch<_NaiveAlgorithm>(std::move(__first), std::move(__last), std::move(__out_first));
153 : }
154 0 : }
155 : #endif // _LIBCPP_COMPILER_GCC
156 :
157 : using _Algorithm = __overload<_NaiveAlgorithm, _OptimizedAlgorithm>;
158 2462 : return std::__unwrap_and_dispatch<_Algorithm>(std::move(__first), std::move(__last), std::move(__out_first));
159 2435 : }
160 :
161 : _LIBCPP_END_NAMESPACE_STD
162 :
163 : #endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
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