1 //===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===// 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 // This file provides useful additions to the standard type_traits library. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #ifndef LLVM_SUPPORT_TYPE_TRAITS_H 14 #define LLVM_SUPPORT_TYPE_TRAITS_H 15 16 #include "llvm/Support/Compiler.h" 17 #include <type_traits> 18 #include <utility> 19 20 namespace llvm { 21 22 23 /// Metafunction that determines whether the given type is either an 24 /// integral type or an enumeration type, including enum classes. 25 /// 26 /// Note that this accepts potentially more integral types than is_integral 27 /// because it is based on being implicitly convertible to an integral type. 28 /// Also note that enum classes aren't implicitly convertible to integral types, 29 /// the value may therefore need to be explicitly converted before being used. 30 template <typename T> class is_integral_or_enum { 31 using UnderlyingT = std::remove_reference_t<T>; 32 33 public: 34 static const bool value = 35 !std::is_class<UnderlyingT>::value && // Filter conversion operators. 36 !std::is_pointer<UnderlyingT>::value && 37 !std::is_floating_point<UnderlyingT>::value && 38 (std::is_enum<UnderlyingT>::value || 39 std::is_convertible<UnderlyingT, unsigned long long>::value); 40 }; 41 42 /// If T is a pointer, just return it. If it is not, return T&. 43 template<typename T, typename Enable = void> 44 struct add_lvalue_reference_if_not_pointer { using type = T &; }; 45 46 template <typename T> 47 struct add_lvalue_reference_if_not_pointer< 48 T, std::enable_if_t<std::is_pointer<T>::value>> { 49 using type = T; 50 }; 51 52 /// If T is a pointer to X, return a pointer to const X. If it is not, 53 /// return const T. 54 template<typename T, typename Enable = void> 55 struct add_const_past_pointer { using type = const T; }; 56 57 template <typename T> 58 struct add_const_past_pointer<T, std::enable_if_t<std::is_pointer<T>::value>> { 59 using type = const std::remove_pointer_t<T> *; 60 }; 61 62 template <typename T, typename Enable = void> 63 struct const_pointer_or_const_ref { 64 using type = const T &; 65 }; 66 template <typename T> 67 struct const_pointer_or_const_ref<T, 68 std::enable_if_t<std::is_pointer<T>::value>> { 69 using type = typename add_const_past_pointer<T>::type; 70 }; 71 72 namespace detail { 73 /// Internal utility to detect trivial copy construction. 74 template<typename T> union copy_construction_triviality_helper { 75 T t; 76 copy_construction_triviality_helper() = default; 77 copy_construction_triviality_helper(const copy_construction_triviality_helper&) = default; 78 ~copy_construction_triviality_helper() = default; 79 }; 80 /// Internal utility to detect trivial move construction. 81 template<typename T> union move_construction_triviality_helper { 82 T t; 83 move_construction_triviality_helper() = default; 84 move_construction_triviality_helper(move_construction_triviality_helper&&) = default; 85 ~move_construction_triviality_helper() = default; 86 }; 87 88 template<class T> 89 union trivial_helper { 90 T t; 91 }; 92 93 } // end namespace detail 94 95 /// An implementation of `std::is_trivially_copy_constructible` since we have 96 /// users with STLs that don't yet include it. 97 template <typename T> 98 struct is_trivially_copy_constructible 99 : std::is_copy_constructible< 100 ::llvm::detail::copy_construction_triviality_helper<T>> {}; 101 template <typename T> 102 struct is_trivially_copy_constructible<T &> : std::true_type {}; 103 template <typename T> 104 struct is_trivially_copy_constructible<T &&> : std::false_type {}; 105 106 /// An implementation of `std::is_trivially_move_constructible` since we have 107 /// users with STLs that don't yet include it. 108 template <typename T> 109 struct is_trivially_move_constructible 110 : std::is_move_constructible< 111 ::llvm::detail::move_construction_triviality_helper<T>> {}; 112 template <typename T> 113 struct is_trivially_move_constructible<T &> : std::true_type {}; 114 template <typename T> 115 struct is_trivially_move_constructible<T &&> : std::true_type {}; 116 117 118 template <typename T> 119 struct is_copy_assignable { 120 template<class F> 121 static auto get(F*) -> decltype(std::declval<F &>() = std::declval<const F &>(), std::true_type{}); 122 static std::false_type get(...); 123 static constexpr bool value = decltype(get((T*)nullptr))::value; 124 }; 125 126 template <typename T> 127 struct is_move_assignable { 128 template<class F> 129 static auto get(F*) -> decltype(std::declval<F &>() = std::declval<F &&>(), std::true_type{}); 130 static std::false_type get(...); 131 static constexpr bool value = decltype(get((T*)nullptr))::value; 132 }; 133 134 135 // An implementation of `std::is_trivially_copyable` since STL version 136 // is not equally supported by all compilers, especially GCC 4.9. 137 // Uniform implementation of this trait is important for ABI compatibility 138 // as it has an impact on SmallVector's ABI (among others). 139 template <typename T> 140 class is_trivially_copyable { 141 142 // copy constructors 143 static constexpr bool has_trivial_copy_constructor = 144 std::is_copy_constructible<detail::trivial_helper<T>>::value; 145 static constexpr bool has_deleted_copy_constructor = 146 !std::is_copy_constructible<T>::value; 147 148 // move constructors 149 static constexpr bool has_trivial_move_constructor = 150 std::is_move_constructible<detail::trivial_helper<T>>::value; 151 static constexpr bool has_deleted_move_constructor = 152 !std::is_move_constructible<T>::value; 153 154 // copy assign 155 static constexpr bool has_trivial_copy_assign = 156 is_copy_assignable<detail::trivial_helper<T>>::value; 157 static constexpr bool has_deleted_copy_assign = 158 !is_copy_assignable<T>::value; 159 160 // move assign 161 static constexpr bool has_trivial_move_assign = 162 is_move_assignable<detail::trivial_helper<T>>::value; 163 static constexpr bool has_deleted_move_assign = 164 !is_move_assignable<T>::value; 165 166 // destructor 167 static constexpr bool has_trivial_destructor = 168 std::is_destructible<detail::trivial_helper<T>>::value; 169 170 public: 171 172 static constexpr bool value = 173 has_trivial_destructor && 174 (has_deleted_move_assign || has_trivial_move_assign) && 175 (has_deleted_move_constructor || has_trivial_move_constructor) && 176 (has_deleted_copy_assign || has_trivial_copy_assign) && 177 (has_deleted_copy_constructor || has_trivial_copy_constructor); 178 179 #ifdef HAVE_STD_IS_TRIVIALLY_COPYABLE 180 static_assert(value == std::is_trivially_copyable<T>::value, 181 "inconsistent behavior between llvm:: and std:: implementation of is_trivially_copyable"); 182 #endif 183 }; 184 template <typename T> 185 class is_trivially_copyable<T*> : public std::true_type { 186 }; 187 188 189 } // end namespace llvm 190 191 #endif // LLVM_SUPPORT_TYPE_TRAITS_H 192
Indexes created Tue Jun 16 00:25:01 UTC 2026