1 //===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file provides useful additions to the standard type_traits library.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_SUPPORT_TYPE_TRAITS_H
15 #define LLVM_SUPPORT_TYPE_TRAITS_H
17 #include "llvm/Support/Compiler.h"
18 #include <type_traits>
22 #define LLVM_DEFINED_HAS_FEATURE
23 #define __has_feature(x) 0
28 /// isPodLike - This is a type trait that is used to determine whether a given
29 /// type can be copied around with memcpy instead of running ctors etc.
32 // std::is_trivially_copyable is available in libc++ with clang, libstdc++
33 // that comes with GCC 5. MSVC 2015 and newer also have
34 // std::is_trivially_copyable.
35 #if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) || \
36 (defined(__GNUC__) && __GNUC__ >= 5) || defined(_MSC_VER)
37 // If the compiler supports the is_trivially_copyable trait use it, as it
38 // matches the definition of isPodLike closely.
39 static const bool value = std::is_trivially_copyable<T>::value;
40 #elif __has_feature(is_trivially_copyable)
41 // Use the internal name if the compiler supports is_trivially_copyable but we
42 // don't know if the standard library does. This is the case for clang in
43 // conjunction with libstdc++ from GCC 4.x.
44 static const bool value = __is_trivially_copyable(T);
46 // If we don't know anything else, we can (at least) assume that all non-class
48 static const bool value = !std::is_class<T>::value;
52 // std::pair's are pod-like if their elements are.
53 template<typename T, typename U>
54 struct isPodLike<std::pair<T, U>> {
55 static const bool value = isPodLike<T>::value && isPodLike<U>::value;
58 /// Metafunction that determines whether the given type is either an
59 /// integral type or an enumeration type, including enum classes.
61 /// Note that this accepts potentially more integral types than is_integral
62 /// because it is based on being implicitly convertible to an integral type.
63 /// Also note that enum classes aren't implicitly convertible to integral types,
64 /// the value may therefore need to be explicitly converted before being used.
65 template <typename T> class is_integral_or_enum {
66 using UnderlyingT = typename std::remove_reference<T>::type;
69 static const bool value =
70 !std::is_class<UnderlyingT>::value && // Filter conversion operators.
71 !std::is_pointer<UnderlyingT>::value &&
72 !std::is_floating_point<UnderlyingT>::value &&
73 (std::is_enum<UnderlyingT>::value ||
74 std::is_convertible<UnderlyingT, unsigned long long>::value);
77 /// If T is a pointer, just return it. If it is not, return T&.
78 template<typename T, typename Enable = void>
79 struct add_lvalue_reference_if_not_pointer { using type = T &; };
82 struct add_lvalue_reference_if_not_pointer<
83 T, typename std::enable_if<std::is_pointer<T>::value>::type> {
87 /// If T is a pointer to X, return a pointer to const X. If it is not,
89 template<typename T, typename Enable = void>
90 struct add_const_past_pointer { using type = const T; };
93 struct add_const_past_pointer<
94 T, typename std::enable_if<std::is_pointer<T>::value>::type> {
95 using type = const typename std::remove_pointer<T>::type *;
98 template <typename T, typename Enable = void>
99 struct const_pointer_or_const_ref {
100 using type = const T &;
102 template <typename T>
103 struct const_pointer_or_const_ref<
104 T, typename std::enable_if<std::is_pointer<T>::value>::type> {
105 using type = typename add_const_past_pointer<T>::type;
109 /// Internal utility to detect trivial copy construction.
110 template<typename T> union copy_construction_triviality_helper {
112 copy_construction_triviality_helper() = default;
113 copy_construction_triviality_helper(const copy_construction_triviality_helper&) = default;
114 ~copy_construction_triviality_helper() = default;
116 /// Internal utility to detect trivial move construction.
117 template<typename T> union move_construction_triviality_helper {
119 move_construction_triviality_helper() = default;
120 move_construction_triviality_helper(move_construction_triviality_helper&&) = default;
121 ~move_construction_triviality_helper() = default;
123 } // end namespace detail
125 /// An implementation of `std::is_trivially_copy_constructible` since we have
126 /// users with STLs that don't yet include it.
127 template <typename T>
128 struct is_trivially_copy_constructible
129 : std::is_copy_constructible<
130 ::llvm::detail::copy_construction_triviality_helper<T>> {};
131 template <typename T>
132 struct is_trivially_copy_constructible<T &> : std::true_type {};
133 template <typename T>
134 struct is_trivially_copy_constructible<T &&> : std::false_type {};
136 /// An implementation of `std::is_trivially_move_constructible` since we have
137 /// users with STLs that don't yet include it.
138 template <typename T>
139 struct is_trivially_move_constructible
140 : std::is_move_constructible<
141 ::llvm::detail::move_construction_triviality_helper<T>> {};
142 template <typename T>
143 struct is_trivially_move_constructible<T &> : std::true_type {};
144 template <typename T>
145 struct is_trivially_move_constructible<T &&> : std::true_type {};
147 } // end namespace llvm
149 // If the compiler supports detecting whether a class is final, define
150 // an LLVM_IS_FINAL macro. If it cannot be defined properly, this
151 // macro will be left undefined.
152 #if __cplusplus >= 201402L || defined(_MSC_VER)
153 #define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
154 #elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
155 #define LLVM_IS_FINAL(Ty) __is_final(Ty)
158 #ifdef LLVM_DEFINED_HAS_FEATURE
162 #endif // LLVM_SUPPORT_TYPE_TRAITS_H