LLVM  8.0.0svn
type_traits.h
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1 //===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file provides useful additions to the standard type_traits library.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_SUPPORT_TYPE_TRAITS_H
15 #define LLVM_SUPPORT_TYPE_TRAITS_H
16 
17 #include "llvm/Support/Compiler.h"
18 #include <type_traits>
19 #include <utility>
20 
21 #ifndef __has_feature
22 #define LLVM_DEFINED_HAS_FEATURE
23 #define __has_feature(x) 0
24 #endif
25 
26 namespace llvm {
27 
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.
30 template <typename T>
31 struct isPodLike {
32  // std::is_trivially_copyable is available in libc++ with clang, libstdc++
33  // that comes with GCC 5.
34 #if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) || \
35  (defined(__GNUC__) && __GNUC__ >= 5)
36  // If the compiler supports the is_trivially_copyable trait use it, as it
37  // matches the definition of isPodLike closely.
38  static const bool value = std::is_trivially_copyable<T>::value;
39 #elif __has_feature(is_trivially_copyable)
40  // Use the internal name if the compiler supports is_trivially_copyable but we
41  // don't know if the standard library does. This is the case for clang in
42  // conjunction with libstdc++ from GCC 4.x.
43  static const bool value = __is_trivially_copyable(T);
44 #else
45  // If we don't know anything else, we can (at least) assume that all non-class
46  // types are PODs.
47  static const bool value = !std::is_class<T>::value;
48 #endif
49 };
50 
51 // std::pair's are pod-like if their elements are.
52 template<typename T, typename U>
53 struct isPodLike<std::pair<T, U>> {
55 };
56 
57 /// Metafunction that determines whether the given type is either an
58 /// integral type or an enumeration type, including enum classes.
59 ///
60 /// Note that this accepts potentially more integral types than is_integral
61 /// because it is based on being implicitly convertible to an integral type.
62 /// Also note that enum classes aren't implicitly convertible to integral types,
63 /// the value may therefore need to be explicitly converted before being used.
64 template <typename T> class is_integral_or_enum {
65  using UnderlyingT = typename std::remove_reference<T>::type;
66 
67 public:
68  static const bool value =
69  !std::is_class<UnderlyingT>::value && // Filter conversion operators.
70  !std::is_pointer<UnderlyingT>::value &&
71  !std::is_floating_point<UnderlyingT>::value &&
72  (std::is_enum<UnderlyingT>::value ||
73  std::is_convertible<UnderlyingT, unsigned long long>::value);
74 };
75 
76 /// If T is a pointer, just return it. If it is not, return T&.
77 template<typename T, typename Enable = void>
79 
80 template <typename T>
82  T, typename std::enable_if<std::is_pointer<T>::value>::type> {
83  using type = T;
84 };
85 
86 /// If T is a pointer to X, return a pointer to const X. If it is not,
87 /// return const T.
88 template<typename T, typename Enable = void>
89 struct add_const_past_pointer { using type = const T; };
90 
91 template <typename T>
93  T, typename std::enable_if<std::is_pointer<T>::value>::type> {
94  using type = const typename std::remove_pointer<T>::type *;
95 };
96 
97 template <typename T, typename Enable = void>
99  using type = const T &;
100 };
101 template <typename T>
103  T, typename std::enable_if<std::is_pointer<T>::value>::type> {
105 };
106 
107 namespace detail {
108 /// Internal utility to detect trivial copy construction.
109 template<typename T> union copy_construction_triviality_helper {
110  T t;
114 };
115 /// Internal utility to detect trivial move construction.
116 template<typename T> union move_construction_triviality_helper {
117  T t;
121 };
122 } // end namespace detail
123 
124 /// An implementation of `std::is_trivially_copy_constructible` since we have
125 /// users with STLs that don't yet include it.
126 template <typename T>
128  : std::is_copy_constructible<
129  ::llvm::detail::copy_construction_triviality_helper<T>> {};
130 template <typename T>
131 struct is_trivially_copy_constructible<T &> : std::true_type {};
132 template <typename T>
133 struct is_trivially_copy_constructible<T &&> : std::false_type {};
134 
135 /// An implementation of `std::is_trivially_move_constructible` since we have
136 /// users with STLs that don't yet include it.
137 template <typename T>
139  : std::is_move_constructible<
140  ::llvm::detail::move_construction_triviality_helper<T>> {};
141 template <typename T>
142 struct is_trivially_move_constructible<T &> : std::true_type {};
143 template <typename T>
144 struct is_trivially_move_constructible<T &&> : std::true_type {};
145 
146 } // end namespace llvm
147 
148 // If the compiler supports detecting whether a class is final, define
149 // an LLVM_IS_FINAL macro. If it cannot be defined properly, this
150 // macro will be left undefined.
151 #if __cplusplus >= 201402L || defined(_MSC_VER)
152 #define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
153 #elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
154 #define LLVM_IS_FINAL(Ty) __is_final(Ty)
155 #endif
156 
157 #ifdef LLVM_DEFINED_HAS_FEATURE
158 #undef __has_feature
159 #endif
160 
161 #endif // LLVM_SUPPORT_TYPE_TRAITS_H
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
static const bool value
Definition: type_traits.h:47
Definition: BitVector.h:938
Metafunction that determines whether the given type is either an integral type or an enumeration type...
Definition: type_traits.h:64
#define T
An implementation of std::is_trivially_move_constructible since we have users with STLs that don&#39;t ye...
Definition: type_traits.h:138
An implementation of std::is_trivially_copy_constructible since we have users with STLs that don&#39;t ye...
Definition: type_traits.h:127
If T is a pointer to X, return a pointer to const X.
Definition: type_traits.h:89
isPodLike - This is a type trait that is used to determine whether a given type can be copied around ...
Definition: ArrayRef.h:530
Internal utility to detect trivial copy construction.
Definition: type_traits.h:109
If T is a pointer, just return it. If it is not, return T&.
Definition: type_traits.h:78
Internal utility to detect trivial move construction.
Definition: type_traits.h:116