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.
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);
45 // If we don't know anything else, we can (at least) assume that all non-class
47 static const bool value = !std::is_class<T>::value;
51 // std::pair's are pod-like if their elements are.
52 template<typename T, typename U>
53 struct isPodLike<std::pair<T, U>> {
54 static const bool value = isPodLike<T>::value && isPodLike<U>::value;
57 /// \brief Metafunction that determines whether the given type is either an
58 /// integral type or an enumeration type, including enum classes.
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;
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);
76 /// \brief If T is a pointer, just return it. If it is not, return T&.
77 template<typename T, typename Enable = void>
78 struct add_lvalue_reference_if_not_pointer { using type = T &; };
81 struct add_lvalue_reference_if_not_pointer<
82 T, typename std::enable_if<std::is_pointer<T>::value>::type> {
86 /// \brief If T is a pointer to X, return a pointer to const X. If it is not,
88 template<typename T, typename Enable = void>
89 struct add_const_past_pointer { using type = const T; };
92 struct add_const_past_pointer<
93 T, typename std::enable_if<std::is_pointer<T>::value>::type> {
94 using type = const typename std::remove_pointer<T>::type *;
97 template <typename T, typename Enable = void>
98 struct const_pointer_or_const_ref {
99 using type = const T &;
101 template <typename T>
102 struct const_pointer_or_const_ref<
103 T, typename std::enable_if<std::is_pointer<T>::value>::type> {
104 using type = typename add_const_past_pointer<T>::type;
107 } // end namespace llvm
109 // If the compiler supports detecting whether a class is final, define
110 // an LLVM_IS_FINAL macro. If it cannot be defined properly, this
111 // macro will be left undefined.
112 #if __cplusplus >= 201402L
113 #define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
114 #elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
115 #define LLVM_IS_FINAL(Ty) __is_final(Ty)
118 #ifdef LLVM_DEFINED_HAS_FEATURE
122 #endif // LLVM_SUPPORT_TYPE_TRAITS_H