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 <type_traits>
21 #define LLVM_DEFINED_HAS_FEATURE
22 #define __has_feature(x) 0
27 /// isPodLike - This is a type trait that is used to determine whether a given
28 /// type can be copied around with memcpy instead of running ctors etc.
31 // std::is_trivially_copyable is available in libc++ with clang, libstdc++
32 // that comes with GCC 5.
33 #if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) || \
34 (defined(__GNUC__) && __GNUC__ >= 5)
35 // If the compiler supports the is_trivially_copyable trait use it, as it
36 // matches the definition of isPodLike closely.
37 static const bool value = std::is_trivially_copyable<T>::value;
38 #elif __has_feature(is_trivially_copyable)
39 // Use the internal name if the compiler supports is_trivially_copyable but we
40 // don't know if the standard library does. This is the case for clang in
41 // conjunction with libstdc++ from GCC 4.x.
42 static const bool value = __is_trivially_copyable(T);
44 // If we don't know anything else, we can (at least) assume that all non-class
46 static const bool value = !std::is_class<T>::value;
50 // std::pair's are pod-like if their elements are.
51 template<typename T, typename U>
52 struct isPodLike<std::pair<T, U> > {
53 static const bool value = isPodLike<T>::value && isPodLike<U>::value;
56 /// \brief Metafunction that determines whether the given type is either an
57 /// integral type or an enumeration type.
59 /// Note that this accepts potentially more integral types than is_integral
60 /// because it is based on merely being convertible implicitly to an integral
62 template <typename T> class is_integral_or_enum {
63 typedef typename std::remove_reference<T>::type UnderlyingT;
66 static const bool value =
67 !std::is_class<UnderlyingT>::value && // Filter conversion operators.
68 !std::is_pointer<UnderlyingT>::value &&
69 !std::is_floating_point<UnderlyingT>::value &&
70 std::is_convertible<UnderlyingT, unsigned long long>::value;
73 /// \brief If T is a pointer, just return it. If it is not, return T&.
74 template<typename T, typename Enable = void>
75 struct add_lvalue_reference_if_not_pointer { typedef T &type; };
78 struct add_lvalue_reference_if_not_pointer<
79 T, typename std::enable_if<std::is_pointer<T>::value>::type> {
83 /// \brief If T is a pointer to X, return a pointer to const X. If it is not,
85 template<typename T, typename Enable = void>
86 struct add_const_past_pointer { typedef const T type; };
89 struct add_const_past_pointer<
90 T, typename std::enable_if<std::is_pointer<T>::value>::type> {
91 typedef const typename std::remove_pointer<T>::type *type;
96 // If the compiler supports detecting whether a class is final, define
97 // an LLVM_IS_FINAL macro. If it cannot be defined properly, this
98 // macro will be left undefined.
99 #if __cplusplus >= 201402L
100 #define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
101 #elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
102 #define LLVM_IS_FINAL(Ty) __is_final(Ty)
105 #ifdef LLVM_DEFINED_HAS_FEATURE