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 <type_traits>
18#include <utility>
19
20#include "llvm/Support/Compiler.h"
21
22#ifndef __has_feature
23#define LLVM_DEFINED_HAS_FEATURE
24#define __has_feature(x) 0
25#endif
26
27namespace llvm {
28
29/// isPodLike - This is a type trait that is used to determine whether a given
30/// type can be copied around with memcpy instead of running ctors etc.
31template <typename T>
32struct isPodLike {
33  // std::is_trivially_copyable is available in libc++ with clang, libstdc++
34  // that comes with GCC 5.
35#if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) ||      \
36    (defined(__GNUC__) && __GNUC__ >= 5)
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);
45#else
46  // If we don't know anything else, we can (at least) assume that all non-class
47  // types are PODs.
48  static const bool value = !std::is_class<T>::value;
49#endif
50};
51
52// std::pair's are pod-like if their elements are.
53template<typename T, typename U>
54struct isPodLike<std::pair<T, U> > {
55  static const bool value = isPodLike<T>::value && isPodLike<U>::value;
56};
57
58/// \brief Metafunction that determines whether the given type is either an
59/// integral type or an enumeration type, including enum classes.
60///
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.
65template <typename T> class is_integral_or_enum {
66  typedef typename std::remove_reference<T>::type UnderlyingT;
67
68public:
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);
75};
76
77/// \brief If T is a pointer, just return it. If it is not, return T&.
78template<typename T, typename Enable = void>
79struct add_lvalue_reference_if_not_pointer { typedef T &type; };
80
81template <typename T>
82struct add_lvalue_reference_if_not_pointer<
83    T, typename std::enable_if<std::is_pointer<T>::value>::type> {
84  typedef T type;
85};
86
87/// \brief If T is a pointer to X, return a pointer to const X. If it is not,
88/// return const T.
89template<typename T, typename Enable = void>
90struct add_const_past_pointer { typedef const T type; };
91
92template <typename T>
93struct add_const_past_pointer<
94    T, typename std::enable_if<std::is_pointer<T>::value>::type> {
95  typedef const typename std::remove_pointer<T>::type *type;
96};
97
98}
99
100// If the compiler supports detecting whether a class is final, define
101// an LLVM_IS_FINAL macro. If it cannot be defined properly, this
102// macro will be left undefined.
103#if __cplusplus >= 201402L
104#define LLVM_IS_FINAL(Ty) std::is_final<Ty>()
105#elif __has_feature(is_final) || LLVM_GNUC_PREREQ(4, 7, 0)
106#define LLVM_IS_FINAL(Ty) __is_final(Ty)
107#endif
108
109#ifdef LLVM_DEFINED_HAS_FEATURE
110#undef __has_feature
111#endif
112
113#endif
114