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#ifndef __has_feature
21#define LLVM_DEFINED_HAS_FEATURE
22#define __has_feature(x) 0
23#endif
24
25namespace llvm {
26
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.
29template <typename T>
30struct isPodLike {
31#if __has_feature(is_trivially_copyable)
32  // If the compiler supports the is_trivially_copyable trait use it, as it
33  // matches the definition of isPodLike closely.
34  static const bool value = __is_trivially_copyable(T);
35#else
36  // If we don't know anything else, we can (at least) assume that all non-class
37  // types are PODs.
38  static const bool value = !std::is_class<T>::value;
39#endif
40};
41
42// std::pair's are pod-like if their elements are.
43template<typename T, typename U>
44struct isPodLike<std::pair<T, U> > {
45  static const bool value = isPodLike<T>::value && isPodLike<U>::value;
46};
47
48/// \brief Metafunction that determines whether the given type is either an
49/// integral type or an enumeration type.
50///
51/// Note that this accepts potentially more integral types than is_integral
52/// because it is based on merely being convertible implicitly to an integral
53/// type.
54template <typename T> class is_integral_or_enum {
55  typedef typename std::remove_reference<T>::type UnderlyingT;
56
57public:
58  static const bool value =
59      !std::is_class<UnderlyingT>::value && // Filter conversion operators.
60      !std::is_pointer<UnderlyingT>::value &&
61      !std::is_floating_point<UnderlyingT>::value &&
62      std::is_convertible<UnderlyingT, unsigned long long>::value;
63};
64
65/// \brief If T is a pointer, just return it. If it is not, return T&.
66template<typename T, typename Enable = void>
67struct add_lvalue_reference_if_not_pointer { typedef T &type; };
68
69template <typename T>
70struct add_lvalue_reference_if_not_pointer<
71    T, typename std::enable_if<std::is_pointer<T>::value>::type> {
72  typedef T type;
73};
74
75/// \brief If T is a pointer to X, return a pointer to const X. If it is not,
76/// return const T.
77template<typename T, typename Enable = void>
78struct add_const_past_pointer { typedef const T type; };
79
80template <typename T>
81struct add_const_past_pointer<
82    T, typename std::enable_if<std::is_pointer<T>::value>::type> {
83  typedef const typename std::remove_pointer<T>::type *type;
84};
85
86}
87
88#ifdef LLVM_DEFINED_HAS_FEATURE
89#undef __has_feature
90#endif
91
92#endif
93