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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 <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 
25 namespace 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.
29 template <typename T>
30 struct 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.
43 template<typename T, typename U>
44 struct 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.
54 template <typename T> class is_integral_or_enum {
55   typedef typename std::remove_reference<T>::type UnderlyingT;
56 
57 public:
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&.
66 template<typename T, typename Enable = void>
67 struct add_lvalue_reference_if_not_pointer { typedef T &type; };
68 
69 template <typename T>
70 struct 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.
77 template<typename T, typename Enable = void>
78 struct add_const_past_pointer { typedef const T type; };
79 
80 template <typename T>
81 struct 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