LLVM  6.0.0svn
PointerLikeTypeTraits.h
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1 //===- llvm/Support/PointerLikeTypeTraits.h - Pointer 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 defines the PointerLikeTypeTraits class. This allows data
11 // structures to reason about pointers and other things that are pointer sized.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_SUPPORT_POINTERLIKETYPETRAITS_H
16 #define LLVM_SUPPORT_POINTERLIKETYPETRAITS_H
17 
18 #include "llvm/Support/DataTypes.h"
19 #include <type_traits>
20 
21 namespace llvm {
22 
23 /// A traits type that is used to handle pointer types and things that are just
24 /// wrappers for pointers as a uniform entity.
25 template <typename T> struct PointerLikeTypeTraits;
26 
27 namespace detail {
28 /// A tiny meta function to compute the log2 of a compile time constant.
29 template <size_t N>
31  : std::integral_constant<size_t, ConstantLog2<N / 2>::value + 1> {};
32 template <> struct ConstantLog2<1> : std::integral_constant<size_t, 0> {};
33 
34 // Provide a trait to check if T is pointer-like.
35 template <typename T, typename U = void> struct HasPointerLikeTypeTraits {
36  static const bool value = false;
37 };
38 
39 // sizeof(T) is valid only for a complete T.
40 template <typename T> struct HasPointerLikeTypeTraits<
41  T, decltype((sizeof(PointerLikeTypeTraits<T>) + sizeof(T)), void())> {
42  static const bool value = true;
43 };
44 
45 template <typename T> struct IsPointerLike {
46  static const bool value = HasPointerLikeTypeTraits<T>::value;
47 };
48 
49 template <typename T> struct IsPointerLike<T *> {
50  static const bool value = true;
51 };
52 } // namespace detail
53 
54 // Provide PointerLikeTypeTraits for non-cvr pointers.
55 template <typename T> struct PointerLikeTypeTraits<T *> {
56  static inline void *getAsVoidPointer(T *P) { return P; }
57  static inline T *getFromVoidPointer(void *P) { return static_cast<T *>(P); }
58 
59  enum { NumLowBitsAvailable = detail::ConstantLog2<alignof(T)>::value };
60 };
61 
62 template <> struct PointerLikeTypeTraits<void *> {
63  static inline void *getAsVoidPointer(void *P) { return P; }
64  static inline void *getFromVoidPointer(void *P) { return P; }
65 
66  /// Note, we assume here that void* is related to raw malloc'ed memory and
67  /// that malloc returns objects at least 4-byte aligned. However, this may be
68  /// wrong, or pointers may be from something other than malloc. In this case,
69  /// you should specify a real typed pointer or avoid this template.
70  ///
71  /// All clients should use assertions to do a run-time check to ensure that
72  /// this is actually true.
73  enum { NumLowBitsAvailable = 2 };
74 };
75 
76 // Provide PointerLikeTypeTraits for const things.
77 template <typename T> struct PointerLikeTypeTraits<const T> {
79 
80  static inline const void *getAsVoidPointer(const T P) {
81  return NonConst::getAsVoidPointer(P);
82  }
83  static inline const T getFromVoidPointer(const void *P) {
84  return NonConst::getFromVoidPointer(const_cast<void *>(P));
85  }
86  enum { NumLowBitsAvailable = NonConst::NumLowBitsAvailable };
87 };
88 
89 // Provide PointerLikeTypeTraits for const pointers.
90 template <typename T> struct PointerLikeTypeTraits<const T *> {
92 
93  static inline const void *getAsVoidPointer(const T *P) {
94  return NonConst::getAsVoidPointer(const_cast<T *>(P));
95  }
96  static inline const T *getFromVoidPointer(const void *P) {
97  return NonConst::getFromVoidPointer(const_cast<void *>(P));
98  }
99  enum { NumLowBitsAvailable = NonConst::NumLowBitsAvailable };
100 };
101 
102 // Provide PointerLikeTypeTraits for uintptr_t.
103 template <> struct PointerLikeTypeTraits<uintptr_t> {
104  static inline void *getAsVoidPointer(uintptr_t P) {
105  return reinterpret_cast<void *>(P);
106  }
107  static inline uintptr_t getFromVoidPointer(void *P) {
108  return reinterpret_cast<uintptr_t>(P);
109  }
110  // No bits are available!
111  enum { NumLowBitsAvailable = 0 };
112 };
113 
114 } // end namespace llvm
115 
116 #endif
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
A tiny meta function to compute the log2 of a compile time constant.
A traits type that is used to handle pointer types and things that are just wrappers for pointers as ...
static const T * getFromVoidPointer(const void *P)
static const void * getAsVoidPointer(const T *P)
#define P(N)
static const T getFromVoidPointer(const void *P)
static const void * getAsVoidPointer(const T P)
aarch64 promote const