LLVM  4.0.0
PointerEmbeddedInt.h
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1 //===- llvm/ADT/PointerEmbeddedInt.h ----------------------------*- 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 #ifndef LLVM_ADT_POINTEREMBEDDEDINT_H
11 #define LLVM_ADT_POINTEREMBEDDEDINT_H
12 
13 #include "llvm/ADT/DenseMapInfo.h"
16 #include <climits>
17 
18 namespace llvm {
19 
20 /// Utility to embed an integer into a pointer-like type. This is specifically
21 /// intended to allow embedding integers where fewer bits are required than
22 /// exist in a pointer, and the integer can participate in abstractions along
23 /// side other pointer-like types. For example it can be placed into a \c
24 /// PointerSumType or \c PointerUnion.
25 ///
26 /// Note that much like pointers, an integer value of zero has special utility
27 /// due to boolean conversions. For example, a non-null value can be tested for
28 /// in the above abstractions without testing the particular active member.
29 /// Also, the default constructed value zero initializes the integer.
30 template <typename IntT, int Bits = sizeof(IntT) * CHAR_BIT>
32  uintptr_t Value;
33 
34  // Note: This '<' is correct; using '<=' would result in some shifts
35  // overflowing their storage types.
36  static_assert(Bits < sizeof(uintptr_t) * CHAR_BIT,
37  "Cannot embed more bits than we have in a pointer!");
38 
39  enum : uintptr_t {
40  // We shift as many zeros into the value as we can while preserving the
41  // number of bits desired for the integer.
42  Shift = sizeof(uintptr_t) * CHAR_BIT - Bits,
43 
44  // We also want to be able to mask out the preserved bits for asserts.
45  Mask = static_cast<uintptr_t>(-1) << Bits
46  };
47 
48  struct RawValueTag {
49  explicit RawValueTag() = default;
50  };
51 
53 
54  explicit PointerEmbeddedInt(uintptr_t Value, RawValueTag) : Value(Value) {}
55 
56 public:
58 
60  *this = I;
61  }
62 
64  assert((std::is_signed<IntT>::value ? llvm::isInt<Bits>(I)
65  : llvm::isUInt<Bits>(I)) &&
66  "Integer has bits outside those preserved!");
67  Value = static_cast<uintptr_t>(I) << Shift;
68  return *this;
69  }
70 
71  // Note that this implicit conversion additionally allows all of the basic
72  // comparison operators to work transparently, etc.
73  operator IntT() const {
74  if (std::is_signed<IntT>::value)
75  return static_cast<IntT>(static_cast<intptr_t>(Value) >> Shift);
76  return static_cast<IntT>(Value >> Shift);
77  }
78 };
79 
80 // Provide pointer like traits to support use with pointer unions and sum
81 // types.
82 template <typename IntT, int Bits>
85 
86 public:
87  static inline void *getAsVoidPointer(const T &P) {
88  return reinterpret_cast<void *>(P.Value);
89  }
90  static inline T getFromVoidPointer(void *P) {
91  return T(reinterpret_cast<uintptr_t>(P), typename T::RawValueTag());
92  }
93  static inline T getFromVoidPointer(const void *P) {
94  return T(reinterpret_cast<uintptr_t>(P), typename T::RawValueTag());
95  }
96 
97  enum { NumLowBitsAvailable = T::Shift };
98 };
99 
100 // Teach DenseMap how to use PointerEmbeddedInt objects as keys if the Int type
101 // itself can be a key.
102 template <typename IntT, int Bits>
105 
107 
108  static inline T getEmptyKey() { return IntInfo::getEmptyKey(); }
109  static inline T getTombstoneKey() { return IntInfo::getTombstoneKey(); }
110  static unsigned getHashValue(const T &Arg) {
111  return IntInfo::getHashValue(Arg);
112  }
113  static bool isEqual(const T &LHS, const T &RHS) { return LHS == RHS; }
114 };
115 }
116 
117 #endif
A traits type that is used to handle pointer types and things that are just wrappers for pointers as ...
Utility to embed an integer into a pointer-like type.
#define T
PointerEmbeddedInt & operator=(IntT I)
#define P(N)
static bool isEqual(const T &LHS, const T &RHS)
#define I(x, y, z)
Definition: MD5.cpp:54
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
LLVM Value Representation.
Definition: Value.h:71