1//===- llvm/ADT/PointerIntPair.h - Pair for pointer and int -----*- 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 PointerIntPair class.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ADT_POINTERINTPAIR_H
15#define LLVM_ADT_POINTERINTPAIR_H
16
17#include "llvm/Support/Compiler.h"
18#include "llvm/Support/PointerLikeTypeTraits.h"
19#include <cassert>
20#include <limits>
21
22namespace llvm {
23
24template <typename T> struct DenseMapInfo;
25
26template <typename PointerT, unsigned IntBits, typename PtrTraits>
27struct PointerIntPairInfo;
28
29/// PointerIntPair - This class implements a pair of a pointer and small
30/// integer.  It is designed to represent this in the space required by one
31/// pointer by bitmangling the integer into the low part of the pointer.  This
32/// can only be done for small integers: typically up to 3 bits, but it depends
33/// on the number of bits available according to PointerLikeTypeTraits for the
34/// type.
35///
36/// Note that PointerIntPair always puts the IntVal part in the highest bits
37/// possible.  For example, PointerIntPair<void*, 1, bool> will put the bit for
38/// the bool into bit #2, not bit #0, which allows the low two bits to be used
39/// for something else.  For example, this allows:
40///   PointerIntPair<PointerIntPair<void*, 1, bool>, 1, bool>
41/// ... and the two bools will land in different bits.
42///
43template <typename PointerTy, unsigned IntBits, typename IntType = unsigned,
44          typename PtrTraits = PointerLikeTypeTraits<PointerTy>,
45          typename Info = PointerIntPairInfo<PointerTy, IntBits, PtrTraits>>
46class PointerIntPair {
47  intptr_t Value;
48
49public:
50  PointerIntPair() : Value(0) {}
51  PointerIntPair(PointerTy PtrVal, IntType IntVal) {
52    setPointerAndInt(PtrVal, IntVal);
53  }
54  explicit PointerIntPair(PointerTy PtrVal) { initWithPointer(PtrVal); }
55
56  PointerTy getPointer() const { return Info::getPointer(Value); }
57
58  IntType getInt() const {
59    return (IntType)Info::getInt(Value);
60  }
61
62  void setPointer(PointerTy PtrVal) {
63    Value = Info::updatePointer(Value, PtrVal);
64  }
65
66  void setInt(IntType IntVal) {
67    Value = Info::updateInt(Value, static_cast<intptr_t>(IntVal));
68  }
69
70  void initWithPointer(PointerTy PtrVal) {
71    Value = Info::updatePointer(0, PtrVal);
72  }
73
74  void setPointerAndInt(PointerTy PtrVal, IntType IntVal) {
75    Value = Info::updateInt(Info::updatePointer(0, PtrVal),
76                            static_cast<intptr_t>(IntVal));
77  }
78
79  PointerTy const *getAddrOfPointer() const {
80    return const_cast<PointerIntPair *>(this)->getAddrOfPointer();
81  }
82
83  PointerTy *getAddrOfPointer() {
84    assert(Value == reinterpret_cast<intptr_t>(getPointer()) &&
85           "Can only return the address if IntBits is cleared and "
86           "PtrTraits doesn't change the pointer");
87    return reinterpret_cast<PointerTy *>(&Value);
88  }
89
90  void *getOpaqueValue() const { return reinterpret_cast<void *>(Value); }
91  void setFromOpaqueValue(void *Val) {
92    Value = reinterpret_cast<intptr_t>(Val);
93  }
94
95  static PointerIntPair getFromOpaqueValue(void *V) {
96    PointerIntPair P;
97    P.setFromOpaqueValue(V);
98    return P;
99  }
100
101  // Allow PointerIntPairs to be created from const void * if and only if the
102  // pointer type could be created from a const void *.
103  static PointerIntPair getFromOpaqueValue(const void *V) {
104    (void)PtrTraits::getFromVoidPointer(V);
105    return getFromOpaqueValue(const_cast<void *>(V));
106  }
107
108  bool operator==(const PointerIntPair &RHS) const {
109    return Value == RHS.Value;
110  }
111  bool operator!=(const PointerIntPair &RHS) const {
112    return Value != RHS.Value;
113  }
114  bool operator<(const PointerIntPair &RHS) const { return Value < RHS.Value; }
115  bool operator>(const PointerIntPair &RHS) const { return Value > RHS.Value; }
116  bool operator<=(const PointerIntPair &RHS) const {
117    return Value <= RHS.Value;
118  }
119  bool operator>=(const PointerIntPair &RHS) const {
120    return Value >= RHS.Value;
121  }
122};
123
124template <typename PointerT, unsigned IntBits, typename PtrTraits>
125struct PointerIntPairInfo {
126  static_assert(PtrTraits::NumLowBitsAvailable <
127                    std::numeric_limits<uintptr_t>::digits,
128                "cannot use a pointer type that has all bits free");
129  static_assert(IntBits <= PtrTraits::NumLowBitsAvailable,
130                "PointerIntPair with integer size too large for pointer");
131  enum : uintptr_t {
132    /// PointerBitMask - The bits that come from the pointer.
133    PointerBitMask =
134        ~(uintptr_t)(((intptr_t)1 << PtrTraits::NumLowBitsAvailable) - 1),
135
136    /// IntShift - The number of low bits that we reserve for other uses, and
137    /// keep zero.
138    IntShift = (uintptr_t)PtrTraits::NumLowBitsAvailable - IntBits,
139
140    /// IntMask - This is the unshifted mask for valid bits of the int type.
141    IntMask = (uintptr_t)(((intptr_t)1 << IntBits) - 1),
142
143    // ShiftedIntMask - This is the bits for the integer shifted in place.
144    ShiftedIntMask = (uintptr_t)(IntMask << IntShift)
145  };
146
147  static PointerT getPointer(intptr_t Value) {
148    return PtrTraits::getFromVoidPointer(
149        reinterpret_cast<void *>(Value & PointerBitMask));
150  }
151
152  static intptr_t getInt(intptr_t Value) {
153    return (Value >> IntShift) & IntMask;
154  }
155
156  static intptr_t updatePointer(intptr_t OrigValue, PointerT Ptr) {
157    intptr_t PtrWord =
158        reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(Ptr));
159    assert((PtrWord & ~PointerBitMask) == 0 &&
160           "Pointer is not sufficiently aligned");
161    // Preserve all low bits, just update the pointer.
162    return PtrWord | (OrigValue & ~PointerBitMask);
163  }
164
165  static intptr_t updateInt(intptr_t OrigValue, intptr_t Int) {
166    intptr_t IntWord = static_cast<intptr_t>(Int);
167    assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
168
169    // Preserve all bits other than the ones we are updating.
170    return (OrigValue & ~ShiftedIntMask) | IntWord << IntShift;
171  }
172};
173
174template <typename T> struct isPodLike;
175template <typename PointerTy, unsigned IntBits, typename IntType>
176struct isPodLike<PointerIntPair<PointerTy, IntBits, IntType>> {
177  static const bool value = true;
178};
179
180// Provide specialization of DenseMapInfo for PointerIntPair.
181template <typename PointerTy, unsigned IntBits, typename IntType>
182struct DenseMapInfo<PointerIntPair<PointerTy, IntBits, IntType>> {
183  typedef PointerIntPair<PointerTy, IntBits, IntType> Ty;
184  static Ty getEmptyKey() {
185    uintptr_t Val = static_cast<uintptr_t>(-1);
186    Val <<= PointerLikeTypeTraits<Ty>::NumLowBitsAvailable;
187    return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
188  }
189  static Ty getTombstoneKey() {
190    uintptr_t Val = static_cast<uintptr_t>(-2);
191    Val <<= PointerLikeTypeTraits<PointerTy>::NumLowBitsAvailable;
192    return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
193  }
194  static unsigned getHashValue(Ty V) {
195    uintptr_t IV = reinterpret_cast<uintptr_t>(V.getOpaqueValue());
196    return unsigned(IV) ^ unsigned(IV >> 9);
197  }
198  static bool isEqual(const Ty &LHS, const Ty &RHS) { return LHS == RHS; }
199};
200
201// Teach SmallPtrSet that PointerIntPair is "basically a pointer".
202template <typename PointerTy, unsigned IntBits, typename IntType,
203          typename PtrTraits>
204class PointerLikeTypeTraits<
205    PointerIntPair<PointerTy, IntBits, IntType, PtrTraits>> {
206public:
207  static inline void *
208  getAsVoidPointer(const PointerIntPair<PointerTy, IntBits, IntType> &P) {
209    return P.getOpaqueValue();
210  }
211  static inline PointerIntPair<PointerTy, IntBits, IntType>
212  getFromVoidPointer(void *P) {
213    return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
214  }
215  static inline PointerIntPair<PointerTy, IntBits, IntType>
216  getFromVoidPointer(const void *P) {
217    return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
218  }
219  enum { NumLowBitsAvailable = PtrTraits::NumLowBitsAvailable - IntBits };
220};
221
222} // end namespace llvm
223#endif
224