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