1//===- llvm/ADT/PointerIntPair.h - Pair for pointer and int -----*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the PointerIntPair class.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_ADT_POINTERINTPAIR_H
14#define LLVM_ADT_POINTERINTPAIR_H
15
16#include "llvm/Support/Compiler.h"
17#include "llvm/Support/PointerLikeTypeTraits.h"
18#include "llvm/Support/type_traits.h"
19#include <cassert>
20#include <cstdint>
21#include <limits>
22
23namespace llvm {
24
25template <typename T> struct DenseMapInfo;
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.
42template <typename PointerTy, unsigned IntBits, typename IntType = unsigned,
43          typename PtrTraits = PointerLikeTypeTraits<PointerTy>,
44          typename Info = PointerIntPairInfo<PointerTy, IntBits, PtrTraits>>
45class PointerIntPair {
46  // Used by MSVC visualizer and generally helpful for debugging/visualizing.
47  using InfoTy = Info;
48  intptr_t Value = 0;
49
50public:
51  constexpr PointerIntPair() = default;
52
53  PointerIntPair(PointerTy PtrVal, IntType IntVal) {
54    setPointerAndInt(PtrVal, IntVal);
55  }
56
57  explicit PointerIntPair(PointerTy PtrVal) { initWithPointer(PtrVal); }
58
59  PointerTy getPointer() const { return Info::getPointer(Value); }
60
61  IntType getInt() const { return (IntType)Info::getInt(Value); }
62
63  void setPointer(PointerTy PtrVal) LLVM_LVALUE_FUNCTION {
64    Value = Info::updatePointer(Value, PtrVal);
65  }
66
67  void setInt(IntType IntVal) LLVM_LVALUE_FUNCTION {
68    Value = Info::updateInt(Value, static_cast<intptr_t>(IntVal));
69  }
70
71  void initWithPointer(PointerTy PtrVal) LLVM_LVALUE_FUNCTION {
72    Value = Info::updatePointer(0, PtrVal);
73  }
74
75  void setPointerAndInt(PointerTy PtrVal, IntType IntVal) LLVM_LVALUE_FUNCTION {
76    Value = Info::updateInt(Info::updatePointer(0, PtrVal),
77                            static_cast<intptr_t>(IntVal));
78  }
79
80  PointerTy const *getAddrOfPointer() const {
81    return const_cast<PointerIntPair *>(this)->getAddrOfPointer();
82  }
83
84  PointerTy *getAddrOfPointer() {
85    assert(Value == reinterpret_cast<intptr_t>(getPointer()) &&
86           "Can only return the address if IntBits is cleared and "
87           "PtrTraits doesn't change the pointer");
88    return reinterpret_cast<PointerTy *>(&Value);
89  }
90
91  void *getOpaqueValue() const { return reinterpret_cast<void *>(Value); }
92
93  void setFromOpaqueValue(void *Val) LLVM_LVALUE_FUNCTION {
94    Value = reinterpret_cast<intptr_t>(Val);
95  }
96
97  static PointerIntPair getFromOpaqueValue(void *V) {
98    PointerIntPair P;
99    P.setFromOpaqueValue(V);
100    return P;
101  }
102
103  // Allow PointerIntPairs to be created from const void * if and only if the
104  // pointer type could be created from a const void *.
105  static PointerIntPair getFromOpaqueValue(const void *V) {
106    (void)PtrTraits::getFromVoidPointer(V);
107    return getFromOpaqueValue(const_cast<void *>(V));
108  }
109
110  bool operator==(const PointerIntPair &RHS) const {
111    return Value == RHS.Value;
112  }
113
114  bool operator!=(const PointerIntPair &RHS) const {
115    return Value != RHS.Value;
116  }
117
118  bool operator<(const PointerIntPair &RHS) const { return Value < RHS.Value; }
119  bool operator>(const PointerIntPair &RHS) const { return Value > RHS.Value; }
120
121  bool operator<=(const PointerIntPair &RHS) const {
122    return Value <= RHS.Value;
123  }
124
125  bool operator>=(const PointerIntPair &RHS) const {
126    return Value >= RHS.Value;
127  }
128};
129
130// Specialize is_trivially_copyable to avoid limitation of llvm::is_trivially_copyable
131// when compiled with gcc 4.9.
132template <typename PointerTy, unsigned IntBits, typename IntType,
133          typename PtrTraits,
134          typename Info>
135struct is_trivially_copyable<PointerIntPair<PointerTy, IntBits, IntType, PtrTraits, Info>> : std::true_type {
136#ifdef HAVE_STD_IS_TRIVIALLY_COPYABLE
137  static_assert(std::is_trivially_copyable<PointerIntPair<PointerTy, IntBits, IntType, PtrTraits, Info>>::value,
138                "inconsistent behavior between llvm:: and std:: implementation of is_trivially_copyable");
139#endif
140};
141
142
143template <typename PointerT, unsigned IntBits, typename PtrTraits>
144struct PointerIntPairInfo {
145  static_assert(PtrTraits::NumLowBitsAvailable <
146                    std::numeric_limits<uintptr_t>::digits,
147                "cannot use a pointer type that has all bits free");
148  static_assert(IntBits <= PtrTraits::NumLowBitsAvailable,
149                "PointerIntPair with integer size too large for pointer");
150  enum : uintptr_t {
151    /// PointerBitMask - The bits that come from the pointer.
152    PointerBitMask =
153        ~(uintptr_t)(((intptr_t)1 << PtrTraits::NumLowBitsAvailable) - 1),
154
155    /// IntShift - The number of low bits that we reserve for other uses, and
156    /// keep zero.
157    IntShift = (uintptr_t)PtrTraits::NumLowBitsAvailable - IntBits,
158
159    /// IntMask - This is the unshifted mask for valid bits of the int type.
160    IntMask = (uintptr_t)(((intptr_t)1 << IntBits) - 1),
161
162    // ShiftedIntMask - This is the bits for the integer shifted in place.
163    ShiftedIntMask = (uintptr_t)(IntMask << IntShift)
164  };
165
166  static PointerT getPointer(intptr_t Value) {
167    return PtrTraits::getFromVoidPointer(
168        reinterpret_cast<void *>(Value & PointerBitMask));
169  }
170
171  static intptr_t getInt(intptr_t Value) {
172    return (Value >> IntShift) & IntMask;
173  }
174
175  static intptr_t updatePointer(intptr_t OrigValue, PointerT Ptr) {
176    intptr_t PtrWord =
177        reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(Ptr));
178    assert((PtrWord & ~PointerBitMask) == 0 &&
179           "Pointer is not sufficiently aligned");
180    // Preserve all low bits, just update the pointer.
181    return PtrWord | (OrigValue & ~PointerBitMask);
182  }
183
184  static intptr_t updateInt(intptr_t OrigValue, intptr_t Int) {
185    intptr_t IntWord = static_cast<intptr_t>(Int);
186    assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
187
188    // Preserve all bits other than the ones we are updating.
189    return (OrigValue & ~ShiftedIntMask) | IntWord << IntShift;
190  }
191};
192
193// Provide specialization of DenseMapInfo for PointerIntPair.
194template <typename PointerTy, unsigned IntBits, typename IntType>
195struct DenseMapInfo<PointerIntPair<PointerTy, IntBits, IntType>> {
196  using Ty = PointerIntPair<PointerTy, IntBits, IntType>;
197
198  static Ty getEmptyKey() {
199    uintptr_t Val = static_cast<uintptr_t>(-1);
200    Val <<= PointerLikeTypeTraits<Ty>::NumLowBitsAvailable;
201    return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
202  }
203
204  static Ty getTombstoneKey() {
205    uintptr_t Val = static_cast<uintptr_t>(-2);
206    Val <<= PointerLikeTypeTraits<PointerTy>::NumLowBitsAvailable;
207    return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
208  }
209
210  static unsigned getHashValue(Ty V) {
211    uintptr_t IV = reinterpret_cast<uintptr_t>(V.getOpaqueValue());
212    return unsigned(IV) ^ unsigned(IV >> 9);
213  }
214
215  static bool isEqual(const Ty &LHS, const Ty &RHS) { return LHS == RHS; }
216};
217
218// Teach SmallPtrSet that PointerIntPair is "basically a pointer".
219template <typename PointerTy, unsigned IntBits, typename IntType,
220          typename PtrTraits>
221struct PointerLikeTypeTraits<
222    PointerIntPair<PointerTy, IntBits, IntType, PtrTraits>> {
223  static inline void *
224  getAsVoidPointer(const PointerIntPair<PointerTy, IntBits, IntType> &P) {
225    return P.getOpaqueValue();
226  }
227
228  static inline PointerIntPair<PointerTy, IntBits, IntType>
229  getFromVoidPointer(void *P) {
230    return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
231  }
232
233  static inline PointerIntPair<PointerTy, IntBits, IntType>
234  getFromVoidPointer(const void *P) {
235    return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
236  }
237
238  enum { NumLowBitsAvailable = PtrTraits::NumLowBitsAvailable - IntBits };
239};
240
241} // end namespace llvm
242
243#endif // LLVM_ADT_POINTERINTPAIR_H
244