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/PointerLikeTypeTraits.h"
18#include <cassert>
19#include <cstdint>
20#include <limits>
21
22namespace llvm {
23
24template <typename T> struct DenseMapInfo;
25template <typename PointerT, unsigned IntBits, typename PtrTraits>
26struct PointerIntPairInfo;
27
28/// PointerIntPair - This class implements a pair of a pointer and small
29/// integer. It is designed to represent this in the space required by one
30/// pointer by bitmangling the integer into the low part of the pointer. This
31/// can only be done for small integers: typically up to 3 bits, but it depends
32/// on the number of bits available according to PointerLikeTypeTraits for the
33/// type.
34///
35/// Note that PointerIntPair always puts the IntVal part in the highest bits
36/// possible. For example, PointerIntPair<void*, 1, bool> will put the bit for
37/// the bool into bit #2, not bit #0, which allows the low two bits to be used
38/// for something else. For example, this allows:
39/// PointerIntPair<PointerIntPair<void*, 1, bool>, 1, bool>
40/// ... and the two bools will land in different bits.
41template <typename PointerTy, unsigned IntBits, typename IntType = unsigned,
42 typename PtrTraits = PointerLikeTypeTraits<PointerTy>,
43 typename Info = PointerIntPairInfo<PointerTy, IntBits, PtrTraits>>
44class PointerIntPair {
45 // Used by MSVC visualizer and generally helpful for debugging/visualizing.
46 using InfoTy = Info;
47 intptr_t Value = 0;
48
49public:
50 constexpr PointerIntPair() = default;
51
52 PointerIntPair(PointerTy PtrVal, IntType IntVal) {
53 setPointerAndInt(PtrVal, IntVal);
54 }
55
56 explicit PointerIntPair(PointerTy PtrVal) { initWithPointer(PtrVal); }
57
58 PointerTy getPointer() const { return Info::getPointer(Value); }
59
60 IntType getInt() const { return (IntType)Info::getInt(Value); }
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
92 void setFromOpaqueValue(void *Val) {
93 Value = reinterpret_cast<intptr_t>(Val);
94 }
95
96 static PointerIntPair getFromOpaqueValue(void *V) {
97 PointerIntPair P;
98 P.setFromOpaqueValue(V);
99 return P;
100 }
101
102 // Allow PointerIntPairs to be created from const void * if and only if the
103 // pointer type could be created from a const void *.
104 static PointerIntPair getFromOpaqueValue(const void *V) {
105 (void)PtrTraits::getFromVoidPointer(V);
106 return getFromOpaqueValue(const_cast<void *>(V));
107 }
108
109 bool operator==(const PointerIntPair &RHS) const {
110 return Value == RHS.Value;
111 }
112
113 bool operator!=(const PointerIntPair &RHS) const {
114 return Value != RHS.Value;
115 }
116
117 bool operator<(const PointerIntPair &RHS) const { return Value < RHS.Value; }
118 bool operator>(const PointerIntPair &RHS) const { return Value > RHS.Value; }
119
120 bool operator<=(const PointerIntPair &RHS) const {
121 return Value <= RHS.Value;
122 }
123
124 bool operator>=(const PointerIntPair &RHS) const {
125 return Value >= RHS.Value;
126 }
127};
128
129template <typename PointerT, unsigned IntBits, typename PtrTraits>
130struct PointerIntPairInfo {
131 static_assert(PtrTraits::NumLowBitsAvailable <
132 std::numeric_limits<uintptr_t>::digits,
133 "cannot use a pointer type that has all bits free");
134 static_assert(IntBits <= PtrTraits::NumLowBitsAvailable,
135 "PointerIntPair with integer size too large for pointer");
136 enum : uintptr_t {
137 /// PointerBitMask - The bits that come from the pointer.
138 PointerBitMask =
139 ~(uintptr_t)(((intptr_t)1 << PtrTraits::NumLowBitsAvailable) - 1),
140
141 /// IntShift - The number of low bits that we reserve for other uses, and
142 /// keep zero.
143 IntShift = (uintptr_t)PtrTraits::NumLowBitsAvailable - IntBits,
144
145 /// IntMask - This is the unshifted mask for valid bits of the int type.
146 IntMask = (uintptr_t)(((intptr_t)1 << IntBits) - 1),
147
148 // ShiftedIntMask - This is the bits for the integer shifted in place.
149 ShiftedIntMask = (uintptr_t)(IntMask << IntShift)
150 };
151
152 static PointerT getPointer(intptr_t Value) {
153 return PtrTraits::getFromVoidPointer(
154 reinterpret_cast<void *>(Value & PointerBitMask));
155 }
156
157 static intptr_t getInt(intptr_t Value) {
158 return (Value >> IntShift) & IntMask;
159 }
160
161 static intptr_t updatePointer(intptr_t OrigValue, PointerT Ptr) {
162 intptr_t PtrWord =
163 reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(Ptr));
164 assert((PtrWord & ~PointerBitMask) == 0 &&
165 "Pointer is not sufficiently aligned");
166 // Preserve all low bits, just update the pointer.
167 return PtrWord | (OrigValue & ~PointerBitMask);
168 }
169
170 static intptr_t updateInt(intptr_t OrigValue, intptr_t Int) {
171 intptr_t IntWord = static_cast<intptr_t>(Int);
172 assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
173
174 // Preserve all bits other than the ones we are updating.
175 return (OrigValue & ~ShiftedIntMask) | IntWord << IntShift;
176 }
177};
178
179template <typename T> struct isPodLike;
180template <typename PointerTy, unsigned IntBits, typename IntType>
181struct isPodLike<PointerIntPair<PointerTy, IntBits, IntType>> {
182 static const bool value = true;
183};
184
185// Provide specialization of DenseMapInfo for PointerIntPair.
186template <typename PointerTy, unsigned IntBits, typename IntType>
187struct DenseMapInfo<PointerIntPair<PointerTy, IntBits, IntType>> {
188 using Ty = PointerIntPair<PointerTy, IntBits, IntType>;
189
190 static Ty getEmptyKey() {
191 uintptr_t Val = static_cast<uintptr_t>(-1);
192 Val <<= PointerLikeTypeTraits<Ty>::NumLowBitsAvailable;
193 return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
194 }
195
196 static Ty getTombstoneKey() {
197 uintptr_t Val = static_cast<uintptr_t>(-2);
198 Val <<= PointerLikeTypeTraits<PointerTy>::NumLowBitsAvailable;
199 return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
200 }
201
202 static unsigned getHashValue(Ty V) {
203 uintptr_t IV = reinterpret_cast<uintptr_t>(V.getOpaqueValue());
204 return unsigned(IV) ^ unsigned(IV >> 9);
205 }
206
207 static bool isEqual(const Ty &LHS, const Ty &RHS) { return LHS == RHS; }
208};
209
210// Teach SmallPtrSet that PointerIntPair is "basically a pointer".
211template <typename PointerTy, unsigned IntBits, typename IntType,
212 typename PtrTraits>
213struct PointerLikeTypeTraits<
214 PointerIntPair<PointerTy, IntBits, IntType, PtrTraits>> {
215 static inline void *
216 getAsVoidPointer(const PointerIntPair<PointerTy, IntBits, IntType> &P) {
217 return P.getOpaqueValue();
218 }
219
220 static inline PointerIntPair<PointerTy, IntBits, IntType>
221 getFromVoidPointer(void *P) {
222 return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
223 }
224
225 static inline PointerIntPair<PointerTy, IntBits, IntType>
226 getFromVoidPointer(const void *P) {
227 return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
228 }
229
230 enum { NumLowBitsAvailable = PtrTraits::NumLowBitsAvailable - IntBits };
231};
232
233} // end namespace llvm
234
235#endif // LLVM_ADT_POINTERINTPAIR_H
236