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/PointerLikeTypeTraits.h"
17#include "llvm/Support/type_traits.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
129// Specialize is_trivially_copyable to avoid limitation of llvm::is_trivially_copyable
130// when compiled with gcc 4.9.
131template <typename PointerTy, unsigned IntBits, typename IntType,
132 typename PtrTraits,
133 typename Info>
134struct is_trivially_copyable<PointerIntPair<PointerTy, IntBits, IntType, PtrTraits, Info>> : std::true_type {
135#ifdef HAVE_STD_IS_TRIVIALLY_COPYABLE
136 static_assert(std::is_trivially_copyable<PointerIntPair<PointerTy, IntBits, IntType, PtrTraits, Info>>::value,
137 "inconsistent behavior between llvm:: and std:: implementation of is_trivially_copyable");
138#endif
139};
140
141
142template <typename PointerT, unsigned IntBits, typename PtrTraits>
143struct PointerIntPairInfo {
144 static_assert(PtrTraits::NumLowBitsAvailable <
145 std::numeric_limits<uintptr_t>::digits,
146 "cannot use a pointer type that has all bits free");
147 static_assert(IntBits <= PtrTraits::NumLowBitsAvailable,
148 "PointerIntPair with integer size too large for pointer");
149 enum : uintptr_t {
150 /// PointerBitMask - The bits that come from the pointer.
151 PointerBitMask =
152 ~(uintptr_t)(((intptr_t)1 << PtrTraits::NumLowBitsAvailable) - 1),
153
154 /// IntShift - The number of low bits that we reserve for other uses, and
155 /// keep zero.
156 IntShift = (uintptr_t)PtrTraits::NumLowBitsAvailable - IntBits,
157
158 /// IntMask - This is the unshifted mask for valid bits of the int type.
159 IntMask = (uintptr_t)(((intptr_t)1 << IntBits) - 1),
160
161 // ShiftedIntMask - This is the bits for the integer shifted in place.
162 ShiftedIntMask = (uintptr_t)(IntMask << IntShift)
163 };
164
165 static PointerT getPointer(intptr_t Value) {
166 return PtrTraits::getFromVoidPointer(
167 reinterpret_cast<void *>(Value & PointerBitMask));
168 }
169
170 static intptr_t getInt(intptr_t Value) {
171 return (Value >> IntShift) & IntMask;
172 }
173
174 static intptr_t updatePointer(intptr_t OrigValue, PointerT Ptr) {
175 intptr_t PtrWord =
176 reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(Ptr));
177 assert((PtrWord & ~PointerBitMask) == 0 &&
178 "Pointer is not sufficiently aligned");
179 // Preserve all low bits, just update the pointer.
180 return PtrWord | (OrigValue & ~PointerBitMask);
181 }
182
183 static intptr_t updateInt(intptr_t OrigValue, intptr_t Int) {
184 intptr_t IntWord = static_cast<intptr_t>(Int);
185 assert((IntWord & ~IntMask) == 0 && "Integer too large for field");
186
187 // Preserve all bits other than the ones we are updating.
188 return (OrigValue & ~ShiftedIntMask) | IntWord << IntShift;
189 }
190};
191
192// Provide specialization of DenseMapInfo for PointerIntPair.
193template <typename PointerTy, unsigned IntBits, typename IntType>
194struct DenseMapInfo<PointerIntPair<PointerTy, IntBits, IntType>> {
195 using Ty = PointerIntPair<PointerTy, IntBits, IntType>;
196
197 static Ty getEmptyKey() {
198 uintptr_t Val = static_cast<uintptr_t>(-1);
199 Val <<= PointerLikeTypeTraits<Ty>::NumLowBitsAvailable;
200 return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
201 }
202
203 static Ty getTombstoneKey() {
204 uintptr_t Val = static_cast<uintptr_t>(-2);
205 Val <<= PointerLikeTypeTraits<PointerTy>::NumLowBitsAvailable;
206 return Ty::getFromOpaqueValue(reinterpret_cast<void *>(Val));
207 }
208
209 static unsigned getHashValue(Ty V) {
210 uintptr_t IV = reinterpret_cast<uintptr_t>(V.getOpaqueValue());
211 return unsigned(IV) ^ unsigned(IV >> 9);
212 }
213
214 static bool isEqual(const Ty &LHS, const Ty &RHS) { return LHS == RHS; }
215};
216
217// Teach SmallPtrSet that PointerIntPair is "basically a pointer".
218template <typename PointerTy, unsigned IntBits, typename IntType,
219 typename PtrTraits>
220struct PointerLikeTypeTraits<
221 PointerIntPair<PointerTy, IntBits, IntType, PtrTraits>> {
222 static inline void *
223 getAsVoidPointer(const PointerIntPair<PointerTy, IntBits, IntType> &P) {
224 return P.getOpaqueValue();
225 }
226
227 static inline PointerIntPair<PointerTy, IntBits, IntType>
228 getFromVoidPointer(void *P) {
229 return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
230 }
231
232 static inline PointerIntPair<PointerTy, IntBits, IntType>
233 getFromVoidPointer(const void *P) {
234 return PointerIntPair<PointerTy, IntBits, IntType>::getFromOpaqueValue(P);
235 }
236
237 enum { NumLowBitsAvailable = PtrTraits::NumLowBitsAvailable - IntBits };
238};
239
240} // end namespace llvm
241
242#endif // LLVM_ADT_POINTERINTPAIR_H
243