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 MaskAndShiftConstants : 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 static constexpr int NumLowBitsAvailable =
239 PtrTraits::NumLowBitsAvailable - IntBits;
240};
241
242} // end namespace llvm
243
244#endif // LLVM_ADT_POINTERINTPAIR_H
245