1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
|
// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_ADDRESS_MAP_H_
#define V8_ADDRESS_MAP_H_
#include "src/assert-scope.h"
#include "src/base/hashmap.h"
#include "src/objects.h"
namespace v8 {
namespace internal {
class AddressMapBase {
protected:
static void SetValue(base::HashMap::Entry* entry, uint32_t v) {
entry->value = reinterpret_cast<void*>(v);
}
static uint32_t GetValue(base::HashMap::Entry* entry) {
return static_cast<uint32_t>(reinterpret_cast<intptr_t>(entry->value));
}
inline static base::HashMap::Entry* LookupEntry(base::HashMap* map,
HeapObject* obj,
bool insert) {
if (insert) {
map->LookupOrInsert(Key(obj), Hash(obj));
}
return map->Lookup(Key(obj), Hash(obj));
}
private:
static uint32_t Hash(HeapObject* obj) {
return static_cast<int32_t>(reinterpret_cast<intptr_t>(obj->address()));
}
static void* Key(HeapObject* obj) {
return reinterpret_cast<void*>(obj->address());
}
};
class RootIndexMap : public AddressMapBase {
public:
explicit RootIndexMap(Isolate* isolate);
static const int kInvalidRootIndex = -1;
int Lookup(HeapObject* obj) {
base::HashMap::Entry* entry = LookupEntry(map_, obj, false);
if (entry) return GetValue(entry);
return kInvalidRootIndex;
}
private:
base::HashMap* map_;
DISALLOW_COPY_AND_ASSIGN(RootIndexMap);
};
class SerializerReference {
public:
SerializerReference() : bitfield_(Special(kInvalidValue)) {}
static SerializerReference FromBitfield(uint32_t bitfield) {
return SerializerReference(bitfield);
}
static SerializerReference BackReference(AllocationSpace space,
uint32_t chunk_index,
uint32_t chunk_offset) {
DCHECK(IsAligned(chunk_offset, kObjectAlignment));
DCHECK_NE(LO_SPACE, space);
return SerializerReference(
SpaceBits::encode(space) | ChunkIndexBits::encode(chunk_index) |
ChunkOffsetBits::encode(chunk_offset >> kObjectAlignmentBits));
}
static SerializerReference MapReference(uint32_t index) {
return SerializerReference(SpaceBits::encode(MAP_SPACE) |
ValueIndexBits::encode(index));
}
static SerializerReference LargeObjectReference(uint32_t index) {
return SerializerReference(SpaceBits::encode(LO_SPACE) |
ValueIndexBits::encode(index));
}
static SerializerReference AttachedReference(uint32_t index) {
return SerializerReference(SpaceBits::encode(kAttachedReferenceSpace) |
ValueIndexBits::encode(index));
}
static SerializerReference DummyReference() {
return SerializerReference(Special(kDummyValue));
}
bool is_valid() const { return bitfield_ != Special(kInvalidValue); }
bool is_back_reference() const {
return SpaceBits::decode(bitfield_) <= LAST_SPACE;
}
AllocationSpace space() const {
DCHECK(is_back_reference());
return static_cast<AllocationSpace>(SpaceBits::decode(bitfield_));
}
uint32_t chunk_offset() const {
DCHECK(is_back_reference());
return ChunkOffsetBits::decode(bitfield_) << kObjectAlignmentBits;
}
uint32_t map_index() const {
DCHECK(is_back_reference());
return ValueIndexBits::decode(bitfield_);
}
uint32_t large_object_index() const {
DCHECK(is_back_reference());
return ValueIndexBits::decode(bitfield_);
}
uint32_t chunk_index() const {
DCHECK(is_back_reference());
return ChunkIndexBits::decode(bitfield_);
}
uint32_t back_reference() const {
DCHECK(is_back_reference());
return bitfield_ & (ChunkOffsetBits::kMask | ChunkIndexBits::kMask);
}
bool is_attached_reference() const {
return SpaceBits::decode(bitfield_) == kAttachedReferenceSpace;
}
int attached_reference_index() const {
DCHECK(is_attached_reference());
return ValueIndexBits::decode(bitfield_);
}
private:
explicit SerializerReference(uint32_t bitfield) : bitfield_(bitfield) {}
inline static uint32_t Special(int value) {
return SpaceBits::encode(kSpecialValueSpace) |
ValueIndexBits::encode(value);
}
// We use the 32-bit bitfield to encode either a back reference, a special
// value, or an attached reference index.
// Back reference:
// [ Space index ] [ Chunk index ] [ Chunk offset ]
// [ LO_SPACE ] [ large object index ]
// Special value
// [ kSpecialValueSpace ] [ Special value index ]
// Attached reference
// [ kAttachedReferenceSpace ] [ Attached reference index ]
static const int kChunkOffsetSize = kPageSizeBits - kObjectAlignmentBits;
static const int kChunkIndexSize = 32 - kChunkOffsetSize - kSpaceTagSize;
static const int kValueIndexSize = kChunkOffsetSize + kChunkIndexSize;
static const int kSpecialValueSpace = LAST_SPACE + 1;
static const int kAttachedReferenceSpace = kSpecialValueSpace + 1;
STATIC_ASSERT(kAttachedReferenceSpace < (1 << kSpaceTagSize));
static const int kInvalidValue = 0;
static const int kDummyValue = 1;
// The chunk offset can also be used to encode the index of special values.
class ChunkOffsetBits : public BitField<uint32_t, 0, kChunkOffsetSize> {};
class ChunkIndexBits
: public BitField<uint32_t, ChunkOffsetBits::kNext, kChunkIndexSize> {};
class ValueIndexBits : public BitField<uint32_t, 0, kValueIndexSize> {};
STATIC_ASSERT(ChunkIndexBits::kNext == ValueIndexBits::kNext);
class SpaceBits : public BitField<int, kValueIndexSize, kSpaceTagSize> {};
STATIC_ASSERT(SpaceBits::kNext == 32);
uint32_t bitfield_;
friend class SerializerReferenceMap;
};
// Mapping objects to their location after deserialization.
// This is used during building, but not at runtime by V8.
class SerializerReferenceMap : public AddressMapBase {
public:
SerializerReferenceMap()
: no_allocation_(), map_(), attached_reference_index_(0) {}
SerializerReference Lookup(HeapObject* obj) {
base::HashMap::Entry* entry = LookupEntry(&map_, obj, false);
return entry ? SerializerReference(GetValue(entry)) : SerializerReference();
}
void Add(HeapObject* obj, SerializerReference b) {
DCHECK(b.is_valid());
DCHECK_NULL(LookupEntry(&map_, obj, false));
base::HashMap::Entry* entry = LookupEntry(&map_, obj, true);
SetValue(entry, b.bitfield_);
}
SerializerReference AddAttachedReference(HeapObject* attached_reference) {
SerializerReference reference =
SerializerReference::AttachedReference(attached_reference_index_++);
Add(attached_reference, reference);
return reference;
}
private:
DisallowHeapAllocation no_allocation_;
base::HashMap map_;
int attached_reference_index_;
DISALLOW_COPY_AND_ASSIGN(SerializerReferenceMap);
};
} // namespace internal
} // namespace v8
#endif // V8_ADDRESS_MAP_H_
|
