Line data Source code
1 : // Copyright 2017 the V8 project authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : #ifndef V8_OBJECTS_DESCRIPTOR_ARRAY_H_
6 : #define V8_OBJECTS_DESCRIPTOR_ARRAY_H_
7 :
8 : #include "src/objects.h"
9 : #include "src/objects/fixed-array.h"
10 : #include "src/objects/struct.h"
11 : #include "src/utils.h"
12 :
13 : // Has to be the last include (doesn't have include guards):
14 : #include "src/objects/object-macros.h"
15 :
16 : namespace v8 {
17 : namespace internal {
18 :
19 : template <typename T>
20 : class Handle;
21 :
22 : class Isolate;
23 :
24 : // An EnumCache is a pair used to hold keys and indices caches.
25 : class EnumCache : public Tuple2 {
26 : public:
27 : DECL_ACCESSORS(keys, FixedArray)
28 : DECL_ACCESSORS(indices, FixedArray)
29 :
30 : DECL_CAST(EnumCache)
31 :
32 : // Layout description.
33 : static const int kKeysOffset = kValue1Offset;
34 : static const int kIndicesOffset = kValue2Offset;
35 :
36 392 : OBJECT_CONSTRUCTORS(EnumCache, Tuple2);
37 : };
38 :
39 : // A DescriptorArray is a custom array that holds instance descriptors.
40 : // It has the following layout:
41 : // Header:
42 : // [16:0 bits]: number_of_all_descriptors (including slack)
43 : // [32:16 bits]: number_of_descriptors
44 : // [48:32 bits]: raw_number_of_marked_descriptors (used by GC)
45 : // [64:48 bits]: alignment filler
46 : // [kEnumCacheOffset]: enum cache
47 : // Elements:
48 : // [kHeaderSize + 0]: first key (and internalized String)
49 : // [kHeaderSize + 1]: first descriptor details (see PropertyDetails)
50 : // [kHeaderSize + 2]: first value for constants / Smi(1) when not used
51 : // Slack:
52 : // [kHeaderSize + number of descriptors * 3]: start of slack
53 : // The "value" fields store either values or field types. A field type is either
54 : // FieldType::None(), FieldType::Any() or a weak reference to a Map. All other
55 : // references are strong.
56 : class DescriptorArray : public HeapObject {
57 : public:
58 : DECL_INT16_ACCESSORS(number_of_all_descriptors)
59 : DECL_INT16_ACCESSORS(number_of_descriptors)
60 : inline int16_t number_of_slack_descriptors() const;
61 : inline int number_of_entries() const;
62 : DECL_ACCESSORS(enum_cache, EnumCache)
63 :
64 : void ClearEnumCache();
65 : inline void CopyEnumCacheFrom(DescriptorArray array);
66 : static void InitializeOrChangeEnumCache(Handle<DescriptorArray> descriptors,
67 : Isolate* isolate,
68 : Handle<FixedArray> keys,
69 : Handle<FixedArray> indices);
70 :
71 : // Accessors for fetching instance descriptor at descriptor number.
72 : inline Name GetKey(int descriptor_number) const;
73 : inline Object GetStrongValue(int descriptor_number);
74 : inline void SetValue(int descriptor_number, Object value);
75 : inline MaybeObject GetValue(int descriptor_number);
76 : inline PropertyDetails GetDetails(int descriptor_number);
77 : inline int GetFieldIndex(int descriptor_number);
78 : inline FieldType GetFieldType(int descriptor_number);
79 :
80 : inline Name GetSortedKey(int descriptor_number);
81 : inline int GetSortedKeyIndex(int descriptor_number);
82 : inline void SetSortedKey(int pointer, int descriptor_number);
83 :
84 : // Accessor for complete descriptor.
85 : inline void Set(int descriptor_number, Descriptor* desc);
86 : inline void Set(int descriptor_number, Name key, MaybeObject value,
87 : PropertyDetails details);
88 : void Replace(int descriptor_number, Descriptor* descriptor);
89 :
90 : // Generalizes constness, representation and field type of all field
91 : // descriptors.
92 : void GeneralizeAllFields();
93 :
94 : // Append automatically sets the enumeration index. This should only be used
95 : // to add descriptors in bulk at the end, followed by sorting the descriptor
96 : // array.
97 : inline void Append(Descriptor* desc);
98 :
99 : static Handle<DescriptorArray> CopyUpTo(Isolate* isolate,
100 : Handle<DescriptorArray> desc,
101 : int enumeration_index, int slack = 0);
102 :
103 : static Handle<DescriptorArray> CopyUpToAddAttributes(
104 : Isolate* isolate, Handle<DescriptorArray> desc, int enumeration_index,
105 : PropertyAttributes attributes, int slack = 0);
106 :
107 : static Handle<DescriptorArray> CopyForFastObjectClone(
108 : Isolate* isolate, Handle<DescriptorArray> desc, int enumeration_index,
109 : int slack = 0);
110 :
111 : // Sort the instance descriptors by the hash codes of their keys.
112 : void Sort();
113 :
114 : // Search the instance descriptors for given name.
115 : V8_INLINE int Search(Name name, int number_of_own_descriptors);
116 : V8_INLINE int Search(Name name, Map map);
117 :
118 : // As the above, but uses DescriptorLookupCache and updates it when
119 : // necessary.
120 : V8_INLINE int SearchWithCache(Isolate* isolate, Name name, Map map);
121 :
122 : bool IsEqualUpTo(DescriptorArray desc, int nof_descriptors);
123 :
124 : // Allocates a DescriptorArray, but returns the singleton
125 : // empty descriptor array object if number_of_descriptors is 0.
126 : static Handle<DescriptorArray> Allocate(
127 : Isolate* isolate, int nof_descriptors, int slack,
128 : PretenureFlag pretenure = NOT_TENURED);
129 :
130 : void Initialize(EnumCache enum_cache, HeapObject undefined_value,
131 : int nof_descriptors, int slack);
132 :
133 : DECL_CAST(DescriptorArray)
134 :
135 : // Constant for denoting key was not found.
136 : static const int kNotFound = -1;
137 :
138 : // Layout description.
139 : #define DESCRIPTOR_ARRAY_FIELDS(V) \
140 : V(kNumberOfAllDescriptorsOffset, kUInt16Size) \
141 : V(kNumberOfDescriptorsOffset, kUInt16Size) \
142 : V(kRawNumberOfMarkedDescriptorsOffset, kUInt16Size) \
143 : V(kFiller16BitsOffset, kUInt16Size) \
144 : V(kPointersStartOffset, 0) \
145 : V(kEnumCacheOffset, kTaggedSize) \
146 : V(kHeaderSize, 0)
147 :
148 : DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize,
149 : DESCRIPTOR_ARRAY_FIELDS)
150 : #undef DESCRIPTOR_ARRAY_FIELDS
151 :
152 : STATIC_ASSERT(IsAligned(kPointersStartOffset, kTaggedSize));
153 : STATIC_ASSERT(IsAligned(kHeaderSize, kTaggedSize));
154 :
155 : // Garbage collection support.
156 : DECL_INT16_ACCESSORS(raw_number_of_marked_descriptors)
157 : // Atomic compare-and-swap operation on the raw_number_of_marked_descriptors.
158 : int16_t CompareAndSwapRawNumberOfMarkedDescriptors(int16_t expected,
159 : int16_t value);
160 : int16_t UpdateNumberOfMarkedDescriptors(unsigned mark_compact_epoch,
161 : int16_t number_of_marked_descriptors);
162 :
163 56 : static constexpr int SizeFor(int number_of_all_descriptors) {
164 92389292 : return offset(number_of_all_descriptors * kEntrySize);
165 : }
166 : static constexpr int OffsetOfDescriptorAt(int descriptor) {
167 58401564 : return offset(descriptor * kEntrySize);
168 : }
169 : inline ObjectSlot GetFirstPointerSlot();
170 : inline ObjectSlot GetDescriptorSlot(int descriptor);
171 : inline ObjectSlot GetKeySlot(int descriptor);
172 : inline MaybeObjectSlot GetValueSlot(int descriptor);
173 :
174 : typedef FlexibleWeakBodyDescriptor<kPointersStartOffset> BodyDescriptor;
175 :
176 : // Layout of descriptor.
177 : // Naming is consistent with Dictionary classes for easy templating.
178 : static const int kEntryKeyIndex = 0;
179 : static const int kEntryDetailsIndex = 1;
180 : static const int kEntryValueIndex = 2;
181 : static const int kEntrySize = 3;
182 :
183 : // Print all the descriptors.
184 : void PrintDescriptors(std::ostream& os);
185 : void PrintDescriptorDetails(std::ostream& os, int descriptor,
186 : PropertyDetails::PrintMode mode);
187 :
188 : DECL_PRINTER(DescriptorArray)
189 : DECL_VERIFIER(DescriptorArray)
190 :
191 : #ifdef DEBUG
192 : // Is the descriptor array sorted and without duplicates?
193 : bool IsSortedNoDuplicates(int valid_descriptors = -1);
194 :
195 : // Are two DescriptorArrays equal?
196 : bool IsEqualTo(DescriptorArray other);
197 : #endif
198 :
199 784 : static constexpr int ToDetailsIndex(int descriptor_number) {
200 5365016001 : return (descriptor_number * kEntrySize) + kEntryDetailsIndex;
201 : }
202 :
203 : // Conversion from descriptor number to array indices.
204 5168 : static constexpr int ToKeyIndex(int descriptor_number) {
205 1187268572 : return (descriptor_number * kEntrySize) + kEntryKeyIndex;
206 : }
207 :
208 4816 : static constexpr int ToValueIndex(int descriptor_number) {
209 289370104 : return (descriptor_number * kEntrySize) + kEntryValueIndex;
210 : }
211 :
212 : private:
213 : DECL_INT16_ACCESSORS(filler16bits)
214 : // Low-level per-element accessors.
215 56 : static constexpr int offset(int index) {
216 6992475237 : return kHeaderSize + index * kTaggedSize;
217 : }
218 : inline int length() const;
219 : inline MaybeObject get(int index) const;
220 : inline void set(int index, MaybeObject value);
221 :
222 : // Transfer a complete descriptor from the src descriptor array to this
223 : // descriptor array.
224 : void CopyFrom(int index, DescriptorArray src);
225 :
226 : // Swap first and second descriptor.
227 : inline void SwapSortedKeys(int first, int second);
228 :
229 81541815 : OBJECT_CONSTRUCTORS(DescriptorArray, HeapObject);
230 : };
231 :
232 : class NumberOfMarkedDescriptors {
233 : public:
234 : // Bit positions for |bit_field|.
235 : #define BIT_FIELD_FIELDS(V, _) \
236 : V(Epoch, unsigned, 2, _) \
237 : V(Marked, int16_t, 14, _)
238 : DEFINE_BIT_FIELDS(BIT_FIELD_FIELDS)
239 : #undef BIT_FIELD_FIELDS
240 : static const int kMaxNumberOfMarkedDescriptors = Marked::kMax;
241 : // Decodes the raw value of the number of marked descriptors for the
242 : // given mark compact garbage collection epoch.
243 : static inline int16_t decode(unsigned mark_compact_epoch, int16_t raw_value) {
244 6 : unsigned epoch_from_value = Epoch::decode(static_cast<uint16_t>(raw_value));
245 : int16_t marked_from_value =
246 : Marked::decode(static_cast<uint16_t>(raw_value));
247 46851859 : unsigned actual_epoch = mark_compact_epoch & Epoch::kMask;
248 46851865 : if (actual_epoch == epoch_from_value) return marked_from_value;
249 : // If the epochs do not match, then either the raw_value is zero (freshly
250 : // allocated descriptor array) or the epoch from value lags by 1.
251 : DCHECK_IMPLIES(raw_value != 0,
252 : Epoch::decode(epoch_from_value + 1) == actual_epoch);
253 : // Not matching epochs means that the no descriptors were marked in the
254 : // current epoch.
255 : return 0;
256 : }
257 :
258 : // Encodes the number of marked descriptors for the given mark compact
259 : // garbage collection epoch.
260 : static inline int16_t encode(unsigned mark_compact_epoch, int16_t value) {
261 : // TODO(ulan): avoid casting to int16_t by adding support for uint16_t
262 : // atomics.
263 : return static_cast<int16_t>(
264 : Epoch::encode(mark_compact_epoch & Epoch::kMask) |
265 75198862 : Marked::encode(value));
266 : }
267 : };
268 :
269 : } // namespace internal
270 : } // namespace v8
271 :
272 : #include "src/objects/object-macros-undef.h"
273 :
274 : #endif // V8_OBJECTS_DESCRIPTOR_ARRAY_H_
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