1 // Copyright 2011 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 #include "src/heap/objects-visiting.h"
6
7 #include "src/heap/mark-compact-inl.h"
8 #include "src/heap/objects-visiting-inl.h"
9
10 namespace v8 {
11 namespace internal {
12
13
GetVisitorId(Map * map)14 StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(Map* map) {
15 return GetVisitorId(map->instance_type(), map->instance_size(),
16 FLAG_unbox_double_fields && !map->HasFastPointerLayout());
17 }
18
19
GetVisitorId(int instance_type,int instance_size,bool has_unboxed_fields)20 StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(
21 int instance_type, int instance_size, bool has_unboxed_fields) {
22 if (instance_type < FIRST_NONSTRING_TYPE) {
23 switch (instance_type & kStringRepresentationMask) {
24 case kSeqStringTag:
25 if ((instance_type & kStringEncodingMask) == kOneByteStringTag) {
26 return kVisitSeqOneByteString;
27 } else {
28 return kVisitSeqTwoByteString;
29 }
30
31 case kConsStringTag:
32 if (IsShortcutCandidate(instance_type)) {
33 return kVisitShortcutCandidate;
34 } else {
35 return kVisitConsString;
36 }
37
38 case kSlicedStringTag:
39 return kVisitSlicedString;
40
41 case kExternalStringTag:
42 return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
43 instance_size, has_unboxed_fields);
44 }
45 UNREACHABLE();
46 }
47
48 switch (instance_type) {
49 case BYTE_ARRAY_TYPE:
50 return kVisitByteArray;
51
52 case BYTECODE_ARRAY_TYPE:
53 return kVisitBytecodeArray;
54
55 case FREE_SPACE_TYPE:
56 return kVisitFreeSpace;
57
58 case FIXED_ARRAY_TYPE:
59 return kVisitFixedArray;
60
61 case FIXED_DOUBLE_ARRAY_TYPE:
62 return kVisitFixedDoubleArray;
63
64 case ODDBALL_TYPE:
65 return kVisitOddball;
66
67 case MAP_TYPE:
68 return kVisitMap;
69
70 case CODE_TYPE:
71 return kVisitCode;
72
73 case CELL_TYPE:
74 return kVisitCell;
75
76 case PROPERTY_CELL_TYPE:
77 return kVisitPropertyCell;
78
79 case WEAK_CELL_TYPE:
80 return kVisitWeakCell;
81
82 case TRANSITION_ARRAY_TYPE:
83 return kVisitTransitionArray;
84
85 case JS_WEAK_MAP_TYPE:
86 case JS_WEAK_SET_TYPE:
87 return kVisitJSWeakCollection;
88
89 case JS_REGEXP_TYPE:
90 return kVisitJSRegExp;
91
92 case SHARED_FUNCTION_INFO_TYPE:
93 return kVisitSharedFunctionInfo;
94
95 case JS_PROXY_TYPE:
96 return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
97 instance_size, has_unboxed_fields);
98
99 case SYMBOL_TYPE:
100 return kVisitSymbol;
101
102 case JS_ARRAY_BUFFER_TYPE:
103 return kVisitJSArrayBuffer;
104
105 case JS_OBJECT_TYPE:
106 case JS_ERROR_TYPE:
107 case JS_ARGUMENTS_TYPE:
108 case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
109 case JS_GENERATOR_OBJECT_TYPE:
110 case JS_MODULE_TYPE:
111 case JS_VALUE_TYPE:
112 case JS_DATE_TYPE:
113 case JS_ARRAY_TYPE:
114 case JS_GLOBAL_PROXY_TYPE:
115 case JS_GLOBAL_OBJECT_TYPE:
116 case JS_MESSAGE_OBJECT_TYPE:
117 case JS_TYPED_ARRAY_TYPE:
118 case JS_DATA_VIEW_TYPE:
119 case JS_SET_TYPE:
120 case JS_MAP_TYPE:
121 case JS_SET_ITERATOR_TYPE:
122 case JS_MAP_ITERATOR_TYPE:
123 case JS_PROMISE_TYPE:
124 case JS_BOUND_FUNCTION_TYPE:
125 return GetVisitorIdForSize(kVisitJSObject, kVisitJSObjectGeneric,
126 instance_size, has_unboxed_fields);
127 case JS_API_OBJECT_TYPE:
128 case JS_SPECIAL_API_OBJECT_TYPE:
129 return GetVisitorIdForSize(kVisitJSApiObject, kVisitJSApiObjectGeneric,
130 instance_size, has_unboxed_fields);
131
132 case JS_FUNCTION_TYPE:
133 return kVisitJSFunction;
134
135 case FILLER_TYPE:
136 if (instance_size == kPointerSize) return kVisitDataObjectGeneric;
137 // Fall through.
138 case FOREIGN_TYPE:
139 case HEAP_NUMBER_TYPE:
140 case MUTABLE_HEAP_NUMBER_TYPE:
141 case SIMD128_VALUE_TYPE:
142 return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
143 instance_size, has_unboxed_fields);
144
145 case FIXED_UINT8_ARRAY_TYPE:
146 case FIXED_INT8_ARRAY_TYPE:
147 case FIXED_UINT16_ARRAY_TYPE:
148 case FIXED_INT16_ARRAY_TYPE:
149 case FIXED_UINT32_ARRAY_TYPE:
150 case FIXED_INT32_ARRAY_TYPE:
151 case FIXED_FLOAT32_ARRAY_TYPE:
152 case FIXED_UINT8_CLAMPED_ARRAY_TYPE:
153 return kVisitFixedTypedArray;
154
155 case FIXED_FLOAT64_ARRAY_TYPE:
156 return kVisitFixedFloat64Array;
157
158 #define MAKE_STRUCT_CASE(NAME, Name, name) case NAME##_TYPE:
159 STRUCT_LIST(MAKE_STRUCT_CASE)
160 #undef MAKE_STRUCT_CASE
161 if (instance_type == ALLOCATION_SITE_TYPE) {
162 return kVisitAllocationSite;
163 }
164
165 return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
166 instance_size, has_unboxed_fields);
167
168 default:
169 UNREACHABLE();
170 return kVisitorIdCount;
171 }
172 }
173
174
175 // We don't record weak slots during marking or scavenges. Instead we do it
176 // once when we complete mark-compact cycle. Note that write barrier has no
177 // effect if we are already in the middle of compacting mark-sweep cycle and we
178 // have to record slots manually.
MustRecordSlots(Heap * heap)179 static bool MustRecordSlots(Heap* heap) {
180 return heap->gc_state() == Heap::MARK_COMPACT &&
181 heap->mark_compact_collector()->is_compacting();
182 }
183
184
185 template <class T>
186 struct WeakListVisitor;
187
188
189 template <class T>
VisitWeakList(Heap * heap,Object * list,WeakObjectRetainer * retainer)190 Object* VisitWeakList(Heap* heap, Object* list, WeakObjectRetainer* retainer) {
191 Object* undefined = heap->undefined_value();
192 Object* head = undefined;
193 T* tail = NULL;
194 MarkCompactCollector* collector = heap->mark_compact_collector();
195 bool record_slots = MustRecordSlots(heap);
196
197 while (list != undefined) {
198 // Check whether to keep the candidate in the list.
199 T* candidate = reinterpret_cast<T*>(list);
200
201 Object* retained = retainer->RetainAs(list);
202 if (retained != NULL) {
203 if (head == undefined) {
204 // First element in the list.
205 head = retained;
206 } else {
207 // Subsequent elements in the list.
208 DCHECK(tail != NULL);
209 WeakListVisitor<T>::SetWeakNext(tail, retained);
210 if (record_slots) {
211 Object** next_slot =
212 HeapObject::RawField(tail, WeakListVisitor<T>::WeakNextOffset());
213 collector->RecordSlot(tail, next_slot, retained);
214 }
215 }
216 // Retained object is new tail.
217 DCHECK(!retained->IsUndefined(heap->isolate()));
218 candidate = reinterpret_cast<T*>(retained);
219 tail = candidate;
220
221 // tail is a live object, visit it.
222 WeakListVisitor<T>::VisitLiveObject(heap, tail, retainer);
223
224 } else {
225 WeakListVisitor<T>::VisitPhantomObject(heap, candidate);
226 }
227
228 // Move to next element in the list.
229 list = WeakListVisitor<T>::WeakNext(candidate);
230 }
231
232 // Terminate the list if there is one or more elements.
233 if (tail != NULL) WeakListVisitor<T>::SetWeakNext(tail, undefined);
234 return head;
235 }
236
237
238 template <class T>
ClearWeakList(Heap * heap,Object * list)239 static void ClearWeakList(Heap* heap, Object* list) {
240 Object* undefined = heap->undefined_value();
241 while (list != undefined) {
242 T* candidate = reinterpret_cast<T*>(list);
243 list = WeakListVisitor<T>::WeakNext(candidate);
244 WeakListVisitor<T>::SetWeakNext(candidate, undefined);
245 }
246 }
247
248
249 template <>
250 struct WeakListVisitor<JSFunction> {
SetWeakNextv8::internal::WeakListVisitor251 static void SetWeakNext(JSFunction* function, Object* next) {
252 function->set_next_function_link(next, UPDATE_WEAK_WRITE_BARRIER);
253 }
254
WeakNextv8::internal::WeakListVisitor255 static Object* WeakNext(JSFunction* function) {
256 return function->next_function_link();
257 }
258
WeakNextOffsetv8::internal::WeakListVisitor259 static int WeakNextOffset() { return JSFunction::kNextFunctionLinkOffset; }
260
VisitLiveObjectv8::internal::WeakListVisitor261 static void VisitLiveObject(Heap*, JSFunction*, WeakObjectRetainer*) {}
262
VisitPhantomObjectv8::internal::WeakListVisitor263 static void VisitPhantomObject(Heap*, JSFunction*) {}
264 };
265
266
267 template <>
268 struct WeakListVisitor<Code> {
SetWeakNextv8::internal::WeakListVisitor269 static void SetWeakNext(Code* code, Object* next) {
270 code->set_next_code_link(next, UPDATE_WEAK_WRITE_BARRIER);
271 }
272
WeakNextv8::internal::WeakListVisitor273 static Object* WeakNext(Code* code) { return code->next_code_link(); }
274
WeakNextOffsetv8::internal::WeakListVisitor275 static int WeakNextOffset() { return Code::kNextCodeLinkOffset; }
276
VisitLiveObjectv8::internal::WeakListVisitor277 static void VisitLiveObject(Heap*, Code*, WeakObjectRetainer*) {}
278
VisitPhantomObjectv8::internal::WeakListVisitor279 static void VisitPhantomObject(Heap*, Code*) {}
280 };
281
282
283 template <>
284 struct WeakListVisitor<Context> {
SetWeakNextv8::internal::WeakListVisitor285 static void SetWeakNext(Context* context, Object* next) {
286 context->set(Context::NEXT_CONTEXT_LINK, next, UPDATE_WEAK_WRITE_BARRIER);
287 }
288
WeakNextv8::internal::WeakListVisitor289 static Object* WeakNext(Context* context) {
290 return context->next_context_link();
291 }
292
WeakNextOffsetv8::internal::WeakListVisitor293 static int WeakNextOffset() {
294 return FixedArray::SizeFor(Context::NEXT_CONTEXT_LINK);
295 }
296
VisitLiveObjectv8::internal::WeakListVisitor297 static void VisitLiveObject(Heap* heap, Context* context,
298 WeakObjectRetainer* retainer) {
299 // Process the three weak lists linked off the context.
300 DoWeakList<JSFunction>(heap, context, retainer,
301 Context::OPTIMIZED_FUNCTIONS_LIST);
302
303 if (heap->gc_state() == Heap::MARK_COMPACT) {
304 // Record the slots of the weak entries in the native context.
305 MarkCompactCollector* collector = heap->mark_compact_collector();
306 for (int idx = Context::FIRST_WEAK_SLOT;
307 idx < Context::NATIVE_CONTEXT_SLOTS; ++idx) {
308 Object** slot = Context::cast(context)->RawFieldOfElementAt(idx);
309 collector->RecordSlot(context, slot, *slot);
310 }
311 // Code objects are always allocated in Code space, we do not have to
312 // visit
313 // them during scavenges.
314 DoWeakList<Code>(heap, context, retainer, Context::OPTIMIZED_CODE_LIST);
315 DoWeakList<Code>(heap, context, retainer, Context::DEOPTIMIZED_CODE_LIST);
316 }
317 }
318
319 template <class T>
DoWeakListv8::internal::WeakListVisitor320 static void DoWeakList(Heap* heap, Context* context,
321 WeakObjectRetainer* retainer, int index) {
322 // Visit the weak list, removing dead intermediate elements.
323 Object* list_head = VisitWeakList<T>(heap, context->get(index), retainer);
324
325 // Update the list head.
326 context->set(index, list_head, UPDATE_WRITE_BARRIER);
327
328 if (MustRecordSlots(heap)) {
329 // Record the updated slot if necessary.
330 Object** head_slot =
331 HeapObject::RawField(context, FixedArray::SizeFor(index));
332 heap->mark_compact_collector()->RecordSlot(context, head_slot, list_head);
333 }
334 }
335
VisitPhantomObjectv8::internal::WeakListVisitor336 static void VisitPhantomObject(Heap* heap, Context* context) {
337 ClearWeakList<JSFunction>(heap,
338 context->get(Context::OPTIMIZED_FUNCTIONS_LIST));
339 ClearWeakList<Code>(heap, context->get(Context::OPTIMIZED_CODE_LIST));
340 ClearWeakList<Code>(heap, context->get(Context::DEOPTIMIZED_CODE_LIST));
341 }
342 };
343
344
345 template <>
346 struct WeakListVisitor<AllocationSite> {
SetWeakNextv8::internal::WeakListVisitor347 static void SetWeakNext(AllocationSite* obj, Object* next) {
348 obj->set_weak_next(next, UPDATE_WEAK_WRITE_BARRIER);
349 }
350
WeakNextv8::internal::WeakListVisitor351 static Object* WeakNext(AllocationSite* obj) { return obj->weak_next(); }
352
WeakNextOffsetv8::internal::WeakListVisitor353 static int WeakNextOffset() { return AllocationSite::kWeakNextOffset; }
354
VisitLiveObjectv8::internal::WeakListVisitor355 static void VisitLiveObject(Heap*, AllocationSite*, WeakObjectRetainer*) {}
356
VisitPhantomObjectv8::internal::WeakListVisitor357 static void VisitPhantomObject(Heap*, AllocationSite*) {}
358 };
359
360
361 template Object* VisitWeakList<Context>(Heap* heap, Object* list,
362 WeakObjectRetainer* retainer);
363
364 template Object* VisitWeakList<AllocationSite>(Heap* heap, Object* list,
365 WeakObjectRetainer* retainer);
366 } // namespace internal
367 } // namespace v8
368