deps/v8/src/heap/objects-visiting.cc

   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/v8.h"
   6
   7 #include "src/heap/objects-visiting.h"
   8
   9 namespace v8 {
  10 namespace internal {
  11
  12
  13 StaticVisitorBase::VisitorId StaticVisitorBase::GetVisitorId(
  14     int instance_type, int instance_size, bool has_unboxed_fields) {
  15   if (instance_type < FIRST_NONSTRING_TYPE) {
  16     switch (instance_type & kStringRepresentationMask) {
  17       case kSeqStringTag:
  18         if ((instance_type & kStringEncodingMask) == kOneByteStringTag) {
  19           return kVisitSeqOneByteString;
  20         } else {
  21           return kVisitSeqTwoByteString;
  22         }
  23
  24       case kConsStringTag:
  25         if (IsShortcutCandidate(instance_type)) {
  26           return kVisitShortcutCandidate;
  27         } else {
  28           return kVisitConsString;
  29         }
  30
  31       case kSlicedStringTag:
  32         return kVisitSlicedString;
  33
  34       case kExternalStringTag:
  35         return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
  36                                    instance_size, has_unboxed_fields);
  37     }
  38     UNREACHABLE();
  39   }
  40
  41   switch (instance_type) {
  42     case BYTE_ARRAY_TYPE:
  43       return kVisitByteArray;
  44
  45     case FREE_SPACE_TYPE:
  46       return kVisitFreeSpace;
  47
  48     case FIXED_ARRAY_TYPE:
  49       return kVisitFixedArray;
  50
  51     case FIXED_DOUBLE_ARRAY_TYPE:
  52       return kVisitFixedDoubleArray;
  53
  54     case CONSTANT_POOL_ARRAY_TYPE:
  55       return kVisitConstantPoolArray;
  56
  57     case ODDBALL_TYPE:
  58       return kVisitOddball;
  59
  60     case MAP_TYPE:
  61       return kVisitMap;
  62
  63     case CODE_TYPE:
  64       return kVisitCode;
  65
  66     case CELL_TYPE:
  67       return kVisitCell;
  68
  69     case PROPERTY_CELL_TYPE:
  70       return kVisitPropertyCell;
  71
  72     case WEAK_CELL_TYPE:
  73       return kVisitWeakCell;
  74
  75     case JS_SET_TYPE:
  76       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
  77                                  JSSet::kSize, has_unboxed_fields);
  78
  79     case JS_MAP_TYPE:
  80       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
  81                                  JSMap::kSize, has_unboxed_fields);
  82
  83     case JS_WEAK_MAP_TYPE:
  84     case JS_WEAK_SET_TYPE:
  85       return kVisitJSWeakCollection;
  86
  87     case JS_REGEXP_TYPE:
  88       return kVisitJSRegExp;
  89
  90     case SHARED_FUNCTION_INFO_TYPE:
  91       return kVisitSharedFunctionInfo;
  92
  93     case JS_PROXY_TYPE:
  94       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
  95                                  JSProxy::kSize, has_unboxed_fields);
  96
  97     case JS_FUNCTION_PROXY_TYPE:
  98       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
  99                                  JSFunctionProxy::kSize, has_unboxed_fields);
 100
 101     case FOREIGN_TYPE:
 102       return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
 103                                  Foreign::kSize, has_unboxed_fields);
 104
 105     case SYMBOL_TYPE:
 106       return kVisitSymbol;
 107
 108     case FILLER_TYPE:
 109       return kVisitDataObjectGeneric;
 110
 111     case JS_ARRAY_BUFFER_TYPE:
 112       return kVisitJSArrayBuffer;
 113
 114     case JS_TYPED_ARRAY_TYPE:
 115       return kVisitJSTypedArray;
 116
 117     case JS_DATA_VIEW_TYPE:
 118       return kVisitJSDataView;
 119
 120     case JS_OBJECT_TYPE:
 121     case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
 122     case JS_GENERATOR_OBJECT_TYPE:
 123     case JS_MODULE_TYPE:
 124     case JS_VALUE_TYPE:
 125     case JS_DATE_TYPE:
 126     case JS_ARRAY_TYPE:
 127     case JS_GLOBAL_PROXY_TYPE:
 128     case JS_GLOBAL_OBJECT_TYPE:
 129     case JS_BUILTINS_OBJECT_TYPE:
 130     case JS_MESSAGE_OBJECT_TYPE:
 131     case JS_SET_ITERATOR_TYPE:
 132     case JS_MAP_ITERATOR_TYPE:
 133       return GetVisitorIdForSize(kVisitJSObject, kVisitJSObjectGeneric,
 134                                  instance_size, has_unboxed_fields);
 135
 136     case JS_FUNCTION_TYPE:
 137       return kVisitJSFunction;
 138
 139     case HEAP_NUMBER_TYPE:
 140     case MUTABLE_HEAP_NUMBER_TYPE:
 141 #define EXTERNAL_ARRAY_CASE(Type, type, TYPE, ctype, size) \
 142   case EXTERNAL_##TYPE##_ARRAY_TYPE:
 143
 144       TYPED_ARRAYS(EXTERNAL_ARRAY_CASE)
 145       return GetVisitorIdForSize(kVisitDataObject, kVisitDataObjectGeneric,
 146                                  instance_size, has_unboxed_fields);
 147 #undef EXTERNAL_ARRAY_CASE
 148
 149     case FIXED_UINT8_ARRAY_TYPE:
 150     case FIXED_INT8_ARRAY_TYPE:
 151     case FIXED_UINT16_ARRAY_TYPE:
 152     case FIXED_INT16_ARRAY_TYPE:
 153     case FIXED_UINT32_ARRAY_TYPE:
 154     case FIXED_INT32_ARRAY_TYPE:
 155     case FIXED_FLOAT32_ARRAY_TYPE:
 156     case FIXED_UINT8_CLAMPED_ARRAY_TYPE:
 157       return kVisitFixedTypedArray;
 158
 159     case FIXED_FLOAT64_ARRAY_TYPE:
 160       return kVisitFixedFloat64Array;
 161
 162 #define MAKE_STRUCT_CASE(NAME, Name, name) case NAME##_TYPE:
 163       STRUCT_LIST(MAKE_STRUCT_CASE)
 164 #undef MAKE_STRUCT_CASE
 165       if (instance_type == ALLOCATION_SITE_TYPE) {
 166         return kVisitAllocationSite;
 167       }
 168
 169       return GetVisitorIdForSize(kVisitStruct, kVisitStructGeneric,
 170                                  instance_size, has_unboxed_fields);
 171
 172     default:
 173       UNREACHABLE();
 174       return kVisitorIdCount;
 175   }
 176 }
 177
 178
 179 // We don't record weak slots during marking or scavenges. Instead we do it
 180 // once when we complete mark-compact cycle.  Note that write barrier has no
 181 // effect if we are already in the middle of compacting mark-sweep cycle and we
 182 // have to record slots manually.
 183 static bool MustRecordSlots(Heap* heap) {
 184   return heap->gc_state() == Heap::MARK_COMPACT &&
 185          heap->mark_compact_collector()->is_compacting();
 186 }
 187
 188
 189 template <class T>
 190 struct WeakListVisitor;
 191
 192
 193 template <class T>
 194 Object* VisitWeakList(Heap* heap, Object* list, WeakObjectRetainer* retainer,
 195                       bool stop_after_young) {
 196   Object* undefined = heap->undefined_value();
 197   Object* head = undefined;
 198   T* tail = NULL;
 199   MarkCompactCollector* collector = heap->mark_compact_collector();
 200   bool record_slots = MustRecordSlots(heap);
 201
 202   while (list != undefined) {
 203     // Check whether to keep the candidate in the list.
 204     T* candidate = reinterpret_cast<T*>(list);
 205
 206     Object* retained = retainer->RetainAs(list);
 207     if (retained != NULL) {
 208       if (head == undefined) {
 209         // First element in the list.
 210         head = retained;
 211       } else {
 212         // Subsequent elements in the list.
 213         DCHECK(tail != NULL);
 214         WeakListVisitor<T>::SetWeakNext(tail, retained);
 215         if (record_slots) {
 216           Object** next_slot =
 217               HeapObject::RawField(tail, WeakListVisitor<T>::WeakNextOffset());
 218           collector->RecordSlot(next_slot, next_slot, retained);
 219         }
 220       }
 221       // Retained object is new tail.
 222       DCHECK(!retained->IsUndefined());
 223       candidate = reinterpret_cast<T*>(retained);
 224       tail = candidate;
 225
 226       // tail is a live object, visit it.
 227       WeakListVisitor<T>::VisitLiveObject(heap, tail, retainer);
 228
 229     } else {
 230       WeakListVisitor<T>::VisitPhantomObject(heap, candidate);
 231     }
 232
 233     // Move to next element in the list.
 234     list = WeakListVisitor<T>::WeakNext(candidate);
 235   }
 236
 237   // Terminate the list if there is one or more elements.
 238   if (tail != NULL) {
 239     WeakListVisitor<T>::SetWeakNext(tail, undefined);
 240   }
 241   return head;
 242 }
 243
 244
 245 Object* VisitNewArrayBufferViewsWeakList(Heap* heap, Object* list,
 246                                          WeakObjectRetainer* retainer) {
 247   Object* undefined = heap->undefined_value();
 248   Object* previous = undefined;
 249   Object* head = undefined;
 250   Object* next;
 251   MarkCompactCollector* collector = heap->mark_compact_collector();
 252   bool record_slots = MustRecordSlots(heap);
 253
 254   for (Object* o = list; o != undefined;) {
 255     JSArrayBufferView* view = JSArrayBufferView::cast(o);
 256     next = view->weak_next();
 257     if (!heap->InNewSpace(view)) {
 258       if (previous != undefined) {
 259         // We are in the middle of the list, skip the old space element.
 260         JSArrayBufferView* previous_view = JSArrayBufferView::cast(previous);
 261         previous_view->set_weak_next(next);
 262         if (record_slots) {
 263           Object** next_slot = HeapObject::RawField(
 264               previous_view, JSArrayBufferView::kWeakNextOffset);
 265           collector->RecordSlot(next_slot, next_slot, next);
 266         }
 267       }
 268       JSArrayBuffer* buffer = JSArrayBuffer::cast(view->buffer());
 269       view->set_weak_next(buffer->weak_first_view());
 270       if (record_slots) {
 271         Object** next_slot =
 272             HeapObject::RawField(view, JSArrayBufferView::kWeakNextOffset);
 273         collector->RecordSlot(next_slot, next_slot, buffer->weak_first_view());
 274       }
 275       buffer->set_weak_first_view(view);
 276       if (record_slots) {
 277         Object** slot =
 278             HeapObject::RawField(buffer, JSArrayBuffer::kWeakFirstViewOffset);
 279         heap->mark_compact_collector()->RecordSlot(slot, slot, view);
 280       }
 281     } else {
 282       // We found a valid new space view, remember it.
 283       previous = view;
 284       if (head == undefined) {
 285         // We are at the list head.
 286         head = view;
 287       }
 288     }
 289     o = next;
 290   }
 291   return head;
 292 }
 293
 294
 295 template <class T>
 296 static void ClearWeakList(Heap* heap, Object* list) {
 297   Object* undefined = heap->undefined_value();
 298   while (list != undefined) {
 299     T* candidate = reinterpret_cast<T*>(list);
 300     list = WeakListVisitor<T>::WeakNext(candidate);
 301     WeakListVisitor<T>::SetWeakNext(candidate, undefined);
 302   }
 303 }
 304
 305
 306 template <>
 307 struct WeakListVisitor<JSFunction> {
 308   static void SetWeakNext(JSFunction* function, Object* next) {
 309     function->set_next_function_link(next);
 310   }
 311
 312   static Object* WeakNext(JSFunction* function) {
 313     return function->next_function_link();
 314   }
 315
 316   static int WeakNextOffset() { return JSFunction::kNextFunctionLinkOffset; }
 317
 318   static void VisitLiveObject(Heap*, JSFunction*, WeakObjectRetainer*) {}
 319
 320   static void VisitPhantomObject(Heap*, JSFunction*) {}
 321 };
 322
 323
 324 template <>
 325 struct WeakListVisitor<Code> {
 326   static void SetWeakNext(Code* code, Object* next) {
 327     code->set_next_code_link(next);
 328   }
 329
 330   static Object* WeakNext(Code* code) { return code->next_code_link(); }
 331
 332   static int WeakNextOffset() { return Code::kNextCodeLinkOffset; }
 333
 334   static void VisitLiveObject(Heap*, Code*, WeakObjectRetainer*) {}
 335
 336   static void VisitPhantomObject(Heap*, Code*) {}
 337 };
 338
 339
 340 template <>
 341 struct WeakListVisitor<Context> {
 342   static void SetWeakNext(Context* context, Object* next) {
 343     context->set(Context::NEXT_CONTEXT_LINK, next, UPDATE_WRITE_BARRIER);
 344   }
 345
 346   static Object* WeakNext(Context* context) {
 347     return context->get(Context::NEXT_CONTEXT_LINK);
 348   }
 349
 350   static int WeakNextOffset() {
 351     return FixedArray::SizeFor(Context::NEXT_CONTEXT_LINK);
 352   }
 353
 354   static void VisitLiveObject(Heap* heap, Context* context,
 355                               WeakObjectRetainer* retainer) {
 356     // Process the three weak lists linked off the context.
 357     DoWeakList<JSFunction>(heap, context, retainer,
 358                            Context::OPTIMIZED_FUNCTIONS_LIST);
 359
 360     // Code objects are always allocated in Code space, we do not have to visit
 361     // them during scavenges.
 362     if (heap->gc_state() == Heap::MARK_COMPACT) {
 363       DoWeakList<Code>(heap, context, retainer, Context::OPTIMIZED_CODE_LIST);
 364       DoWeakList<Code>(heap, context, retainer, Context::DEOPTIMIZED_CODE_LIST);
 365     }
 366   }
 367
 368   template <class T>
 369   static void DoWeakList(Heap* heap, Context* context,
 370                          WeakObjectRetainer* retainer, int index) {
 371     // Visit the weak list, removing dead intermediate elements.
 372     Object* list_head =
 373         VisitWeakList<T>(heap, context->get(index), retainer, false);
 374
 375     // Update the list head.
 376     context->set(index, list_head, UPDATE_WRITE_BARRIER);
 377
 378     if (MustRecordSlots(heap)) {
 379       // Record the updated slot if necessary.
 380       Object** head_slot =
 381           HeapObject::RawField(context, FixedArray::SizeFor(index));
 382       heap->mark_compact_collector()->RecordSlot(head_slot, head_slot,
 383                                                  list_head);
 384     }
 385   }
 386
 387   static void VisitPhantomObject(Heap* heap, Context* context) {
 388     ClearWeakList<JSFunction>(heap,
 389                               context->get(Context::OPTIMIZED_FUNCTIONS_LIST));
 390     ClearWeakList<Code>(heap, context->get(Context::OPTIMIZED_CODE_LIST));
 391     ClearWeakList<Code>(heap, context->get(Context::DEOPTIMIZED_CODE_LIST));
 392   }
 393 };
 394
 395
 396 template <>
 397 struct WeakListVisitor<JSArrayBufferView> {
 398   static void SetWeakNext(JSArrayBufferView* obj, Object* next) {
 399     obj->set_weak_next(next);
 400   }
 401
 402   static Object* WeakNext(JSArrayBufferView* obj) { return obj->weak_next(); }
 403
 404   static int WeakNextOffset() { return JSArrayBufferView::kWeakNextOffset; }
 405
 406   static void VisitLiveObject(Heap*, JSArrayBufferView*, WeakObjectRetainer*) {}
 407
 408   static void VisitPhantomObject(Heap*, JSArrayBufferView*) {}
 409 };
 410
 411
 412 template <>
 413 struct WeakListVisitor<JSArrayBuffer> {
 414   static void SetWeakNext(JSArrayBuffer* obj, Object* next) {
 415     obj->set_weak_next(next);
 416   }
 417
 418   static Object* WeakNext(JSArrayBuffer* obj) { return obj->weak_next(); }
 419
 420   static int WeakNextOffset() { return JSArrayBuffer::kWeakNextOffset; }
 421
 422   static void VisitLiveObject(Heap* heap, JSArrayBuffer* array_buffer,
 423                               WeakObjectRetainer* retainer) {
 424     Object* typed_array_obj = VisitWeakList<JSArrayBufferView>(
 425         heap, array_buffer->weak_first_view(), retainer, false);
 426     array_buffer->set_weak_first_view(typed_array_obj);
 427     if (typed_array_obj != heap->undefined_value() && MustRecordSlots(heap)) {
 428       Object** slot = HeapObject::RawField(array_buffer,
 429                                            JSArrayBuffer::kWeakFirstViewOffset);
 430       heap->mark_compact_collector()->RecordSlot(slot, slot, typed_array_obj);
 431     }
 432   }
 433
 434   static void VisitPhantomObject(Heap* heap, JSArrayBuffer* phantom) {
 435     Runtime::FreeArrayBuffer(heap->isolate(), phantom);
 436   }
 437 };
 438
 439
 440 template <>
 441 struct WeakListVisitor<AllocationSite> {
 442   static void SetWeakNext(AllocationSite* obj, Object* next) {
 443     obj->set_weak_next(next);
 444   }
 445
 446   static Object* WeakNext(AllocationSite* obj) { return obj->weak_next(); }
 447
 448   static int WeakNextOffset() { return AllocationSite::kWeakNextOffset; }
 449
 450   static void VisitLiveObject(Heap*, AllocationSite*, WeakObjectRetainer*) {}
 451
 452   static void VisitPhantomObject(Heap*, AllocationSite*) {}
 453 };
 454
 455
 456 template Object* VisitWeakList<Context>(Heap* heap, Object* list,
 457                                         WeakObjectRetainer* retainer,
 458                                         bool stop_after_young);
 459
 460
 461 template Object* VisitWeakList<JSArrayBuffer>(Heap* heap, Object* list,
 462                                               WeakObjectRetainer* retainer,
 463                                               bool stop_after_young);
 464
 465 template Object* VisitWeakList<JSArrayBufferView>(Heap* heap, Object* list,
 466                                                   WeakObjectRetainer* retainer,
 467                                                   bool stop_after_young);
 468
 469 template Object* VisitWeakList<AllocationSite>(Heap* heap, Object* list,
 470                                                WeakObjectRetainer* retainer,
 471                                                bool stop_after_young);
 472 }
 473 }  // namespace v8::internal