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1 // Copyright 2006-2008 the V8 project authors. All rights reserved. | 1 // Copyright 2006-2008 the V8 project authors. All rights reserved. |
2 // Redistribution and use in source and binary forms, with or without | 2 // Redistribution and use in source and binary forms, with or without |
3 // modification, are permitted provided that the following conditions are | 3 // modification, are permitted provided that the following conditions are |
4 // met: | 4 // met: |
5 // | 5 // |
6 // * Redistributions of source code must retain the above copyright | 6 // * Redistributions of source code must retain the above copyright |
7 // notice, this list of conditions and the following disclaimer. | 7 // notice, this list of conditions and the following disclaimer. |
8 // * Redistributions in binary form must reproduce the above | 8 // * Redistributions in binary form must reproduce the above |
9 // copyright notice, this list of conditions and the following | 9 // copyright notice, this list of conditions and the following |
10 // disclaimer in the documentation and/or other materials provided | 10 // disclaimer in the documentation and/or other materials provided |
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214 // have been reached and marked but their children have not been visited yet. | 214 // have been reached and marked but their children have not been visited yet. |
215 // After emptying the marking stack, we clear the overflow flag and traverse | 215 // After emptying the marking stack, we clear the overflow flag and traverse |
216 // the heap looking for objects marked as overflowed, push them on the stack, | 216 // the heap looking for objects marked as overflowed, push them on the stack, |
217 // and continue with marking. This process repeats until all reachable | 217 // and continue with marking. This process repeats until all reachable |
218 // objects have been marked. | 218 // objects have been marked. |
219 | 219 |
220 static MarkingStack marking_stack; | 220 static MarkingStack marking_stack; |
221 | 221 |
222 | 222 |
223 inline HeapObject* ShortCircuitConsString(Object** p) { | 223 inline HeapObject* ShortCircuitConsString(Object** p) { |
224 // Optimization: If the heap object pointed to by p is a cons string whose | 224 // Optimization: If the heap object pointed to by p is a non-symbol |
225 // right substring is Heap::empty_string, update it in place to its left | 225 // cons string whose right substring is Heap::empty_string, update |
226 // substring. Return the updated value. | 226 // it in place to its left substring. Return the updated value. |
227 // | 227 // |
228 // Here we assume that if we change *p, we replace it with a heap object | 228 // Here we assume that if we change *p, we replace it with a heap object |
229 // (ie, the left substring of a cons string is always a heap object). | 229 // (ie, the left substring of a cons string is always a heap object). |
230 // | 230 // |
231 // The check performed is: | 231 // The check performed is: |
232 // object->IsConsString() && | 232 // object->IsConsString() && !object->IsSymbol() && |
233 // (ConsString::cast(object)->second() == Heap::empty_string()) | 233 // (ConsString::cast(object)->second() == Heap::empty_string()) |
234 // except the maps for the object and its possible substrings might be | 234 // except the maps for the object and its possible substrings might be |
235 // marked. | 235 // marked. |
236 HeapObject* object = HeapObject::cast(*p); | 236 HeapObject* object = HeapObject::cast(*p); |
237 MapWord map_word = object->map_word(); | 237 MapWord map_word = object->map_word(); |
238 map_word.ClearMark(); | 238 map_word.ClearMark(); |
239 InstanceType type = map_word.ToMap()->instance_type(); | 239 InstanceType type = map_word.ToMap()->instance_type(); |
240 if (type >= FIRST_NONSTRING_TYPE) return object; | 240 if (type >= FIRST_NONSTRING_TYPE || (type & kIsSymbolMask) != 0) { |
| 241 return object; |
| 242 } |
241 | 243 |
242 StringRepresentationTag rep = | 244 StringRepresentationTag rep = |
243 static_cast<StringRepresentationTag>(type & kStringRepresentationMask); | 245 static_cast<StringRepresentationTag>(type & kStringRepresentationMask); |
244 if (rep != kConsStringTag) return object; | 246 if (rep != kConsStringTag) return object; |
245 | 247 |
246 Object* second = reinterpret_cast<ConsString*>(object)->second(); | 248 Object* second = reinterpret_cast<ConsString*>(object)->second(); |
247 if (reinterpret_cast<String*>(second) != Heap::empty_string()) return object; | 249 if (reinterpret_cast<String*>(second) != Heap::empty_string()) return object; |
248 | 250 |
249 // Since we don't have the object's start, it is impossible to update the | 251 // Since we don't have the object's start, it is impossible to update the |
250 // remembered set. Therefore, we only replace the string with its left | 252 // remembered set. Therefore, we only replace the string with its left |
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1777 | 1779 |
1778 void MarkCompactCollector::RebuildRSets() { | 1780 void MarkCompactCollector::RebuildRSets() { |
1779 #ifdef DEBUG | 1781 #ifdef DEBUG |
1780 ASSERT(state_ == RELOCATE_OBJECTS); | 1782 ASSERT(state_ == RELOCATE_OBJECTS); |
1781 state_ = REBUILD_RSETS; | 1783 state_ = REBUILD_RSETS; |
1782 #endif | 1784 #endif |
1783 Heap::RebuildRSets(); | 1785 Heap::RebuildRSets(); |
1784 } | 1786 } |
1785 | 1787 |
1786 } } // namespace v8::internal | 1788 } } // namespace v8::internal |
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