Parallelize marking phase of mark-sweep/compact collection cycle.

src/objects-inl.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1092 matching lines @@
 void HeapObject::IteratePointer(ObjectVisitor* v, int offset) {
   v->VisitPointer(reinterpret_cast<Object**>(FIELD_ADDR(this, offset)));
 }
 
 
 bool HeapObject::IsMarked() {
   return map_word().IsMarked();
 }
 
 
-void HeapObject::SetMark() {
-  ASSERT(!IsMarked());
+bool HeapObject::SetMark() {
   MapWord first_word = map_word();
-  first_word.SetMark();
-  set_map_word(first_word);
+
+  if (!first_word.IsMarked()) {
+    first_word.SetMark();
+    set_map_word(first_word);
+    return true;
+  }
+
+  return false;
 }
 
 
+bool HeapObject::SetMarkExclusively() {
+  MapWord first_word = map_word();
+
+  if (!first_word.IsMarked()) {
+    MapWord new_first_word = first_word;
+    new_first_word.SetMark();
+
+    AtomicWord* map_word_slot =
+        reinterpret_cast<AtomicWord*>(this->address() + kMapOffset);
+
+    return AtomicCompareAndSwap(map_word_slot,
+                                static_cast<AtomicWord>(first_word.value_),
+                                static_cast<AtomicWord>(new_first_word.value_));
+  }
+
+  return false;
+}
+
+
 void HeapObject::ClearMark() {
   ASSERT(IsMarked());
   MapWord first_word = map_word();
   first_word.ClearMark();
   set_map_word(first_word);
 }
 
 
 bool HeapObject::IsOverflowed() {
   return map_word().IsOverflowed();
@@ skipping 2419 matching lines @@
 #undef WRITE_INT_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_