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

src/objects-visiting.h

 // Copyright 2006-2009 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 128 matching lines @@
 
 template<typename Callback>
 class VisitorDispatchTable {
  public:
   inline Callback GetVisitor(Map* map) {
     return callbacks_[map->visitor_id()];
   }
 
   void Register(StaticVisitorBase::VisitorId id, Callback callback) {
     ASSERT((0 <= id) && (id < StaticVisitorBase::kVisitorIdCount));
-    callbacks_[id] = callback;
+    if (callbacks_[id] != callback) callbacks_[id] = callback;
   }
 
   template<typename Visitor,
            StaticVisitorBase::VisitorId base,
            StaticVisitorBase::VisitorId generic,
            int object_size_in_words>
   void RegisterSpecialization() {
     static const int size = object_size_in_words * kPointerSize;
     Register(StaticVisitorBase::GetVisitorIdForSize(base, generic, size),
              &Visitor::template VisitSpecialized<size>);
@@ skipping 220 matching lines @@
 
   StaticVisitor::VisitPointer(
       reinterpret_cast<Object**>(this->address() + kRelocationInfoOffset));
 
   for (; !it.done(); it.next()) {
     it.rinfo()->template Visit<StaticVisitor>();
   }
 }
 
 
+template<typename StaticVisitor, typename Data>
+void Code::CodeIterateBody(Data data) {
+  int mode_mask = RelocInfo::kCodeTargetMask |
+                  RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT) |
+                  RelocInfo::ModeMask(RelocInfo::EXTERNAL_REFERENCE) |
+                  RelocInfo::ModeMask(RelocInfo::JS_RETURN) |
+                  RelocInfo::ModeMask(RelocInfo::DEBUG_BREAK_SLOT) |
+                  RelocInfo::ModeMask(RelocInfo::RUNTIME_ENTRY);
+
+  // Use the relocation info pointer before it is visited by
+  // the heap compaction in the next statement.
+  RelocIterator it(this, mode_mask);
+
+  StaticVisitor::VisitPointer(
+      reinterpret_cast<Object**>(this->address() + kRelocationInfoOffset), data);
+
+  for (; !it.done(); it.next()) {
+    it.rinfo()->template Visit<StaticVisitor, Data>(data);
+  }
+}
+
+
+
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_VISITING_H_