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

src/objects-visiting.h

Index: src/objects-visiting.h
diff --git a/src/objects-visiting.h b/src/objects-visiting.h
index 90f7ce0b3dfa9e04b2b63bfd9c6b8e06551711d1..09af40ef068cd87f5556f9fe081862904987422e 100644
--- a/src/objects-visiting.h
+++ b/src/objects-visiting.h
@@ -146,7 +146,7 @@ class VisitorDispatchTable {
 
   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,
@@ -387,6 +387,29 @@ void Code::CodeIterateBody() {
 }
 
 
+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_