Object ID Ring with tests

runtime/vm/gc_marker.cc

Index: runtime/vm/gc_marker.cc
diff --git a/runtime/vm/gc_marker.cc b/runtime/vm/gc_marker.cc
index b7ae253b911a5eccc7bdf976d9632b9e8b6e38e3..aa4396ed4b4046c27357536535bf0a8535af451a 100644
--- a/runtime/vm/gc_marker.cc
+++ b/runtime/vm/gc_marker.cc
@@ -14,6 +14,7 @@
 #include "vm/raw_object.h"
 #include "vm/stack_frame.h"
 #include "vm/visitor.h"
+#include "vm/object_id_ring.h"
 
 namespace dart {
 
@@ -399,6 +400,36 @@ void GCMarker::ProcessWeakTables(PageSpace* page_space) {
 }
 
 
+class ObjectIdRingClearPointerVisitor : public ObjectPointerVisitor {
+ public:
+  explicit ObjectIdRingClearPointerVisitor(Isolate* isolate) :
+      ObjectPointerVisitor(isolate) {}
+
+  void Clear(RawObject** current) {
+    RawObject* raw_obj = *current;
+    ASSERT(raw_obj->IsHeapObject());
+    if (!raw_obj->IsMarked()) {

[Ivan Posva, 2013/07/11 17:01:42]

You need to be checking the mark bits on old objects only! You do not know what
these bits indicate for new gen objects. In the current system this will lead to
an old gc clearing ALL new objects which is not what you want, they should not
be touched at all.

[Cutch, 2013/07/11 21:31:47]

Done.

+      // Object has become garbage. Replace it will null.
+      *current = Object::null();
+    }
+  }
+
+  void VisitPointers(RawObject** first, RawObject** last) {
+    for (RawObject** current = first; current <= last; current++) {
+      Clear(current);

[Ivan Posva, 2013/07/11 17:01:42]

You can move the logic from Clear in here. The name Clear is a bit confusing as
it implies that you are clearing all entries. I don't think the extra method is
adding much to clarity.

[Cutch, 2013/07/11 21:31:47]

Done.

+    }
+  }
+};
+
+
+void GCMarker::ProcessObjectIdTable(Isolate* isolate) {
+  ObjectIdRingClearPointerVisitor visitor(isolate);
+  ObjectIdRing* ring = isolate->object_id_ring();
+  ASSERT(ring != NULL);
+  ring->VisitPointers(&visitor);
+}
+
+
 void GCMarker::MarkObjects(Isolate* isolate,
                            PageSpace* page_space,
                            bool invoke_api_callbacks) {
@@ -412,6 +443,9 @@ void GCMarker::MarkObjects(Isolate* isolate,
   IterateWeakRoots(isolate, &mark_weak, invoke_api_callbacks);
   mark.Finalize();
   ProcessWeakTables(page_space);
+  ProcessObjectIdTable(isolate);
+
+
   Epilogue(isolate, invoke_api_callbacks);
 }