Object ID Ring with tests

runtime/vm/gc_marker.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/gc_marker.h"
 
 #include <map>
 #include <utility>
 
 #include "vm/allocation.h"
 #include "vm/dart_api_state.h"
 #include "vm/isolate.h"
 #include "vm/pages.h"
 #include "vm/raw_object.h"
 #include "vm/stack_frame.h"
 #include "vm/visitor.h"
+#include "vm/object_id_ring.h"
 
 namespace dart {
 
 // A simple chunked marking stack.
 class MarkingStack : public ValueObject {
  public:
   MarkingStack()
       : head_(new MarkingStackChunk()),
         empty_chunks_(NULL),
         marking_stack_(NULL),
@@ skipping 365 matching lines @@
         ASSERT(raw_obj->IsHeapObject());
         if (!raw_obj->IsMarked()) {
           table->InvalidateAt(i);
         }
       }
     }
   }
 }
 
 
+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) {
   MarkingStack marking_stack;
   Prologue(isolate, invoke_api_callbacks);
   MarkingVisitor mark(isolate, heap_, page_space, &marking_stack);
   IterateRoots(isolate, &mark, !invoke_api_callbacks);
   DrainMarkingStack(isolate, &mark);
   IterateWeakReferences(isolate, &mark);
   MarkingWeakVisitor mark_weak;
   IterateWeakRoots(isolate, &mark_weak, invoke_api_callbacks);
   mark.Finalize();
   ProcessWeakTables(page_space);
+  ProcessObjectIdTable(isolate);
+
+
   Epilogue(isolate, invoke_api_callbacks);
 }
 
 }  // namespace dart