Support allocation sinking for compound objects.

runtime/vm/deferred_objects.h

 // Copyright (c) 2013, 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.
 
 #ifndef VM_DEFERRED_OBJECTS_H_
 #define VM_DEFERRED_OBJECTS_H_
 
 #include "platform/globals.h"
 
 namespace dart {
@@ skipping 139 matching lines @@
       : field_count_(field_count),
         args_(reinterpret_cast<RawObject**>(args)),
         object_(NULL) { }
 
   intptr_t ArgumentCount() const {
     return kFieldsStartIndex + kFieldEntrySize * field_count_;
   }
 
   RawInstance* object();
 
+  // Fill object with actual field values.
+  void Fill();
+
  private:
   enum {
     kClassIndex = 0,
     kFieldsStartIndex = kClassIndex + 1
   };
 
   enum {
     kOffsetIndex = 0,
     kValueIndex,
     kFieldEntrySize,
   };
 
-  // Materializes the object. Returns amount of values that were consumed
-  // and should be removed from the expression stack at the very end of
-  // deoptimization.
-  void Materialize();
+  // Allocate the object but keep its fields null-initialized. Actual field
+  // values will be filled later by the Fill method. This separation between
+  // allocation and filling is needed because dematerialized objects form
+  // a graph which can contain cycles.
+  void Create();
 
   RawObject* GetClass() const {
     return args_[kClassIndex];
   }
 
   RawObject* GetFieldOffset(intptr_t index) const {
     return args_[kFieldsStartIndex + kFieldEntrySize * index + kOffsetIndex];
   }
 
   RawObject* GetValue(intptr_t index) const {
@@ skipping 10 matching lines @@
 
   // Object materialized from this description.
   const Instance* object_;
 
   DISALLOW_COPY_AND_ASSIGN(DeferredObject);
 };
 
 }  // namespace dart
 
 #endif  // VM_DEFERRED_OBJECTS_H_