For background compilation we copy ICData so that it is immutable during comnpilation. However, we …

runtime/vm/object.h

 // Copyright (c) 2012, 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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 1730 matching lines @@
   void set_script(const Script& value) const;
 
   static RawPatchClass* New();
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(PatchClass, Object);
   friend class Class;
 };
 
 
 // Object holding information about an IC: test classes and their
-// corresponding targets.
+// corresponding targets. The owner of the ICData can be either the function
+// or the original ICData object. In case of background compilation we
+// copy the ICData in a child object, thus freezing it during background
+// compilation. Code may contain only original ICData objects.
 class ICData : public Object {
  public:
-  RawFunction* owner() const {
-    return raw_ptr()->owner_;
+  RawFunction* Owner() const;
+
+  RawICData* Original() const;
+
+  void SetOriginal(const ICData& value) const;
+
+  bool IsOriginal() const {
+    return Original() == this->raw();
   }
 
   RawString* target_name() const {
     return raw_ptr()->target_name_;
   }
 
   RawArray* arguments_descriptor() const {
     return raw_ptr()->args_descriptor_;
   }
 
@@ skipping 6457 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_