Make sure we don't accidentially serialize type feedback

src/type-feedback-vector.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/ic/ic.h"
 #include "src/ic/ic-state.h"
 #include "src/objects.h"
 #include "src/type-feedback-vector-inl.h"
@@ skipping 189 matching lines @@
         KeyedLoadICNexus nexus(this, slot);
         if (ClearLogic(heap, ic_age, kind, nexus.StateFromFeedback())) {
           nexus.Clear(host);
         }
       }
     }
   }
 }
 
 
+bool TypeFeedbackVector::IsCleared() {
+  int slots = Slots();
+  Isolate* isolate = GetIsolate();
+  Object* uninitialized_sentinel =
+      TypeFeedbackVector::RawUninitializedSentinel(isolate->heap());
+
+  for (int i = 0; i < slots; i++) {
+    FeedbackVectorSlot slot(i);
+    Object* obj = Get(slot);
+    if (obj->IsHeapObject()) {
+      InstanceType instance_type =
+          HeapObject::cast(obj)->map()->instance_type();
+      // AllocationSites are exempt from clearing. They don't store Maps
+      // or Code pointers which can cause memory leaks if not cleared
+      // regularly.
+      if (instance_type != ALLOCATION_SITE_TYPE) {
+        return false;
+      }
+    }
+  }
+
+  slots = ICSlots();
+  if (slots == 0) return true;
+
+  // Now check vector-based ICs.
+  for (int i = 0; i < slots; i++) {
+    FeedbackVectorICSlot slot(i);
+    Object* obj = Get(slot);
+    if (obj != uninitialized_sentinel) {
+      return false;
+    }
+  }
+  return true;
+}
+
+
 Handle<FixedArray> FeedbackNexus::EnsureArrayOfSize(int length) {
   Isolate* isolate = GetIsolate();
   Handle<Object> feedback = handle(GetFeedback(), isolate);
   if (!feedback->IsFixedArray() ||
       FixedArray::cast(*feedback)->length() != length) {
     Handle<FixedArray> array = isolate->factory()->NewFixedArray(length);
     SetFeedback(*array);
     return array;
   }
   return Handle<FixedArray>::cast(feedback);
@@ skipping 268 matching lines @@
   if (feedback->IsFixedArray()) {
     FixedArray* array = FixedArray::cast(feedback);
     DCHECK(array->length() >= 3);
     Object* name = array->get(0);
     if (name->IsName()) return Name::cast(name);
   }
   return NULL;
 }
 }
 }  // namespace v8::internal