When clearing filled call target caches we should go back to the

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 10619 matching lines @@
   }
 }
 
 
 void Code::ClearTypeFeedbackInfo(Heap* heap) {
   if (kind() != FUNCTION) return;
   Object* raw_info = type_feedback_info();
   if (raw_info->IsTypeFeedbackInfo()) {
     FixedArray* feedback_vector =
         TypeFeedbackInfo::cast(raw_info)->feedback_vector();
+    Object* premonomorphic_sentinel =
+        TypeFeedbackInfo::RawPremonomorphicSentinel(heap);
     for (int i = 0; i < feedback_vector->length(); i++) {
       Object* obj = feedback_vector->get(i);
-      if (!obj->IsAllocationSite()) {
-        // TODO(mvstanton): Can't I avoid a write barrier for this sentinel?
-        feedback_vector->set(i,
-                             TypeFeedbackInfo::RawUninitializedSentinel(heap));
+      // If the cache is monomorphic (non-arrays) or megamorphic we go
+      // back to premonomorphic.
+      ASSERT_EQ(*TypeFeedbackInfo::MegamorphicSentinel(heap->isolate()),
+          heap->undefined_value());
+      if (obj->IsUndefined() || obj->IsJSFunction()) {
+        feedback_vector->set(i, premonomorphic_sentinel, SKIP_WRITE_BARRIER);
       }
     }
   }
 }
 
 
 BailoutId Code::TranslatePcOffsetToAstId(uint32_t pc_offset) {
   DisallowHeapAllocation no_gc;
   ASSERT(kind() == FUNCTION);
   BackEdgeTable back_edges(this, &no_gc);
@@ skipping 5840 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal