Add flag --collect-megamorphic-maps-from-stub-cache to help diagnose a

src/type-info.cc

 // Copyright 2011 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 397 matching lines @@
   Handle<Object> object = GetInfo(ast_id);
   if (object->IsUndefined() || object->IsSmi()) return;
 
   if (*object ==
       isolate_->builtins()->builtin(Builtins::kStoreIC_GlobalProxy)) {
     // TODO(fschneider): We could collect the maps and signal that
     // we need a generic store (or load) here.
     ASSERT(Handle<Code>::cast(object)->ic_state() == MEGAMORPHIC);
   } else if (object->IsMap()) {
     types->Add(Handle<Map>::cast(object));
-  } else if (Handle<Code>::cast(object)->ic_state() == MEGAMORPHIC) {
+  } else if (FLAG_collect_megamorphic_maps_from_stub_cache &&
+      Handle<Code>::cast(object)->ic_state() == MEGAMORPHIC) {
     types->Reserve(4);
     ASSERT(object->IsCode());
     isolate_->stub_cache()->CollectMatchingMaps(types, *name, flags);
   }
 }
 
 
 static void AddMapIfMissing(Handle<Map> map, SmallMapList* list) {
   for (int i = 0; i < list->length(); ++i) {
     if (list->at(i).is_identical_to(map)) return;
@@ skipping 135 matching lines @@
   USE(maybe_result);
 #ifdef DEBUG
   Object* result = NULL;
   // Dictionary has been allocated with sufficient size for all elements.
   ASSERT(maybe_result->ToObject(&result));
   ASSERT(*dictionary_ == result);
 #endif
 }
 
 } }  // namespace v8::internal