Make sure builtins preserve guarantees about empty element array prototypes.

src/objects.cc

 // Copyright 2013 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 <iomanip>
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
@@ skipping 12727 matching lines @@
   DCHECK(object->HasFastSmiOrObjectElements() ||
          object->HasFastArgumentsElements());
 
   Isolate* isolate = object->GetIsolate();
 
   // Array optimizations rely on the prototype lookups of Array objects always
   // returning undefined. If there is a store to the initial prototype object,
   // make sure all of these optimizations are invalidated.
   if (isolate->is_initial_object_prototype(*object) ||
       isolate->is_initial_array_prototype(*object)) {
+    PrintF("Deopting\n");

[Jakob Kummerow, 2015/04/20 10:52:05]

debugging leftover?

[mvstanton, 2015/04/20 14:10:39]

Done.

     object->map()->dependent_code()->DeoptimizeDependentCodeGroup(isolate,
         DependentCode::kElementsCantBeAddedGroup);
   }
 
   Handle<FixedArray> backing_store(FixedArray::cast(object->elements()));
   if (backing_store->map() ==
       isolate->heap()->sloppy_arguments_elements_map()) {
     backing_store = handle(FixedArray::cast(backing_store->get(1)));
   } else {
     backing_store = EnsureWritableFastElements(object);
@@ skipping 4388 matching lines @@
                                                CompilationInfo* info) {
   Handle<DependentCode> codes = DependentCode::InsertCompilationInfo(
       handle(cell->dependent_code(), info->isolate()),
       DependentCode::kPropertyCellChangedGroup, info->object_wrapper());
   if (*codes != cell->dependent_code()) cell->set_dependent_code(*codes);
   info->dependencies(DependentCode::kPropertyCellChangedGroup)->Add(
       cell, info->zone());
 }
 
 } }  // namespace v8::internal