Fix array boilerplate object transitioning.

src/runtime.cc

 // Copyright 2012 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 4651 matching lines @@
 RUNTIME_FUNCTION(MaybeObject*, Runtime_StoreArrayLiteralElement) {
   RUNTIME_ASSERT(args.length() == 5);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
   CONVERT_SMI_ARG_CHECKED(store_index, 1);
   Handle<Object> value = args.at<Object>(2);
   CONVERT_ARG_HANDLE_CHECKED(FixedArray, literals, 3);
   CONVERT_SMI_ARG_CHECKED(literal_index, 4);
   HandleScope scope;
 
   Object* raw_boilerplate_object = literals->get(literal_index);
-  Handle<JSArray> boilerplate_object(JSArray::cast(raw_boilerplate_object));
+  Handle<JSArray> boilerplate(JSArray::cast(raw_boilerplate_object));
 #if DEBUG
   ElementsKind elements_kind = object->GetElementsKind();
 #endif
   ASSERT(elements_kind <= FAST_DOUBLE_ELEMENTS);
   // Smis should never trigger transitions.
   ASSERT(!value->IsSmi());
 
   if (value->IsNumber()) {
     ASSERT(elements_kind == FAST_SMI_ONLY_ELEMENTS);
     JSObject::TransitionElementsKind(object, FAST_DOUBLE_ELEMENTS);
-    JSObject::TransitionElementsKind(boilerplate_object, FAST_DOUBLE_ELEMENTS);
+    if (IsMoreGeneralElementsKindTransition(boilerplate->GetElementsKind(),
+                                            FAST_DOUBLE_ELEMENTS)) {
+      JSObject::TransitionElementsKind(boilerplate, FAST_DOUBLE_ELEMENTS);
+    }
     ASSERT(object->GetElementsKind() == FAST_DOUBLE_ELEMENTS);
-    FixedDoubleArray* double_array =
-        FixedDoubleArray::cast(object->elements());
+    FixedDoubleArray* double_array = FixedDoubleArray::cast(object->elements());
     HeapNumber* number = HeapNumber::cast(*value);
     double_array->set(store_index, number->Number());
   } else {
     ASSERT(elements_kind == FAST_SMI_ONLY_ELEMENTS ||
            elements_kind == FAST_DOUBLE_ELEMENTS);
     JSObject::TransitionElementsKind(object, FAST_ELEMENTS);
-    JSObject::TransitionElementsKind(boilerplate_object, FAST_ELEMENTS);
-    FixedArray* object_array =
-        FixedArray::cast(object->elements());
+    if (IsMoreGeneralElementsKindTransition(boilerplate->GetElementsKind(),
+                                            FAST_ELEMENTS)) {
+      JSObject::TransitionElementsKind(boilerplate, FAST_ELEMENTS);
+    }
+    FixedArray* object_array = FixedArray::cast(object->elements());
     object_array->set(store_index, *value);
   }
   return *object;
 }
 
 
 // Set a local property, even if it is READ_ONLY.  If the property does not
 // exist, it will be added with attributes NONE.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_IgnoreAttributesAndSetProperty) {
   NoHandleAllocation ha;
@@ skipping 8636 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal