Optimize Crankshaft array literal initialization from boilerplate.

src/runtime.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 607 matching lines @@
 RUNTIME_FUNCTION(MaybeObject*, Runtime_CreateArrayLiteralShallow) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 3);
   CONVERT_ARG_CHECKED(FixedArray, literals, 0);
   CONVERT_SMI_ARG_CHECKED(literals_index, 1);
   CONVERT_ARG_CHECKED(FixedArray, elements, 2);
 
   // Check if boilerplate exists. If not, create it first.
   Handle<Object> boilerplate(literals->get(literals_index), isolate);
   if (*boilerplate == isolate->heap()->undefined_value()) {
+    ASSERT(*elements != isolate->heap()->empty_fixed_array());
     boilerplate = CreateArrayLiteralBoilerplate(isolate, literals, elements);
     if (boilerplate.is_null()) return Failure::Exception();
     // Update the functions literal and return the boilerplate.
     literals->set(literals_index, *boilerplate);
   }
   if (JSObject::cast(*boilerplate)->elements()->map() ==
       isolate->heap()->fixed_cow_array_map()) {
     isolate->counters()->cow_arrays_created_runtime()->Increment();
   }
   return isolate->heap()->CopyJSObject(JSObject::cast(*boilerplate));
@@ skipping 4006 matching lines @@
 #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);
     TransitionElementsKind(object, FAST_DOUBLE_ELEMENTS);
+    TransitionElementsKind(boilerplate_object, FAST_DOUBLE_ELEMENTS);
     ASSERT(object->GetElementsKind() == FAST_DOUBLE_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);
     TransitionElementsKind(object, FAST_ELEMENTS);
+    TransitionElementsKind(boilerplate_object, 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.
@@ skipping 8889 matching lines @@
   } else {
     // 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);
   }
 }
 
 
 } }  // namespace v8::internal