Avoid double initialization of arrays.

src/objects.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 9265 matching lines @@
 MaybeObject* JSObject::SetFastElementsCapacityAndLength(
     int capacity,
     int length,
     SetFastElementsCapacitySmiMode smi_mode) {
   Heap* heap = GetHeap();
   // We should never end in here with a pixel or external array.
   ASSERT(!HasExternalArrayElements());
 
   // Allocate a new fast elements backing store.
   FixedArray* new_elements;
-  { MaybeObject* maybe = heap->AllocateFixedArrayWithHoles(capacity);
-    if (!maybe->To(&new_elements)) return maybe;
-  }
+  MaybeObject* maybe = heap->AllocateUninitializedFixedArray(capacity);
+  if (!maybe->To(&new_elements)) return maybe;
 
   ElementsKind elements_kind = GetElementsKind();
   ElementsKind new_elements_kind;
   // The resized array has FAST_*_SMI_ELEMENTS if the capacity mode forces it,
   // or if it's allowed and the old elements array contained only SMIs.
   bool has_fast_smi_elements =
       (smi_mode == kForceSmiElements) ||
       ((smi_mode == kAllowSmiElements) && HasFastSmiElements());
   if (has_fast_smi_elements) {
     if (IsHoleyElementsKind(elements_kind)) {
       new_elements_kind = FAST_HOLEY_SMI_ELEMENTS;
     } else {
       new_elements_kind = FAST_SMI_ELEMENTS;
     }
   } else {
     if (IsHoleyElementsKind(elements_kind)) {
       new_elements_kind = FAST_HOLEY_ELEMENTS;
     } else {
       new_elements_kind = FAST_ELEMENTS;
     }
   }
   FixedArrayBase* old_elements = elements();
   ElementsAccessor* accessor = ElementsAccessor::ForKind(elements_kind);
-  { MaybeObject* maybe_obj =
-        accessor->CopyElements(this, new_elements, new_elements_kind);
-    if (maybe_obj->IsFailure()) return maybe_obj;
-  }
+  MaybeObject* maybe_obj =
+      accessor->CopyElements(this, new_elements, new_elements_kind);
+  if (maybe_obj->IsFailure()) return maybe_obj;
+
   if (elements_kind != NON_STRICT_ARGUMENTS_ELEMENTS) {
     Map* new_map = map();
     if (new_elements_kind != elements_kind) {
       MaybeObject* maybe =
           GetElementsTransitionMap(GetIsolate(), new_elements_kind);
       if (!maybe->To(&new_map)) return maybe;
     }
     ValidateElements();
     set_map_and_elements(new_map, new_elements);
   } else {
@@ skipping 4559 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal