Preallocate transitioned maps for TypedArrays.

src/objects-inl.h

 // 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 1466 matching lines @@
 }
 
 
 void JSObject::initialize_properties() {
   ASSERT(!GetHeap()->InNewSpace(GetHeap()->empty_fixed_array()));
   WRITE_FIELD(this, kPropertiesOffset, GetHeap()->empty_fixed_array());
 }
 
 
 void JSObject::initialize_elements() {
-  ASSERT(map()->has_fast_smi_or_object_elements() ||
-         map()->has_fast_double_elements());
-  ASSERT(!GetHeap()->InNewSpace(GetHeap()->empty_fixed_array()));
-  WRITE_FIELD(this, kElementsOffset, GetHeap()->empty_fixed_array());
+  if (map()->has_fast_smi_or_object_elements() ||
+      map()->has_fast_double_elements()) {
+    ASSERT(!GetHeap()->InNewSpace(GetHeap()->empty_fixed_array()));
+    WRITE_FIELD(this, kElementsOffset, GetHeap()->empty_fixed_array());
+  } else if (map()->has_external_array_elements()) {
+    ExternalArray* empty_array = GetHeap()->EmptyExternalArrayForMap(map());
+    ASSERT(!GetHeap()->InNewSpace(empty_array));
+    WRITE_FIELD(this, kElementsOffset, empty_array);
+  } else {
+    UNREACHABLE();
+  }
 }
 
 
 MaybeObject* JSObject::ResetElements() {
   if (map()->is_observed()) {
     // Maintain invariant that observed elements are always in dictionary mode.
     SeededNumberDictionary* dictionary;
     MaybeObject* maybe = SeededNumberDictionary::Allocate(GetHeap(), 0);
     if (!maybe->To(&dictionary)) return maybe;
     if (map() == GetHeap()->non_strict_arguments_elements_map()) {
@@ skipping 4713 matching lines @@
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_