Version 2.2.11...

src/objects-inl.h

 // Copyright 2006-2008 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 1673 matching lines @@
 bool String::Equals(String* other) {
   if (other == this) return true;
   if (StringShape(this).IsSymbol() && StringShape(other).IsSymbol()) {
     return false;
   }
   return SlowEquals(other);
 }
 
 
 Object* String::TryFlatten(PretenureFlag pretenure) {
-  // We don't need to flatten strings that are already flat.  Since this code
-  // is inlined, it can be helpful in the flat case to not call out to Flatten.
-  if (IsFlat()) return this;
+  if (!StringShape(this).IsCons()) return this;
+  ConsString* cons = ConsString::cast(this);
+  if (cons->second()->length() == 0) return cons->first();
   return SlowTryFlatten(pretenure);
 }
 
 
+String* String::TryFlattenGetString(PretenureFlag pretenure) {
+  Object* flat = TryFlatten(pretenure);
+  return flat->IsFailure() ? this : String::cast(flat);
+}
+
+
 uint16_t String::Get(int index) {
   ASSERT(index >= 0 && index < length());
   switch (StringShape(this).full_representation_tag()) {
     case kSeqStringTag | kAsciiStringTag:
       return SeqAsciiString::cast(this)->SeqAsciiStringGet(index);
     case kSeqStringTag | kTwoByteStringTag:
       return SeqTwoByteString::cast(this)->SeqTwoByteStringGet(index);
     case kConsStringTag | kAsciiStringTag:
     case kConsStringTag | kTwoByteStringTag:
       return ConsString::cast(this)->ConsStringGet(index);
@@ skipping 1446 matching lines @@
 #undef WRITE_INT_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_