Use direct copy and templates to speed up flattening of strings.

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 1351 matching lines @@
 bool String::is_ascii_representation() {
   return is_ascii_representation_map(map());
 }
 
 
 bool String::is_ascii_representation_map(Map* map) {
   return (map->instance_type() & kStringEncodingMask) != 0;
 }
 
 
+int String::full_representation_tag() {

[Christian Plesner Hansen, 2008/10/21 14:16:22]

We have a lot of these methods with lower-case names that do nontrivial work. 
We have to be sure they're really fast, otherwise we should rename them to upper
camel case names.

[Erik Corry, 2008/10/22 11:59:48]

This one is certainly trivial.

+  return map()->instance_type() &
+         (kStringRepresentationMask | kStringEncodingMask);
+}
+
+
 StringRepresentationTag String::representation_tag() {
   return map_representation_tag(map());
 }
 
 
 StringRepresentationTag String::map_representation_tag(Map* map) {
   uint32_t tag = map->instance_type() & kStringRepresentationMask;
   return static_cast<StringRepresentationTag>(tag);
 }
 
@@ skipping 946 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_