Optimized scanner to avoid virtual calls for every character read.

src/compiler.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
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@@ skipping 262 matching lines @@
     // the script.
     // Building preparse data that is only used immediately after is only a
     // saving if we might skip building the AST for lazily compiled functions.
     // I.e., preparse data isn't relevant when the lazy flag is off, and
     // for small sources, odds are that there aren't many functions
     // that would be compiled lazily anyway, so we skip the preparse step
     // in that case too.
     ScriptDataImpl* pre_data = input_pre_data;
     if (pre_data == NULL
         && source_length >= FLAG_min_preparse_length) {
-      pre_data = ParserApi::PartialPreParse(source, NULL, extension);
+      if (source->IsExternalTwoByteString()) {
+        ExternalTwoByteStringUC16CharacterStream stream(
+            Handle<ExternalTwoByteString>::cast(source), 0, source->length());

[Erik Corry, 2010/12/07 12:27:30]

This is found several places.  Perhaps the constructor should just take a string
and do the cast in the constructor.  That way you concentrate the ugliness in
one place.

[Lasse Reichstein, 2010/12/07 14:05:54]

As discussed offline, let's leave it so that the case is near the test.

+        pre_data = ParserApi::PartialPreParse(&stream, extension);
+      } else {
+        GenericStringUC16CharacterStream stream(source, 0, source->length());
+        pre_data = ParserApi::PartialPreParse(&stream, extension);
+      }
     }
 
     // Create a script object describing the script to be compiled.
     Handle<Script> script = Factory::NewScript(source);
     if (natives == NATIVES_CODE) {
       script->set_type(Smi::FromInt(Script::TYPE_NATIVE));
     }
     if (!script_name.is_null()) {
       script->set_name(*script_name);
       script->set_line_offset(Smi::FromInt(line_offset));
@@ skipping 255 matching lines @@
                               *code,
                               *name));
       OPROFILE(CreateNativeCodeRegion(*name,
                                       code->instruction_start(),
                                       code->instruction_size()));
     }
   }
 }
 
 } }  // namespace v8::internal