Don't generate preparse data if lazy-flag is false.

src/compiler.cc

 // Copyright 2010 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 251 matching lines @@
   // Do a lookup in the compilation cache but not for extensions.
   Handle<SharedFunctionInfo> result;
   if (extension == NULL) {
     result = CompilationCache::LookupScript(source,
                                             script_name,
                                             line_offset,
                                             column_offset);
   }
 
   if (result.is_null()) {
-    // No cache entry found. Do pre-parsing and compile the script.
+    // No cache entry found. Do pre-parsing, if it makes sense, and compile
+    // 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.
+    // TODO(lrn): Maybe *only* collect function info, not symbol info, in
+    // this case, since it's just replacing one hash-lookup with another.
     ScriptDataImpl* pre_data = input_pre_data;
-    if (pre_data == NULL && source_length >= FLAG_min_preparse_length) {
+    if (pre_data == NULL
+        && FLAG_lazy
+        && source_length >= FLAG_min_preparse_length) {
       pre_data = PreParse(source, NULL, 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);
@@ skipping 284 matching lines @@
       PROFILE(CodeCreateEvent(Logger::ToNativeByScript(tag, *script),
                               *code, *func_name));
       OPROFILE(CreateNativeCodeRegion(*func_name,
                                       code->instruction_start(),
                                       code->instruction_size()));
     }
   }
 }
 
 } }  // namespace v8::internal