Allocate arguments object on-demand instead of at function entry....

src/ast.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 784 matching lines @@
 
   // Type testing & conversion
   virtual Property* AsProperty() {
     return var_ == NULL ? NULL : var_->AsProperty();
   }
   virtual VariableProxy* AsVariableProxy()  { return this; }
 
   Variable* AsVariable() {
     return this == NULL || var_ == NULL ? NULL : var_->AsVariable();
   }
+
   virtual bool IsValidLeftHandSide() {
     return var_ == NULL ? true : var_->IsValidLeftHandSide();
   }
+
   bool IsVariable(Handle<String> n) {
     return !is_this() && name().is_identical_to(n);
   }
 
+  bool IsArguments() {
+    Variable* variable = AsVariable();
+    return (variable == NULL) ? false : variable->is_arguments();
+  }
+
   // If this assertion fails it means that some code has tried to
   // treat the special "this" variable as an ordinary variable with
   // the name "this".
   Handle<String> name() const  { return name_; }
   Variable* var() const  { return var_; }
   UseCount* var_uses()  { return &var_uses_; }
   UseCount* obj_uses()  { return &obj_uses_; }
   bool is_this() const  { return is_this_; }
   bool inside_with() const  { return inside_with_; }
 
@@ skipping 61 matching lines @@
   };
 
   Slot(Variable* var, Type type, int index)
       : var_(var), type_(type), index_(index) {
     ASSERT(var != NULL);
   }
 
   virtual void Accept(AstVisitor* v);
 
   // Type testing & conversion
-  virtual Slot* AsSlot()  { return this; }
+  virtual Slot* AsSlot() { return this; }
 
   // Accessors
-  Variable* var() const  { return var_; }
-  Type type() const  { return type_; }
-  int index() const  { return index_; }
+  Variable* var() const { return var_; }
+  Type type() const { return type_; }
+  int index() const { return index_; }
+  bool is_arguments() const { return var_->is_arguments(); }
 
  private:
   Variable* var_;
   Type type_;
   int index_;
 };
 
 
 class Property: public Expression {
  public:
@@ skipping 800 matching lines @@
 #undef DEF_VISIT
 
  private:
   bool stack_overflow_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_AST_H_