anchor.diff:                   (t
                     (slot-missing (class-of object) object slot-name 'setf new-value)
                     new-value))))))
  +
  +(defun (sys.int::cas std-slot-value) (old new instance slot-name)
  +  (multiple-value-bind (slots location)
  +      (slot-location-in-instance instance slot-name)
  +    (when (not location)
  +      (return-from std-slot-value
  +        (slot-missing (class-of instance) instance slot-name 'sys.int::cas (list old new))))
  +    (sys.int::cas (slot-contents slots location) old new)))
  +(defun (sys.int::cas slot-value) (old new object slot-name)
  +  (cond ((std-class-p (class-of (class-of object)))
  +         (sys.int::cas (std-slot-value object slot-name) old new))
  +        (t
  +         (let ((slot (find-effective-slot object slot-name)))
  +           (cond (slot
  +                  (sys.int::cas (slot-value-using-class (class-of object) object slot) old new))
  +                 (t
  +                  (values (slot-missing (class-of object) object slot-name 'sys.int::cas (list old new)))))))))
   
   (defun std-slot-boundp (instance slot-name)
     (multiple-value-bind (slots location)
  
positive.code:   (if (consp location)
        (setf (cdr location) new-value)
        (setf (svref slots location) new-value)))
  
  (defun fast-sv-position (value simple-vector)
    (dotimes (i (array-dimension simple-vector 0))
  
negative.code: (defmethod (setf slot-value-using-class) (new-value (class std-class) instance (slot standard-effective-slot-definition))
    (setf (std-slot-value instance (slot-definition-name slot)) new-value))
  
  (defgeneric (sys.int::cas slot-value-using-class) (old new class instance slot))
  (defmethod (sys.int::cas slot-value-using-class) (old new (class std-class) instance (slot standard-effective-slot-definition))
    (sys.int::cas (std-slot-value instance (slot-definition-name slot)) old new))
  
  (defgeneric slot-boundp-using-class (class instance slot))
  (defmethod slot-boundp-using-class ((class std-class) instance (slot standard-effective-slot-definition))
    (std-slot-boundp instance (slot-definition-name slot)))
  