anchor.diff:  (defclass ior-instruction (single-successor-instruction in-out-mixin)
     ())
   
  +(defmethod compile-ast ((ast ior-ast) value-context successor)
  +  (multiple-value-bind (new-successor new-value-context)
  +      (adapt-value-context value-context 1 1 successor)
  +    (let* ((temps (make-temps (arguments ast)))
  +	   (instruction (make-instance 'ior-instruction
  +				       :inputs temps
  +				       :outputs new-value-context
  +				       :next new-successor)))
  +      (compile-arguments (arguments ast) temps instruction))))
  +
   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   ;;;
   ;;; Word operation XOR.
  
positive.code: (defclass ==-instruction (single-successor-instruction in-out-mixin)
    ())
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;;;
  ;;; Word operation s<.
  
negative.code:   ())
  
  (defmethod compile-ast ((ast memset-ast) value-context successor)
    (multiple-value-bind (new-value-context new-successor)
        (adapt-value-context value-context 0 0 successor)
      (let* ((temps (make-temps (arguments ast)))
  	   (instruction (make-instance 'memset-instruction
  				       :inputs temps
  				       :outputs new-value-context
  				       :next new-successor)))
        (compile-arguments (arguments ast) temps instruction))))
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;;;
  