anchor.diff:  
   
   (defmacro define-fast-memcpy (&key memcpy-name type size)
  +  (declare (ignore type))
     (let ((%memcpy-name (concat-symbols '% memcpy-name)))
       `(progn
          (eval-always
  
positive.code:            (let ((memset-fun ',%memset-name))
               `(,memset-fun ,ptr ,index ,n-words ,fill-word ,scale ,offset)))))))
  
  (define-fast-memset :memset-name fast-memset/4 :type (unsigned-byte 32) :size :dword)
  
  #+x86-64
  
negative.code: 
  
  (defmacro define-fast-memset (&key memset-name type size)
    (declare (ignorable size))
    (let ((%memset-name (concat-symbols '% memset-name)))
      `(progn
         (eval-always
  