anchor.diff:  
   (defun mod64* (a b)
     (declare (type (unsigned-byte 64) a b))
  +  #+ecl
  +  (ffi:c-inline (a b)
  +                (:uint64-t :uint64-t)
  +                :uint64-t
  +                "#0 * #1"
  +                :one-liner t
  +                :side-effects nil)
  +  #-ecl
     (ldb (byte 64 0) (* a b)))
   
   #+sbcl
  
positive.code: 
  (defun mod64- (a b)
    (declare (type (unsigned-byte 64) a b))
    (ldb (byte 64 0) (- a b)))
  
  #+sbcl
  
negative.code:          (ftype (function ((unsigned-byte 64)) (unsigned-byte 64)) mod64lognot))
  
  (defun mod64lognot (num)
    (declare (type (unsigned-byte 64) num))
    #+ecl
    (ffi:c-inline (num)
                  (:uint64-t)
                  :uint64-t
                  "~#0"
                  :one-liner t
                  :side-effects nil)
    #-ecl
    (ldb (byte 64 0) (lognot num)))
  
  #+sbcl
  