anchor.diff:  (defun salsa-core (n-rounds buffer state)
     (declare (type salsa20-keystream-buffer buffer))
     (declare (type salsa20-state state))
  +  #+(and sbcl x86-64)
  +  (x-salsa-core n-rounds buffer state)
  +  #-(and sbcl x86-64)
     (let ((x (make-array 16 :element-type '(unsigned-byte 32))))
       (declare (dynamic-extent x))
       (replace x state)
  
positive.code: (defun salsa20/20-core (buffer state)
    (declare (type salsa20-keystream-buffer buffer))
    (declare (type salsa20-state state))
    (salsa-core 10 buffer state))
  
  (defclass salsa20 (stream-cipher)
    ((state :reader salsa20-state
  
negative.code:         (quarter-round 12 13 14 15))
        (dotimes (i 16)
          (setf (ub32ref/le buffer (* i 4))
                (mod32+ (aref x i) (aref state i))))))
    (values))
  
  (defun salsa20/8-core (buffer state)
    (declare (type salsa20-keystream-buffer buffer))
  