anchor.diff:    (setf *r8-value* (list (gensym))))
   
   ;;; TODO: Check for constants here.
  -(defbuiltin sys.int::%%bind (symbol value) ()
  +(defbuiltin sys.int::%%bind (symbol value) (t nil)
     ;; Don't kill here, going to reload & kill later in the function.
     (load-in-reg :r9 symbol)
     (smash-r8)
  
positive.code:         `(sys.lap-x86:add64 (,+binding-stack-gs-offset+) 16))
    ''nil)
  
  (defbuiltin sys.int::%%disestablish-block-or-tagbody () ()
    ;; Top entry in the binding stack is a block or tagbody entry.
    ;; It's a environment simple-vector & an offset.
    ;; Pop the stack & set env[offset] = NIL.
  
negative.code:         `(sys.lap-x86:mov64 :r8 (,+binding-stack-gs-offset+)))
    (setf *r8-value* (list (gensym))))
  
  (defbuiltin sys.int::%%block-info-binding-stack-pointer (block-info) ()
    ;; Read the saved binding stack pointer from a block-info.
    (load-in-r8 block-info t)
    (smash-r8)
    (emit `(sys.lap-x86:mov64 :r8 (:r8 8)))
    (setf *r8-value* (list (gensym))))
  
  (defbuiltin sys.int::%%tagbody-info-binding-stack-pointer (tagbody-info) ()
    ;; Read the saved binding stack pointer from a tagbody-info.
    (load-in-r8 tagbody-info t)
    (smash-r8)
  