anchor.diff:    (reg-field rsp                445)
     (reg-field ss                 446))
   
  +;;; Aliases for a few registers.
  +
   (defun thread-frame-pointer (thread)
     (thread-state-rbp thread))
   
  
positive.code:        list)
      (push current list)))
  
  (defun %pop-foothold ()
    (safe-without-interrupts ()
      (pop (thread-pending-footholds (current-thread)))))
  
negative.code: (defun (setf thread-stack-pointer) (value thread)
    (setf (thread-state-rsp thread) value))
  
  ;;; Locking macros.
  
  (defmacro with-global-thread-lock ((&optional) &body body)
    `(with-symbol-spinlock (*global-thread-lock*)
       ,@body))
  
  (defmacro with-thread-lock ((thread) &body body)
    (let ((sym (gensym "thread")))
  