(when (>= size +stable-sort-fast-merge-limit+)
(cond ((not (funcall test (funcall key (car list2)) ; stability
(funcall key (car tail1)))) ; trickery
(when (>= size +stable-sort-fast-merge-limit+)
(cond ((not (funcall test (funcall key (car list2)) ; stability
(funcall key (car tail1)))) ; trickery