(unless (tn-sc tn)
(let* ((scs (primitive-type-scs (tn-primitive-type tn)))
(sc (if (rest scs)
(select-tn-representation tn scs costs)
(svref *backend-sc-numbers* (first scs)))))
(unless (tn-sc tn)
(let* ((scs (primitive-type-scs (tn-primitive-type tn)))
(sc (if (rest scs)
(select-tn-representation tn scs costs)
(svref *backend-sc-numbers* (first scs)))))