U8_ISASCII
if (U8_ISASCII(*s1) && ((s1 + 1) >= s1last ||
((s1 + 1) < s1last && U8_ISASCII(*(s1 + 1))))) {
if (U8_ISASCII(*s2) && ((s2 + 1) >= s2last ||
((s2 + 1) < s2last && U8_ISASCII(*(s2 + 1))))) {
if (U8_ISASCII(*ib) && ((ib + 1) >= ibtail ||
((ib + 1) < ibtail && U8_ISASCII(*(ib + 1))))) {