rotate_left
payload = rotate_left(in->ptr, in->len, rrc, &rotated);
rotate_left(head, node); \
rotate_left(head, parent->_f.parent); \
rotate_left(head, parent); \
rotate_left(head, parent); \
rotate_left(head, tmp); \
rotate_left(struct _n##_rb_head *head, _t *node) \