vtw_next
base = vtw_next(ctl, base);
base = vtw_next(ctl, base);
ctl->alloc.v = vtw_next(ctl, vtw);
ctl->oldest.v = vtw = vtw_next(ctl, vtw);
vtw = vtw_next(ctl, vtw);
vtw = vtw_next(ctl, vtw);
ctl->oldest.v = vtw_next(ctl, vtw);