fun Rx_dest(var inst : InstOp, i0) {
    val ii = i0?ext(32);
    if(ii >= 8) {
	val win = (CWP?cvt(ulong) - (ii / 16) + 8 ) % 8 ;
	ii = ii & 0xf?ext(32);
	inst.destq?push_back(rmap_dest(2 ,16*win+ii));
    } else if(ii > 0) {
	inst.destq?push_back(rmap_dest(1 ,ii-1));
    } else {
	val dest : DestRef;
	dest.rtype = 0 ?cvt(uchar);
	dest.regnum = 0?cvt(uchar);
	inst.destq?push_back(dest);
    }
}