n, i, ok := dtoi(mask)
	if !ok || i != len(mask) || n < 0 || n > ipAddr.BitLen() {
		return nil, nil, &ParseError{Type: "CIDR address", Text: s}
	}
	m := CIDRMask(n, ipAddr.BitLen())
	addr16 := ipAddr.As16()
	return IP(addr16[:]), &IPNet{IP: IP(addr16[:]).Mask(m), Mask: m}, nil
}

func copyIP(x IP) IP {
	y := make(IP, len(x))
	copy(y, x)
	return y

	}
	if prefixBits&haveHintTaken != 0 {
		prefix += "hint-taken "
	}
	if prefixBits&haveHintNotTaken != 0 {
		prefix += "hint-not-taken "
	}
	if prefixBits&haveAddr16 != 0 {
		prefix += "addr16 "
	}
	if prefixBits&haveAddr32 != 0 {
		prefix += "addr32 "
	}
	if prefixBits&haveData16 != 0 {
		prefix += "data16 "
	}
	if prefixBits&haveData32 != 0 {
		prefix += "data32 "
	}

	PrefixGS:       "GS",
	PrefixSS:       "SS",
	PrefixLOCK:     "LOCK",
	PrefixREP:      "REP",
	PrefixREPN:     "REPN",
	PrefixAddrSize: "ADDRSIZE",
	PrefixDataSize: "DATASIZE",
	PrefixAddr16:   "ADDR16",
	PrefixData16:   "DATA16",
	PrefixAddr32:   "ADDR32",
	PrefixData32:   "DATA32",
	PrefixBND:      "BND",
	PrefixXACQUIRE: "XACQUIRE",
	PrefixXRELEASE: "XRELEASE",
	PrefixREX:      "REX",

	inst.DataSize = dataMode
	inst.AddrSize = addrMode
	inst.Mode = mode
	inst.Len = pos
	return inst, nil
}

var errInternal = errors.New("internal error")

// addr16 records the eight 16-bit addressing modes.
var addr16 = [8]Mem{
	{Base: BX, Scale: 1, Index: SI},
	{Base: BX, Scale: 1, Index: DI},
	{Base: BP, Scale: 1, Index: SI},
	{Base: BP, Scale: 1, Index: DI},
	{Base: SI},
	{Base: DI},

		case PrefixPN:
			op += ",pn"
			continue

		case PrefixPT:
			op += ",pt"
			continue

		case PrefixAddrSize, PrefixAddr16, PrefixAddr32:
			// For unknown reasons, if the addr16 prefix is repeated,
			// libopcodes displays all but the last as addr32, even though
			// the addressing form used in a memory reference is clearly
			// still 16-bit.
			n := 32
			if inst.Mode == 32 {
				n = 16