case arg_registers:
		return RegList(x & (1<<16 - 1))

	case arg_registers2:
		x &= 1<<16 - 1
		n := 0
		for i := 0; i < 16; i++ {
			if x>>uint(i)&1 != 0 {
				n++
			}
		}
		if n < 2 {
			return nil
		}
		return RegList(x)

	case arg_registers1:
		Rt := (x >> 12) & (1<<4 - 1)
		return RegList(1 << Rt)

	case arg_satimm4:

			return fmt.Sprintf("%s(SB)", s)
		}
		return fmt.Sprintf("%#x", addr)

	case Reg:
		if a < 16 {
			return fmt.Sprintf("R%d", int(a))
		}

	case RegList:
		var buf bytes.Buffer
		start := -2
		end := -2
		fmt.Fprintf(&buf, "[")
		flush := func() {
			if start >= 0 {
				if buf.Len() > 1 {
					fmt.Fprintf(&buf, ",")
				}
				if start == end {