case RegExtshiftAmount:
		reg := plan9gpr(a.reg)
		extshift := ""
		amount := ""
		if a.extShift != ExtShift(0) {
			switch a.extShift {
			default:
				extshift = "." + a.extShift.String()

			case lsl:
				extshift = "<<"
				amount = fmt.Sprintf("%d", a.amount)
				return reg + extshift + amount

			case lsr:
				extshift = ">>"
				amount = fmt.Sprintf("%d", a.amount)

	}
	return fmt.Sprintf("#%#x, MSL #%d", is.imm, is.shift-128)
}

type ExtShift uint8

const (
	_ ExtShift = iota
	uxtb
	uxth
	uxtw
	uxtx
	sxtb
	sxth
	sxtw
	sxtx
	lsl
	lsr
	asr
	ror
)

func (extShift ExtShift) String() string {
	switch extShift {
	case uxtb:
		return "UXTB"

	case uxth:
		return "UXTH"

	case uxtw:

				rea.extShift = lsl
			} else {
				rea.extShift = ExtShift(0)
			}
		} else {
			rea.extShift = uxtx
		}
	case 4:
		rea.extShift = sxtb
	case 5:
		rea.extShift = sxth
	case 6:
		rea.extShift = sxtw
	case 7:
		rea.extShift = sxtx
	}
	rea.show_zero = false
	rea.amount = uint8(imm3)
	return rea
}