}
			a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_4H & 15) << 5)
		case "H8":
			if isIndex {
				return errors.New("invalid register extension")
			}
			a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_8H & 15) << 5)
		case "S2":
			if isIndex {
				return errors.New("invalid register extension")
			}
			a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_2S & 15) << 5)
		case "S4":
			if isIndex {