return errors.New("unsupported general register extension type: " + ext)

		}
	} else if reg <= arm64.REG_V31 && reg >= arm64.REG_V0 {
		switch ext {
		case "B8":
			if isIndex {
				return errors.New("invalid register extension")
			}
			a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_8B & 15) << 5)
		case "B16":
			if isIndex {
				return errors.New("invalid register extension")
			}