}
			a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_8B & 15) << 5)
		case "B16":
			if isIndex {
				return errors.New("invalid register extension")
			}
			a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_16B & 15) << 5)
		case "H4":
			if isIndex {
				return errors.New("invalid register extension")
			}
			a.Reg = arm64.REG_ARNG + (reg & 31) + ((arm64.ARNG_4H & 15) << 5)
		case "H8":
			if isIndex {