a.Reg = arm64.REG_UXTW + Rnum
			}
		case "UXTX":
			if a.Type == obj.TYPE_MEM {
				return errors.New("invalid shift for the register offset addressing mode")
			}
			a.Reg = arm64.REG_UXTX + Rnum
		case "SXTB":
			if a.Type == obj.TYPE_MEM {
				return errors.New("invalid shift for the register offset addressing mode")
			}
			a.Reg = arm64.REG_SXTB + Rnum
		case "SXTH":
			if a.Type == obj.TYPE_MEM {

	SUBW	ZR<<14, R19, R13                // 6d3a1f4b
	CMP	R2.SXTH, R13                    // bfa122eb
	CMN	R1.SXTX<<2, R10                 // 5fe921ab
	CMPW	R2.UXTH<<3, R11                 // 7f2d226b
	CMNW	R1.SXTB, R9                     // 3f81212b
	ADD	R1<<1, RSP, R3                  // e367218b
	ADDW	R1<<2, R3, RSP                  // 7f48210b
	SUB	R1<<3, RSP                      // ff6f21cb