}
		switch ext {
		case "UXTB":
			if a.Type == obj.TYPE_MEM {
				return errors.New("invalid shift for the register offset addressing mode")
			}
			a.Reg = arm64.REG_UXTB + Rnum
		case "UXTH":
			if a.Type == obj.TYPE_MEM {
				return errors.New("invalid shift for the register offset addressing mode")
			}
			a.Reg = arm64.REG_UXTH + Rnum
		case "UXTW":

	SUB	R19.UXTH<<4, R2, R21            // 553033cb
	SUBW	R1.UXTX<<1, R3, R2              // 6264214b
	SUBS	R3.UXTX, R8, R9                 // 096123eb
	SUBSW	R17.UXTH, R15, R21              // f521316b
	SUBW	ZR<<14, R19, R13                // 6d3a1f4b
	CMP	R2.SXTH, R13                    // bfa122eb
	CMN	R1.SXTX<<2, R10                 // 5fe921ab
	CMPW	R2.UXTH<<3, R11                 // 7f2d226b