case arg_immediate_optional_0_15_CRm:
		crm := (x >> 8) & (1<<4 - 1)
		return Imm_clrex(crm)

	case arg_immediate_optional_0_65535_imm16:
		imm16 := (x >> 5) & (1<<16 - 1)
		return Imm_dcps(imm16)

	case arg_immediate_OptLSL_amount_16_0_16:
		imm16 := (x >> 5) & (1<<16 - 1)
		hw := (x >> 21) & (1<<2 - 1)
		shift := hw * 16
		if shift > 16 {
			return nil
		}