The manual entry about --idiv_support currently says ...

    If this hardware is available, use --idiv_support=idiv0 to cause these instructions to be used.

But it does not say how to know whether the hardware is available.  One way to do it is to look at the datasheet for the particular device.  If it shows this bullet ...

    Support for Fast Integer Division (FINTDIV)

Then --idiv_support is available.  Otherwise it is not.