extractinv - extract explicit inverter cells for invertible cell pins

    extractinv [options] [selection]

Searches the design for all cells with invertible pins controlled by a cell
parameter (eg. IS_CLK_INVERTED on many Xilinx cells) and removes the parameter.
If the parameter was set to 1, inserts an explicit inverter cell in front of
the pin instead.  Normally used for output to ISE, which does not support the
inversion parameters.

To mark a cell port as invertible, use (* invertible_pin = "param_name" *)
on the wire in the blackbox module.  The parameter value should have
the same width as the port, and will be effectively XORed with it.

    -inv <celltype> <portname_out>:<portname_in>
        Specifies the cell type to use for the inverters and its port names.
        This option is required.