Error(19173): The instance name "altshift_taps:datwords_rr_rtl_0" is already in use elsewhere in this scope. If instantiated in a generate block, ensure the block is named.

Due to a problem in the Intel® Quartus® Prime Pro Edition Software version 18.0 Update 1 and earlier, you may see this synthesis error message during compilation when a 50G Interlaken Intel® FPGA IP is instantiated in an Intel® Arria® 10 design.

To work around this problem,  add the following in the Quartus Setting File (.qsf) to prevent the affected register being inferred as altshift_taps.

For example:

set_instance_assignment -name AUTO_SHIFT_REGISTER_RECOGNITION OFF -to * -entity ilk_iw4_rx_channel_filter 

This problem is fixed starting in the Intel® Quartus® Prime Pro Edition Software version 18.1.