dff entity name seems to conflict with Quartus Prime reserved primitve name
The synthesis for PCIe board and Intel SoC run by Quartus reports next problem
Warning (12018): Entity "dff" will be ignored because it conflicts with Quartus Prime primitive name File: /home/pi/fpga/altera/db4cgx15/pcie-ctu_can_fd/mod ules/ctu_can_fd/src/common/dff.vhd Line: 50
I am not sure by what kind of component/entity is instance replaced. May it be that it is totally harmless warning but I would vote for rename anyway.