In the following figure, a create_clock constraint is defined on the
MMCM instance pin CLKOUT0. This overrides the automatically derived
clock created by Vivado and removes the relationship with the incoming clock.
To rename the auto-derived clock, add this constraint immediately after defining the master clock in your constraint files:
create_generated_clock -name clkName [get_pins clk_gen_i0/clk_core_i0/inst/mmcme3_adv_inst/CLKOUT0]Figure 1. Invalid Primary Clock on Clock Modifying Block