set_input_delay dc_shell
Hi...
Use set_input_delay when the input to your module is delayed (due to logic outside your module and inside another module).
This will let DC know that your logic does not have the entire clock cycle to meet timing.
For example, if the input pin "request" is sent from another module, and that module has decoding logic, arbirtrationl logic, etc .... the input "request" to your module may not get to you until 2 ns later. Therefore, you have the clock_period minus 2 ns to go through your own logic.
Usually, 2 ns of set_input_delay is a good start. But you need to check where the signals are coming from and adjust accordingly.