Design rule checks (DRCs) examine the design and report common issues. During implementation, the tools run DRCs again. After placement and routing, the DRCs become more complete and comprehensive.
Review the DRC messages, critical warnings, and warnings early in the flow to avoid issues later.
Critical warnings during early design stages become errors later during
implementation and block bitstream creation. In the previous example from a
post-synthesized design, the optional report DRC step reports a critical warning for
unconstrained I/Os. The post-route DRC report also lists these critical warnings. At the
write_bitstream stage, these critical warnings
escalate to error-level severity and prevent bitstream generation.
Review the DRC reports early to identify and correct areas in the design that require modification.