Synthesis supports the set_multicycle_path
constraint. It can greatly improve the timing QoR (for setup only) by relaxing long
paths that are not functionally active at every clock cycle.
As for synthesis, multicycle path exceptions help the implementation timing-driven
algorithms to focus on the real critical paths. The hold requirements are important only
during routing. If a setup relationship was adjusted with a set_multicycle_path constraint but not its corresponding hold
relationships, the worst hold requirement can become too hard to meet if it is over 2 or
3 ns. This situation can have a negative impact on setup slack because of the additional
delay inserted by the router while fixing hold violations.