1. A computer readable medium storing computer executable instructions for a method useful in synthesis of an integrated circuit, the method comprising: using a computer to: receiving a constraint set for each mode at which a circuit to be synthesized is expected to be operable, each constraint set including a voltage and a frequency corresponding to that voltage; selecting a voltage as a base mode voltage; translating frequencies corresponding to voltages different from the base mode voltage into equivalent frequencies, each corresponding to the base mode voltage, and indicative of the relative difficulty to synthesize the circuit to be operable within each constraint set; and based at least in part on the equivalent frequencies, selecting a constraint set for use in a first synthesis of the circuit.