Scalable min-register retiming under timing and initializability constraints

We demonstrate that a maximum-flow-based approach to register-minimization is a useful platform for incorporating varied design constraints. In this work, we extend the flow-based formulation to include timing constraints and to guarantee the existence of an equivalent initial state. Reducing the register count is motivated by positive consequences for physical design, verification, and power consumption, but it is critically necessary for synthesis that these timing and functionality requirements are also met. Our solution is optimum in the number of registers under either or both constraints and also possesses several other distinct advantages: the runtime is significantly faster than comparable techniques, the algorithm is capable of early termination with a timing-feasible solution, and both maximum and minimum path constraints can be specified.