Performance optimization of pipelined logic circuits using peripheral retiming and resynthesis

We consider the problem of minimizing the cycle time of a given pipelined circuit. Existing approaches are suboptimal since they do not consider the possibility of simultaneously resynthesizing the combinational logic and moving the latches using retiming. In 1101 the idea of simultaneous retiming and resynthesis was introduced. We use the concepts presented there to optimize a pipelined circuit to meet a given cycle time. An instance of the pipelined cycle optimization problem is specified by the circuit, a set of input arrival times relative to the clock, a set of output required times relative to the clock, and a given cycle time that it must meet. Given the instance of the pipelined performance optimization problem we construct an instance of a combinational speedup problem. This is specified by a combinational logic circuit, a set of arrival times on the inputs, and a set of required times for the outputs which must be met. We then give a constructive proof that the pipelined problem has a solution if and only if the combinational problem has a solution. This result is significant since it shows it is enough to consider only the combinational speedup problem and all known techniques for that (e.g., [12], [13]) can be directly applied to generate a solution for the pipelined problem.