Lazy man's logic synthesis

Deriving a circuit for a Boolean function or improving an available circuit are typical tasks solved by logic synthesis. Numerous algorithms in this area have been proposed and implemented over the last 50 years. This paper presents a "lazy” approach to logic synthesis based on the following observations: (a) optimal or near-optimal circuits for many practical functions are already derived by the tools, making it unnecessary to implement new algorithms or even run the old ones repeatedly; (b) larger circuits are composed of smaller ones, which are often isomorphic up to a permutation/negation of inputs/outputs. Experiments confirm these observations. Moreover, a case-study shows that logic level minimization using lazy man's synthesis improves delay after LUT mapping into 4- and 6-input LUTs, compared to earlier work on high-effort delay optimization.