Although tremendous advances have been accomplished in logic synthesis in the past two decades, in some cases logic synthesis still cannot attain the improvements possible by clever designers. This, in part, is a result of logic synthesis not optimizing across register boundaries. In this paper we focus on precomputation as a resynthesis technique capable of resynthesizing across register boundaries. By using precomputation, a critical signal is computed earlier in time, thus allowing it to be

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... ombinationally optimized with logic from previous pipeline stages. Precomputation automatically discovers some standard circuit transformations like b ypassing and lookahead. In addition, precomputation can be used in conjunction with combinational logic synthesis to resynthesize a circuit to obtain better performance. This paper contributes to the understanding and development of precomputation. First, it provides a synthesis algorithm for precomputation. Second, it demonstrates how precomputation can be used to improve sequential logic resynthesis and reports the results of applyinga heuristic to a subset of the MCNC benchmarks. Third, it illustrates how precomputation generalizes and uni es bypassing and lookahead two important and practical architectural transformations often used in processor design and high-level synthesis of DSP processors. Finally, it clari es the relationships among precomputation, retiming, and implicit retiming.