Fast Compiled Logic Simulation Using Linear BDDs

Abstract

This paper presents a new technique for compiled zero delay logic simulation, and includes extensive experiments that demonstrate its performance on standard benchmarks. Our compiler partitions the circuit into fanout-free regions (FFRs), transforms each FFR into a linear sized BDD, and converts each BDD into executable code. In our approach, the computation is sublinear in the number of variables within each partition because only one path, from root to leaf, of the BDD is executed; therefore in many cases, substantial computation is avoided. In this way, our approach gets some of the advantages of oblivious as well as demand-driven evaluation. We investigated the impact of various heuristics on performance, and based on this data, we recommend good values for design parameters. A performance improvement of up to 67% over oblivious simulation is observed for our benchmarks.