Sequential Rewriting and Synthesis
نویسندگان
چکیده
Present industrial applications require that logic synthesis should be scalable, which means that the algorithms used should have essentially linear complexity in circuit size. For this, we propose sequential rewriting and mapping with sequential choices. Sequential rewriting includes combinational rewriting and inherits its low computational complexity. During sequential rewriting, a history And-Inverter-Graph (HAIG) can be constructed, which compactly records all logic structures created, in a graph using sequential choice nodes. These combine both combinationally and sequentially equivalent nodes in a single equivalence class. The HAIG, which represents multiple structures, can be used to substantially improve the quality of technology mapping. An invariant is maintained for discarding rewriting steps for which an equivalent initial state does not exist. Experiments indicate that the HAIG can be constructed with less than 5% overhead in runtime for very large practical circuits.
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