Logic synthesis and circuit customization using extensive external don't-cares

Abstract

Traditional digital circuit synthesis flows start from an HDL behavioral definition and assume that circuit functions are almost completely defined, making don't-care conditions rare. However, recent design methodologies do not always satisfy these assumptions. For instance, third-party IP blocks used in a system-on-chip are often overdesigned for the requirements at hand. By focusing only on the input combinations occurring in a specific application, one could resynthesize the system to greatly reduce its area and power consumption. Therefore we extend modern digital synthesis with a novel technique, called SWEDE, that makes use of extensive external don't-cares. In addition, we utilize such don't-cares present implicitly in existing simulation-based verification environments for circuit customization. Experiments indicate that SWEDE scales to large ICs with half-million input vectors and handles practical cases well.