Comprehensive search for ECO rectification using symbolic sampling
The task of an engineering change order (ECO) is to update the current implementation of a design according to its revised specification with minimum modification. Prior studies show that the amount of design modification majorly depends on the selection of rectification points, i.e., the input pins of gates whose functionality should be rectified with some patch circuitry. In realistic ECOs, as the netlist of the current implementation has been heavily optimized to meet design objectives, it is usually structurally dissimilar to the netlist of a revised specification, which is synthesized only by lightweight optimization. This paper proposes an ECO solution for optimized designs, which is robust against structural dissimilarity caused by design optimization. It locates candidate rectification points in a sampling domain, which significantly improves the scalability of rectification search. To synthesize the circuitry of patches, a structurally independent rewiring formulation is proposed to reuse existing logic in the implementation. Based on the proposed method, a newly developed engine is evaluated on the engineering changes arising in the design of microprocessors. Its ability to derive patches of superior quality is demonstrated in comparison to industrial tools.