Heuristics for area minimization in LUT-based FPGA technology mapping
In this paper, an iterative technology-mapping tool called IMap is presented. It supports depth-oriented (area is a secondary objective), area-oriented (depth is a secondary objective), and duplication-free mapping modes. The edge-delay model (as opposed to the more commonly used unit-delay model) is used throughout. Two new heuristics are used to obtain area reductions over previously published methods. The first heuristic predicts the effects of various mapping decisions on the area of the final solution, and the second heuristic bounds the depth of the mapping solution at each, node. In depth-oriented mode, when targeting five lookup tables (LUTs), IMap obtains depth optimal solutions that are 44.4%, 19.4%, and 5% smaller than those produced by FlowMap, CutMap, and DAOMap, respectively. Targeting the same LUT size in area-oriented mode, IMap obtains solutions that are 17.5% and 9.4% smaller than those produced by duplication-free mapping and ZMap, respectively. IMap is also shown to be highly efficient. Runtime improvements of between 2.3x and 82x are obtained over existing algorithms when targeting five LUTs. Area and runtime results comparing IMap to the other mappers when targeting four and six LUTs are also presented.
circuit optimization circuit synthesis design automation field programmable gate arrays logic design