Trade-off between energy and quality of service through dynamic operand truncation and fusion

Energy efficiency has emerged as a major design concern for embedded and portable electronics. Conventional approaches typically impact performance and often require significant design-time modifications. In this paper, we propose a novel approach for improving energy efficiency through judicious fusion of operations. The proposed approach has two major distinctions: (1) the fusion is enabled by operand truncation, which allows representing multiple operations into a reasonably sized lookup table (LUT); and (2) it works for large varieties of functions. Most applications in the domain of digital signal processing (DSP) and graphics can tolerate some computation error without large degradation in output quality. Our approach improves energy efficiency with graceful degradation in quality. The proposed fusion approach can be applied to trade-off energy efficiency with quality at run time and requires virtually no circuit or architecture level modifications in a processor. Using our software tool for automatic fusion and truncation, the effectiveness of the approach is studied for four common applications. Simulation results show promising improvements (19-90\%) in energy delay product with minimal impact on quality.