In current System-on-Chip (SoC) design, the main engineering trade-off concerns hardware efficiency and design effort. Hardware efficiency traditionally regards cost versus performance (in high-volume electronics), but recently energy consumption emerged as a dominant criterion, even in products without batteries. "The" most effective way to increase HW efficiency is to exploit application characteristics in the HW. The traditional way of looking at HW design tends to consider it a time-consuming and tedious task, however. Given the current lack of HW designers, and the pressure of time-to-market, clearly a desire exists to fine-balance the merits and effort of tuning your HW to your application. This paper discusses methods and tool support for HW application-tuning at different levels of granularity. Furthermore we treat several ways of applying reconfigurable HW to allow both silicon reuse and the ability to tune the HW to the application after fabrication. Our main focus is on a methodology for application-tuning the architecture of DSP datapaths. Our primary contribution is on reusing and generalizing this methodology to application-tuning DSP instruction sets, and providing tool support for efficient compilation for these instruction sets. Furthermore, we propose an architecure for a reconfigurable instruction-decoder, enabling application-tuning of the instruction-set after fabrication.
Exact and approximate algorithms for the extension of embedded processor instruction sets