A Chisel Framework for Flexible Design Space Exploration through a Functional Approach

Abstract

As the need for efficient digital circuits is ever growing in the industry, the design of such systems remains daunting, requiring both expertise and time. In an attempt to close the gap between software development and hardware design, powerful features such as functional and object-oriented programming have been used to define new languages, known as Hardware Construction Languages. In this article, we investigate the usage of such languages — more precisely, of Chisel — in the context of Design Space Exploration, and propose a novel design methodology to build custom and adaptable design flows. We apply an innovative functional approach to define flexible strategies for design space exploration, based on the composition of basic exploration steps, and provide a library of basic strategies along with a proof-of-concept framework — which we believe to be the first Chisel-based DSE framework. This framework fully integrates within the ecosystem of Chisel, to allow users to define their DSE processes in the same framework (and language) they use to describe their designs. We demonstrate our methodology through several use cases, illustrating how our functional approach makes it possible to consider various metrics of interest when building exploration processes — in particular, we provide a quality of service -driven exploration example. The methodology presented in this work makes use of designers’ expertise to reduce the time required for hardware design, in particular for Design Space Exploration, and its application should ease digital design and enhance hardware developpers’ productivity.