Speculation in elastic systems

Abstract

Speculation is a well-known technique for increasing parallelism of the microprocessor pipelines and hence their performance. While implementing speculation in modern design practice is error-prone and mostly ad-hoc, this paper proposes a correct-by-construction method for implementing speculation in Elastic Systems. The technique is based on applying provably correct transformations such as early evaluation, insertion of anti-tokens and bubbles, retiming, and sharing. It allows to explore different micro-architectural solutions for better design trade-offs. The benefits of speculation are illustrated with two examples in which these transformations are systematically applied. The method proposed in this paper is amenable for automation in a synthesis flow.