Using ACL2 to Verify Loop Pipelining in Behavioral Synthesis

TL;DR

This paper explores using ACL2 to formally verify the complex loop pipelining transformations in behavioral synthesis, addressing the semantic gap challenge with a novel invariant and ongoing proof efforts.

Contribution

It introduces a new key invariant formalized in ACL2 for verifying loop pipelining, providing insights and trade-offs in the proof process.

Findings

Key invariant formalized in ACL2 for loop pipelining verification

Insights into the verification process and challenges

Preliminary proof progress and potential value to ACL2 community

Abstract

Behavioral synthesis involves compiling an Electronic System-Level (ESL) design into its Register-Transfer Level (RTL) implementation. Loop pipelining is one of the most critical and complex transformations employed in behavioral synthesis. Certifying the loop pipelining algorithm is challenging because there is a huge semantic gap between the input sequential design and the output pipelined implementation making it infeasible to verify their equivalence with automated sequential equivalence checking techniques. We discuss our ongoing effort using ACL2 to certify loop pipelining transformation. The completion of the proof is work in progress. However, some of the insights developed so far may already be of value to the ACL2 community. In particular, we discuss the key invariant we formalized, which is very different from that used in most pipeline proofs. We discuss the needs for this invariant, its formalization in ACL2, and our envisioned proof using the invariant. We also discuss some trade-offs, challenges, and insights developed in course of the project.