A Multipurpose Formal RISC-V Specification

RISC-V is a relatively new, open instruction set architecture with a mature ecosystem and an official formal machine-readable specification. It is therefore a promising playground for formal-methods research. However, we observe that different formal-methods research projects are interested in different aspects of RISC-V and want to simplify, abstract, approximate, or ignore the other aspects. Often, they also require different encoding styles, resulting in each project starting a new formalization from-scratch. We set out to identify the commonalities between projects and to represent the RISC-V specification as a program with holes that can be instantiated differently by different projects. Our formalization of the RISC-V specification is written in Haskell and leverages existing tools rather than requiring new domain-specific tools, contrary to other approaches. To our knowledge, it is the first RISC-V specification able to serve as the interface between a processor-correctness proof and a compiler-correctness proof, while supporting several other projects with diverging requirements as well.