MoXIchecker: An Extensible Model Checker for MoXI

TL;DR

MoXIchecker is a novel, extensible model checker that directly verifies MoXI language tasks using SMT solvers, overcoming limitations of translation-based approaches and supporting complex theories like integer and real arithmetic.

Contribution

It introduces MoXIchecker, the first model checker for MoXI that directly handles complex theories and is solver-agnostic, enhancing extensibility and expressiveness.

Findings

MoXIchecker successfully verifies tasks with integer and real arithmetic.

It performs comparably to existing translation-based model checkers.

It demonstrates extensibility by supporting complex theories beyond bit-vectors.

Abstract

MoXI is a new intermediate verification language introduced in 2024 to promote the standardization and open-source implementations for symbolic model checking by extending the SMT-LIB 2 language with constructs to define state-transition systems. The tool suite of MoXI provides a translator from MoXI to Btor2, which is a lower-level intermediate language for hardware verification, and a translation-based model checker, which invokes mature hardware model checkers for Btor2 to analyze the translated verification tasks. The extensibility of such a translation-based model checker is restricted because more complex theories, such as integer or real arithmetics, cannot be precisely expressed with bit-vectors of fixed lengths in Btor2. We present MoXIchecker, the first model checker that solves MoXI verification tasks directly. Instead of translating MoXI to lower-level languages, MoXIchecker uses the solver-agnostic library PySMT for SMT solvers as backend for its verification algorithms. MoXIchecker is extensible because it accommodates verification tasks involving more complex theories, not limited by lower-level languages, facilitates the implementation of new algorithms, and is solver-agnostic by using the API of PySMT. In our evaluation, MoXIchecker uniquely solved tasks that use integer or real arithmetics, and achieved a comparable performance against the translation-based model checker from the MoXI tool suite.