On ESL verification of memory consistency for system-on-chip multiprocessing

Chip multiprocessing is key to Mobile and high-end Embedded Computing. It requires sophisticated multilevel hierarchies where private and shared caches coexist. It relies on hardware support to implicitly manage relaxed program order and write atomicity so as to provide well-defined shared-memory semantics (captured by the axioms of a memory consistency model) at the hardware-software interface. This paper addresses the problem of checking if an executable representation of the memory system complies with a specified consistency model. Conventional verification techniques encode the axioms as edges of a single directed graph, infer extra edges from memory traces, and indicate an error when a cycle is detected. Unlike them, we propose a novel technique that decomposes the verification problem into multiple instances of an extended bipartite graph matching problem. Since the decomposition was judiciously designed to induce independent instances, the target problem can be solved by a parallel verification algorithm. Our technique, which is proven to be complete for several memory consistency models, outperformed a conventional checker for a suite of 2400 randomly-generated use cases. On average, it found a higher percentage of faults (90%) as compared to that checker (69%) and did it, on average, 272 times faster.