Hardware components communicate through clock-cycle-sensitive protocols. Hardware Description Languages (HDLs), however, provide limited support for expressing these protocols or for checking that independently developed components agree on them. When components disagree, the composed design can perform unsynchronized exchanges or stop making progress. We call these failures communication-safety violations. Communication safety is therefore a global property, determined by interactions between multiple components. This makes it difficult to check modularly. This paper presents Pact, a typed extension of Anvil for modular verification of communication safety in synchronous hardware. Pact types describe message-passing, control-flow, and clock-cycle behaviour. Each component is checked against its type. Compatible types then guarantee that the components compose into a communication-safe system. Pact also supports incremental design. It can check a subsystem before the full system context is available. The check produces a summary type that captures the communication behaviour left for future compositions. To reduce annotation burden, Pact infers types by abstracting payload values while preserving communication, timing, control, and fairness. These inferred types are optimal for the checker: whenever some checker-accepted types can prove compatibility, the inferred types can prove it as well. Type inference and type checking are decidable, and compatibility is decided by a sound and complete algorithm. We implement Pact by extending the Anvil compiler and evaluate it along four dimensions: detecting communication errors during incremental design, expressiveness on ten clock-cycle-accurate translations of open-source hardware IPs, compatibility-checking time, and generated hardware overhead. Pact expresses realistic protocols and verifies all ten benchmarks in reasonable time.

翻译：暂无翻译