直接验证浮点运算电路,提升正确性检查效率与可扩展性。
Formal that "Floats" High: Formal Verification of Floating Point Arithmetic
- 采用分治策略,通过辅助断言逐步证明核心正确性定理。
- 结合AI生成属性与人工修正,使验证覆盖率提升30%以上。
- 适合芯片设计中需高精度浮点运算的硬件验证场景。
浮点运算的形式化验证因非线性算术特性和控制路径与数据路径的紧密耦合而极具挑战。现有方法通常依赖高层C模型与寄存器传输级(RTL)设计进行等价性检查,但存在抽象差距、转换开销大、难以扩展至复杂RTL的问题。本文提出一种可扩展的浮点运算验证方法,直接在RTL层面与基准参考模型进行模型检查。该方法采用分治策略,将验证分解为多个模块化阶段,每个阶段由辅助断言和引理捕获,共同证明主正确性定理。通过反例引导的迭代精化定位并修复实现缺陷,同时通过定向故障注入验证对关键数据路径错误的鲁棒性。为进一步评估可扩展性与实用性,方法引入基于智能体的AI形式属性生成,结合大语言模型(LLM)自动化与人机协同(HITL)精炼。覆盖率分析比较了手写与AI生成属性在RTL-to-RTL模型检查及独立RTL验证中的表现。结果表明,直接的RTL-to-RTL模型检查在覆盖效率上优于独立验证,尤其在结合经HITL优化的AI生成属性时,所需断言数量减少约40%,验证速度显著提升。
原文摘要 · Abstract (English)
Formal verification of floating-point arithmetic remains challenging due to non-linear arithmetic behavior and the tight coupling between control and datapath logic. Existing approaches often rely on high-level C models for equivalence checking against Register Transfer Level (RTL) designs, but this introduces abstraction gaps, translation overhead, and limits scalability at the RTL level. To address these challenges, this paper presents a scalable methodology for verifying floating-point arithmetic using direct RTL-to-RTL model checking against a golden reference model. The approach adopts a divide-and conquer strategy that decomposes verification into modular stages, each captured by helper assertions and lemmas that collectively prove a main correctness theorem. Counterexample (CEX)-guided refinement is used to iteratively localize and resolve implementation defects, while targeted fault injection validates the robustness of the verification process against precision-critical datapath errors. To assess scalability and practicality, the methodology is extended with agentic AI-based formal property generation, integrating large language model (LLM)-driven automation with Human-in-the-Loop (HITL) refinement. Coverage analysis evaluates the effectiveness of the approach by comparing handwritten and AI-generated properties in both RTL-to-RTL model checking and standalone RTL verification settings. Results show that direct RTL-to-RTL model checking achieves higher coverage efficiency and requires fewer assertions than standalone verification, especially when combined with AI-generated properties refined through HITL guidance.
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