A Novel HDL Code Generator for Effectively Testing FPGA Logic Synthesis Compilers

TL;DR

This work addresses defects in FPGA logic synthesis compilers by introducing LegoHDL, a CPS-based HDL code generator that yields diverse, syntax-valid designs across Verilog, VHDL, and SystemVerilog. LegoHDL combines a function-generation component with a syntax-guidance component that leverage AST feedback to iteratively build CPS models and translate them via HDL Coder. Empirical evaluation in a three-month deployment across multiple toolchains reveals LegoHDL detected 20 defects (16 confirmed), outperforming the state-of-the-art Verismith in both defect coverage and language diversity. The results underscore the method’s practical impact for improving FPGA tool chain reliability and provide a replication package for future research.

Abstract

Field Programmable Gate Array (FPGA) logic synthesis compilers (e.g., Vivado, Iverilog, Yosys, and Quartus) are widely applied in Electronic Design Automation (EDA), such as the development of FPGA programs.However, defects (i.e., incorrect synthesis) in logic synthesis compilers may lead to unexpected behaviors in target applications, posing security risks. Therefore, it is crucial to thoroughly test logic synthesis compilers to eliminate such defects.Despite several Hardware Design Language (HDL) code generators (e.g., Verismith) have been proposed to find defects in logic synthesis compilers, the effectiveness of these generators is still limited by the simple code generation strategy and the monogeneity of the generated HDL code.This paper proposes LegoHDL, a novel method to generate syntax valid HDL code for comprehensively testing FPGA logic synthesis compilers.LegoHDL can generate more complex and diverse defect-trigger HDL code (e.g., Verilog, VHDL, and SystemVerilog) by leveraging the guidance of abstract syntax tree and the extensive function block libraries of cyber-physical systems. Extensive experiments show that the diversity and defect-trigger capability of HDL code generated by LegoHDL are significantly better than the state-of-the-art method (i.e., Verismith).In three months, LegoHDL has reported 20 new defects--many of which are deep and important; 16 of them have been confirmed.

Figures (11)

• Figure 1: The role of logic synthesis in Intel FPGA playbook
• Figure 2: The process of logic synthesis
• Figure 3: Example of translating CPS function model to HDL code by HDL Coder tool
• Figure 4: The overall framework of LegoHDL
• Figure 5: Example iteration process of CPS model and AST of HDL Code