Debugging Framework for FPGA-based Soft Processors

Soft processors are one way to raise the computational abstraction of FPGAs while keeping the advantages of reconfigurable hardware, such as adaptability, deterministic performance and high performance/watt. Software developers can quickly build, test and deploy applications using familiar tools while still leveraging important optimizations such as application-specific custom instructions. However, they also present unique debugging problems. For example, the higher-level programming abstraction runs contradictory to classical low-level debugging tools like logic analyzers. In this work we present a debugging framework for FPGA-based soft processors that enables step-by-step debugging at the level of all soft processor instructions, timetravel debugging, post-mortem memory dumps, and performance metrics. By using knowledge about the soft processor's internals, our framework can capture execution traces up to 60x more space-efficient than traditional embedded logic analyzers.