This dissertation introduces a novel approach for exposing the internal, source-level expressions of circuits generated by high-level synthesis (HLS) for in-circuit debug. The approach uses source-to-source transformations to instrument specific source-level expressions with debug ports. These debug ports allow a user to connect a debugging instrument (e.g. an embedded logic analyzer) to record the activity of the expression corresponding to the debug port. This dissertation demonstrates that a debugging solution based on these source-to-source transformations is feasible and that individual debug ports can be added for a cost of a 1-2% increase in circuit area on average. It also introduces another transformation that permits pointer-valued expressions to be instrumented for debug. It is demonstrated that all pointers in the CHStone benchmarks can be instrumented for an average 4% increase in circuit area. The debug port transformations are demonstrated on two HLS tools – Vivado HLS and Legup. The architecture of the source-to-source compiler allowed the necessary adaptations for the second tool (Legup) to be implemented using a minimal amount of additional code. Due to limitations in the Legup compiler an additional optimization was added to reduce the latency overhead incurred by the debug ports. User manuals and other documentation from 10 additional C-based HLS tools is examined to determine whether they are amenable to debug instrumentation using the source-to-source transformations. Of the 10 additional HLS tools examined, 6 were amenable to the transformations, 3 were likely to be amenable, and 1 was not. This dissertation estimates the cost of a complete debugging solution (i.e. one with debug ports and a debugging instrument) and identifies a possible worst case bound for adding debug ports. Finally, this dissertation analyzes two different debugging instruments and determines which instrument would be best for most HLS circuit mapped to FPGAs. It then estimates the overhead of this debugging solution.
College and Department
Ira A. Fulton College of Engineering and Technology; Electrical and Computer Engineering
BYU ScholarsArchive Citation
Monson, Joshua Scott, "Using Source-to-Source Transformations to Add Debug Observability to HLS-Synthesized Circuits" (2016). Theses and Dissertations. 5871.
FPGA, high-level synthesis, debugging, source-to-source transformations, embedded logic analyzer