Enabling Long Debug Traces of HLS Circuits Using Bandwidth-Limited Off-Chip Storage Devices

High-level synthesis (HLS) has gained considerable traction in recent years. Despite considerable strides in the development of quality HLS compilers, one area that is often cited as a barrier to HLS adoption is the difficulty in debugging HLS produced circuits. Recent academic work has presented techniques that use on-chip memories to efficiently record execution of HLS circuits, and map the captured data back to the original source code to provide the user with a software-like debug experience. However, limited on-chip memory results in very short debug traces, which may force a designer to spend multiple debug iterations to resolve complicated bugs. In this work we present techniques to enable off-chip capture of HLS debug information. While off-chip storage does not suffer from the capacity limitations of on-chip memory, its usage introduces a new challenge: limited bandwidth. In this work we show how information from within the HLS flow can be leveraged to generated a streamed debug trace within given bandwidth constraints. For a bandwidth limited interface, we show that our techniques allow the user to observe 19x more source code variables than using a basic approach.