Area-Efficient Memory Scheduling for Dynamically Scheduled High-Level Synthesis

Abstract

In high-level synthesis, scheduling maps operations into clock cycles. It can either be done at compile time (statically) or run time (dynamically). There has been recent interests in dynamic scheduling as it can potentially achieve a better performance. The state-of-the-art dynamically scheduled HLS tool Dynamatic generates dataflow-style hardware in a netlist of pre-defined components connected using handshake signals. The memory operations are executed by a component named load-store queue (LSQ), which can achieve run-time out-of-order memory accesses for high performance. However, the additional logic for the LSQ leads to significant area overhead compared to static scheduling. In this paper, we propose an area-efficient approach for scheduling memory operations at run time. We approximate the memory dependence distance to its minimal value and efficiently parallelise memory accesses in dynamically scheduled hardware. Over several benchmarks from related works, our results show that our approach achieves on average $0.2\times$ of the area-delay product compared to the original designs using LSQs.