Shrink It or Shed It! Minimize the Use of LSQs in Dataflow Designs

When applications have unpredictable memory accesses or irregular control flow, dataflow circuits overcome the limitations of statically scheduled high-level synthesis (HLS). If memory dependences cannot be determined at compile time, dataflow circuits rely on load-store queues (LSQs) to resolve the dependences dynamically, as the circuit runs. However, when employed on reconfigurable platforms, these LSQs are resource-expensive, slow, and power-consuming. In this work, we explore techniques for reducing the cost of the memory interface in dataflow designs. Apart from exploiting standard memory analysis techniques, we present a novel approach which relies on the topology of the control and dataflow graphs to infer memory order with the purpose of minimizing the LSQ size and complexity. On benchmarks obtained automatically from C code, we show that our approach results in significant area reductions, as well as increased performance, compared to naive solutions.