Extending High-Level Synthesis for Task-Parallel Programs

C/C++/OpenCL-based high-level synthesis (HLS) becomes more and more popular for field-programmable gate array (FPGA) accelerators in many application domains in recent years, thanks to its competitive quality of result (QoR) and short development cycle compared with the traditional register-transfer level (RTL) design approach. Yet, limited by the sequential C semantics, it remains challenging to adopt the same highly productive high-level programming approach in many other application domains, where coarse-grained tasks run in parallel and communicate with each other at a fine-grained level. While current HLS tools support task-parallel programs, the productivity is greatly limited in the code development, correctness verification, and QoR tuning cycles, due to the poor programmability, restricted software simulation, and slow code generation, respectively. Such limited productivity often defeats the purpose of HLS and hinder programmers from adopting HLS for task-parallel FPGA accelerators.