HeteroHalide - From Image Processing DSL to Efficient FPGA Acceleration.

The domain-specific language (DSL) for image processing, Halide, has generated a lot of interest because of its capability of decoupling algorithms from schedules that allow programmers to search for optimized mappings targeting CPU and GPU. Unfortunately, while the Halide community has been growing rapidly, there is currently no way to easily map the vast number of Halide programs to efficient FPGA accelerators. To tackle this challenge, we propose HeteroHalide, an end-to-end system for compiling Halide programs to FPGA accelerators. This system makes use of both algorithm and scheduling information specified in a Halide program. Compared to the existing approaches, flow provided by HeteroHalide is significantly simplified, as it only requires moderate modifications for Halide programs on the scheduling part to be applicable to FPGAs. For part of the compilation flow, and to act as the intermediate representation (IR) of HeteroHalide, we choose HeteroCL, a heterogeneous programming infrastructure which supports multiple implementation backends (such as systolic arrays and stencil implementations). By using HeteroCL, HeteroHalide can generate efficient accelerators by choosing different backends according to the application. The performance evaluation compares the accelerator generated by HeteroHalide with multi-core CPU and an existing Halide-HLS compiler. As a result, HeteroHalide achieves 4.15\texttimes speedup on average over 28 CPU cores, and 2 \textasciitilde 4\texttimes throughput improvement compared with the existing Halide-HLS compiler.