Domain-specific augmentations for High-Level Synthesis

High-Level Synthesis (HLS) has become a very popular instrument to facilitate rapid development of production-ready implementations for FPGAs. Ever increasing flexibility of the frameworks, however, demands a very high level of domain-specific knowledge from the designer. Examples for such knowledge in window-based image processing are median computation and border handling. Depending on the size of the considered window, writing the code to perform such operations may become overwhelming even at very high abstraction levels. To increase productivity and to make the underlying architecture accessible to non-experts, we propose to combine HLS with domain-specific augmentations. Specifically, we propose a new language extension in form of a reduction for sorting and median computation. Furthermore, we introduce a new high-level transformation to perform multiple kinds of border treatment automatically. Both augmentations may reduce the required amount of code lines considerably. The increase in productivity is analyzed by comparing the lines of code necessary to specify a median filter for HLS in PAULA for synthesis using PARO and in C++ for synthesis using a commercial HLS tool.