Hardware Synthesis from Functional Embedded Domain-Specific Languages: A Case Study in Regular Expression Compilation

Although FPGAs have the potential to bring software-like flexibility and agility to the hardware world, designing for FPGAs remains a difficult task divorced from standard software engineering norms. A better programming flow would go far towards realizing the potential of widely deployed, programmable hardware. We propose a general methodology based on domain specific languages embedded in the functional language Haskell to bridge the gap between high level abstractions that support programmer productivity and the need for high performance in FPGA circuit implementations. We illustrate this methodology with a framework for regular expression to hardware compilers, written in Haskell, that supports high programmer productivity while producing circuits whose performance matches and, indeed, exceeds that of a state of the art, hand-optimized VHDL-based tool. For example, after applying a novel optimization pass, throughput increased an average of 28.3 percent over the state of the art tool for one set of benchmarks.