HECTOR: A Multi-level Intermediate Representation for Hardware Synthesis Methodologies

Abstract

Hardware synthesis requires a complicated process to generate synthesizable register transfer level (RTL) code. High-level synthesis tools can automatically transform a high-level description into hardware design, while hardware generators adopt domain specific languages and synthesis flows for specific applications. The implementation of these tools generally requires substantial engineering efforts due to RTL’s weak expressivity and low level of abstraction. Furthermore, different synthesis tools adopt different levels of intermediate representations (IR) and transformations. A unified IR obviously is a good way to lower the engineering cost and get competitive hardware design rapidly by exploring different synthesis methodologies.In this paper, we propose Hector, a two-level IR providing a unified intermediate representation for hardware synthesis methodologies. The high-level IR binds computation with a control graph annotated with timing information, while the low-level IR provides a concise way to describe hardware modules and elastic interconnections among them. Implemented based on the multi-level compiler infrastructure (MLIR), Hector’s IRs can be converted to synthesizable RTL designs. To demonstrate the expressivity and versatility, we implement three synthesis approaches based on Hector: a high-level synthesis (HLS) tool, a systolic array generator, and a hardware accelerator. The hardware generated by Hector’s HLS approach is comparable to that generated by the state-of-the-art HLS tools, and the other two cases outperform HLS implementations in performance and productivity.