1LegUp: An Open Source High-Level Synthesis Tool for FPGA-Based Processor/Accelerator Systems

It is generally accepted that a custom hardware implementation of a set of computations will provide supe-rior speed and energy-efficiency relative to a software implementation. However, the cost and difficulty of hardware design is often prohibitive, and consequently, a software approach is used for most applications. In this paper, we introduce a new high-level synthesis tool called LegUp that allows software techniques to be used for hardware design. LegUp accepts a standard C program as input and automatically compiles the program to a hybrid architecture containing an FPGA-based MIPS soft processor and custom hardware accelerators that communicate through a standard bus interface. In the hybrid processor/accelerator archi-tecture, program segments that are unsuitable for hardware implementation can execute in software on the processor. LegUp can synthesize most of the C language to hardware, including fixed-sized multi-dimensional arrays, structs, global variables and pointer arithmetic. Results show that the tool produces hardware so-lutions of comparable quality to a commercial high-level synthesis tool. We also give results demonstrating the ability of the tool to explore the hardware/software co-design space by varying the amount of a program that runs in software vs. hardware. LegUp, along with a set of benchmark C programs, is open source and freely downloadable, providing a powerful platform that can be leveraged for new research on a wide range of high-level synthesis topics