LUTstructions: Self-loading FPGA-based Reconfigurable Instructions
It provides a new paradigm for reconfigurable computing in softcore processors, enabling efficient execution of arbitrary tasks that cannot be efficiently expressed by fixed instruction sets.
This paper introduces LUTstructions, a custom FPGA architecture that enables self-loading reconfigurable instructions in a softcore processor, allowing seamless loading of instruction bitstreams from main memory without operating frequency overhead.
General-purpose processors feature a limited number of instructions based on an instruction set. They can be numerous, such as with vector extensions that include hundreds or thousands of instructions, but this comes at a cost; they are often unable to express arbitrary tasks efficiently. This paper explores the concept of having reconfigurable instructions by incorporating reconfigurable areas in a softcore. It follows a relatively new computing paradigm for seamlessly loading instruction implementation-carrying bitstreams from main memory. The resulting softcore is entirely evaluated on an FPGA, essentially having an FPGA-on-FPGA for the instruction implementations, with no notable operating frequency overhead. This is achieved with a custom FPGA architecture called LUTstruction, which is tailored towards low-latency for custom instructions and wide reconfiguration, as well as a soft implementation for the purposes of architectural exploration. All code is open-source to foster further research on reconfigurable instructions.