RISC-V²: A Scalable RISC-V Vector Processor

Abstract

Machine learning adoption has seen a widespread bloom in recent years, with neural network implementations being at the forefront. In light of these developments, vector processors are currently experiencing a resurgence of interest, due to their inherent amenability to accelerate data-parallel algorithms required in machine learning environments. In this paper, we propose a scalable and high-performance RISC-V vector processor core. The presented processor employs a triptych of novel mechanisms that work synergistically to achieve the desired goals. An enhanced vector-specific incarnation of register renaming is proposed to facilitate dynamic hardware loop unrolling and alleviate instruction dependencies. Moreover, a cost-efficient decoupled execution scheme splits instructions into execution and memory-access streams, while hardware support for reductions accelerates the execution of key instructions in the RISC-V ISA. Extensive performance evaluation and hardware synthesis analysis validate the efficiency of the new architecture.