Instruction prefetching using branch prediction information

Abstract

Instruction prefetching can effectively reduce instruction cache misses, thus improving the performance. In this paper, we propose a prefetching scheme, which employs a branch predictor to run ahead of the execution unit and to prefetch potentially useful instructions. Branch prediction-based (BP-based) prefetching has a separate small fetching unit, allowing it to compute and predict targets autonomously. Our simulations show that a 4-issue machine with BP-based prefetching achieves higher performance than a plain cache 4 times the size. In addition, BP-based prefetching outperforms other hardware instruction fetching schemes, such as next-n line prefetching and wrong-path prefetching, by a factor of 17-44% in stall overhead.