A low-power misprediction recovery mechanism

Abstract

In modern superscalar processor, branch misprediction penalty becomes a critical factor in overall processor performance. Previous researches proposed dual (or multi) path execution methods attempt to reduce the misprediction penalty, but these methods are quite complex and high power consumption. Most of the reasons are due to simultaneously fetching and executing instructions from multiple. In this paper, we reduce branch misprediction penalties based on the balance between complexity, power, and performance. We present a novel technique-Decode Recovery Cache (DRC) - for reducing misprediction penalty, giving consideration to complexity and power consumption simultaneously. The DRC stores decoded instructions that are mispredicted. Then during subsequent mispredictions, a hit in the DRC can reduce the re-fill time of pipeline, and eliminate instruction re-fetch and its subsequent decoding. The bypassing of both re-fetching and re-decoding reduces processor power. Experimental results employing SPECint 2000 benchmark show that, using a processor with DRC, IPC value is significantly improved by 10.4% on average over the traditional processors and average power consumption is reduced by 62.6%, compared with dual Path Instruction Processing.