Dataflow analysis of branch mispredictions and its application to early resolution of branch outcomes
Alexandre Farcy, Olivier Temam, Roger Espasa, Toni Juan · 1998
The goal of this study is twofold: to analyze in detail the nature of conditional branch mispredictions in correlationbased branch predictors, and, based on this analysis, to reduce the impact of branch mispredictions on processor performance by decreasing the branch resolution delay instead of improving the branch prediction accuracy. We classify conditional branches with the highest number of mispredictions according to the nature of their branch condition analytical expression. Based on these expressions, we can analyze and even precisely explain the origin of mispredictions in many cases. Moreover, we find that many such branches belong to small sets of blocks inside loops, and within such sets we find that some of the branch expressions have regularity properties. We show how to exploit this regularity property by anticipating the branch outcome, where anticipation is a combination of value prediction and normal dataflow execution. We investigate a hardware mechanism to implement...