Control-flow speculation through value prediction for superscalar processors
J. M. Gonzalez Castro, Antonio M. González · 1999
In this paper, we introduce a new branch predictor that predicts the outcomes of branches by predicting the value of their inputs and performing an early computation of their results according to the predicted values. The design of a hybrid predictor comprising our branch predictor and a correlating branch predictor is presented. We also propose a new selector that chooses the most reliable prediction for each branch. This selector is based on the path followed to reach the branch. Results for immediate updates show that for a processor that already has a value prediction unit, our hybrid predictor, with a size of 4KB, achieves the same miss ratio as a conventional hybrid predictor of 64KB. The reduction in misprediction penalty is about 40% for all predictor sizes. Furthermore, if the cost of the value predictor is considered as an additional cost of the hybrid predictor, our proposal still reduces the miss ratio with respect to a conventional hybrid predictor for all different predic...