To improve branch prediction accuracy for the two-level adaptive branch predictor, two schemes dealing respectively with the prediction and dispatch parts, are presented in this paper. The proposed VCR prediction scheme is able to achieve desirable prediction accuracy, with reasonably low time complexity and no extra hardware cost, by variably cross-referring traces in the PHT to make predictions. The Iterative dispatch approach utilizes the PHT history to do dispatching for an additional layer of pattern history which helps providing more information for making better predictions. To attain desirable prediction accuracy at reduced cost, a combined predictor formed by the proposed VCR scheme and the optimal PPM algorithm is also considered. Extensive trace-driven simulation runs have been conducted to evaluate the performance of our proposed schemes and other predictors. As the results indicate, our proposed schemes compare favorably in most of the situations in terms of prediction accuracy.
淡江理工學刊=Tamkang journal of science and engineering 11(1)，頁37-48