Alternative implementations of hybrid branch predictors
Po-Ying Chang, Eric Hao, Yale N. Patt · 1995
Very accurate branch prediction is an important requirement for achieving high performance on deeply pipelined, superscalar processors. To improve on the prediction accuracy of current single-scheme branch predictors, hybrid (multiple-scheme) branch predictors have been proposed [6, 7]. These predictors combine multiple single-scheme predictors into a single predictor. They use a selection mechanism to decide for each branch, which single-scheme predictor to use. The performance of a hybrid predictor depends on its singlescheme predictor components and its selection mechanism. Using known single-scheme predictors and selection mechanisms, this paper identifies the most effective hybrid predictor implementation. In addition, it introduces a new selection mechanism, the 2-level selector, which further improves the performance of the hybrid branch predictor. 1 Introduction Branches can significantly reduce the performance of high-performance processors. Speculative execution is one solu...