This paper presents two schemes, the variable cross-reference (VCR) prediction scheme and the iterative dispatch approach, to improve branch prediction accuracy for the two-level adaptive branch predictor. The VCR prediction scheme makes predictions by variably cross-referring traces in the pattern history table (PHT); it achieves desirable prediction accuracy with low time complexity and at no extra hardware cost. The iterative dispatch approach enhances prediction accuracy using the PHT history to do dispatching for an additional layer of pattern history. The proposed VCR scheme is then joined by the optimal PPM algorithm to form a combined predictor which maintains desirable prediction accuracy at reduced cost. Extensive trace-driven simulation runs have been conducted to evaluate the performance of our proposed schemes and other predictors.
Proceedings of 2003 National Computer Symposium (Ⅲ)=2003年全國計算機會議論文集 (Ⅲ)---二十一世紀資訊時代的挑戰, pp.1768-1775