Branch Prediction. Literature. Tse -Yu Yeh and Yale N. Patt , “ A Comparison of Dynamic Branch Predictors that use Two Levels of Branch History,” Proceedings of the 20th annual international symposium on computer architecture, ISCA '93 Also important: Reference 1,2,3 and 4 of this paper
Two-Level Adaptive Branch Prediction
First level, execution history register(s):History of the last k branches encountered.
Second level, pattern history table(s): k refers to a place in the pattern history table that contains the prediction based on the outcome of the branches at the last j occurences of k,Predictor is for instance a prediction counter.
1st Level Branch History Register or Table (BHR or BHT)
2nd levelPattern History Table (PHT)
Branch prediction is a very important factor in reducing CPI in modern processors that use extensive pipelining.
A counter is often used for prediction (2 bit)
Two-Level Adaptive Dynamic Branch Prediction ‘learns’ the outcome of branches in different program states.
9 Variations of 2-L.A.B.P. (Global, Per-Address and Per-Set for both levels), but only 4 useful.