Reducing misprediction penalty in the Branch Target Buffer

Abstract

Ideal speedup in pipelined processors is seldom achieved due to stalls and breaks in the execution stream. These interrupts are caused by data and control hazards, the latter, however, can be the most detrimental to pipeline performance. Branch Target Buffer (BTB) can reduce performance penalty of branches in pipelined processors by predicting the path of the branch and caching information used by the branch. No stalls will be encountered if the branch entry is found in BTB and the prediction is correct; otherwise, the penalty will be at least two cycles. This paper proposes a novel algorithm based on changing the BTB structure to eliminate the branch misprediction penalty. It also highlights a problem in the previous BTB algorithms (nested branches problem) and proposes a solution to it.