Bit-level Perceptron Prediction for Indirect Branches

摘要

Modern software uses indirect branches for various purposes including, but not limited to, virtual method dispatch and implementation of switch statements. Because an indirect branch's target address cannot be determined prior to execution, high-performance processors depend on highly-accurate indirect branch prediction techniques to mitigate control hazards. This paper proposes a new indirect branch prediction scheme that predicts target addresses at the bit level. Using a series of perceptron-based predictors, our predictor predicts individual branch target address bits based on correlations within branch history. Our evaluations show this new branch target predictor is competitive with state-of-the-art branch target predictors at an equivalent hardware budget. For instance, over a set of workloads including SPEC and mobile applications, our predictor achieves a misprediction rate of 0.183 mispredictions per 1000 instructions, compared with 0.193 for the state-of-the-art ITTAGE predictor and 0.29 for a VPC-based indirect predictor.