On the in-field test of Branch Prediction Units using the correlated predictor mechanism

Branch Prediction Units (BPUs) are widely used to reduce the performance penalties caused by branch instructions in pipelined processors. BPUs may be implemented in different forms: the Branch History Table (BHT) is an effective solution when the goal is predicting the result of conditional branches. In this paper we propose a method to generate test programs able to detect faults affecting the memory existing within a BHT implementing the correlated predictors approach. Our method is particularly suited to be used for the in-field test of a processor and allows detecting any stuck-at fault in the BPU memory. The method does not require the detailed knowledge of the BPU implementation, but only relies on the key parameters of its architecture. We gathered experimental results using the SimpleScalar environment.