AN INTERACTIVE GRAPHICAL TRACE-DRIVEN SIMULATOR FOR TEACHING BRANCH PREDICTION IN COMPUTER ARCHITECTURE

In modern superscalar microarchitectures that speculatively execute a great quantity of code, without performing branch prediction, it won't be possible to aggressively exploit instruction level parallelism from programs. Both the architectural and technological complexity of current processors emphasizes the negative impact on performance due to every branch misprediction. Due to this importance, branch prediction becomes a core topic in Computer Architecture curricula. The fast development of computer science and information technology domains, and of computer architecture especially, have determined that many software tools used not long ago in research, to be enhanced with an interactive graphical interface and to be taught in Introductory Computer Organization respectively Computer Architecture courses. The lack of simulators dedicated to branch prediction used for didactical purposes despite of plenty used in research goals, represents the starting point of this paper. The main aim of this work consists in identifying the difficult-to-predict branches, to quantify them at benchmarks level and to find the relevant information in order to reduce their numbers. Finally, we evaluate the impact of these branches on three commonly used prediction contexts (local, global and path) and their corresponding predictors, ranging from classical two-level predictors to present-day predictors (neural - Simple Perceptron and Fast Path-based Perceptron). The developed ABPS simulator provides a wide variety of configuration options. Beside statistics related to the number of difficult-to-predict branches, the simulator generates graphical results illustrating the influence of different simulation parameters (number of entries in prediction table, history length, etc.) on prediction accuracy, resource usage, etc., for every implemented predictor.