The effects of mispredicted-path execution on branch prediction structures
نویسندگان
چکیده
Branch prediction accuracies determined using tracedriven simulation do not include the eflects of executing branches along a mispredicted path. However, branches along a mispredicted path will pollute the branch prediction structures i f no recovery mechanisms are provided. Without recovery mechanisms, prediction rates will suger. In this paper, we determine the appropriateness of recovery mechanisms for the four structures of the Two-Level Adaptive Branch Predictor: the Branch Target Buger (BTB), the Branch History Register (BHR), the Pattern History Tables (PHTs), and the Return Address Stack (RAS). We then propose cost-eflective recovery mechanisms for these branch prediction structures. For five benchmarks from the SPECint92 suite, we show that performance is not aflected if recovery mechanisms are not provided for the B T B and the PHTs. On the other hand, without any recovery mechanisms for the BHR and RAS, performance drops b y an average of 29%.
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The E ects of Mispredicted - Path Execution on BranchPrediction
Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works, must be obtained from the IEEE. Abstract Branch prediction accuracies determined using trace-driven simu...
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