Modern microprocessors are increasingly relying on speculation as a key technique for improving performance and reducing power, temperature and energy. Confidence estimators are necessary to prevent likely misspeculations. These confidence estimators are commonly realized using a Finite State Machine (FSM) called a saturating counter. This paper presents a hardware method that allows FSMs to dynamically optimize their state transitions and confidence thresholds to improve CPU performance by automatically adapting to the current workload. The technique further allows the FSMs to continuously adjust to changing program conditions. These adaptable, self-optimizing confidence estimators are evaluated as a component in a value predictor on the C programs from the SPECcpu2000 benchmark suite. On average, the self-optimizing method achieves a miss rate reduction of 11 % with a maximum of 47%. The selfoptimizing confidence estimator can provide a speedup of 4%. 1
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