Characterizing and Predicting Value Degree of Use

A value's degree of use---the number of dynamic uses of that value---provides the most essential information needed to optimize its communication. We present simulation results demonstrating the properties of degree of use of values, including their predictability: most static instructions generate values with few degrees of use and these exhibit temporal locality. We use these results to guide the design of a degree of use predictor. The development and detailed characterization of this predictor is the focus of this paper. Our predictor leverages future control flow information (e.g., branch predictions) to select among different possible degrees of use. We study the effects of several optimizations and variations in the predictor's algorithms to tune the predictor for maximum performance. The resulting predictor generates correct degree of use predictions for over 92% of all dynamic values and has a misprediction rate below 2.5%. Such a predictor has a wide range of potential applications in optimizing value communication