Exploiting Speculative Value Reuse Using Value Prediction

Data dependencies between instructions greatly impede instruction-level parallelism. Recently two hardware techniques – Value Prediction and Value Reuse – have been proposed to overcome the limits imposed by data dependencies. We introduce a new hardware scheme for exploiting speculative value reuse by using value prediction. We propose a new microarchitecture which uses value prediction to provide speculative value reuse. We use Value Prediction to predict operands of all integer ALU instructions and all load/store instructions. Value Reuse – including speculative and non-speculative reuse – is used for repeating instructions. Repeating instructions, which are found by a value reuse test, are those instructions which are executed repeatedly with the same input values and produce the same results. We use execution-driven simulation to evaluate the performance of our scheme. On average, we found ~9% speedup over a baseline architecture and ~84% correctly predicted speculative value reuse in speculative reuse lookup operations (~5.7% of executed instructions).