Proceedings. 1998 International Conference on Parallel Architectures and Compilation Techniques (Cat. No.98EX192) (1998)
Oct. 12, 1998 to Oct. 18, 1998
Bohuslav Rychlik , Carnegie Mellon University
John Faistl , Carnegie Mellon University
Bryon Krug , Carnegie Mellon University
John P. Shen , Carnegie Mellon University
Value prediction is a technique that bypasses inter-instruction data dependencies by speculating on the outcomes of producer instructions, thereby allowing dependent consumer instructions to execute in parallel. This work makes several contributions in value prediction research. A hybrid value predictor that achieves an overall prediction rate of up to 83% is presented. The design of a value-predicting eight-wide superscalar machine with its speculative execution core is described. This design is able to achieve 8.6% to 23% IPC improvements on the SPEC benchmarks. Furthermore, it is shown that prediction rate is not a good indicator of speedup because over 40% of predictions made may not be useful in enhancing performance, and a simple hardware mechanism that eliminates many of these useless predictions is introduced.
value prediction, hybrid predictor, speculative execution, usefulness tracking, superscalar processor, instruction level parallelism
B. Rychlik, J. Faistl, J. P. Shen and B. Krug, "Efficacy and Performance Impact of Value Prediction," Proceedings. 1998 International Conference on Parallel Architectures and Compilation Techniques (Cat. No.98EX192)(PACT), Paris, France, 1998, pp. 148.