Path Prediction For High Issue-Rate Processors

  • Authors:
  • K. N. Menezes;S. W. Sathaye;T. M. Coate

  • Affiliations:
  • -;-;-

  • Venue:
  • PACT '97 Proceedings of the 1997 International Conference on Parallel Architectures and Compilation Techniques
  • Year:
  • 1997

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Abstract

Rapid developments in the exploitation of instruction-level parallelism are prompting deeper-pipelined, wider machines with high issue rates. Speculative execution has been used to provide the required issue bandwidth. Current methods predict a single branch at a time. Performance improvement is possible by predicting multiple branches in a single cycle. The paper presents a technique to predict paths in a single access. The correlation of a path with the branches executed before it, is exploited to provide high prediction accuracy. A novel path prediction automaton is presented The automaton is easily scalable to predict long paths through arbitrary subgraphs. It also predicts a path through a subgraph in a single access. The automaton requires only n+1 bits for predicting the 2/sup n/ paths in a subgraph of depth n. The performance of the proposed path predictor is measured. The full path accuracy (accuracy in predicting all the branches in a path) is higher than or equal to other predictors found in the literature. This performance is achieved at a low hardware cost. The scalability single access prediction and low hardware cost of the path prediction technique presented in the paper make it suitable for machines requiring high issue bandwidth.