Storageless value prediction using prior register values

  • Authors:

  • Dean M. Tullsen;John S. Seng

  • Affiliations:

  • Dept. of Computer Science and Engineering, University of California, San Diego, La Jolla, CA;Dept. of Computer Science and Engineering, University of California, San Diego, La Jolla, CA

  • Venue:
  • ISCA '99 Proceedings of the 26th annual international symposium on Computer architecture
  • Year:
  • 1999

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Abstract

This paper presents a technique called register value prediction (RVP) which uses a type of locality called register-value reuse. By predicting that an instruction will produce the value that is already stored in the destination register, we eliminate the need for large value buffers to enable value prediction. Even without the large buffers, register-value prediction can be made as or more effective than last-value prediction, particularly with the aid of compiler management of values in the register file.Both static and dynamic register value prediction techniques are demonstrated to exploit register-value reuse, the former requiring minimal instruction set architecture changes and the latter requiring a set of small confidence counters. We show an average gain of 12% with dynamic RVP and moderate compiler assistance on a next generation processor, and 15% on a 16-wide processor.