Hardware Support for Prescient Instruction Prefetch

TitleHardware Support for Prescient Instruction Prefetch
Publication TypeConference Paper
Year of Publication2004
AuthorsAamodt, T. M., P. Chow, P. Hammarlund, H. Wang, and J. P. Shen
Conference NameHigh Performance Computer Architecture, 2004. HPCA-10. Proceedings. 10th International Symposium on
Pagination84 - 84
Date Publishedfeb.

This paper proposes and evaluates hardware mechanisms for supporting prescient instruction prefetch #8212; an approach to improving single-threaded application performance by using helper threads to perform instruction prefetch. We demonstrate the need for enabling store-to-load communication and selective instruction execution when directly pre-executing future regions of an application that suffer I-cache misses. Two novel hardware mechanisms, safe-store and YAT-bits, are introduced that help satisfy these requirements. This paper also proposes and evaluates .nite state machine recall, a technique for limiting pre-execution to branches that are hard to predict by leveraging a counted I-prefetch mechanism. On a research Itanium #174;SMT processor with next line and streaming I-prefetch mechanisms that incurs latencies representative of next generation processors, prescient instruction prefetch can improve performance by an average of 10.0% to 22% on a set of SPEC 2000 benchmarks that suffer significant I-cache misses. Prescient instruction prefetch is found to be competitive against even the most aggressive research hardware instruction prefetch technique: fetch directed instruction prefetch.


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