Rebasing Instruction Prefetching: An Industry Perspective

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Abstract
Instruction prefetching can play a pivotal role in improving the performance of workloads with large instruction footprints and frequent, costly frontend stalls. In particular, Fetch Directed Prefetching (FDP) is an effective technique to mitigate frontend stalls since it leverages existing branch prediction resources in a processor and incurs very little hardware overhead. Modern processors have been trending towards provisioning more frontend resources, and this bodes well for FDP as it requires these resources to be effective. However, recent academic research has been using outdated and less than optimal frontend baselines that employ smaller structures, which may result in misleading outcomes. In this paper, we present a detailed FDP microarchitecture and evaluate two improvements, better branch history management and post fetch correction. We believe that our FDP-based frontend design can serve as a new reference baseline for instruction prefetching research to bridge the gap between academia and industry.