Arm Limited

Marco Coletta

Damien Matthieu Valentin Cathrine

Ugo Castorina

Diogo Augusto Pereira Marques

Igor Burovenko

An apparatus for improving the tracking of streams of memory accesses for training a stride prefetcher is provided, comprising a training data structure storing entries for training a stride prefetcher, a given entry specifying: a stride offset, a target address, a program counter address, and a bypass indicator indicating whether a program counter match condition is to be bypassed for the given entry; and training control circuitry to determine whether to update the stride offset for the given entry of the training data structure to specify a current stride between a target address of a current memory access and the target address for the last memory access of the tracked stream, in which the determination by the training control circuitry is controlled to be either dependent on a determination of whether the program counter match condition is satisfied or independent of whether the program counter match condition is satisfied, based on the bypass indicator.

Bypassing program counter match conditions

There is provided an apparatus, medium and method. The apparatus comprises candidate offset storage circuitry to store a list comprising a plurality of candidate offset values having a default order, and prefetch circuitry to generate prefetch addresses by modifying a base address using a current offset, and to issue prefetch requests to cause information beginning at a corresponding prefetch address to be prefetched into the storage structure in anticipation of a demand request for that information. The apparatus further comprises prefetch training circuitry to select a new offset from the list of candidate offset values through comparison of the plurality of candidate offset values against data indicative of recent requests. The prefetch training circuitry is configured to identify a subset of the candidate offset values based on the current offset and to dynamically modify the default order to increase priority of the subset.

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Biot, France

Marco Coletta