Data processing apparatus and method for updating prediction data based on ...

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(12) United States Patent

Ozer et al.

(io) Patent No.: (45) Date of Patent:

US 7,805,595 B2 Sep.28, 2010

(54) DATA PROCESSING APPARATUS AND

METHOD FOR UPDATING PREDICTION
DATA BASED ON AN OPERATION'S
PRIORITY LEVEL

(75) Inventors: Emre Ozer, Cambridge (GB); Alastair David Reid, Fulbourn (GB); Stuart David Biles, Little Thurlow (GB)

(73) Assignee: ARM Limited, Cambridge (GB)

( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 301 days.

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TN-36, Jun. 1993, pp. 1-25.

N. Riley et al, "Probabilistic Counter Updates for Predictor Hyster-
esis and Bias" IEEE Computer Architecture Letters, vol. 5, 2006.
N. Riley et al, "Probabilistic Counter Updates for Predictor Hyster-
esis and Stratification" IEEE 2006, pp. 111-121.

* cited by examiner

A data processing apparatus has processing circuitry for performing processing operations including high priority operations and low priority operations, events occurring during performance of those processing operations. Prediction circuitry includes a history storage having a plurality of counter entries for storing count values, and index circuitry for identifying, dependent on the received event, at least one counter entry and for causing the history storage to output the count value stored in that at least one counter entry, with the prediction data being derived from the output count value. Update control circuitry modifies at least one count value stored in the history storage in response to update data generated by the processing circuitry. The update control circuitry has a priority dependent modification mechanism such that the modification is dependent on the priority of the processing operation with which that update data is associated.

16 Claims, 10 Drawing Sheets