A 64-Kbytes ITTAGE indirect branch predictor

André Seznec 1
1 ALF - Amdahl's Law is Forever
Inria Rennes – Bretagne Atlantique , IRISA-D3 - ARCHITECTURE
Abstract : The ITTAGE, Indirect Target TAgged GEometric length predictor, was introduced in [5] at the same time as the TAGE conditional branch predictor. ITTAGE relies on the same principles as the TAGE predictor several predictor tables in- dexed through independent functions of the global branch/path history and the branch address. Like the TAGE predictor, ITTAGE uses (partially) tagged components as the PPM-like predictor [2]. It relies on (partial) match to select the predicted target of an indirect jump. TAGE also uses GEometric history length as the O-GEHL predictor [3], i.e. , the set of used global history lengths forms a geometric series. This allows to e ciently capture correlation on recent branch outcomes as well as on very old branches. Due to the huge storage budget available for the ChampionShip, we propose an ITTAGE predictor fea- turing 16 prediction tables. On the distributed set of traces, using a path history vector recording only in- formation from indirect jumps and calls was found to be (slightly) more e cient than using a path/branch history vector combining information from all kind of branches.
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https://hal.inria.fr/hal-00639041
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Submitted on : Tuesday, November 8, 2011 - 9:25:47 AM
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André Seznec. A 64-Kbytes ITTAGE indirect branch predictor. JWAC-2: Championship Branch Prediction, JILP, Jun 2011, San Jose, United States. ⟨hal-00639041⟩

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