A 64-Kbytes ITTAGE indirect branch predictor

International audienceThe 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