The cascaded predictor: economical and adaptive branch target prediction
Karel Driesen, Urs Hölzle · 1998
this paper use a total path length of 24 bits). The lower-order branch address bits are xor-ed with this pattern, resulting in a 24-bit key pattern. Two-level predictors with longer path lengths use fewer bits of each target address, so that the length of the pattern remains constant. For example, a path length 6 predictor uses 4 bits from each target address. Note that a two-level predictor with path length 0 reverts to a BTB. The 24-bit key pattern is used, as in a BTB, to access the prediction table (History Table or Target Cache in [CHP97]) by splitting it into table index and tag as explained in the previous section.