Editing Branch predictor (section)

===Hybrid predictor===
A hybrid predictor, also called combined predictor, implements more than one prediction mechanism. The final prediction is based either on a meta-predictor that remembers which of the predictors has made the best predictions in the past, or a majority vote function based on an odd number of different predictors.

[[Scott McFarling]] proposed combined branch prediction in his 1993 paper.<ref name="decwrl-tn-36"/>

On the SPEC'89 benchmarks, such a predictor is about as good as the local predictor.{{Citation needed|date=April 2009}}

Predictors like gshare use multiple table entries to track the behavior of any particular branch. This multiplication of entries makes it much more likely that two branches will map to the same table entry (a situation called aliasing), which in turn makes it much more likely that prediction accuracy will suffer for those branches. Once you have multiple predictors, it is beneficial to arrange that each predictor will have different aliasing patterns, so that it is more likely that at least one predictor will have no aliasing. Combined predictors with different indexing functions for the different predictors are called ''gskew'' predictors, and are analogous to [[CPU cache#Two-way skewed associative cache|skewed associative caches]] used for data and instruction caching.