The idea here is about maintaining a "path history"! When looking up a register that tracks the "local" history of outcomes for a particular branch, you want t

The idea here is about maintaining a "path history"! When looking up a register that tracks the "local" history of outcomes for a particular branch, you want to have a hash function that captures enough context to distinguish the different situations where that branch might be encountered. Apart from folding a long "global history" of recent outcomes and mixing in the current program counter, I think many modern machines also mix in the target addresses of recently-taken branches.