Two-level adaptive predictorsSimulations of Yeh and Patt using the SPEC89 benchmarks
The performance of the global history schemes is sensitive to the branch history length.
Interference of different branches that are mapped to the same pattern history table is decreased by lengthening the global BHR.
Similarly adding PHTs reduces the possibility of pattern history interference by mapping interfering branches into different tables.
Global history schemes are better than the per-address schemes for the integer SPEC89 programs,
- utilize branch correlation, which is often the case in the frequent if-then-else statements in integer programs
Per-address schemes are better for the floating-point intensive programs.
- better in predicting loop-control branches which are frequent in the floating-point SPEC89 benchmark programs.
The per-set history schemes are in between both other schemes.