diff options
Diffstat (limited to 'cpu/beta_cpu/2bit_local_pred.cc')
| -rw-r--r-- | cpu/beta_cpu/2bit_local_pred.cc | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/cpu/beta_cpu/2bit_local_pred.cc b/cpu/beta_cpu/2bit_local_pred.cc index 88c39a9b0..ef7f23d49 100644 --- a/cpu/beta_cpu/2bit_local_pred.cc +++ b/cpu/beta_cpu/2bit_local_pred.cc @@ -75,18 +75,34 @@ DefaultBP::getLocalIndex(Addr &branch_addr) bool DefaultBP::lookup(Addr &branch_addr) { + bool taken; uint8_t local_prediction; unsigned local_predictor_idx = getLocalIndex(branch_addr); DPRINTF(Fetch, "Branch predictor: Looking up index %#x\n", local_predictor_idx); + assert(local_predictor_idx < localPredictorSize); + local_prediction = localCtrs[local_predictor_idx].read(); DPRINTF(Fetch, "Branch predictor: prediction is %i.\n", (int)local_prediction); - return getPrediction(local_prediction); + taken = getPrediction(local_prediction); + +#if 0 + // Speculative update. + if (taken) { + DPRINTF(Fetch, "Branch predictor: Branch updated as taken.\n"); + localCtrs[local_predictor_idx].increment(); + } else { + DPRINTF(Fetch, "Branch predictor: Branch updated as not taken.\n"); + localCtrs[local_predictor_idx].decrement(); + } +#endif + + return taken; } void @@ -100,11 +116,17 @@ DefaultBP::update(Addr &branch_addr, bool taken) DPRINTF(Fetch, "Branch predictor: Looking up index %#x\n", local_predictor_idx); + assert(local_predictor_idx < localPredictorSize); + + // Increment or decrement twice to undo speculative update, then + // properly update if (taken) { DPRINTF(Fetch, "Branch predictor: Branch updated as taken.\n"); localCtrs[local_predictor_idx].increment(); +// localCtrs[local_predictor_idx].increment(); } else { DPRINTF(Fetch, "Branch predictor: Branch updated as not taken.\n"); localCtrs[local_predictor_idx].decrement(); +// localCtrs[local_predictor_idx].decrement(); } } |