diff options
Diffstat (limited to 'src/cpu/pred/bpred_unit.cc')
| -rw-r--r-- | src/cpu/pred/bpred_unit.cc | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/src/cpu/pred/bpred_unit.cc b/src/cpu/pred/bpred_unit.cc index 660475017..05770cba9 100644 --- a/src/cpu/pred/bpred_unit.cc +++ b/src/cpu/pred/bpred_unit.cc @@ -330,13 +330,9 @@ BPredUnit::update(const InstSeqNum &done_sn, ThreadID tid) while (!predHist[tid].empty() && predHist[tid].back().seqNum <= done_sn) { // Update the branch predictor with the correct results. - if (!predHist[tid].back().wasSquashed) { - update(tid, predHist[tid].back().pc, - predHist[tid].back().predTaken, - predHist[tid].back().bpHistory, false); - } else { - retireSquashed(tid, predHist[tid].back().bpHistory); - } + update(tid, predHist[tid].back().pc, + predHist[tid].back().predTaken, + predHist[tid].back().bpHistory, false); predHist[tid].pop_back(); } @@ -430,12 +426,23 @@ BPredUnit::squash(const InstSeqNum &squashed_sn, tid, hist_it->seqNum); } - // Have to get GHR here because the update deletes bpHistory + // Get the underlying Global History Register unsigned ghr = getGHR(tid, hist_it->bpHistory); + // There are separate functions for in-order and out-of-order + // branch prediction, but not for update. Therefore, this + // call should take into account that the mispredicted branch may + // be on the wrong path (i.e., OoO execution), and that the counter + // counter table(s) should not be updated. Thus, this call should + // restore the state of the underlying predictor, for instance the + // local/global histories. The counter tables will be updated when + // the branch actually commits. + + // Remember the correct direction for the update at commit. + pred_hist.front().predTaken = actually_taken; + update(tid, (*hist_it).pc, actually_taken, pred_hist.front().bpHistory, true); - hist_it->wasSquashed = true; if (actually_taken) { if (hist_it->wasReturn && !hist_it->usedRAS) { |