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-rw-r--r--src/cpu/pred/tournament.cc97
1 files changed, 54 insertions, 43 deletions
diff --git a/src/cpu/pred/tournament.cc b/src/cpu/pred/tournament.cc
index 3adafb608..b6320ca8a 100644
--- a/src/cpu/pred/tournament.cc
+++ b/src/cpu/pred/tournament.cc
@@ -258,59 +258,70 @@ TournamentBP::update(Addr &branch_addr, bool taken, void *bp_history,
local_predictor_hist = localHistoryTable[local_history_idx];
local_predictor_idx = local_predictor_hist & localPredictorMask;
- // Update the choice predictor to tell it which one was correct if
- // there was a prediction.
if (bp_history) {
BPHistory *history = static_cast<BPHistory *>(bp_history);
- if (history->localPredTaken != history->globalPredTaken) {
- // If the local prediction matches the actual outcome,
- // decerement the counter. Otherwise increment the
- // counter.
- if (history->localPredTaken == taken) {
- choiceCtrs[history->globalHistory].decrement();
- } else if (history->globalPredTaken == taken){
- choiceCtrs[history->globalHistory].increment();
- }
-
- }
-
- // Update the counters and local history with the proper
- // resolution of the branch. Global history is updated
- // speculatively and restored upon squash() calls, so it does not
- // need to be updated.
+ // Update may also be called if the Branch target is incorrect even if
+ // the prediction is correct. In that case do not update the counters.
+ bool historyPred = false;
unsigned old_local_pred_index = history->localHistory
- & localPredictorMask;
- if (taken) {
- globalCtrs[history->globalHistory].increment();
- if (old_local_pred_index != invalidPredictorIndex) {
- localCtrs[old_local_pred_index].increment();
- }
+ & localPredictorMask;
+ if (history->globalUsed) {
+ historyPred = history->globalPredTaken;
} else {
- globalCtrs[history->globalHistory].decrement();
- if (old_local_pred_index != invalidPredictorIndex) {
- localCtrs[old_local_pred_index].decrement();
- }
- }
-
- if (squashed) {
- if (taken) {
- globalHistory = (history->globalHistory << 1) | 1;
- globalHistory = globalHistory & globalHistoryMask;
- if (history->localHistory != invalidPredictorIndex)
- localHistoryTable[local_history_idx] =
+ historyPred = history->localPredTaken;
+ }
+ if (historyPred != taken || !squashed) {
+ // Update the choice predictor to tell it which one was correct if
+ // there was a prediction.
+ if (history->localPredTaken != history->globalPredTaken) {
+ // If the local prediction matches the actual outcome,
+ // decerement the counter. Otherwise increment the
+ // counter.
+ if (history->localPredTaken == taken) {
+ choiceCtrs[history->globalHistory].decrement();
+ } else if (history->globalPredTaken == taken) {
+ choiceCtrs[history->globalHistory].increment();
+ }
+
+ }
+
+ // Update the counters and local history with the proper
+ // resolution of the branch. Global history is updated
+ // speculatively and restored upon squash() calls, so it does not
+ // need to be updated.
+ if (taken) {
+ globalCtrs[history->globalHistory].increment();
+ if (old_local_pred_index != invalidPredictorIndex) {
+ localCtrs[old_local_pred_index].increment();
+ }
+ } else {
+ globalCtrs[history->globalHistory].decrement();
+ if (old_local_pred_index != invalidPredictorIndex) {
+ localCtrs[old_local_pred_index].decrement();
+ }
+ }
+ }
+ if (squashed) {
+ if (taken) {
+ globalHistory = (history->globalHistory << 1) | 1;
+ globalHistory = globalHistory & globalHistoryMask;
+ if (old_local_pred_index != invalidPredictorIndex) {
+ localHistoryTable[old_local_pred_index] =
(history->localHistory << 1) | 1;
- } else {
- globalHistory = (history->globalHistory << 1);
- globalHistory = globalHistory & globalHistoryMask;
- if (history->localHistory != invalidPredictorIndex) {
- localHistoryTable[local_history_idx] =
+ }
+ } else {
+ globalHistory = (history->globalHistory << 1);
+ globalHistory = globalHistory & globalHistoryMask;
+ if (old_local_pred_index != invalidPredictorIndex) {
+ localHistoryTable[old_local_pred_index] =
history->localHistory << 1;
- }
- }
+ }
+ }
}
// We're done with this history, now delete it.
delete history;
+
}
assert(globalHistory < globalPredictorSize &&