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-rw-r--r--src/cpu/pred/tournament.cc297
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diff --git a/src/cpu/pred/tournament.cc b/src/cpu/pred/tournament.cc
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+/*
+ * Copyright (c) 2004-2006 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Kevin Lim
+ */
+
+#include "base/intmath.hh"
+#include "cpu/pred/tournament.hh"
+
+TournamentBP::TournamentBP(unsigned _localPredictorSize,
+ unsigned _localCtrBits,
+ unsigned _localHistoryTableSize,
+ unsigned _localHistoryBits,
+ unsigned _globalPredictorSize,
+ unsigned _globalCtrBits,
+ unsigned _globalHistoryBits,
+ unsigned _choicePredictorSize,
+ unsigned _choiceCtrBits,
+ unsigned _instShiftAmt)
+ : localPredictorSize(_localPredictorSize),
+ localCtrBits(_localCtrBits),
+ localHistoryTableSize(_localHistoryTableSize),
+ localHistoryBits(_localHistoryBits),
+ globalPredictorSize(_globalPredictorSize),
+ globalCtrBits(_globalCtrBits),
+ globalHistoryBits(_globalHistoryBits),
+ choicePredictorSize(_globalPredictorSize),
+ choiceCtrBits(_choiceCtrBits),
+ instShiftAmt(_instShiftAmt)
+{
+ if (!isPowerOf2(localPredictorSize)) {
+ fatal("Invalid local predictor size!\n");
+ }
+
+ //Setup the array of counters for the local predictor
+ localCtrs.resize(localPredictorSize);
+
+ for (int i = 0; i < localPredictorSize; ++i)
+ localCtrs[i].setBits(localCtrBits);
+
+ localPredictorMask = floorPow2(localPredictorSize) - 1;
+
+ if (!isPowerOf2(localHistoryTableSize)) {
+ fatal("Invalid local history table size!\n");
+ }
+
+ //Setup the history table for the local table
+ localHistoryTable.resize(localHistoryTableSize);
+
+ for (int i = 0; i < localHistoryTableSize; ++i)
+ localHistoryTable[i] = 0;
+
+ // Setup the local history mask
+ localHistoryMask = (1 << localHistoryBits) - 1;
+
+ if (!isPowerOf2(globalPredictorSize)) {
+ fatal("Invalid global predictor size!\n");
+ }
+
+ //Setup the array of counters for the global predictor
+ globalCtrs.resize(globalPredictorSize);
+
+ for (int i = 0; i < globalPredictorSize; ++i)
+ globalCtrs[i].setBits(globalCtrBits);
+
+ //Clear the global history
+ globalHistory = 0;
+ // Setup the global history mask
+ globalHistoryMask = (1 << globalHistoryBits) - 1;
+
+ if (!isPowerOf2(choicePredictorSize)) {
+ fatal("Invalid choice predictor size!\n");
+ }
+
+ //Setup the array of counters for the choice predictor
+ choiceCtrs.resize(choicePredictorSize);
+
+ for (int i = 0; i < choicePredictorSize; ++i)
+ choiceCtrs[i].setBits(choiceCtrBits);
+
+ // @todo: Allow for different thresholds between the predictors.
+ threshold = (1 << (localCtrBits - 1)) - 1;
+ threshold = threshold / 2;
+}
+
+inline
+unsigned
+TournamentBP::calcLocHistIdx(Addr &branch_addr)
+{
+ // Get low order bits after removing instruction offset.
+ return (branch_addr >> instShiftAmt) & (localHistoryTableSize - 1);
+}
+
+inline
+void
+TournamentBP::updateGlobalHistTaken()
+{
+ globalHistory = (globalHistory << 1) | 1;
+ globalHistory = globalHistory & globalHistoryMask;
+}
+
+inline
+void
+TournamentBP::updateGlobalHistNotTaken()
+{
+ globalHistory = (globalHistory << 1);
+ globalHistory = globalHistory & globalHistoryMask;
+}
+
+inline
+void
+TournamentBP::updateLocalHistTaken(unsigned local_history_idx)
+{
+ localHistoryTable[local_history_idx] =
+ (localHistoryTable[local_history_idx] << 1) | 1;
+}
+
+inline
+void
+TournamentBP::updateLocalHistNotTaken(unsigned local_history_idx)
+{
+ localHistoryTable[local_history_idx] =
+ (localHistoryTable[local_history_idx] << 1);
+}
+
+bool
+TournamentBP::lookup(Addr &branch_addr, void * &bp_history)
+{
+ bool local_prediction;
+ unsigned local_history_idx;
+ unsigned local_predictor_idx;
+
+ bool global_prediction;
+ bool choice_prediction;
+
+ //Lookup in the local predictor to get its branch prediction
+ local_history_idx = calcLocHistIdx(branch_addr);
+ local_predictor_idx = localHistoryTable[local_history_idx]
+ & localPredictorMask;
+ local_prediction = localCtrs[local_predictor_idx].read() > threshold;
+
+ //Lookup in the global predictor to get its branch prediction
+ global_prediction = globalCtrs[globalHistory].read() > threshold;
+
+ //Lookup in the choice predictor to see which one to use
+ choice_prediction = choiceCtrs[globalHistory].read() > threshold;
+
+ // Create BPHistory and pass it back to be recorded.
+ BPHistory *history = new BPHistory;
+ history->globalHistory = globalHistory;
+ history->localPredTaken = local_prediction;
+ history->globalPredTaken = global_prediction;
+ history->globalUsed = choice_prediction;
+ bp_history = (void *)history;
+
+ assert(globalHistory < globalPredictorSize &&
+ local_history_idx < localHistoryTableSize &&
+ local_predictor_idx < localPredictorSize);
+
+ // Commented code is for doing speculative update of counters and
+ // all histories.
+ if (choice_prediction) {
+ if (global_prediction) {
+// updateHistoriesTaken(local_history_idx);
+// globalCtrs[globalHistory].increment();
+// localCtrs[local_history_idx].increment();
+ updateGlobalHistTaken();
+ return true;
+ } else {
+// updateHistoriesNotTaken(local_history_idx);
+// globalCtrs[globalHistory].decrement();
+// localCtrs[local_history_idx].decrement();
+ updateGlobalHistNotTaken();
+ return false;
+ }
+ } else {
+ if (local_prediction) {
+// updateHistoriesTaken(local_history_idx);
+// globalCtrs[globalHistory].increment();
+// localCtrs[local_history_idx].increment();
+ updateGlobalHistTaken();
+ return true;
+ } else {
+// updateHistoriesNotTaken(local_history_idx);
+// globalCtrs[globalHistory].decrement();
+// localCtrs[local_history_idx].decrement();
+ updateGlobalHistNotTaken();
+ return false;
+ }
+ }
+}
+
+void
+TournamentBP::uncondBr(void * &bp_history)
+{
+ // Create BPHistory and pass it back to be recorded.
+ BPHistory *history = new BPHistory;
+ history->globalHistory = globalHistory;
+ history->localPredTaken = true;
+ history->globalPredTaken = true;
+ bp_history = static_cast<void *>(history);
+
+ updateGlobalHistTaken();
+}
+
+void
+TournamentBP::update(Addr &branch_addr, bool taken, void *bp_history)
+{
+ unsigned local_history_idx;
+ unsigned local_predictor_idx;
+ unsigned local_predictor_hist;
+
+ // Get the local predictor's current prediction
+ local_history_idx = calcLocHistIdx(branch_addr);
+ 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[globalHistory].decrement();
+ } else if (history->globalPredTaken == taken){
+ choiceCtrs[globalHistory].increment();
+ }
+ }
+
+ // We're done with this history, now delete it.
+ delete history;
+ }
+
+ assert(globalHistory < globalPredictorSize &&
+ local_history_idx < localHistoryTableSize &&
+ local_predictor_idx < localPredictorSize);
+
+ // 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) {
+ localCtrs[local_predictor_idx].increment();
+ globalCtrs[globalHistory].increment();
+
+ updateLocalHistTaken(local_history_idx);
+ } else {
+ localCtrs[local_predictor_idx].decrement();
+ globalCtrs[globalHistory].decrement();
+
+ updateLocalHistNotTaken(local_history_idx);
+ }
+}
+
+void
+TournamentBP::squash(void *bp_history)
+{
+ BPHistory *history = static_cast<BPHistory *>(bp_history);
+
+ // Restore global history to state prior to this branch.
+ globalHistory = history->globalHistory;
+
+ // Delete this BPHistory now that we're done with it.
+ delete history;
+}
+
+#ifdef DEBUG
+int
+TournamentBP::BPHistory::newCount = 0;
+#endif
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