diff options
| -rw-r--r-- | src/cpu/pred/BranchPredictor.py | 1 | ||||
| -rw-r--r-- | src/cpu/pred/ltage.cc | 18 | ||||
| -rw-r--r-- | src/cpu/pred/ltage.hh | 3 |
3 files changed, 13 insertions, 9 deletions
diff --git a/src/cpu/pred/BranchPredictor.py b/src/cpu/pred/BranchPredictor.py index a42819419..aa6cd4a25 100644 --- a/src/cpu/pred/BranchPredictor.py +++ b/src/cpu/pred/BranchPredictor.py @@ -100,6 +100,7 @@ class LTAGE(BranchPredictor): logSizeLoopPred = Param.Unsigned(8, "Log size of the loop predictor") nHistoryTables = Param.Unsigned(12, "Number of history tables") tagTableCounterBits = Param.Unsigned(3, "Number of tag table counter bits") + tagTableUBits = Param.Unsigned(2, "Number of tag table u bits") histBufferSize = Param.Unsigned(2097152, "A large number to track all branch histories(2MEntries default)") minHist = Param.Unsigned(4, "Minimum history size of LTAGE") diff --git a/src/cpu/pred/ltage.cc b/src/cpu/pred/ltage.cc index 85ae2b304..b049d4fde 100644 --- a/src/cpu/pred/ltage.cc +++ b/src/cpu/pred/ltage.cc @@ -55,6 +55,7 @@ LTAGE::LTAGE(const LTAGEParams *params) logSizeLoopPred(params->logSizeLoopPred), nHistoryTables(params->nHistoryTables), tagTableCounterBits(params->tagTableCounterBits), + tagTableUBits(params->tagTableUBits), histBufferSize(params->histBufferSize), minHist(params->minHist), maxHist(params->maxHist), @@ -68,6 +69,11 @@ LTAGE::LTAGE(const LTAGEParams *params) loopNumIterMask((1 << loopTableIterBits) - 1), threadHistory(params->numThreads) { + // Current method for periodically resetting the u counter bits only + // works for 1 or 2 bits + // Also make sure that it is not 0 + assert(tagTableUBits <= 2 && (tagTableUBits > 0)); + // we use uint16_t type for these vales, so they cannot be more than // 16 bits assert(loopTableTagBits <= 16); @@ -576,7 +582,7 @@ LTAGE::update(ThreadID tid, Addr branch_pc, bool taken, void* bp_history, if (alloc) { // is there some "unuseful" entry to allocate - int8_t min = 1; + uint8_t min = 1; for (int i = nHistoryTables; i > bi->hitBank; i--) { if (gtable[i][bi->tableIndices[i]].u < min) { min = gtable[i][bi->tableIndices[i]].u; @@ -605,7 +611,6 @@ LTAGE::update(ThreadID tid, Addr branch_pc, bool taken, void* bp_history, if ((gtable[i][bi->tableIndices[i]].u == 0)) { gtable[i][bi->tableIndices[i]].tag = bi->tableTags[i]; gtable[i][bi->tableIndices[i]].ctr = (taken) ? 0 : -1; - gtable[i][bi->tableIndices[i]].u = 0; //? break; } } @@ -643,12 +648,9 @@ LTAGE::update(ThreadID tid, Addr branch_pc, bool taken, void* bp_history, } // update the u counter - if (longest_match_pred != bi->altTaken) { - if (longest_match_pred == taken) { - if (gtable[bi->hitBank][bi->hitBankIndex].u < 1) { - gtable[bi->hitBank][bi->hitBankIndex].u++; - } - } + if (bi->tagePred != bi->altTaken) { + unsignedCtrUpdate(gtable[bi->hitBank][bi->hitBankIndex].u, + bi->tagePred == taken, tagTableUBits); } } else { baseUpdate(pc, taken, bi); diff --git a/src/cpu/pred/ltage.hh b/src/cpu/pred/ltage.hh index 2119156b7..68aef1cc9 100644 --- a/src/cpu/pred/ltage.hh +++ b/src/cpu/pred/ltage.hh @@ -94,7 +94,7 @@ class LTAGE: public BPredUnit { int8_t ctr; uint16_t tag; - int8_t u; + uint8_t u; TageEntry() : ctr(0), tag(0), u(0) { } }; @@ -360,6 +360,7 @@ class LTAGE: public BPredUnit const unsigned logSizeLoopPred; const unsigned nHistoryTables; const unsigned tagTableCounterBits; + const unsigned tagTableUBits; const unsigned histBufferSize; const unsigned minHist; const unsigned maxHist; |