diff options
Diffstat (limited to 'src/cpu/pred/BranchPredictor.py')
| -rw-r--r-- | src/cpu/pred/BranchPredictor.py | 53 |
1 files changed, 37 insertions, 16 deletions
diff --git a/src/cpu/pred/BranchPredictor.py b/src/cpu/pred/BranchPredictor.py index 9d83abb0b..2c622cd02 100644 --- a/src/cpu/pred/BranchPredictor.py +++ b/src/cpu/pred/BranchPredictor.py @@ -87,34 +87,55 @@ class BiModeBP(BranchPredictor): choicePredictorSize = Param.Unsigned(8192, "Size of choice predictor") choiceCtrBits = Param.Unsigned(2, "Bits of choice counters") -class LTAGE(BranchPredictor): - type = 'LTAGE' - cxx_class = 'LTAGE' - cxx_header = "cpu/pred/ltage.hh" +# TAGE branch predictor as described in https://www.jilp.org/vol8/v8paper1.pdf +# The default sizes below are for the 8C-TAGE configuration (63.5 Kbits) +class TAGE(BranchPredictor): + type = 'TAGE' + cxx_class = 'TAGE' + cxx_header = "cpu/pred/tage.hh" + nHistoryTables = Param.Unsigned(7, "Number of history tables") + minHist = Param.Unsigned(5, "Minimum history size of LTAGE") + maxHist = Param.Unsigned(130, "Maximum history size of LTAGE") + + tagTableTagWidths = VectorParam.Unsigned( + [0, 9, 9, 10, 10, 11, 11, 12], "Tag size in TAGE tag tables") + logTagTableSizes = VectorParam.Int( + [13, 9, 9, 9, 9, 9, 9, 9], "Log2 of TAGE table sizes") logRatioBiModalHystEntries = Param.Unsigned(2, "Log num of prediction entries for a shared hysteresis bit " \ "for the Bimodal") - 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") - maxHist = Param.Unsigned(640, "Maximum history size of LTAGE") + pathHistBits = Param.Unsigned(16, "Path history size") - tagTableTagWidths = VectorParam.Unsigned( - [0, 7, 7, 8, 8, 9, 10, 11, 12, 12, 13, 14, 15], - "Tag size in TAGE tag tables") - logTagTableSizes = VectorParam.Int( - [14, 10, 10, 11, 11, 11, 11, 10, 10, 10, 10, 9, 9], - "Log2 of TAGE table sizes") - logUResetPeriod = Param.Unsigned(19, + logUResetPeriod = Param.Unsigned(18, "Log period in number of branches to reset TAGE useful counters") useAltOnNaBits = Param.Unsigned(4, "Size of the USE_ALT_ON_NA counter") - withLoopBits = Param.Unsigned(7, "Size of the WITHLOOP counter") + +# LTAGE branch predictor as described in +# https://www.irisa.fr/caps/people/seznec/L-TAGE.pdf +# It is basically a TAGE predictor plus a loop predictor +# The differnt TAGE sizes are updated according to the paper values (256 Kbits) +class LTAGE(TAGE): + type = 'LTAGE' + cxx_class = 'LTAGE' + cxx_header = "cpu/pred/ltage.hh" + + nHistoryTables = 12 + minHist = 4 + maxHist = 640 + tagTableTagWidths = [0, 7, 7, 8, 8, 9, 10, 11, 12, 12, 13, 14, 15] + logTagTableSizes = [14, 10, 10, 11, 11, 11, 11, 10, 10, 10, 10, 9, 9] + logUResetPeriod = 19 + + logSizeLoopPred = Param.Unsigned(8, "Log size of the loop predictor") + withLoopBits = Param.Unsigned(7, "Size of the WITHLOOP counter") loopTableAgeBits = Param.Unsigned(8, "Number of age bits per loop entry") loopTableConfidenceBits = Param.Unsigned(2, "Number of confidence bits per loop entry") |