1# Copyright (c) 2012 Mark D. Hill and David A. Wood 2# Copyright (c) 2015 The University of Wisconsin 3# All rights reserved. 4# 5# Redistribution and use in source and binary forms, with or without 6# modification, are permitted provided that the following conditions are 7# met: redistributions of source code must retain the above copyright 8# notice, this list of conditions and the following disclaimer; 9# redistributions in binary form must reproduce the above copyright 10# notice, this list of conditions and the following disclaimer in the 11# documentation and/or other materials provided with the distribution; 12# neither the name of the copyright holders nor the names of its 13# contributors may be used to endorse or promote products derived from 14# this software without specific prior written permission. 15# 16# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27# 28# Authors: Nilay Vaish and Dibakar Gope 29 30from m5.SimObject import SimObject 31from m5.params import * 32from m5.proxy import * 33 34class BranchPredictor(SimObject): 35 type = 'BranchPredictor' 36 cxx_class = 'BPredUnit' 37 cxx_header = "cpu/pred/bpred_unit.hh" 38 abstract = True 39 40 numThreads = Param.Unsigned(Parent.numThreads, "Number of threads") 41 BTBEntries = Param.Unsigned(4096, "Number of BTB entries") 42 BTBTagSize = Param.Unsigned(16, "Size of the BTB tags, in bits") 43 RASSize = Param.Unsigned(16, "RAS size") 44 instShiftAmt = Param.Unsigned(2, "Number of bits to shift instructions by") 45 46 useIndirect = Param.Bool(True, "Use indirect branch predictor") 47 indirectHashGHR = Param.Bool(True, "Hash branch predictor GHR") 48 indirectHashTargets = Param.Bool(True, "Hash path history targets") 49 indirectSets = Param.Unsigned(256, "Cache sets for indirect predictor") 50 indirectWays = Param.Unsigned(2, "Ways for indirect predictor") 51 indirectTagSize = Param.Unsigned(16, "Indirect target cache tag bits") 52 indirectPathLength = Param.Unsigned(3, 53 "Previous indirect targets to use for path history") 54 55 56 57class LocalBP(BranchPredictor): 58 type = 'LocalBP' 59 cxx_class = 'LocalBP' 60 cxx_header = "cpu/pred/2bit_local.hh" 61 62 localPredictorSize = Param.Unsigned(2048, "Size of local predictor") 63 localCtrBits = Param.Unsigned(2, "Bits per counter") 64 65 66class TournamentBP(BranchPredictor): 67 type = 'TournamentBP' 68 cxx_class = 'TournamentBP' 69 cxx_header = "cpu/pred/tournament.hh" 70 71 localPredictorSize = Param.Unsigned(2048, "Size of local predictor") 72 localCtrBits = Param.Unsigned(2, "Bits per counter") 73 localHistoryTableSize = Param.Unsigned(2048, "size of local history table") 74 globalPredictorSize = Param.Unsigned(8192, "Size of global predictor") 75 globalCtrBits = Param.Unsigned(2, "Bits per counter") 76 choicePredictorSize = Param.Unsigned(8192, "Size of choice predictor") 77 choiceCtrBits = Param.Unsigned(2, "Bits of choice counters") 78 79 80class BiModeBP(BranchPredictor): 81 type = 'BiModeBP' 82 cxx_class = 'BiModeBP' 83 cxx_header = "cpu/pred/bi_mode.hh" 84 85 globalPredictorSize = Param.Unsigned(8192, "Size of global predictor") 86 globalCtrBits = Param.Unsigned(2, "Bits per counter") 87 choicePredictorSize = Param.Unsigned(8192, "Size of choice predictor") 88 choiceCtrBits = Param.Unsigned(2, "Bits of choice counters") 89 90# TAGE branch predictor as described in https://www.jilp.org/vol8/v8paper1.pdf 91# The default sizes below are for the 8C-TAGE configuration (63.5 Kbits) 92class TAGE(BranchPredictor): 93 type = 'TAGE' 94 cxx_class = 'TAGE' 95 cxx_header = "cpu/pred/tage.hh" 96 97 nHistoryTables = Param.Unsigned(7, "Number of history tables") 98 minHist = Param.Unsigned(5, "Minimum history size of LTAGE") 99 maxHist = Param.Unsigned(130, "Maximum history size of LTAGE") 100 101 tagTableTagWidths = VectorParam.Unsigned( 102 [0, 9, 9, 10, 10, 11, 11, 12], "Tag size in TAGE tag tables") 103 logTagTableSizes = VectorParam.Int( 104 [13, 9, 9, 9, 9, 9, 9, 9], "Log2 of TAGE table sizes") 105 logRatioBiModalHystEntries = Param.Unsigned(2, 106 "Log num of prediction entries for a shared hysteresis bit " \ 107 "for the Bimodal") 108 109 tagTableCounterBits = Param.Unsigned(3, "Number of tag table counter bits") 110 tagTableUBits = Param.Unsigned(2, "Number of tag table u bits") 111 112 histBufferSize = Param.Unsigned(2097152, 113 "A large number to track all branch histories(2MEntries default)") 114 115 pathHistBits = Param.Unsigned(16, "Path history size") 116 logUResetPeriod = Param.Unsigned(18, 117 "Log period in number of branches to reset TAGE useful counters") 118 useAltOnNaBits = Param.Unsigned(4, "Size of the USE_ALT_ON_NA counter") 119 120 121# LTAGE branch predictor as described in 122# https://www.irisa.fr/caps/people/seznec/L-TAGE.pdf 123# It is basically a TAGE predictor plus a loop predictor 124# The differnt TAGE sizes are updated according to the paper values (256 Kbits) 125class LTAGE(TAGE): 126 type = 'LTAGE' 127 cxx_class = 'LTAGE' 128 cxx_header = "cpu/pred/ltage.hh" 129 130 nHistoryTables = 12 131 minHist = 4 132 maxHist = 640 133 tagTableTagWidths = [0, 7, 7, 8, 8, 9, 10, 11, 12, 12, 13, 14, 15] 134 logTagTableSizes = [14, 10, 10, 11, 11, 11, 11, 10, 10, 10, 10, 9, 9] 135 logUResetPeriod = 19 136 137 logSizeLoopPred = Param.Unsigned(8, "Log size of the loop predictor") 138 withLoopBits = Param.Unsigned(7, "Size of the WITHLOOP counter") 139 loopTableAgeBits = Param.Unsigned(8, "Number of age bits per loop entry") 140 loopTableConfidenceBits = Param.Unsigned(2, 141 "Number of confidence bits per loop entry") 142 loopTableTagBits = Param.Unsigned(14, "Number of tag bits per loop entry") 143 loopTableIterBits = Param.Unsigned(14, "Nuber of iteration bits per loop") 144 logLoopTableAssoc = Param.Unsigned(2, "Log loop predictor associativity") 145
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