BranchPredictor.py

# Copyright (c) 2012 Mark D. Hill and David A. Wood
# Copyright (c) 2015 The University of Wisconsin
# 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
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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from m5.SimObject import SimObject
from m5.params import *
from m5.proxy import *

class BpType(Enum):
    vals = ['Coupled', 'DecoupledStream', 'DecoupledFTB', 'DecoupledBTB']

class IndirectPredictor(SimObject):
    type = 'IndirectPredictor'
    cxx_class = 'gem5::branch_prediction::IndirectPredictor'
    cxx_header = "cpu/pred/indirect.hh"
    abstract = True

    numThreads = Param.Unsigned(Parent.numThreads, "Number of threads")

class SimpleIndirectPredictor(IndirectPredictor):
    type = 'SimpleIndirectPredictor'
    cxx_class = 'gem5::branch_prediction::SimpleIndirectPredictor'
    cxx_header = "cpu/pred/simple_indirect.hh"

    indirectHashGHR = Param.Bool(True, "Hash branch predictor GHR")
    indirectHashTargets = Param.Bool(False, "Hash path history targets")
    indirectSets = Param.Unsigned(256, "Cache sets for indirect predictor")
    indirectWays = Param.Unsigned(2, "Ways for indirect predictor")
    indirectTagSize = Param.Unsigned(16, "Indirect target cache tag bits")
    indirectPathLength = Param.Unsigned(3,
        "Previous indirect targets to use for path history")
    indirectGHRBits = Param.Unsigned(13, "Indirect GHR number of bits")
    instShiftAmt = Param.Unsigned(2, "Number of bits to shift instructions by")

class ITTAGE(IndirectPredictor):
    type = 'ITTAGE'
    cxx_class = 'gem5::branch_prediction::ITTAGE'
    cxx_header = "cpu/pred/ITTAGE.hh"

    indirectPathLength = Param.Unsigned(3, "Previous indirect targets to use for path history")
    numPredictors = Param.Unsigned(11, "Number of TAGE predictors")
    tableSizes = VectorParam.Int(
        [256] * 15, "the ITTAGE T1~Tn length")
    TTagBitSizes = VectorParam.Int(
        [9, 9, 13, 13, 13, 13, 13, 13, 13, 13, 15, 15, 15, 15, 15], "the T1~Tn entry's tag bit size")
    TTagPcShifts = VectorParam.Int(
        [2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2], "when the T1~Tn entry's tag generating, PC right shift")
    histLengths = VectorParam.Int(
        [4, 10, 16, 27, 44, 60, 96, 109, 219, 449, 487], "the ITTAGE T1~Tn history length")
    simpleBTBSize = Param.Unsigned(512, "size of base predictor")


class BranchPredictor(SimObject):
    type = 'BranchPredictor'
    cxx_class = 'gem5::branch_prediction::BPredUnit'
    cxx_header = "cpu/pred/bpred_unit.hh"
    abstract = True

    numThreads = Param.Unsigned(Parent.numThreads, "Number of threads")
    BTBEntries = Param.Unsigned(4096, "Number of BTB entries")
    BTBTagSize = Param.Unsigned(16, "Size of the BTB tags, in bits")
    RASSize = Param.Unsigned(16, "RAS size")
    instShiftAmt = Param.Unsigned(2, "Number of bits to shift instructions by")
    isDumpMisspredPC = Param.Bool(False, "enable dump miss pred pc")
    indirectBranchPred = Param.IndirectPredictor(ITTAGE(),
      "Indirect branch predictor, set to NULL to disable indirect predictions")

class LocalBP(BranchPredictor):
    type = 'LocalBP'
    cxx_class = 'gem5::branch_prediction::LocalBP'
    cxx_header = "cpu/pred/2bit_local.hh"

    localPredictorSize = Param.Unsigned(2048, "Size of local predictor")
    localCtrBits = Param.Unsigned(2, "Bits per counter")


class TournamentBP(BranchPredictor):
    type = 'TournamentBP'
    cxx_class = 'gem5::branch_prediction::TournamentBP'
    cxx_header = "cpu/pred/tournament.hh"

    localPredictorSize = Param.Unsigned(2048, "Size of local predictor")
    localCtrBits = Param.Unsigned(2, "Bits per counter")
    localHistoryTableSize = Param.Unsigned(2048, "size of local history table")
    globalPredictorSize = Param.Unsigned(8192, "Size of global predictor")
    globalCtrBits = Param.Unsigned(2, "Bits per counter")
    choicePredictorSize = Param.Unsigned(8192, "Size of choice predictor")
    choiceCtrBits = Param.Unsigned(2, "Bits of choice counters")


class BiModeBP(BranchPredictor):
    type = 'BiModeBP'
    cxx_class = 'gem5::branch_prediction::BiModeBP'
    cxx_header = "cpu/pred/bi_mode.hh"

    globalPredictorSize = Param.Unsigned(8192, "Size of global predictor")
    globalCtrBits = Param.Unsigned(2, "Bits per counter")
    choicePredictorSize = Param.Unsigned(8192, "Size of choice predictor")
    choiceCtrBits = Param.Unsigned(2, "Bits of choice counters")

class TAGEBase(SimObject):
    type = 'TAGEBase'
    cxx_class = 'gem5::branch_prediction::TAGEBase'
    cxx_header = "cpu/pred/tage_base.hh"

    numThreads = Param.Unsigned(Parent.numThreads, "Number of threads")
    instShiftAmt = Param.Unsigned(Parent.instShiftAmt,
        "Number of bits to shift instructions by")

    nHistoryTables = Param.Unsigned(7, "Number of history tables")
    minHist = Param.Unsigned(5, "Minimum history size of TAGE")
    maxHist = Param.Unsigned(130, "Maximum history size of TAGE")

    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")

    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)")

    pathHistBits = Param.Unsigned(16, "Path history size")
    logUResetPeriod = Param.Unsigned(18,
        "Log period in number of branches to reset TAGE useful counters")
    numUseAltOnNa = Param.Unsigned(1, "Number of USE_ALT_ON_NA counters")
    initialTCounterValue = Param.Int(1 << 17, "Initial value of tCounter")
    useAltOnNaBits = Param.Unsigned(4, "Size of the USE_ALT_ON_NA counter(s)")

    maxNumAlloc = Param.Unsigned(1,
        "Max number of TAGE entries allocted on mispredict")

    # List of enabled TAGE tables. If empty, all are enabled
    noSkip = VectorParam.Bool([], "Vector of enabled TAGE tables")

    speculativeHistUpdate = Param.Bool(True,
        "Use speculative update for histories")

# 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 = 'gem5::branch_prediction::TAGE'
    cxx_header = "cpu/pred/tage.hh"

    tage = Param.TAGEBase(TAGEBase(), "Tage object")

class LTAGE_TAGE(TAGEBase):
    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

class LoopPredictor(SimObject):
    type = 'LoopPredictor'
    cxx_class = 'gem5::branch_prediction::LoopPredictor'
    cxx_header = 'cpu/pred/loop_predictor.hh'

    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")
    loopTableTagBits = Param.Unsigned(14, "Number of tag bits per loop entry")
    loopTableIterBits = Param.Unsigned(14, "Nuber of iteration bits per loop")
    logLoopTableAssoc = Param.Unsigned(2, "Log loop predictor associativity")

    # Parameters for enabling modifications to the loop predictor
    # They have been copied from TAGE-GSC-IMLI
    # (http://www.irisa.fr/alf/downloads/seznec/TAGE-GSC-IMLI.tar)
    #
    # All of them should be disabled to match the original LTAGE implementation
    # (http://hpca23.cse.tamu.edu/taco/camino/cbp2/cbp-src/realistic-seznec.h)

    # Add speculation
    useSpeculation = Param.Bool(False, "Use speculation")

    # Add hashing for calculating the loop table index
    useHashing = Param.Bool(False, "Use hashing")

    # Add a direction bit to the loop table entries
    useDirectionBit = Param.Bool(False, "Use direction info")

    # If true, use random to decide whether to allocate or not, and only try
    # with one entry
    restrictAllocation = Param.Bool(False,
        "Restrict the allocation conditions")

    initialLoopIter = Param.Unsigned(1, "Initial iteration number")
    initialLoopAge = Param.Unsigned(255, "Initial age value")
    optionalAgeReset = Param.Bool(True,
        "Reset age bits optionally in some cases")

class TAGE_SC_L_TAGE(TAGEBase):
    type = 'TAGE_SC_L_TAGE'
    cxx_class = 'gem5::branch_prediction::TAGE_SC_L_TAGE'
    cxx_header = "cpu/pred/tage_sc_l.hh"
    abstract = True

    tagTableTagWidths = [0]
    numUseAltOnNa = 16
    pathHistBits = 27
    maxNumAlloc = 2
    logUResetPeriod = 10
    initialTCounterValue = 1 << 9
    useAltOnNaBits = 5
    # TODO No speculation implemented as of now
    speculativeHistUpdate = False

    # This size does not set the final sizes of the tables (it is just used
    # for some calculations)
    # Instead, the number of TAGE entries comes from shortTagsTageEntries and
    # longTagsTageEntries
    logTagTableSize = Param.Unsigned("Log size of each tag table")

    shortTagsTageFactor = Param.Unsigned(
        "Factor for calculating the total number of short tags TAGE entries")

    longTagsTageFactor = Param.Unsigned(
        "Factor for calculating the total number of long tags TAGE entries")

    shortTagsSize = Param.Unsigned(8, "Size of the short tags")

    longTagsSize = Param.Unsigned("Size of the long tags")

    firstLongTagTable = Param.Unsigned("First table with long tags")

    truncatePathHist = Param.Bool(True,
        "Truncate the path history to its configured size")


class TAGE_SC_L_TAGE_64KB(TAGE_SC_L_TAGE):
    type = 'TAGE_SC_L_TAGE_64KB'
    cxx_class = 'gem5::branch_prediction::TAGE_SC_L_TAGE_64KB'
    cxx_header = "cpu/pred/tage_sc_l_64KB.hh"

    nHistoryTables = 36

    minHist = 6
    maxHist = 3000

    tagTableUBits = 1

    logTagTableSizes = [13]

    # This is used to handle the 2-way associativity
    # (all odd entries are set to one, and if the corresponding even entry
    # is set to one, then there is a 2-way associativity for this pair)
    # Entry 0 is for the bimodal and it is ignored
    # Note: For this implementation, some odd entries are also set to 0 to save
    # some bits
    noSkip = [0,0,1,0,0,0,1,0,0,1,1,1,1,1,1,1,1,1,1,
                1,1,1,1,0,1,0,1,0,1,0,0,0,1,0,0,0,1]

    logTagTableSize = 10
    shortTagsTageFactor = 10
    longTagsTageFactor = 20

    longTagsSize = 12

    firstLongTagTable = 13

class TAGE_SC_L_TAGE_8KB(TAGE_SC_L_TAGE):
    type = 'TAGE_SC_L_TAGE_8KB'
    cxx_class = 'gem5::branch_prediction::TAGE_SC_L_TAGE_8KB'
    cxx_header = "cpu/pred/tage_sc_l_8KB.hh"

    nHistoryTables = 30

    minHist = 4
    maxHist = 1000

    logTagTableSize = 7
    shortTagsTageFactor = 9
    longTagsTageFactor = 17
    longTagsSize = 12

    logTagTableSizes = [12]

    firstLongTagTable = 11

    truncatePathHist = False

    noSkip = [0,0,1,0,1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,0,1,0,1,0,1,0,1]

    tagTableUBits = 2

# 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 = 'gem5::branch_prediction::LTAGE'
    cxx_header = "cpu/pred/ltage.hh"

    tage = LTAGE_TAGE()

    loop_predictor = Param.LoopPredictor(LoopPredictor(), "Loop predictor")

class TAGE_SC_L_LoopPredictor(LoopPredictor):
    type = 'TAGE_SC_L_LoopPredictor'
    cxx_class  = 'gem5::branch_prediction::TAGE_SC_L_LoopPredictor'
    cxx_header = "cpu/pred/tage_sc_l.hh"

    loopTableAgeBits = 4
    loopTableConfidenceBits = 4
    loopTableTagBits = 10
    loopTableIterBits = 10
    useSpeculation = False
    useHashing = True
    useDirectionBit = True
    restrictAllocation = True
    initialLoopIter = 0
    initialLoopAge = 7
    optionalAgeReset = False

class StatisticalCorrector(SimObject):
    type = 'StatisticalCorrector'
    cxx_class  = 'gem5::branch_prediction::StatisticalCorrector'
    cxx_header = "cpu/pred/statistical_corrector.hh"
    abstract = True

    # Statistical corrector parameters

    numEntriesFirstLocalHistories = Param.Unsigned(
        "Number of entries for first local histories")

    bwnb = Param.Unsigned("Num global backward branch GEHL lengths")
    bwm = VectorParam.Int("Global backward branch GEHL lengths")
    logBwnb = Param.Unsigned("Log num of global backward branch GEHL entries")
    bwWeightInitValue = Param.Int(
     "Initial value of the weights of the global backward branch GEHL entries")

    lnb = Param.Unsigned("Num first local history GEHL lenghts")
    lm = VectorParam.Int("First local history GEHL lengths")
    logLnb = Param.Unsigned("Log number of first local history GEHL entries")
    lWeightInitValue = Param.Int(
        "Initial value of the weights of the first local history GEHL entries")

    inb = Param.Unsigned(1, "Num IMLI GEHL lenghts")
    im = VectorParam.Int([8], "IMLI history GEHL lengths")
    logInb = Param.Unsigned("Log number of IMLI GEHL entries")
    iWeightInitValue = Param.Int(
        "Initial value of the weights of the IMLI history GEHL entries")

    logBias = Param.Unsigned("Log size of Bias tables")

    logSizeUp = Param.Unsigned(6,
        "Log size of update threshold counters tables")

    chooserConfWidth = Param.Unsigned(7,
        "Number of bits for the chooser counters")

    updateThresholdWidth = Param.Unsigned(12,
        "Number of bits for the update threshold counter")

    pUpdateThresholdWidth = Param.Unsigned(8,
        "Number of bits for the pUpdate threshold counters")

    extraWeightsWidth = Param.Unsigned(6,
        "Number of bits for the extra weights")

    scCountersWidth = Param.Unsigned(6, "Statistical corrector counters width")

    initialUpdateThresholdValue = Param.Int(0,
        "Initial pUpdate threshold counter value")

# TAGE-SC-L branch predictor as desribed in
# https://www.jilp.org/cbp2016/paper/AndreSeznecLimited.pdf
# It is a modified LTAGE predictor plus a statistical corrector predictor
# The TAGE modifications include bank interleaving and partial associativity
# Two different sizes are proposed in the paper:
# 8KB => See TAGE_SC_L_8KB below
# 64KB => See TAGE_SC_L_64KB below
# The TAGE_SC_L_8KB and TAGE_SC_L_64KB classes differ not only on the values
# of some parameters, but also in some implementation details
# Given this, the TAGE_SC_L class is left abstract
# Note that as it is now, this branch predictor does not handle any type
# of speculation: All the structures/histories are updated at commit time
class TAGE_SC_L(LTAGE):
    type = 'TAGE_SC_L'
    cxx_class = 'gem5::branch_prediction::TAGE_SC_L'
    cxx_header = "cpu/pred/tage_sc_l.hh"
    abstract = True

    statistical_corrector = Param.StatisticalCorrector(
        "Statistical Corrector")

class TAGE_SC_L_64KB_LoopPredictor(TAGE_SC_L_LoopPredictor):
    logSizeLoopPred = 5

class TAGE_SC_L_8KB_LoopPredictor(TAGE_SC_L_LoopPredictor):
    logSizeLoopPred = 3

class TAGE_SC_L_64KB_StatisticalCorrector(StatisticalCorrector):
    type = 'TAGE_SC_L_64KB_StatisticalCorrector'
    cxx_class  = 'gem5::branch_prediction::TAGE_SC_L_64KB_StatisticalCorrector'
    cxx_header = "cpu/pred/tage_sc_l_64KB.hh"

    pnb = Param.Unsigned(3, "Num variation global branch GEHL lengths")
    pm = VectorParam.Int([25, 16, 9], "Variation global branch GEHL lengths")
    logPnb = Param.Unsigned(9,
        "Log number of variation global branch GEHL entries")

    snb = Param.Unsigned(3, "Num second local history GEHL lenghts")
    sm = VectorParam.Int([16, 11, 6], "Second local history GEHL lengths")
    logSnb = Param.Unsigned(9,
        "Log number of second local history GEHL entries")

    tnb = Param.Unsigned(2, "Num third local history GEHL lenghts")
    tm = VectorParam.Int([9, 4], "Third local history GEHL lengths")
    logTnb = Param.Unsigned(10,
        "Log number of third local history GEHL entries")

    imnb = Param.Unsigned(2, "Num second IMLI GEHL lenghts")
    imm = VectorParam.Int([10, 4], "Second IMLI history GEHL lengths")
    logImnb = Param.Unsigned(9, "Log number of second IMLI GEHL entries")

    numEntriesSecondLocalHistories = Param.Unsigned(16,
        "Number of entries for second local histories")
    numEntriesThirdLocalHistories = Param.Unsigned(16,
        "Number of entries for second local histories")

    numEntriesFirstLocalHistories = 256

    logBias = 8

    bwnb = 3
    bwm = [40, 24, 10]
    logBwnb = 10
    bwWeightInitValue = 7

    lnb = 3
    lm = [11, 6, 3]
    logLnb = 10
    lWeightInitValue = 7

    logInb = 8
    iWeightInitValue = 7

class TAGE_SC_L_8KB_StatisticalCorrector(StatisticalCorrector):
    type = 'TAGE_SC_L_8KB_StatisticalCorrector'
    cxx_class  = 'gem5::branch_prediction::TAGE_SC_L_8KB_StatisticalCorrector'
    cxx_header = "cpu/pred/tage_sc_l_8KB.hh"

    gnb = Param.Unsigned(2, "Num global branch GEHL lengths")
    gm = VectorParam.Int([6, 3], "Global branch GEHL lengths")
    logGnb = Param.Unsigned(7, "Log number of global branch GEHL entries")

    numEntriesFirstLocalHistories = 64

    logBias = 7

    bwnb = 2
    logBwnb = 7
    bwm = [16, 8]
    bwWeightInitValue = 7

    lnb = 2
    logLnb = 7
    lm = [6, 3]
    lWeightInitValue = 7

    logInb = 7
    iWeightInitValue = 7

# 64KB TAGE-SC-L branch predictor as described in
# http://www.jilp.org/cbp2016/paper/AndreSeznecLimited.pdf
class TAGE_SC_L_64KB(TAGE_SC_L):
    type = 'TAGE_SC_L_64KB'
    cxx_class = 'gem5::branch_prediction::TAGE_SC_L_64KB'
    cxx_header = "cpu/pred/tage_sc_l_64KB.hh"

    tage = TAGE_SC_L_TAGE_64KB()
    loop_predictor = TAGE_SC_L_64KB_LoopPredictor()
    statistical_corrector = TAGE_SC_L_64KB_StatisticalCorrector()

# 8KB TAGE-SC-L branch predictor as described in
# http://www.jilp.org/cbp2016/paper/AndreSeznecLimited.pdf
class TAGE_SC_L_8KB(TAGE_SC_L):
    type = 'TAGE_SC_L_8KB'
    cxx_class = 'gem5::branch_prediction::TAGE_SC_L_8KB'
    cxx_header = "cpu/pred/tage_sc_l_8KB.hh"

    tage = TAGE_SC_L_TAGE_8KB()
    loop_predictor = TAGE_SC_L_8KB_LoopPredictor()
    statistical_corrector = TAGE_SC_L_8KB_StatisticalCorrector()

class MultiperspectivePerceptron(BranchPredictor):
    type = 'MultiperspectivePerceptron'
    cxx_class = 'gem5::branch_prediction::MultiperspectivePerceptron'
    cxx_header = 'cpu/pred/multiperspective_perceptron.hh'
    abstract = True

    num_filter_entries = Param.Int("Number of filter entries")
    num_local_histories = Param.Int("Number of local history entries")
    local_history_length = Param.Int(11,
        "Length in bits of each history entry")

    block_size = Param.Int(21,
        "number of ghist bits in a 'block'; this is the width of an initial "
        "hash of ghist")
    pcshift = Param.Int(-10, "Shift for hashing PC")
    threshold = Param.Int(1, "Threshold for deciding low/high confidence")
    bias0 = Param.Int(-5,
        "Bias perceptron output this much on all-bits-zero local history")
    bias1 = Param.Int(5,
        "Bias perceptron output this much on all-bits-one local history")
    biasmostly0 = Param.Int(-1,
        "Bias perceptron output this much on almost-all-bits-zero local "
        "history")
    biasmostly1 = Param.Int(1,
        "Bias perceptron output this much on almost-all-bits-one local "
        "history")
    nbest = Param.Int(20,
        "Use this many of the top performing tables on a low-confidence "
        "branch")
    tunebits = Param.Int(24, "Number of bits in misprediction counters")
    hshift = Param.Int(-6,
        "How much to shift initial feauture hash before XORing with PC bits")
    imli_mask1 = Param.UInt64(
        "Which tables should have their indices hashed with the first IMLI "
        "counter")
    imli_mask4 = Param.UInt64(
        "Which tables should have their indices hashed with the fourth IMLI "
        "counter")
    recencypos_mask = Param.UInt64(
        "Which tables should have their indices hashed with the recency "
        "position")
    fudge = Param.Float(0.245, "Fudge factor to multiply by perceptron output")
    n_sign_bits = Param.Int(2, "Number of sign bits per magnitude")
    pcbit = Param.Int(2, "Bit from the PC to use for hashing global history")
    decay = Param.Int(0, "Whether and how often to decay a random weight")
    record_mask = Param.Int(191,
        "Which histories are updated with filtered branch outcomes")
    hash_taken = Param.Bool(False,
        "Hash the taken/not taken value with a PC bit")
    tuneonly = Param.Bool(True,
        "If true, only count mispredictions of low-confidence branches")
    extra_rounds = Param.Int(1,
        "Number of extra rounds of training a single weight on a "
        "low-confidence prediction")
    speed = Param.Int(9, "Adaptive theta learning speed")
    initial_theta = Param.Int(10, "Initial theta")
    budgetbits = Param.Int("Hardware budget in bits")
    speculative_update = Param.Bool(False,
        "Use speculative update for histories")

    initial_ghist_length = Param.Int(1, "Initial GHist length value")
    ignore_path_size = Param.Bool(False, "Ignore the path storage")

class MultiperspectivePerceptron8KB(MultiperspectivePerceptron):
    type = 'MultiperspectivePerceptron8KB'
    cxx_class = 'gem5::branch_prediction::MultiperspectivePerceptron8KB'
    cxx_header = 'cpu/pred/multiperspective_perceptron_8KB.hh'

    budgetbits = 8192 * 8 + 2048
    num_local_histories = 48
    num_filter_entries = 0
    imli_mask1 = 0x6
    imli_mask4 = 0x4400
    recencypos_mask = 0x100000090

class MultiperspectivePerceptron64KB(MultiperspectivePerceptron):
    type = 'MultiperspectivePerceptron64KB'
    cxx_class = 'gem5::branch_prediction::MultiperspectivePerceptron64KB'
    cxx_header = 'cpu/pred/multiperspective_perceptron_64KB.hh'

    budgetbits = 65536 * 8 + 2048
    num_local_histories = 510
    num_filter_entries = 18025
    imli_mask1 = 0xc1000
    imli_mask4 = 0x80008000
    recencypos_mask = 0x100000090

class MPP_TAGE(TAGEBase):
    type = 'MPP_TAGE'
    cxx_class = 'gem5::branch_prediction::MPP_TAGE'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage.hh'

    nHistoryTables = 15
    pathHistBits = 27
    instShiftAmt = 0
    histBufferSize = 16384
    maxHist = 4096;
    tagTableTagWidths = [0, 7, 9, 9, 9, 10, 11, 11, 12, 12,
                         12, 13, 14, 15, 15, 15]
    logTagTableSizes = [14, 10, 11, 11, 11, 11, 11, 12, 12,
                         10, 11, 11, 9, 7, 7, 8]
    tunedHistoryLengths = VectorParam.Unsigned([0, 5, 12, 15, 21, 31, 43, 64,
        93, 137, 200, 292, 424, 612, 877, 1241], "Tuned history lengths")

    logUResetPeriod = 10
    initialTCounterValue = 0
    numUseAltOnNa = 512
    speculativeHistUpdate = False

class MPP_LoopPredictor(LoopPredictor):
    type = 'MPP_LoopPredictor'
    cxx_class = 'gem5::branch_prediction::MPP_LoopPredictor'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage.hh'

    useDirectionBit = True
    useHashing = True
    useSpeculation = False
    loopTableConfidenceBits = 4
    loopTableAgeBits = 4
    initialLoopAge = 7
    initialLoopIter = 0
    loopTableIterBits = 12
    optionalAgeReset = False
    restrictAllocation = True
    logSizeLoopPred = 6
    loopTableTagBits = 10

class MPP_StatisticalCorrector(StatisticalCorrector):
    type = 'MPP_StatisticalCorrector'
    cxx_class = 'gem5::branch_prediction::MPP_StatisticalCorrector'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage.hh'
    abstract = True

    # Unused in this Statistical Corrector
    bwnb = 0
    bwm = [ ]
    logBwnb = 0
    bwWeightInitValue = -1

    # Unused in this Statistical Corrector
    logInb = 0
    iWeightInitValue = -1

    extraWeightsWidth = 0
    pUpdateThresholdWidth = 10
    initialUpdateThresholdValue = 35
    logSizeUp = 5

    lnb = 3
    lm = [11, 6, 3]
    logLnb = 10
    lWeightInitValue = -1

    gnb = Param.Unsigned(4, "Num global branch GEHL lengths")
    gm = VectorParam.Int([27, 22, 17, 14], "Global branch GEHL lengths")
    logGnb = Param.Unsigned(10, "Log number of global branch GEHL entries")

    pnb = Param.Unsigned(4, "Num variation global branch GEHL lengths")
    pm = VectorParam.Int([16, 11, 6, 3],
        "Variation global branch GEHL lengths")
    logPnb = Param.Unsigned(9,
        "Log number of variation global branch GEHL entries")

class MultiperspectivePerceptronTAGE(MultiperspectivePerceptron):
    type = 'MultiperspectivePerceptronTAGE'
    cxx_class = 'gem5::branch_prediction::MultiperspectivePerceptronTAGE'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage.hh'
    abstract = True

    instShiftAmt = 4

    imli_mask1 = 0x70
    imli_mask4 = 0
    num_filter_entries = 0
    num_local_histories = 0
    recencypos_mask = 0 # Unused
    threshold = -1
    initial_ghist_length = 0
    ignore_path_size = True
    n_sign_bits = 1

    tage = Param.TAGEBase("Tage object")
    loop_predictor = Param.LoopPredictor("Loop predictor")
    statistical_corrector = Param.StatisticalCorrector("Statistical Corrector")

class MPP_StatisticalCorrector_64KB(MPP_StatisticalCorrector):
    type = 'MPP_StatisticalCorrector_64KB'
    cxx_class = 'gem5::branch_prediction::MPP_StatisticalCorrector_64KB'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage_64KB.hh'

    logBias = 8

    snb = Param.Unsigned(4, "Num second local history GEHL lenghts")
    sm = VectorParam.Int([16, 11, 6, 3], "Second local history GEHL lengths")
    logSnb = Param.Unsigned(9,
        "Log number of second local history GEHL entries")

    tnb = Param.Unsigned(3, "Num third local history GEHL lenghts")
    tm = VectorParam.Int([22, 17, 14], "Third local history GEHL lengths")
    logTnb = Param.Unsigned(9,
        "Log number of third local history GEHL entries")

    numEntriesSecondLocalHistories = Param.Unsigned(16,
        "Number of entries for second local histories")
    numEntriesThirdLocalHistories = Param.Unsigned(16,
        "Number of entries for second local histories")

    numEntriesFirstLocalHistories = 256

class MultiperspectivePerceptronTAGE64KB(MultiperspectivePerceptronTAGE):
    type = 'MultiperspectivePerceptronTAGE64KB'
    cxx_class = 'gem5::branch_prediction::MultiperspectivePerceptronTAGE64KB'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage_64KB.hh'

    budgetbits = 65536 * 8 + 2048

    tage = MPP_TAGE()
    loop_predictor = MPP_LoopPredictor()
    statistical_corrector = MPP_StatisticalCorrector_64KB()

class MPP_TAGE_8KB(MPP_TAGE):
    type = 'MPP_TAGE_8KB'
    cxx_class = 'gem5::branch_prediction::MPP_TAGE_8KB'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage_8KB.hh'

    nHistoryTables = 10
    tagTableTagWidths = [0, 7, 7, 7, 8, 9, 10, 10, 11, 13, 13]
    logTagTableSizes = [12, 8, 8, 9, 9, 8, 8, 8, 7, 6, 7]
    tunedHistoryLengths = [0, 4, 8, 13, 23, 36, 56, 93, 145, 226, 359]

class MPP_LoopPredictor_8KB(MPP_LoopPredictor):
    type = 'MPP_LoopPredictor_8KB'
    cxx_class = 'gem5::branch_prediction::MPP_LoopPredictor_8KB'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage_8KB.hh'

    loopTableIterBits = 10
    logSizeLoopPred = 4

class MPP_StatisticalCorrector_8KB(MPP_StatisticalCorrector):
    type = 'MPP_StatisticalCorrector_8KB'
    cxx_class = 'gem5::branch_prediction::MPP_StatisticalCorrector_8KB'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage_8KB.hh'

    logBias = 7

    lnb = 2
    lm = [8, 3]
    logLnb = 9

    logGnb = 9

    logPnb = 7

    numEntriesFirstLocalHistories = 64

class MultiperspectivePerceptronTAGE8KB(MultiperspectivePerceptronTAGE):
    type = 'MultiperspectivePerceptronTAGE8KB'
    cxx_class = 'gem5::branch_prediction::MultiperspectivePerceptronTAGE8KB'
    cxx_header = 'cpu/pred/multiperspective_perceptron_tage_8KB.hh'

    budgetbits = 8192 * 8 + 2048

    tage = MPP_TAGE_8KB()
    loop_predictor = MPP_LoopPredictor_8KB()
    statistical_corrector = MPP_StatisticalCorrector_8KB()

class TimedStreamPredictor(SimObject):
    type = 'TimedStreamPredictor'
    cxx_class = 'gem5::branch_prediction::stream_pred::TimedStreamPredictor'
    cxx_header = "cpu/pred/stream/timed_pred.hh"

# class StreamPredictor(TimedStreamPredictor):
#     type = 'StreamPredictor'
#     cxx_class = 'gem5::branch_prediction::StreamPredictor'
#     cxx_header = "cpu/pred/stream_pred.hh"

class StreamUBTB(TimedStreamPredictor):
    type = 'StreamUBTB'
    cxx_class = 'gem5::branch_prediction::stream_pred::StreamUBTB'
    cxx_header = "cpu/pred/stream/ubtb.hh"

class StreamTAGE(TimedStreamPredictor):
    type = 'StreamTAGE'
    cxx_class = 'gem5::branch_prediction::stream_pred::StreamTAGE'
    cxx_header = "cpu/pred/stream/modify_tage.hh"

    numPredictors = Param.Unsigned(16, "Number of TAGE predictors")
    tableSizes = VectorParam.Unsigned(
        [4096, 4096] + [2048, 2048, 1024] + [512]*6 + [256]*5, "the ITTAGE T0~Tn length")
    TTagBitSizes = VectorParam.Unsigned(
        [0] + [9]*2 + [13]*8 + [15]*5, "the T0~Tn entry's tag bit size")
    TTagPcShifts = VectorParam.Unsigned(
        [1] * 20, "when the T0~Tn entry's tag generating, PC right shift")
    # histLengths = VectorParam.Unsigned(
    #     [0, 6, 8, 12, 16, 18, 22, 26,
    #      36, 52, 76, 110, 156,
    #      226, 324, 464],
    #     "the Stream TAGE T0~Tn history length")
    histLengths = VectorParam.Unsigned(
        [0, 12, 16, 24, 32, 36, 44, 52,
         72, 104, 152, 220, 312,
         452, 648, 928],
        "the Stream TAGE T0~Tn history length")
    maxHistLen = Param.Unsigned(970, "The length of history passed from DBP")
    numTablesToAlloc = Param.Unsigned(2, "The number of table to allocated each time")

class StreamLoopDetector(SimObject):
    type = 'StreamLoopDetector'
    cxx_class = 'gem5::branch_prediction::stream_pred::StreamLoopDetector'
    cxx_header = "cpu/pred/stream/loop_detector.hh"

    maxLoopQueueSize = Param.Unsigned(128, "The max size of loop queue")
    tableSize = Param.Unsigned(256, "The size of loop table")

class StreamLoopPredictor(SimObject):
    type = 'StreamLoopPredictor'
    cxx_class = 'gem5::branch_prediction::stream_pred::StreamLoopPredictor'
    cxx_header = "cpu/pred/stream/stream_loop_predictor.hh"

    tableSize = Param.Unsigned(128, "The size of loop table")

class DecoupledStreamBPU(BranchPredictor):
    type = 'DecoupledStreamBPU'
    cxx_class = 'gem5::branch_prediction::stream_pred::DecoupledStreamBPU'
    cxx_header = "cpu/pred/stream/decoupled_bpred.hh"

    # stream_pred = Param.StreamPredictor(StreamPredictor(),
    # "backing stream predictor")

    stream_tage = Param.StreamTAGE(StreamTAGE(), "slower but accurate stream predictor (L2)")
    stream_ubtb = Param.StreamUBTB(StreamUBTB(), "fast stream predictor (L1)")
    loop_detector = Param.StreamLoopDetector(StreamLoopDetector(), "loop detector")
    stream_loop_predictor = Param.StreamLoopPredictor(StreamLoopPredictor(), "stream loop predictor")
    maxHistLen = Param.Unsigned(970, "The length of history")

    ftq_size = Param.Unsigned(128, "Fetch target queue size")
    dump_loop_pred = Param.Bool(False, "Dump loop detector/predictor related traces")

class TimedBaseFTBPredictor(SimObject):
    type = 'TimedBaseFTBPredictor'
    cxx_class = 'gem5::branch_prediction::ftb_pred::TimedBaseFTBPredictor'
    cxx_header = "cpu/pred/ftb/timed_base_pred.hh"

    numBr = Param.Unsigned(Parent.numBr, "Number of maximum branches per entry")
    predictWidth = Param.Unsigned(Parent.predictWidth, "The width of prediction/fetch block")
    # subclass are encouraged to explicitly declare latency as numDelay
    numDelay = Param.Unsigned(1000, "Number of bubbles to put on a prediction")

class DefaultFTB(TimedBaseFTBPredictor):
    type = 'DefaultFTB'
    cxx_class = 'gem5::branch_prediction::ftb_pred::DefaultFTB'
    cxx_header = 'cpu/pred/ftb/ftb.hh'

    numEntries = Param.Unsigned(2048, "Number of entries in the FTB")
    tagBits = Param.Unsigned(20, "Number of bits in the tag")
    instShiftAmt = Param.Unsigned(1, "Amount to shift PC to get inst bits")
    numThreads = Param.Unsigned(1, "Number of threads")
    numWays = Param.Unsigned(4, "Number of ways per set")
    numDelay = 1

class UFTB(DefaultFTB):
    numEntries = 32
    tagBits = 38
    numWays = 32
    numDelay = 0

class FTBRAS(TimedBaseFTBPredictor):
    type = 'FTBRAS'
    cxx_class = 'gem5::branch_prediction::ftb_pred::FTBRAS'
    cxx_header = 'cpu/pred/ftb/ras.hh'

    numEntries = Param.Unsigned(32, "Number of entries in the RAS")
    ctrWidth = Param.Unsigned(8, "Width of the counter")
    numInflightEntries = Param.Unsigned(384, "Number of inflight entries")
    numDelay = 1

class FTBuRAS(TimedBaseFTBPredictor):
    type = 'FTBuRAS'
    cxx_class = 'gem5::branch_prediction::ftb_pred::FTBuRAS'
    cxx_header = 'cpu/pred/ftb/uras.hh'

    numEntries = Param.Unsigned(4, "Number of entries in the RAS")
    ctrWidth = Param.Unsigned(2, "Width of the counter")
    numDelay = 0

class FTBTAGE(TimedBaseFTBPredictor):
    type = 'FTBTAGE'
    cxx_class = 'gem5::branch_prediction::ftb_pred::FTBTAGE'
    cxx_header = "cpu/pred/ftb/ftb_tage.hh"

    enableSC = Param.Bool(True, "Enable SC or not")
    numPredictors = Param.Unsigned(4, "Number of TAGE predictors")
    baseTableSize = Param.Unsigned(2048, "The FTB TAGE base table length")
    tableSizes = VectorParam.Unsigned([2048]*4, "the FTB TAGE T0~Tn length")
    TTagBitSizes = VectorParam.Unsigned([8]*4, "the T0~Tn entry's tag bit size")
    TTagPcShifts = VectorParam.Unsigned([1] * 4, "when the T0~Tn entry's tag generating, PC right shift")

    histLengths = VectorParam.Unsigned([8, 13, 32, 119], "the FTB TAGE T0~Tn history length")
    maxHistLen = Param.Unsigned(970, "The length of history passed from DBP")
    numTablesToAlloc = Param.Unsigned(1,"The number of table to allocated each time")
    numDelay = 1

class FTBITTAGE(TimedBaseFTBPredictor):
    type = 'FTBITTAGE'
    cxx_class = 'gem5::branch_prediction::ftb_pred::FTBITTAGE'
    cxx_header = "cpu/pred/ftb/ftb_ittage.hh"

    numPredictors = Param.Unsigned(5, "Number of TAGE predictors")
    tableSizes = VectorParam.Unsigned([256]*2 + [512]*3, "the ITTAGE T0~Tn length")
    TTagBitSizes = VectorParam.Unsigned([9]*5, "the T0~Tn entry's tag bit size")
    TTagPcShifts = VectorParam.Unsigned([1] * 5, "when the T0~Tn entry's tag generating, PC right shift")

    histLengths = VectorParam.Unsigned([4, 8, 13, 16, 32], "the FTB TAGE T0~Tn history length")
    maxHistLen = Param.Unsigned(970, "The length of history passed from DBP")
    numTablesToAlloc = Param.Unsigned(1,"The number of table to allocated each time")
    numDelay = 2

class DecoupledBPUWithFTB(BranchPredictor):
    type = 'DecoupledBPUWithFTB'
    cxx_class = 'gem5::branch_prediction::ftb_pred::DecoupledBPUWithFTB'
    cxx_header = "cpu/pred/ftb/decoupled_bpred.hh"

    # n = 2
    ftq_size = Param.Unsigned(128, "Fetch target queue size")
    fsq_size = Param.Unsigned(64, "Fetch stream queue size")
    maxHistLen = Param.Unsigned(970, "The length of history")
    numBr = Param.Unsigned(2, "Number of maximum branches per entry")
    predictWidth = Param.Unsigned(32, "The width of prediction/fetch block")
    numStages = Param.Unsigned(3, "Number of stages in the pipeline")
    ftb = Param.DefaultFTB(DefaultFTB(), "FTB")
    tage = Param.FTBTAGE(FTBTAGE(), "TAGE predictor")
    ittage = Param.FTBITTAGE(FTBITTAGE(), "ITTAGE predictor")
    uftb = Param.DefaultFTB(UFTB(), "UFTB predictor")
    ras = Param.FTBRAS(FTBRAS(), "RAS")
    uras = Param.FTBuRAS(FTBuRAS(), "uRAS")

    bpDBSwitches = VectorParam.String([], "Enable which traces in the form of database")
    enableLoopBuffer = Param.Bool(False, "Enable loop buffer to supply inst for loops")
    enableLoopPredictor = Param.Bool(False, "Use loop predictor to predict loop exit")
    enableJumpAheadPredictor = Param.Bool(False, "Use jump ahead predictor to skip no-need-to-predict blocks")
    enableTwoTaken = Param.Bool(False, "Enable predicting two taken blocks per cycle")

class TimedBaseBTBPredictor(SimObject):
    type = 'TimedBaseBTBPredictor'
    cxx_class = 'gem5::branch_prediction::btb_pred::TimedBaseBTBPredictor'
    cxx_header = "cpu/pred/btb/timed_base_pred.hh"

    # TODO: parametrize numBr and numDelay
    blockSize = Param.Unsigned(Parent.predictWidth, "Block size in bytes")
    predictWidth = Param.Unsigned(Parent.predictWidth, "Maximum range in bytes that a single prediction can cover")
    numDelay = Param.Unsigned(1000, "Number of bubbles to put on a prediction")
    resolvedUpdate = Param.Bool(False, "Enable resolved update, no need to wait until commit")
    enabled = Param.Bool(True, "Enable this predictor component")

class MBTB(TimedBaseBTBPredictor):
    type = 'MBTB'
    cxx_class = 'gem5::branch_prediction::btb_pred::MBTB'
    cxx_header = 'cpu/pred/btb/mbtb.hh'

    numEntries = Param.Unsigned(8192, "Number of entries in the MBTB")
    tagBits = Param.Unsigned(20, "Number of bits in the tag")
    instShiftAmt = Param.Unsigned(1, "Amount to shift PC to get inst bits")
    numThreads = Param.Unsigned(1, "Number of threads")
    numWays = Param.Unsigned(4, "Number of ways per set") # for 2 SRAMs, 4 ways per SRAM
    numDelay = 2
    blockSize = 32  # max 64 byte block, 32 byte aligned
    # MBTB is always half-aligned - no parameter needed
    victimCacheSize = Param.Unsigned(0, "Number of entries in the victim cache")

class AheadBTB(TimedBaseBTBPredictor):
    type = 'AheadBTB'
    cxx_class = 'gem5::branch_prediction::btb_pred::AheadBTB'
    cxx_header = 'cpu/pred/btb/abtb.hh'

    numEntries = Param.Unsigned(1024, "Number of entries in the BTB")
    tagBits = Param.Unsigned(38, "Number of bits in the tag")
    instShiftAmt = Param.Unsigned(1, "Amount to shift PC to get inst bits")
    numThreads = Param.Unsigned(1, "Number of threads")
    numWays = Param.Unsigned(8, "Number of ways per set")
    aheadPipelinedStages = Param.Unsigned(1, "Number of stages ahead pipelined")
    entryHalfAligned = Param.Bool(False, "Whether the entries are half-aligned")
    blockSize = 64
    numDelay = 0
    usingS3Pred = Param.Bool(True, "Whether using S3 predictor to update AheadBTB")

class UBTB(TimedBaseBTBPredictor):
    type = 'UBTB'
    cxx_class = 'gem5::branch_prediction::btb_pred::UBTB'
    cxx_header = 'cpu/pred/btb/btb_ubtb.hh'

    numEntries = Param.Unsigned(32, "Number of entries in the uBTB")
    tagBits = Param.Unsigned(38, "Number of bits in the tag")

    aheadPipelinedStages = Param.Unsigned(0, "Number of stages ahead pipelined")
    numDelay = 0
    usingS3Pred = Param.Bool(True, "Whether using S3 predictor to update uBTB")
    # blockSize = 32  not used in uBTB


class BTBRAS(TimedBaseBTBPredictor):
    type = 'BTBRAS'
    cxx_class = 'gem5::branch_prediction::btb_pred::BTBRAS'
    cxx_header = 'cpu/pred/btb/ras.hh'

    numEntries = Param.Unsigned(32, "Number of entries in the RAS")
    ctrWidth = Param.Unsigned(8, "Width of the counter")
    numInflightEntries = Param.Unsigned(384, "Number of inflight entries")
    numDelay = 2

class BTBuRAS(TimedBaseBTBPredictor):
    type = 'BTBuRAS'
    cxx_class = 'gem5::branch_prediction::btb_pred::BTBuRAS'
    cxx_header = 'cpu/pred/btb/uras.hh'

    numEntries = Param.Unsigned(4, "Number of entries in the RAS")
    ctrWidth = Param.Unsigned(2, "Width of the counter")
    numDelay = 0

class BTBTAGE(TimedBaseBTBPredictor):
    type = 'BTBTAGE'
    cxx_class = 'gem5::branch_prediction::btb_pred::BTBTAGE'
    cxx_header = "cpu/pred/btb/btb_tage.hh"

    needMoreHistories = Param.Bool(True, "BTBTAGE needs more histories")
    enableSC = Param.Bool(False, "Enable SC or not")    # TODO: BTBTAGE doesn't support SC
    updateOnRead = Param.Bool(True, "Enable update on read, no need to save tage meta in FTQ")
    numPredictors = Param.Unsigned(8, "Number of TAGE predictors")
    tableSizes = VectorParam.Unsigned([2048]*8, "the TAGE T0~Tn length")
    TTagBitSizes = VectorParam.Unsigned([13]*8, "the T0~Tn entry's tag bit size")
    TTagPcShifts = VectorParam.Unsigned([1] * 8, "when the T0~Tn entry's tag generating, PC right shift")
    blockSize = 32 # tage index function uses 32B aligned block address

    histLengths = VectorParam.Unsigned([4, 9, 17, 29, 56, 109, 211, 397], "the BTB TAGE T0~Tn history length")
    maxHistLen = Param.Unsigned(970, "The length of history passed from DBP")
    numTablesToAlloc = Param.Unsigned(1,"The number of table to allocated each time")
    numWays = Param.Unsigned(2, "Number of ways per set")
    maxBranchPositions = Param.Unsigned(32, "Maximum branch positions per 64-byte block")
    useAltOnNaSize = Param.Unsigned(128, "Size of the useAltOnNa table")
    useAltOnNaWidth = Param.Unsigned(7, "Width of the useAltOnNa table")
    numBanks = Param.Unsigned(4, "Number of banks for bank conflict simulation")
    enableBankConflict = Param.Bool(True, "Enable bank conflict simulation")
    numDelay = 2

class MicroTAGE(TimedBaseBTBPredictor):
    """Micro-sized BTB TAGE predictor used alongside uBTB"""
    type = 'MicroTAGE'
    cxx_class = 'gem5::branch_prediction::btb_pred::MicroTAGE'
    cxx_header = "cpu/pred/btb/microtage.hh"

    needMoreHistories = Param.Bool(True, "MicroTAGE needs more histories")
    updateOnRead = Param.Bool(False,"Enable update on read, no need to save tage meta in FTQ")
    # Keep vector parameters consistent with numPredictors to avoid constructor asserts.
    numPredictors = Param.Unsigned(1, "Number of TAGE predictors")
    tableSizes = VectorParam.Unsigned([512]*2,"the TAGE T0~Tn length")
    TTagBitSizes = VectorParam.Unsigned([16]*2 ,"the T0~Tn entry's tag bit size")
    TTagPcShifts = VectorParam.Unsigned([1]*2 ,"when the T0~Tn entry's tag generating, PC right shift")
    blockSize = Param.Unsigned(32,"tage index function uses 32B aligned block address")

    histLengths = VectorParam.Unsigned([9,18],"the BTB TAGE T0~Tn history length")
    maxHistLen = Param.Unsigned(970,"The length of history passed from DBP")
    numTablesToAlloc = Param.Unsigned(1,"The number of table to allocated each time")
    numWays = Param.Unsigned(1, "Number of ways per set")
    baseTableSize = Param.Unsigned(256,"Base table size")
    maxBranchPositions = Param.Unsigned(32,"Maximum branch positions per 64-byte block")
    useAltOnNaSize = Param.Unsigned(128,"Size of the useAltOnNa table")
    useAltOnNaWidth = Param.Unsigned(7,"Width of the useAltOnNa table")
    numBanks = Param.Unsigned(4,"Number of banks for bank conflict simulation")
    enableBankConflict = Param.Bool(True,"Enable bank conflict simulation")
    numDelay = Param.Unsigned(0,"Prediction latency in cycles")

class BTBITTAGE(TimedBaseBTBPredictor):
    type = 'BTBITTAGE'
    cxx_class = 'gem5::branch_prediction::btb_pred::BTBITTAGE'
    cxx_header = "cpu/pred/btb/btb_ittage.hh"

    needMoreHistories = Param.Bool(True, "BTBITTAGE needs more histories")
    numPredictors = Param.Unsigned(5, "Number of TAGE predictors")
    tableSizes = VectorParam.Unsigned([256]*2 + [512]*3, "the ITTAGE T0~Tn length")
    TTagBitSizes = VectorParam.Unsigned([9]*5, "the T0~Tn entry's tag bit size")
    TTagPcShifts = VectorParam.Unsigned([1] * 5, "when the T0~Tn entry's tag generating, PC right shift")
    blockSize = 32 # ittage index function uses 32B aligned block address

    histLengths = VectorParam.Unsigned([4, 8, 13, 16, 32], "the BTB TAGE T0~Tn history length")
    maxHistLen = Param.Unsigned(970, "The length of history passed from DBP")
    numTablesToAlloc = Param.Unsigned(1,"The number of table to allocated each time")
    numDelay = 2

class BTBMGSC(TimedBaseBTBPredictor):
    type = 'BTBMGSC'
    cxx_class = 'gem5::branch_prediction::btb_pred::BTBMGSC'
    cxx_header = "cpu/pred/btb/btb_mgsc.hh"

    needMoreHistories = Param.Bool(True, "MGSC needs more histories")

    bwTableNum = Param.Unsigned(2, "Num global backward branch GEHL tables")
    bwHistLen = VectorParam.Int([4, 8], "Global backward branch GEHL history lengths")
    bwTableIdxWidth = Param.Unsigned(11,
            "Log num of global backward branch GEHL entries")

    numEntriesFirstLocalHistories = Param.Unsigned(32,
        "Number of entries for first local histories")
    lTableNum = Param.Unsigned(2, "Num first local history GEHL tables")
    lHistLen = VectorParam.Int([4, 8], "First local history GEHL history lengths")
    lTableIdxWidth = Param.Unsigned(11,
            "Log number of first local history GEHL entries")

    iTableNum = Param.Unsigned(1, "Num IMLI GEHL tables")
    iHistLen = VectorParam.Int([8], "IMLI history GEHL history lengths")
    iTableIdxWidth = Param.Unsigned(12, "Log number of IMLI GEHL entries")

    gTableNum = Param.Unsigned(2, "Num global branch GEHL tables")
    gHistLen = VectorParam.Int([8, 16], "Global branch GEHL history lengths")
    gTableIdxWidth = Param.Unsigned(11, "Log number of global branch GEHL entries")

    pTableNum = Param.Unsigned(2, "Num global branch path history tables")
    pHistLen = VectorParam.Int([8, 16], "Global branch path history lengths")
    pTableIdxWidth = Param.Unsigned(11,
                    "Log number of global branch path history entries")

    biasTableNum = Param.Unsigned(1, "Num bias tables")
    biasTableIdxWidth = Param.Unsigned(11, "Log number of bias entries")

    thresholdTablelogSize = Param.Unsigned(6,
        "Log size of update threshold counters tables")

    updateThresholdWidth = Param.Unsigned(12,
        "Number of bits for the update threshold counter")

    pUpdateThresholdWidth = Param.Unsigned(8,
        "Number of bits for the pUpdate threshold counters")

    extraWeightsWidth = Param.Unsigned(6,
        "Number of bits for the extra weights")

    scCountersWidth = Param.Unsigned(6, "Statistical corrector counters width")

    weightTableIdxWidth = Param.Unsigned(5,
        "Log size of weight table")

    # How many counters readed per prediction (usually per cycle)
    numCtrsPerLine = Param.Unsigned(8, "Counters per SRAM line")

    # Test switches for SC tables
    forceUseSC = Param.Bool(False, "Force use SC prediction, ignore TAGE confidence")
    enableBwTable = Param.Bool(True, "Enable BW (backward) table")
    enableLTable = Param.Bool(True, "Enable L (local) table")
    enableITable = Param.Bool(True, "Enable I (IMLI) table")
    enableGTable = Param.Bool(True, "Enable G (global) table")
    enablePTable = Param.Bool(True, "Enable P (path) table")
    enableBiasTable = Param.Bool(True, "Enable Bias table")
    enablePCThreshold = Param.Bool(False, "Enable PC-indexed threshold table")

    numDelay = 2

class DecoupledBPUWithBTB(BranchPredictor):
    type = 'DecoupledBPUWithBTB'
    cxx_class = 'gem5::branch_prediction::btb_pred::DecoupledBPUWithBTB'
    cxx_header = "cpu/pred/btb/decoupled_bpred.hh"

    # n = 2
    ftq_size = Param.Unsigned(128, "Fetch target queue size")
    fsq_size = Param.Unsigned(64, "Fetch stream queue size")
    maxHistLen = Param.Unsigned(970, "The length of history")

    predictWidth = Param.Unsigned(64, "Maximum range in bytes that a single prediction can cover")
    numStages = Param.Unsigned(4, "Maximum number of stages in the pipeline")
    ubtb = Param.UBTB(UBTB(), "UBTB predictor")
    abtb = Param.AheadBTB(AheadBTB(), "ABTB predictor")
    microtage = Param.MicroTAGE(MicroTAGE(), "MicroTAGE predictor to assist uBTB")
    mbtb = Param.MBTB(MBTB(), "MBTB predictor")
    tage = Param.BTBTAGE(BTBTAGE(), "TAGE predictor")
    ittage = Param.BTBITTAGE(BTBITTAGE(), "ITTAGE predictor")
    mgsc = Param.BTBMGSC(BTBMGSC(), "MGSC predictor")
    ras = Param.BTBRAS(BTBRAS(), "RAS")

    bpDBSwitches = VectorParam.String([], "Enable which traces in the form of database")
    resolveBlockThreshold = Param.Unsigned(8, "Consecutive resolve dequeue failures before blocking prediction once")