src/cpu/pred/BranchPredictor.py - testing/jenkins-gem5-prod - Git at Google

 # 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
 # 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: Nilay Vaish and Dibakar Gope

 from m5.SimObject import SimObject
 from m5.params import *
 from m5.proxy import *

 class BranchPredictor(SimObject):
     type = 'BranchPredictor'
     cxx_class = '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")

     useIndirect = Param.Bool(True, "Use indirect branch predictor")
     indirectHashGHR = Param.Bool(True, "Hash branch predictor GHR")
     indirectHashTargets = Param.Bool(True, "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")


 class LocalBP(BranchPredictor):
     type = 'LocalBP'
     cxx_class = '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 = '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 = '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 = '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")
     useAltOnNaBits = Param.Unsigned(4, "Size of the USE_ALT_ON_NA counter")

     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 = '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 = '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")


 # 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"

     tage = LTAGE_TAGE()
     loop_predictor = Param.LoopPredictor(LoopPredictor(), "Loop predictor")
	# 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
	# 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: Nilay Vaish and Dibakar Gope

	from m5.SimObject import SimObject
	from m5.params import *
	from m5.proxy import *

	class BranchPredictor(SimObject):
	type = 'BranchPredictor'
	cxx_class = '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")

	useIndirect = Param.Bool(True, "Use indirect branch predictor")
	indirectHashGHR = Param.Bool(True, "Hash branch predictor GHR")
	indirectHashTargets = Param.Bool(True, "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")



	class LocalBP(BranchPredictor):
	type = 'LocalBP'
	cxx_class = '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 = '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 = '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 = '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")
	useAltOnNaBits = Param.Unsigned(4, "Size of the USE_ALT_ON_NA counter")

	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 = '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 = '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")


	# 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"

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