BranchPredictor.py revision 13443:a111cb197897 
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
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21# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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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
90class LTAGE(BranchPredictor):
91    type = 'LTAGE'
92    cxx_class = 'LTAGE'
93    cxx_header = "cpu/pred/ltage.hh"
94
95    logSizeBiMP = Param.Unsigned(14, "Log size of Bimodal predictor in bits")
96    logRatioBiModalHystEntries = Param.Unsigned(2,
97        "Log num of prediction entries for a shared hysteresis bit " \
98        "for the Bimodal")
99    logSizeTagTables = Param.Unsigned(11, "Log size of tag table in LTAGE")
100    logSizeLoopPred = Param.Unsigned(8, "Log size of the loop predictor")
101    nHistoryTables = Param.Unsigned(12, "Number of history tables")
102    tagTableCounterBits = Param.Unsigned(3, "Number of tag table counter bits")
103    tagTableUBits = Param.Unsigned(2, "Number of tag table u bits")
104    histBufferSize = Param.Unsigned(2097152,
105            "A large number to track all branch histories(2MEntries default)")
106    minHist = Param.Unsigned(4, "Minimum history size of LTAGE")
107    maxHist = Param.Unsigned(640, "Maximum history size of LTAGE")
108    minTagWidth = Param.Unsigned(7, "Minimum tag size in tag tables")
109
110    loopTableAgeBits = Param.Unsigned(8, "Number of age bits per loop entry")
111    loopTableConfidenceBits = Param.Unsigned(2,
112            "Number of confidence bits per loop entry")
113    loopTableTagBits = Param.Unsigned(14, "Number of tag bits per loop entry")
114    loopTableIterBits = Param.Unsigned(14, "Nuber of iteration bits per loop")
115
116