BranchPredictor.py revision 13420:5cb2b90e1cb5 
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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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 *
32
33class BranchPredictor(SimObject):
34    type = 'BranchPredictor'
35    cxx_class = 'BPredUnit'
36    cxx_header = "cpu/pred/bpred_unit.hh"
37    abstract = True
38
39    numThreads = Param.Unsigned(1, "Number of threads")
40    BTBEntries = Param.Unsigned(4096, "Number of BTB entries")
41    BTBTagSize = Param.Unsigned(16, "Size of the BTB tags, in bits")
42    RASSize = Param.Unsigned(16, "RAS size")
43    instShiftAmt = Param.Unsigned(2, "Number of bits to shift instructions by")
44
45    useIndirect = Param.Bool(True, "Use indirect branch predictor")
46    indirectHashGHR = Param.Bool(True, "Hash branch predictor GHR")
47    indirectHashTargets = Param.Bool(True, "Hash path history targets")
48    indirectSets = Param.Unsigned(256, "Cache sets for indirect predictor")
49    indirectWays = Param.Unsigned(2, "Ways for indirect predictor")
50    indirectTagSize = Param.Unsigned(16, "Indirect target cache tag bits")
51    indirectPathLength = Param.Unsigned(3,
52        "Previous indirect targets to use for path history")
53
54
55
56class LocalBP(BranchPredictor):
57    type = 'LocalBP'
58    cxx_class = 'LocalBP'
59    cxx_header = "cpu/pred/2bit_local.hh"
60
61    localPredictorSize = Param.Unsigned(2048, "Size of local predictor")
62    localCtrBits = Param.Unsigned(2, "Bits per counter")
63
64
65class TournamentBP(BranchPredictor):
66    type = 'TournamentBP'
67    cxx_class = 'TournamentBP'
68    cxx_header = "cpu/pred/tournament.hh"
69
70    localPredictorSize = Param.Unsigned(2048, "Size of local predictor")
71    localCtrBits = Param.Unsigned(2, "Bits per counter")
72    localHistoryTableSize = Param.Unsigned(2048, "size of local history table")
73    globalPredictorSize = Param.Unsigned(8192, "Size of global predictor")
74    globalCtrBits = Param.Unsigned(2, "Bits per counter")
75    choicePredictorSize = Param.Unsigned(8192, "Size of choice predictor")
76    choiceCtrBits = Param.Unsigned(2, "Bits of choice counters")
77
78
79class BiModeBP(BranchPredictor):
80    type = 'BiModeBP'
81    cxx_class = 'BiModeBP'
82    cxx_header = "cpu/pred/bi_mode.hh"
83
84    globalPredictorSize = Param.Unsigned(8192, "Size of global predictor")
85    globalCtrBits = Param.Unsigned(2, "Bits per counter")
86    choicePredictorSize = Param.Unsigned(8192, "Size of choice predictor")
87    choiceCtrBits = Param.Unsigned(2, "Bits of choice counters")
88
89class LTAGE(BranchPredictor):
90    type = 'LTAGE'
91    cxx_class = 'LTAGE'
92    cxx_header = "cpu/pred/ltage.hh"
93
94    logSizeBiMP = Param.Unsigned(14, "Log size of Bimodal predictor in bits")
95    logRatioBiModalHystEntries = Param.Unsigned(2,
96        "Log num of prediction entries for a shared hysteresis bit " \
97        "for the Bimodal")
98    logSizeTagTables = Param.Unsigned(11, "Log size of tag table in LTAGE")
99    logSizeLoopPred = Param.Unsigned(8, "Log size of the loop predictor")
100    nHistoryTables = Param.Unsigned(12, "Number of history tables")
101    tagTableCounterBits = Param.Unsigned(3, "Number of tag table counter bits")
102    histBufferSize = Param.Unsigned(2097152,
103            "A large number to track all branch histories(2MEntries default)")
104    minHist = Param.Unsigned(4, "Minimum history size of LTAGE")
105    maxHist = Param.Unsigned(640, "Maximum history size of LTAGE")
106    minTagWidth = Param.Unsigned(7, "Minimum tag size in tag tables")
107
108