summaryrefslogtreecommitdiff
path: root/src/cpu/o3/bpred_unit.hh
blob: e298f51ad0431eec7775ed05fe76aff004d35724 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
/*
 * Copyright (c) 2004-2005 The Regents of The University of Michigan
 * 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: Kevin Lim
 */

#ifndef __BPRED_UNIT_HH__
#define __BPRED_UNIT_HH__

// For Addr type.
#include "arch/isa_traits.hh"
#include "base/statistics.hh"
#include "cpu/inst_seq.hh"

#include "cpu/o3/2bit_local_pred.hh"
#include "cpu/o3/tournament_pred.hh"
#include "cpu/o3/btb.hh"
#include "cpu/o3/ras.hh"

#include <list>

/**
 * Basically a wrapper class to hold both the branch predictor
 * and the BTB.  Right now I'm unsure of the implementation; it would
 * be nicer to have something closer to the CPUPolicy or the Impl where
 * this is just typedefs, but it forces the upper level stages to be
 * aware of the constructors of the BP and the BTB.  The nicer thing
 * to do is have this templated on the Impl, accept the usual Params
 * object, and be able to call the constructors on the BP and BTB.
 */
template<class Impl>
class TwobitBPredUnit
{
  public:
    typedef typename Impl::Params Params;
    typedef typename Impl::DynInstPtr DynInstPtr;

    TwobitBPredUnit(Params &params);

    void regStats();

    bool predict(DynInstPtr &inst, Addr &PC);

    void update(const InstSeqNum &done_sn);

    void squash(const InstSeqNum &squashed_sn);

    void squash(const InstSeqNum &squashed_sn, const Addr &corr_target,
                bool actually_taken);

    bool BPLookup(Addr &inst_PC)
    { return BP.lookup(inst_PC); }

    bool BTBValid(Addr &inst_PC)
    { return BTB.valid(inst_PC); }

    Addr BTBLookup(Addr &inst_PC)
    { return BTB.lookup(inst_PC); }

    // Will want to include global history.
    void BPUpdate(Addr &inst_PC, bool taken)
    { BP.update(inst_PC, taken); }

    void BTBUpdate(Addr &inst_PC, Addr &target_PC)
    { BTB.update(inst_PC, target_PC); }

  private:
    struct PredictorHistory {
        PredictorHistory(const InstSeqNum &seq_num, const Addr &inst_PC,
                         const bool pred_taken)
            : seqNum(seq_num), PC(inst_PC), predTaken(pred_taken),
              globalHistory(0), usedRAS(0), wasCall(0), RASIndex(0),
              RASTarget(0)
        { }

        InstSeqNum seqNum;

        Addr PC;

        bool predTaken;

        unsigned globalHistory;

        bool usedRAS;

        bool wasCall;

        unsigned RASIndex;

        Addr RASTarget;
    };

    std::list<PredictorHistory> predHist;

    DefaultBP BP;

    DefaultBTB BTB;

    ReturnAddrStack RAS;

    Stats::Scalar<> lookups;
    Stats::Scalar<> condPredicted;
    Stats::Scalar<> condIncorrect;
    Stats::Scalar<> BTBLookups;
    Stats::Scalar<> BTBHits;
    Stats::Scalar<> BTBCorrect;
    Stats::Scalar<> usedRAS;
    Stats::Scalar<> RASIncorrect;
};

#endif // __BPRED_UNIT_HH__