src/cpu/o3/bpred_unit.hh

   1 /*
   2  * Copyright (c) 2004-2005 The Regents of The University of Michigan
   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
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef __BPRED_UNIT_HH__
  30 #define __BPRED_UNIT_HH__
  31
  32 // For Addr type.
  33 #include "arch/isa_traits.hh"
  34 #include "base/statistics.hh"
  35 #include "cpu/inst_seq.hh"
  36
  37 #include "cpu/o3/2bit_local_pred.hh"
  38 #include "cpu/o3/tournament_pred.hh"
  39 #include "cpu/o3/btb.hh"
  40 #include "cpu/o3/ras.hh"
  41
  42 #include <list>
  43
  44 /**
  45  * Basically a wrapper class to hold both the branch predictor
  46  * and the BTB.  Right now I'm unsure of the implementation; it would
  47  * be nicer to have something closer to the CPUPolicy or the Impl where
  48  * this is just typedefs, but it forces the upper level stages to be
  49  * aware of the constructors of the BP and the BTB.  The nicer thing
  50  * to do is have this templated on the Impl, accept the usual Params
  51  * object, and be able to call the constructors on the BP and BTB.
  52  */
  53 template<class Impl>
  54 class TwobitBPredUnit
  55 {
  56   public:
  57     typedef typename Impl::Params Params;
  58     typedef typename Impl::DynInstPtr DynInstPtr;
  59
  60     TwobitBPredUnit(Params &params);
  61
  62     void regStats();
  63
  64     bool predict(DynInstPtr &inst, Addr &PC);
  65
  66     void update(const InstSeqNum &done_sn);
  67
  68     void squash(const InstSeqNum &squashed_sn);
  69
  70     void squash(const InstSeqNum &squashed_sn, const Addr &corr_target,
  71                 bool actually_taken);
  72
  73     bool BPLookup(Addr &inst_PC)
  74     { return BP.lookup(inst_PC); }
  75
  76     bool BTBValid(Addr &inst_PC)
  77     { return BTB.valid(inst_PC); }
  78
  79     Addr BTBLookup(Addr &inst_PC)
  80     { return BTB.lookup(inst_PC); }
  81
  82     // Will want to include global history.
  83     void BPUpdate(Addr &inst_PC, bool taken)
  84     { BP.update(inst_PC, taken); }
  85
  86     void BTBUpdate(Addr &inst_PC, Addr &target_PC)
  87     { BTB.update(inst_PC, target_PC); }
  88
  89   private:
  90     struct PredictorHistory {
  91         PredictorHistory(const InstSeqNum &seq_num, const Addr &inst_PC,
  92                          const bool pred_taken)
  93             : seqNum(seq_num), PC(inst_PC), predTaken(pred_taken),
  94               globalHistory(0), usedRAS(0), wasCall(0), RASIndex(0),
  95               RASTarget(0)
  96         { }
  97
  98         InstSeqNum seqNum;
  99
 100         Addr PC;
 101
 102         bool predTaken;
 103
 104         unsigned globalHistory;
 105
 106         bool usedRAS;
 107
 108         bool wasCall;
 109
 110         unsigned RASIndex;
 111
 112         Addr RASTarget;
 113     };
 114
 115     std::list<PredictorHistory> predHist;
 116
 117     DefaultBP BP;
 118
 119     DefaultBTB BTB;
 120
 121     ReturnAddrStack RAS;
 122
 123     Stats::Scalar<> lookups;
 124     Stats::Scalar<> condPredicted;
 125     Stats::Scalar<> condIncorrect;
 126     Stats::Scalar<> BTBLookups;
 127     Stats::Scalar<> BTBHits;
 128     Stats::Scalar<> BTBCorrect;
 129     Stats::Scalar<> usedRAS;
 130     Stats::Scalar<> RASIncorrect;
 131 };
 132
 133 #endif // __BPRED_UNIT_HH__