src/cpu/pred/tage.hh

   1 /*
   2  * Copyright (c) 2014 The University of Wisconsin
   3  *
   4  * Copyright (c) 2006 INRIA (Institut National de Recherche en
   5  * Informatique et en Automatique  / French National Research Institute
   6  * for Computer Science and Applied Mathematics)
   7  *
   8  * All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions are
  12  * met: redistributions of source code must retain the above copyright
  13  * notice, this list of conditions and the following disclaimer;
  14  * redistributions in binary form must reproduce the above copyright
  15  * notice, this list of conditions and the following disclaimer in the
  16  * documentation and/or other materials provided with the distribution;
  17  * neither the name of the copyright holders nor the names of its
  18  * contributors may be used to endorse or promote products derived from
  19  * this software without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  24  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  25  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  26  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  27  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  31  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 /* @file
  35  * Implementation of a TAGE branch predictor. TAGE is a global-history based
  36  * branch predictor. It features a PC-indexed bimodal predictor and N
  37  * partially tagged tables, indexed with a hash of the PC and the global
  38  * branch history. The different lengths of global branch history used to
  39  * index the partially tagged tables grow geometrically. A small path history
  40  * is also used in the hash.
  41  *
  42  * All TAGE tables are accessed in parallel, and the one using the longest
  43  * history that matches provides the prediction (some exceptions apply).
  44  * Entries are allocated in components using a longer history than the
  45  * one that predicted when the prediction is incorrect.
  46  */
  47
  48 #ifndef __CPU_PRED_TAGE
  49 #define __CPU_PRED_TAGE
  50
  51 #include <vector>
  52
  53 #include "base/types.hh"
  54 #include "cpu/pred/bpred_unit.hh"
  55 #include "cpu/pred/tage_base.hh"
  56 #include "params/TAGE.hh"
  57
  58 class TAGE: public BPredUnit
  59 {
  60   protected:
  61     TAGEBase *tage;
  62
  63     struct TageBranchInfo {
  64         TAGEBase::BranchInfo *tageBranchInfo;
  65
  66         TageBranchInfo(TAGEBase &tage) : tageBranchInfo(tage.makeBranchInfo())
  67         {}
  68
  69         virtual ~TageBranchInfo()
  70         {
  71             delete tageBranchInfo;
  72         }
  73     };
  74
  75     virtual bool predict(ThreadID tid, Addr branch_pc, bool cond_branch,
  76                          void* &b);
  77
  78   public:
  79
  80     TAGE(const TAGEParams *params);
  81
  82     // Base class methods.
  83     void uncondBranch(ThreadID tid, Addr br_pc, void* &bp_history) override;
  84     bool lookup(ThreadID tid, Addr branch_addr, void* &bp_history) override;
  85     void btbUpdate(ThreadID tid, Addr branch_addr, void* &bp_history) override;
  86     void update(ThreadID tid, Addr branch_addr, bool taken, void *bp_history,
  87                 bool squashed, const StaticInstPtr & inst,
  88                 Addr corrTarget) override;
  89     virtual void squash(ThreadID tid, void *bp_history) override;
  90 };
  91
  92 #endif // __CPU_PRED_TAGE