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/*
* Copyright (c) 2014 The University of Wisconsin
*
* Copyright (c) 2006 INRIA (Institut National de Recherche en
* Informatique et en Automatique / French National Research Institute
* for Computer Science and Applied Mathematics)
*
* 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: Vignyan Reddy, Dibakar Gope and Arthur Perais,
* from André Seznec's code.
*/
/* @file
* Implementation of a L-TAGE branch predictor. TAGE is a global-history based
* branch predictor. It features a PC-indexed bimodal predictor and N
* partially tagged tables, indexed with a hash of the PC and the global
* branch history. The different lengths of global branch history used to
* index the partially tagged tables grow geometrically. A small path history
* is also used in the hash. L-TAGE also features a loop predictor that records
* iteration count of loops and predicts accordingly.
*
* All TAGE tables are accessed in parallel, and the one using the longest
* history that matches provides the prediction (some exceptions apply).
* Entries are allocated in components using a longer history than the
* one that predicted when the prediction is incorrect.
*/
#ifndef __CPU_PRED_LTAGE
#define __CPU_PRED_LTAGE
#include <vector>
#include "base/types.hh"
#include "cpu/pred/loop_predictor.hh"
#include "cpu/pred/tage.hh"
#include "params/LTAGE.hh"
class LTAGE : public TAGE
{
public:
LTAGE(const LTAGEParams *params);
// Base class methods.
void squash(ThreadID tid, void *bp_history) override;
void update(ThreadID tid, Addr branch_addr, bool taken, void *bp_history,
bool squashed, const StaticInstPtr & inst,
Addr corrTarget = MaxAddr) override;
void init() override;
virtual void regStats() override;
protected:
/** The loop predictor object */
LoopPredictor *loopPredictor;
// more provider types
enum {
LOOP = TAGEBase::LAST_TAGE_PROVIDER_TYPE + 1,
LAST_LTAGE_PROVIDER_TYPE = LOOP
};
// Primary branch history entry
struct LTageBranchInfo : public TageBranchInfo
{
LoopPredictor::BranchInfo *lpBranchInfo;
LTageBranchInfo(TAGEBase &tage, LoopPredictor &lp)
: TageBranchInfo(tage), lpBranchInfo(lp.makeBranchInfo())
{}
virtual ~LTageBranchInfo()
{
delete lpBranchInfo;
}
};
/**
* Get a branch prediction from LTAGE. *NOT* an override of
* BpredUnit::predict().
* @param tid The thread ID to select the global
* histories to use.
* @param branch_pc The unshifted branch PC.
* @param cond_branch True if the branch is conditional.
* @param b Reference to wrapping pointer to allow storing
* derived class prediction information in the base class.
*/
bool predict(
ThreadID tid, Addr branch_pc, bool cond_branch, void* &b) override;
};
#endif // __CPU_PRED_LTAGE
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