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 * Copyright (c) 2022-2023 The University of Edinburgh
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 * modified or unmodified, in source code or in binary form.
 *
 * Copyright (c) 2004-2005 The Regents of The University of Michigan
 * All rights reserved.
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 * 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
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 * neither the name of the copyright holders nor the names of its
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#ifndef __CPU_PRED_BTB_HH__
#define __CPU_PRED_BTB_HH__


#include "arch/generic/pcstate.hh"
#include "base/statistics.hh"
#include "cpu/pred/branch_type.hh"
#include "cpu/static_inst.hh"
#include "params/BranchTargetBuffer.hh"
#include "sim/clocked_object.hh"

namespace gem5
{

namespace branch_prediction
{

class BranchTargetBuffer : public ClockedObject
{
  public:
    typedef BranchTargetBufferParams Params;
    typedef enums::BranchType BranchType;

    BranchTargetBuffer(const Params &params);

    virtual void memInvalidate() override = 0;

    /** Checks if a branch address is in the BTB. Intended as a quick check
     *  before calling lookup. Does not update statistics.
     *  @param inst_PC The address of the branch to look up.
     *  @return Whether or not the branch exists in the BTB.
     */
    virtual bool valid(ThreadID tid, Addr instPC) = 0;

    /** Looks up an address in the BTB to get the target of the branch.
     *  @param inst_PC The address of the branch to look up.
     *  @param type Optional type of the branch to look up.
     *  @return The target of the branch or nullptr if the branch is not
     *          in the BTB.
     */
    virtual const PCStateBase *lookup(ThreadID tid, Addr instPC,
                            BranchType type = BranchType::NoBranch) = 0;

    /** Looks up an address in the BTB and return the instruction
     * information if existant. Does not update statistics.
     *  @param inst_PC The address of the branch to look up.
     *  @return Returns the target of the branch.
     */
    virtual const StaticInstPtr getInst(ThreadID tid, Addr instPC) = 0;


    /** Updates the BTB with the target of a branch.
     *  @param inst_pc The address of the branch being updated.
     *  @param target_pc The target address of the branch.
     */
    virtual void update(ThreadID tid, Addr inst_pc,
                          const PCStateBase &target_pc,
                          BranchType type = BranchType::NoBranch,
                          StaticInstPtr inst = nullptr) = 0;

    /** Update BTB statistics
     */
    virtual void incorrectTarget(Addr inst_pc,
                                  BranchType type = BranchType::NoBranch)
    {
      stats.mispredict[type]++;
    }

  protected:
    /** Number of the threads for which the branch history is maintained. */
    const unsigned numThreads;

    struct BranchTargetBufferStats : public statistics::Group
    {
        BranchTargetBufferStats(statistics::Group *parent);

        statistics::Vector lookups;
        statistics::Vector misses;
        statistics::Vector updates;
        statistics::Vector mispredict;
        statistics::Scalar evictions;

    } stats;

};

} // namespace branch_prediction
} // namespace gem5

#endif // __CPU_PRED_BTB_HH__