86 lines
3.1 KiB
C++
86 lines
3.1 KiB
C++
/*
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* Copyright (c) 2004-2005 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __CPU_O3_CPU_2BIT_LOCAL_PRED_HH__
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#define __CPU_O3_CPU_2BIT_LOCAL_PRED_HH__
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// For Addr type.
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#include "arch/isa_traits.hh"
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#include "cpu/o3/sat_counter.hh"
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class DefaultBP
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{
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public:
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/**
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* Default branch predictor constructor.
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*/
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DefaultBP(unsigned localPredictorSize, unsigned localCtrBits,
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unsigned instShiftAmt);
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/**
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* Looks up the given address in the branch predictor and returns
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* a true/false value as to whether it is taken.
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* @param branch_addr The address of the branch to look up.
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* @return Whether or not the branch is taken.
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*/
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bool lookup(Addr &branch_addr);
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/**
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* Updates the branch predictor with the actual result of a branch.
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* @param branch_addr The address of the branch to update.
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* @param taken Whether or not the branch was taken.
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*/
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void update(Addr &branch_addr, bool taken);
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private:
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/** Returns the taken/not taken prediction given the value of the
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* counter.
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*/
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inline bool getPrediction(uint8_t &count);
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/** Calculates the local index based on the PC. */
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inline unsigned getLocalIndex(Addr &PC);
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/** Array of counters that make up the local predictor. */
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SatCounter *localCtrs;
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/** Size of the local predictor. */
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unsigned localPredictorSize;
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/** Number of bits of the local predictor's counters. */
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unsigned localCtrBits;
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/** Number of bits to shift the PC when calculating index. */
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unsigned instShiftAmt;
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/** Mask to get index bits. */
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unsigned indexMask;
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};
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#endif // __CPU_O3_CPU_2BIT_LOCAL_PRED_HH__
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