| /* |
| * Copyright (c) 2004-2005 The Regents of The University of Michigan |
| * 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: Kevin Lim |
| */ |
| |
| #ifndef __CPU_O3_BPRED_UNIT_HH__ |
| #define __CPU_O3_BPRED_UNIT_HH__ |
| |
| #include "base/statistics.hh" |
| #include "cpu/inst_seq.hh" |
| |
| #include "cpu/o3/2bit_local_pred.hh" |
| #include "cpu/o3/btb.hh" |
| #include "cpu/o3/ras.hh" |
| #include "cpu/o3/tournament_pred.hh" |
| |
| #include "sim/host.hh" |
| |
| #include <list> |
| |
| /** |
| * Basically a wrapper class to hold both the branch predictor |
| * and the BTB. |
| */ |
| template<class Impl> |
| class BPredUnit |
| { |
| private: |
| typedef typename Impl::Params Params; |
| typedef typename Impl::DynInstPtr DynInstPtr; |
| |
| enum PredType { |
| Local, |
| Tournament |
| }; |
| |
| PredType predictor; |
| |
| public: |
| |
| /** |
| * @param params The params object, that has the size of the BP and BTB. |
| */ |
| BPredUnit(Params *params); |
| |
| /** |
| * Registers statistics. |
| */ |
| void regStats(); |
| |
| void switchOut(); |
| |
| void takeOverFrom(); |
| |
| /** |
| * Predicts whether or not the instruction is a taken branch, and the |
| * target of the branch if it is taken. |
| * @param inst The branch instruction. |
| * @param PC The predicted PC is passed back through this parameter. |
| * @param tid The thread id. |
| * @return Returns if the branch is taken or not. |
| */ |
| bool predict(DynInstPtr &inst, Addr &PC, unsigned tid); |
| |
| // @todo: Rename this function. |
| void BPUncond(void * &bp_history); |
| |
| /** |
| * Tells the branch predictor to commit any updates until the given |
| * sequence number. |
| * @param done_sn The sequence number to commit any older updates up until. |
| * @param tid The thread id. |
| */ |
| void update(const InstSeqNum &done_sn, unsigned tid); |
| |
| /** |
| * Squashes all outstanding updates until a given sequence number. |
| * @param squashed_sn The sequence number to squash any younger updates up |
| * until. |
| * @param tid The thread id. |
| */ |
| void squash(const InstSeqNum &squashed_sn, unsigned tid); |
| |
| /** |
| * Squashes all outstanding updates until a given sequence number, and |
| * corrects that sn's update with the proper address and taken/not taken. |
| * @param squashed_sn The sequence number to squash any younger updates up |
| * until. |
| * @param corr_target The correct branch target. |
| * @param actually_taken The correct branch direction. |
| * @param tid The thread id. |
| */ |
| void squash(const InstSeqNum &squashed_sn, const Addr &corr_target, |
| bool actually_taken, unsigned tid); |
| |
| /** |
| * @param bp_history Pointer to the history object. The predictor |
| * will need to update any state and delete the object. |
| */ |
| void BPSquash(void *bp_history); |
| |
| /** |
| * Looks up a given PC in the BP to see if it is taken or not taken. |
| * @param inst_PC The PC to look up. |
| * @param bp_history Pointer that will be set to an object that |
| * has the branch predictor state associated with the lookup. |
| * @return Whether the branch is taken or not taken. |
| */ |
| bool BPLookup(Addr &inst_PC, void * &bp_history); |
| |
| /** |
| * Looks up a given PC in the BTB to see if a matching entry exists. |
| * @param inst_PC The PC to look up. |
| * @return Whether the BTB contains the given PC. |
| */ |
| bool BTBValid(Addr &inst_PC) |
| { return BTB.valid(inst_PC, 0); } |
| |
| /** |
| * Looks up a given PC in the BTB to get the predicted target. |
| * @param inst_PC The PC to look up. |
| * @return The address of the target of the branch. |
| */ |
| Addr BTBLookup(Addr &inst_PC) |
| { return BTB.lookup(inst_PC, 0); } |
| |
| /** |
| * Updates the BP with taken/not taken information. |
| * @param inst_PC The branch's PC that will be updated. |
| * @param taken Whether the branch was taken or not taken. |
| * @param bp_history Pointer to the branch predictor state that is |
| * associated with the branch lookup that is being updated. |
| * @todo Make this update flexible enough to handle a global predictor. |
| */ |
| void BPUpdate(Addr &inst_PC, bool taken, void *bp_history); |
| |
| /** |
| * Updates the BTB with the target of a branch. |
| * @param inst_PC The branch's PC that will be updated. |
| * @param target_PC The branch's target that will be added to the BTB. |
| */ |
| void BTBUpdate(Addr &inst_PC, Addr &target_PC) |
| { BTB.update(inst_PC, target_PC,0); } |
| |
| void dump(); |
| |
| private: |
| struct PredictorHistory { |
| /** |
| * Makes a predictor history struct that contains any |
| * information needed to update the predictor, BTB, and RAS. |
| */ |
| PredictorHistory(const InstSeqNum &seq_num, const Addr &inst_PC, |
| const bool pred_taken, void *bp_history, |
| const unsigned _tid) |
| : seqNum(seq_num), PC(inst_PC), RASTarget(0), |
| RASIndex(0), tid(_tid), predTaken(pred_taken), usedRAS(0), |
| wasCall(0), bpHistory(bp_history) |
| { } |
| |
| /** The sequence number for the predictor history entry. */ |
| InstSeqNum seqNum; |
| |
| /** The PC associated with the sequence number. */ |
| Addr PC; |
| |
| /** The RAS target (only valid if a return). */ |
| Addr RASTarget; |
| |
| /** The RAS index of the instruction (only valid if a call). */ |
| unsigned RASIndex; |
| |
| /** The thread id. */ |
| unsigned tid; |
| |
| /** Whether or not it was predicted taken. */ |
| bool predTaken; |
| |
| /** Whether or not the RAS was used. */ |
| bool usedRAS; |
| |
| /** Whether or not the instruction was a call. */ |
| bool wasCall; |
| |
| /** Pointer to the history object passed back from the branch |
| * predictor. It is used to update or restore state of the |
| * branch predictor. |
| */ |
| void *bpHistory; |
| }; |
| |
| typedef std::list<PredictorHistory> History; |
| |
| /** |
| * The per-thread predictor history. This is used to update the predictor |
| * as instructions are committed, or restore it to the proper state after |
| * a squash. |
| */ |
| History predHist[Impl::MaxThreads]; |
| |
| /** The local branch predictor. */ |
| LocalBP *localBP; |
| |
| /** The tournament branch predictor. */ |
| TournamentBP *tournamentBP; |
| |
| /** The BTB. */ |
| DefaultBTB BTB; |
| |
| /** The per-thread return address stack. */ |
| ReturnAddrStack RAS[Impl::MaxThreads]; |
| |
| /** Stat for number of BP lookups. */ |
| Stats::Scalar<> lookups; |
| /** Stat for number of conditional branches predicted. */ |
| Stats::Scalar<> condPredicted; |
| /** Stat for number of conditional branches predicted incorrectly. */ |
| Stats::Scalar<> condIncorrect; |
| /** Stat for number of BTB lookups. */ |
| Stats::Scalar<> BTBLookups; |
| /** Stat for number of BTB hits. */ |
| Stats::Scalar<> BTBHits; |
| /** Stat for number of times the BTB is correct. */ |
| Stats::Scalar<> BTBCorrect; |
| /** Stat for number of times the RAS is used to get a target. */ |
| Stats::Scalar<> usedRAS; |
| /** Stat for number of times the RAS is incorrect. */ |
| Stats::Scalar<> RASIncorrect; |
| }; |
| |
| #endif // __CPU_O3_BPRED_UNIT_HH__ |