bpred_unit.hh revision 10417:710ee116eb68
19022Sgblack@eecs.umich.edu/* 29022Sgblack@eecs.umich.edu * Copyright (c) 2011-2012, 2014 ARM Limited 39022Sgblack@eecs.umich.edu * Copyright (c) 2010 The University of Edinburgh 49022Sgblack@eecs.umich.edu * All rights reserved 59022Sgblack@eecs.umich.edu * 69022Sgblack@eecs.umich.edu * The license below extends only to copyright in the software and shall 79022Sgblack@eecs.umich.edu * not be construed as granting a license to any other intellectual 89022Sgblack@eecs.umich.edu * property including but not limited to intellectual property relating 99022Sgblack@eecs.umich.edu * to a hardware implementation of the functionality of the software 109022Sgblack@eecs.umich.edu * licensed hereunder. You may use the software subject to the license 119022Sgblack@eecs.umich.edu * terms below provided that you ensure that this notice is replicated 129022Sgblack@eecs.umich.edu * unmodified and in its entirety in all distributions of the software, 139022Sgblack@eecs.umich.edu * modified or unmodified, in source code or in binary form. 149022Sgblack@eecs.umich.edu * 159022Sgblack@eecs.umich.edu * Copyright (c) 2004-2005 The Regents of The University of Michigan 169022Sgblack@eecs.umich.edu * All rights reserved. 179022Sgblack@eecs.umich.edu * 189022Sgblack@eecs.umich.edu * Redistribution and use in source and binary forms, with or without 199022Sgblack@eecs.umich.edu * modification, are permitted provided that the following conditions are 209022Sgblack@eecs.umich.edu * met: redistributions of source code must retain the above copyright 219022Sgblack@eecs.umich.edu * notice, this list of conditions and the following disclaimer; 229022Sgblack@eecs.umich.edu * redistributions in binary form must reproduce the above copyright 239022Sgblack@eecs.umich.edu * notice, this list of conditions and the following disclaimer in the 249022Sgblack@eecs.umich.edu * documentation and/or other materials provided with the distribution; 259022Sgblack@eecs.umich.edu * neither the name of the copyright holders nor the names of its 269022Sgblack@eecs.umich.edu * contributors may be used to endorse or promote products derived from 279022Sgblack@eecs.umich.edu * this software without specific prior written permission. 289022Sgblack@eecs.umich.edu * 299022Sgblack@eecs.umich.edu * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 309022Sgblack@eecs.umich.edu * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 319022Sgblack@eecs.umich.edu * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 329023Sgblack@eecs.umich.edu * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 339023Sgblack@eecs.umich.edu * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 349023Sgblack@eecs.umich.edu * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 359023Sgblack@eecs.umich.edu * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 369023Sgblack@eecs.umich.edu * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 379023Sgblack@eecs.umich.edu * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 389022Sgblack@eecs.umich.edu * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 399022Sgblack@eecs.umich.edu * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 409022Sgblack@eecs.umich.edu * 419023Sgblack@eecs.umich.edu * Authors: Kevin Lim 429023Sgblack@eecs.umich.edu * Korey Sewell 439023Sgblack@eecs.umich.edu * Timothy M. Jones 449023Sgblack@eecs.umich.edu * Nilay Vaish 459023Sgblack@eecs.umich.edu */ 469023Sgblack@eecs.umich.edu 479023Sgblack@eecs.umich.edu#ifndef __CPU_PRED_BPRED_UNIT_HH__ 489023Sgblack@eecs.umich.edu#define __CPU_PRED_BPRED_UNIT_HH__ 499023Sgblack@eecs.umich.edu 509023Sgblack@eecs.umich.edu#include <deque> 519023Sgblack@eecs.umich.edu 529023Sgblack@eecs.umich.edu#include "base/statistics.hh" 539023Sgblack@eecs.umich.edu#include "base/types.hh" 549023Sgblack@eecs.umich.edu#include "cpu/pred/btb.hh" 559023Sgblack@eecs.umich.edu#include "cpu/pred/ras.hh" 569023Sgblack@eecs.umich.edu#include "cpu/inst_seq.hh" 579023Sgblack@eecs.umich.edu#include "cpu/static_inst.hh" 589023Sgblack@eecs.umich.edu#include "params/BranchPredictor.hh" 599023Sgblack@eecs.umich.edu#include "sim/sim_object.hh" 609023Sgblack@eecs.umich.edu 619023Sgblack@eecs.umich.edu/** 629023Sgblack@eecs.umich.edu * Basically a wrapper class to hold both the branch predictor 639023Sgblack@eecs.umich.edu * and the BTB. 649023Sgblack@eecs.umich.edu */ 659023Sgblack@eecs.umich.educlass BPredUnit : public SimObject 669023Sgblack@eecs.umich.edu{ 679023Sgblack@eecs.umich.edu public: 689023Sgblack@eecs.umich.edu typedef BranchPredictorParams Params; 699023Sgblack@eecs.umich.edu /** 709023Sgblack@eecs.umich.edu * @param params The params object, that has the size of the BP and BTB. 719023Sgblack@eecs.umich.edu */ 729023Sgblack@eecs.umich.edu BPredUnit(const Params *p); 739023Sgblack@eecs.umich.edu 749023Sgblack@eecs.umich.edu /** 759023Sgblack@eecs.umich.edu * Registers statistics. 769023Sgblack@eecs.umich.edu */ 779023Sgblack@eecs.umich.edu void regStats(); 789023Sgblack@eecs.umich.edu 799023Sgblack@eecs.umich.edu /** Perform sanity checks after a drain. */ 809023Sgblack@eecs.umich.edu void drainSanityCheck() const; 819023Sgblack@eecs.umich.edu 829023Sgblack@eecs.umich.edu /** 839023Sgblack@eecs.umich.edu * Predicts whether or not the instruction is a taken branch, and the 849023Sgblack@eecs.umich.edu * target of the branch if it is taken. 859023Sgblack@eecs.umich.edu * @param inst The branch instruction. 869023Sgblack@eecs.umich.edu * @param PC The predicted PC is passed back through this parameter. 879023Sgblack@eecs.umich.edu * @param tid The thread id. 889023Sgblack@eecs.umich.edu * @return Returns if the branch is taken or not. 899023Sgblack@eecs.umich.edu */ 909023Sgblack@eecs.umich.edu bool predict(const StaticInstPtr &inst, const InstSeqNum &seqNum, 919023Sgblack@eecs.umich.edu TheISA::PCState &pc, ThreadID tid); 929023Sgblack@eecs.umich.edu bool predictInOrder(const StaticInstPtr &inst, const InstSeqNum &seqNum, 939023Sgblack@eecs.umich.edu int asid, TheISA::PCState &instPC, 949023Sgblack@eecs.umich.edu TheISA::PCState &predPC, ThreadID tid); 959023Sgblack@eecs.umich.edu 969023Sgblack@eecs.umich.edu // @todo: Rename this function. 979023Sgblack@eecs.umich.edu virtual void uncondBranch(void * &bp_history) = 0; 989023Sgblack@eecs.umich.edu 999023Sgblack@eecs.umich.edu /** 1009023Sgblack@eecs.umich.edu * Tells the branch predictor to commit any updates until the given 1019023Sgblack@eecs.umich.edu * sequence number. 1029023Sgblack@eecs.umich.edu * @param done_sn The sequence number to commit any older updates up until. 1039023Sgblack@eecs.umich.edu * @param tid The thread id. 1049023Sgblack@eecs.umich.edu */ 1059023Sgblack@eecs.umich.edu void update(const InstSeqNum &done_sn, ThreadID tid); 1069023Sgblack@eecs.umich.edu 1079023Sgblack@eecs.umich.edu /** 1089023Sgblack@eecs.umich.edu * Squashes all outstanding updates until a given sequence number. 1099023Sgblack@eecs.umich.edu * @param squashed_sn The sequence number to squash any younger updates up 1109023Sgblack@eecs.umich.edu * until. 1119023Sgblack@eecs.umich.edu * @param tid The thread id. 1129023Sgblack@eecs.umich.edu */ 1139023Sgblack@eecs.umich.edu void squash(const InstSeqNum &squashed_sn, ThreadID tid); 1149023Sgblack@eecs.umich.edu 1159023Sgblack@eecs.umich.edu /** 1169023Sgblack@eecs.umich.edu * Squashes all outstanding updates until a given sequence number, and 1179023Sgblack@eecs.umich.edu * corrects that sn's update with the proper address and taken/not taken. 1189023Sgblack@eecs.umich.edu * @param squashed_sn The sequence number to squash any younger updates up 1199023Sgblack@eecs.umich.edu * until. 1209023Sgblack@eecs.umich.edu * @param corr_target The correct branch target. 1219023Sgblack@eecs.umich.edu * @param actually_taken The correct branch direction. 1229023Sgblack@eecs.umich.edu * @param tid The thread id. 1239023Sgblack@eecs.umich.edu */ 1249023Sgblack@eecs.umich.edu void squash(const InstSeqNum &squashed_sn, 1259023Sgblack@eecs.umich.edu const TheISA::PCState &corr_target, 1269023Sgblack@eecs.umich.edu bool actually_taken, ThreadID tid); 1279023Sgblack@eecs.umich.edu 1289023Sgblack@eecs.umich.edu /** 1299023Sgblack@eecs.umich.edu * @param bp_history Pointer to the history object. The predictor 1309023Sgblack@eecs.umich.edu * will need to update any state and delete the object. 1319023Sgblack@eecs.umich.edu */ 1329023Sgblack@eecs.umich.edu virtual void squash(void *bp_history) = 0; 1339023Sgblack@eecs.umich.edu 1349023Sgblack@eecs.umich.edu /** 1359023Sgblack@eecs.umich.edu * Looks up a given PC in the BP to see if it is taken or not taken. 1369023Sgblack@eecs.umich.edu * @param inst_PC The PC to look up. 1379023Sgblack@eecs.umich.edu * @param bp_history Pointer that will be set to an object that 1389023Sgblack@eecs.umich.edu * has the branch predictor state associated with the lookup. 1399023Sgblack@eecs.umich.edu * @return Whether the branch is taken or not taken. 1409023Sgblack@eecs.umich.edu */ 1419023Sgblack@eecs.umich.edu virtual bool lookup(Addr instPC, void * &bp_history) = 0; 1429023Sgblack@eecs.umich.edu 1439023Sgblack@eecs.umich.edu /** 1449023Sgblack@eecs.umich.edu * If a branch is not taken, because the BTB address is invalid or missing, 1459023Sgblack@eecs.umich.edu * this function sets the appropriate counter in the global and local 1469023Sgblack@eecs.umich.edu * predictors to not taken. 1479023Sgblack@eecs.umich.edu * @param inst_PC The PC to look up the local predictor. 1489023Sgblack@eecs.umich.edu * @param bp_history Pointer that will be set to an object that 1499023Sgblack@eecs.umich.edu * has the branch predictor state associated with the lookup. 1509023Sgblack@eecs.umich.edu */ 1519023Sgblack@eecs.umich.edu virtual void btbUpdate(Addr instPC, void * &bp_history) = 0; 1529023Sgblack@eecs.umich.edu 1539023Sgblack@eecs.umich.edu /** 1549023Sgblack@eecs.umich.edu * Looks up a given PC in the BTB to see if a matching entry exists. 1559023Sgblack@eecs.umich.edu * @param inst_PC The PC to look up. 1569023Sgblack@eecs.umich.edu * @return Whether the BTB contains the given PC. 1579023Sgblack@eecs.umich.edu */ 1589023Sgblack@eecs.umich.edu bool BTBValid(Addr instPC) 1599023Sgblack@eecs.umich.edu { return BTB.valid(instPC, 0); } 1609023Sgblack@eecs.umich.edu 1619023Sgblack@eecs.umich.edu /** 1629023Sgblack@eecs.umich.edu * Looks up a given PC in the BTB to get the predicted target. 1639023Sgblack@eecs.umich.edu * @param inst_PC The PC to look up. 1649023Sgblack@eecs.umich.edu * @return The address of the target of the branch. 1659023Sgblack@eecs.umich.edu */ 1669023Sgblack@eecs.umich.edu TheISA::PCState BTBLookup(Addr instPC) 1679023Sgblack@eecs.umich.edu { return BTB.lookup(instPC, 0); } 1689023Sgblack@eecs.umich.edu 1699023Sgblack@eecs.umich.edu /** 1709023Sgblack@eecs.umich.edu * Updates the BP with taken/not taken information. 1719023Sgblack@eecs.umich.edu * @param inst_PC The branch's PC that will be updated. 1729023Sgblack@eecs.umich.edu * @param taken Whether the branch was taken or not taken. 1739023Sgblack@eecs.umich.edu * @param bp_history Pointer to the branch predictor state that is 1749023Sgblack@eecs.umich.edu * associated with the branch lookup that is being updated. 1759023Sgblack@eecs.umich.edu * @param squashed Set to true when this function is called during a 1769023Sgblack@eecs.umich.edu * squash operation. 1779023Sgblack@eecs.umich.edu * @todo Make this update flexible enough to handle a global predictor. 1789023Sgblack@eecs.umich.edu */ 1799023Sgblack@eecs.umich.edu virtual void update(Addr instPC, bool taken, void *bp_history, 1809023Sgblack@eecs.umich.edu bool squashed) = 0; 1819023Sgblack@eecs.umich.edu /** 1829023Sgblack@eecs.umich.edu * Deletes the associated history with a branch, performs no predictor 1839023Sgblack@eecs.umich.edu * updates. Used for branches that mispredict and update tables but 1849023Sgblack@eecs.umich.edu * are still speculative and later retire. 1859023Sgblack@eecs.umich.edu * @param bp_history History to delete associated with this predictor 1869023Sgblack@eecs.umich.edu */ 1879023Sgblack@eecs.umich.edu virtual void retireSquashed(void *bp_history) = 0; 1889023Sgblack@eecs.umich.edu 1899023Sgblack@eecs.umich.edu /** 1909023Sgblack@eecs.umich.edu * Updates the BTB with the target of a branch. 1919023Sgblack@eecs.umich.edu * @param inst_PC The branch's PC that will be updated. 1929023Sgblack@eecs.umich.edu * @param target_PC The branch's target that will be added to the BTB. 1939023Sgblack@eecs.umich.edu */ 1949023Sgblack@eecs.umich.edu void BTBUpdate(Addr instPC, const TheISA::PCState &target) 1959023Sgblack@eecs.umich.edu { BTB.update(instPC, target, 0); } 1969023Sgblack@eecs.umich.edu 1979023Sgblack@eecs.umich.edu void dump(); 1989023Sgblack@eecs.umich.edu 1999023Sgblack@eecs.umich.edu private: 2009023Sgblack@eecs.umich.edu struct PredictorHistory { 2019023Sgblack@eecs.umich.edu /** 2029023Sgblack@eecs.umich.edu * Makes a predictor history struct that contains any 2039023Sgblack@eecs.umich.edu * information needed to update the predictor, BTB, and RAS. 2049023Sgblack@eecs.umich.edu */ 2059023Sgblack@eecs.umich.edu PredictorHistory(const InstSeqNum &seq_num, Addr instPC, 2069023Sgblack@eecs.umich.edu bool pred_taken, void *bp_history, 2079023Sgblack@eecs.umich.edu ThreadID _tid) 2089023Sgblack@eecs.umich.edu : seqNum(seq_num), pc(instPC), bpHistory(bp_history), RASTarget(0), 2099023Sgblack@eecs.umich.edu RASIndex(0), tid(_tid), predTaken(pred_taken), usedRAS(0), pushedRAS(0), 2109023Sgblack@eecs.umich.edu wasCall(0), wasReturn(0), wasSquashed(0) 2119023Sgblack@eecs.umich.edu {} 2129023Sgblack@eecs.umich.edu 2139023Sgblack@eecs.umich.edu bool operator==(const PredictorHistory &entry) const { 2149023Sgblack@eecs.umich.edu return this->seqNum == entry.seqNum; 2159023Sgblack@eecs.umich.edu } 2169023Sgblack@eecs.umich.edu 2179023Sgblack@eecs.umich.edu /** The sequence number for the predictor history entry. */ 2189023Sgblack@eecs.umich.edu InstSeqNum seqNum; 2199023Sgblack@eecs.umich.edu 2209023Sgblack@eecs.umich.edu /** The PC associated with the sequence number. */ 2219023Sgblack@eecs.umich.edu Addr pc; 2229023Sgblack@eecs.umich.edu 2239023Sgblack@eecs.umich.edu /** Pointer to the history object passed back from the branch 2249023Sgblack@eecs.umich.edu * predictor. It is used to update or restore state of the 2259023Sgblack@eecs.umich.edu * branch predictor. 2269023Sgblack@eecs.umich.edu */ 2279023Sgblack@eecs.umich.edu void *bpHistory; 2289023Sgblack@eecs.umich.edu 2299023Sgblack@eecs.umich.edu /** The RAS target (only valid if a return). */ 2309023Sgblack@eecs.umich.edu TheISA::PCState RASTarget; 2319023Sgblack@eecs.umich.edu 2329023Sgblack@eecs.umich.edu /** The RAS index of the instruction (only valid if a call). */ 2339023Sgblack@eecs.umich.edu unsigned RASIndex; 2349023Sgblack@eecs.umich.edu 2359023Sgblack@eecs.umich.edu /** The thread id. */ 2369023Sgblack@eecs.umich.edu ThreadID tid; 2379023Sgblack@eecs.umich.edu 2389023Sgblack@eecs.umich.edu /** Whether or not it was predicted taken. */ 2399023Sgblack@eecs.umich.edu bool predTaken; 2409023Sgblack@eecs.umich.edu 2419023Sgblack@eecs.umich.edu /** Whether or not the RAS was used. */ 2429023Sgblack@eecs.umich.edu bool usedRAS; 2439023Sgblack@eecs.umich.edu 2449023Sgblack@eecs.umich.edu /* Whether or not the RAS was pushed */ 2459023Sgblack@eecs.umich.edu bool pushedRAS; 2469023Sgblack@eecs.umich.edu 2479023Sgblack@eecs.umich.edu /** Whether or not the instruction was a call. */ 2489023Sgblack@eecs.umich.edu bool wasCall; 2499023Sgblack@eecs.umich.edu 2509023Sgblack@eecs.umich.edu /** Whether or not the instruction was a return. */ 2519023Sgblack@eecs.umich.edu bool wasReturn; 2529023Sgblack@eecs.umich.edu 2539023Sgblack@eecs.umich.edu /** Whether this instruction has already mispredicted/updated bp */ 2549023Sgblack@eecs.umich.edu bool wasSquashed; 2559023Sgblack@eecs.umich.edu }; 2569023Sgblack@eecs.umich.edu 2579023Sgblack@eecs.umich.edu typedef std::deque<PredictorHistory> History; 2589023Sgblack@eecs.umich.edu 2599023Sgblack@eecs.umich.edu /** Number of the threads for which the branch history is maintained. */ 2609023Sgblack@eecs.umich.edu uint32_t numThreads; 2619023Sgblack@eecs.umich.edu 2629023Sgblack@eecs.umich.edu /** 2639023Sgblack@eecs.umich.edu * The per-thread predictor history. This is used to update the predictor 2649023Sgblack@eecs.umich.edu * as instructions are committed, or restore it to the proper state after 2659023Sgblack@eecs.umich.edu * a squash. 2669023Sgblack@eecs.umich.edu */ 2679023Sgblack@eecs.umich.edu std::vector<History> predHist; 2689023Sgblack@eecs.umich.edu 2699023Sgblack@eecs.umich.edu /** The BTB. */ 2709023Sgblack@eecs.umich.edu DefaultBTB BTB; 2719023Sgblack@eecs.umich.edu 2729023Sgblack@eecs.umich.edu /** The per-thread return address stack. */ 2739023Sgblack@eecs.umich.edu std::vector<ReturnAddrStack> RAS; 2749023Sgblack@eecs.umich.edu 2759023Sgblack@eecs.umich.edu /** Stat for number of BP lookups. */ 2769023Sgblack@eecs.umich.edu Stats::Scalar lookups; 2779023Sgblack@eecs.umich.edu /** Stat for number of conditional branches predicted. */ 2789023Sgblack@eecs.umich.edu Stats::Scalar condPredicted; 2799023Sgblack@eecs.umich.edu /** Stat for number of conditional branches predicted incorrectly. */ 2809023Sgblack@eecs.umich.edu Stats::Scalar condIncorrect; 2819023Sgblack@eecs.umich.edu /** Stat for number of BTB lookups. */ 2829023Sgblack@eecs.umich.edu Stats::Scalar BTBLookups; 2839023Sgblack@eecs.umich.edu /** Stat for number of BTB hits. */ 2849023Sgblack@eecs.umich.edu Stats::Scalar BTBHits; 2859023Sgblack@eecs.umich.edu /** Stat for number of times the BTB is correct. */ 2869023Sgblack@eecs.umich.edu Stats::Scalar BTBCorrect; 2879023Sgblack@eecs.umich.edu /** Stat for percent times an entry in BTB found. */ 2889023Sgblack@eecs.umich.edu Stats::Formula BTBHitPct; 2899023Sgblack@eecs.umich.edu /** Stat for number of times the RAS is used to get a target. */ 2909023Sgblack@eecs.umich.edu Stats::Scalar usedRAS; 2919023Sgblack@eecs.umich.edu /** Stat for number of times the RAS is incorrect. */ 2929023Sgblack@eecs.umich.edu Stats::Scalar RASIncorrect; 2939023Sgblack@eecs.umich.edu}; 2949023Sgblack@eecs.umich.edu 2959023Sgblack@eecs.umich.edu#endif // __CPU_PRED_BPRED_UNIT_HH__ 2969023Sgblack@eecs.umich.edu