1/* 2 * Copyright (c) 2014 The University of Wisconsin 3 * 4 * Copyright (c) 2006 INRIA (Institut National de Recherche en 5 * Informatique et en Automatique / French National Research Institute 6 * for Computer Science and Applied Mathematics) 7 * 8 * All rights reserved. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions are 12 * met: redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer; 14 * redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution; 17 * neither the name of the copyright holders nor the names of its 18 * contributors may be used to endorse or promote products derived from 19 * this software without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 24 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 25 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 26 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 27 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 31 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 * 33 * Authors: Vignyan Reddy, Dibakar Gope and Arthur Perais, 34 * from André Seznec's code. 35 */ 36 37/* @file 38 * Implementation of a L-TAGE branch predictor 39 */ 40 41#include "cpu/pred/ltage.hh" 42 43#include "base/intmath.hh" 44#include "base/logging.hh"
| 1/* 2 * Copyright (c) 2014 The University of Wisconsin 3 * 4 * Copyright (c) 2006 INRIA (Institut National de Recherche en 5 * Informatique et en Automatique / French National Research Institute 6 * for Computer Science and Applied Mathematics) 7 * 8 * All rights reserved. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions are 12 * met: redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer; 14 * redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution; 17 * neither the name of the copyright holders nor the names of its 18 * contributors may be used to endorse or promote products derived from 19 * this software without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 24 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 25 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 26 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 27 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 31 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 32 * 33 * Authors: Vignyan Reddy, Dibakar Gope and Arthur Perais, 34 * from André Seznec's code. 35 */ 36 37/* @file 38 * Implementation of a L-TAGE branch predictor 39 */ 40 41#include "cpu/pred/ltage.hh" 42 43#include "base/intmath.hh" 44#include "base/logging.hh"
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| 45#include "base/random.hh"
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45#include "base/trace.hh" 46#include "debug/Fetch.hh" 47#include "debug/LTage.hh" 48 49LTAGE::LTAGE(const LTAGEParams *params) 50 : TAGE(params), loopPredictor(params->loop_predictor) 51{ 52} 53
| 46#include "base/trace.hh" 47#include "debug/Fetch.hh" 48#include "debug/LTage.hh" 49 50LTAGE::LTAGE(const LTAGEParams *params) 51 : TAGE(params), loopPredictor(params->loop_predictor) 52{ 53} 54
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| 55void 56LTAGE::init() 57{ 58 TAGE::init(); 59} 60
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54//prediction 55bool 56LTAGE::predict(ThreadID tid, Addr branch_pc, bool cond_branch, void* &b) 57{ 58 LTageBranchInfo *bi = new LTageBranchInfo(*tage, *loopPredictor); 59 b = (void*)(bi); 60 61 bool pred_taken = tage->tagePredict(tid, branch_pc, cond_branch, 62 bi->tageBranchInfo); 63 64 pred_taken = loopPredictor->loopPredict(tid, branch_pc, cond_branch, 65 bi->lpBranchInfo, pred_taken, 66 instShiftAmt); 67 if (cond_branch) { 68 if (bi->lpBranchInfo->loopPredUsed) { 69 bi->tageBranchInfo->provider = LOOP; 70 } 71 DPRINTF(LTage, "Predict for %lx: taken?:%d, loopTaken?:%d, " 72 "loopValid?:%d, loopUseCounter:%d, tagePred:%d, altPred:%d\n", 73 branch_pc, pred_taken, bi->lpBranchInfo->loopPred, 74 bi->lpBranchInfo->loopPredValid, 75 loopPredictor->getLoopUseCounter(), 76 bi->tageBranchInfo->tagePred, bi->tageBranchInfo->altTaken); 77 } 78 79 // record final prediction 80 bi->lpBranchInfo->predTaken = pred_taken; 81 82 return pred_taken; 83} 84
| 61//prediction 62bool 63LTAGE::predict(ThreadID tid, Addr branch_pc, bool cond_branch, void* &b) 64{ 65 LTageBranchInfo *bi = new LTageBranchInfo(*tage, *loopPredictor); 66 b = (void*)(bi); 67 68 bool pred_taken = tage->tagePredict(tid, branch_pc, cond_branch, 69 bi->tageBranchInfo); 70 71 pred_taken = loopPredictor->loopPredict(tid, branch_pc, cond_branch, 72 bi->lpBranchInfo, pred_taken, 73 instShiftAmt); 74 if (cond_branch) { 75 if (bi->lpBranchInfo->loopPredUsed) { 76 bi->tageBranchInfo->provider = LOOP; 77 } 78 DPRINTF(LTage, "Predict for %lx: taken?:%d, loopTaken?:%d, " 79 "loopValid?:%d, loopUseCounter:%d, tagePred:%d, altPred:%d\n", 80 branch_pc, pred_taken, bi->lpBranchInfo->loopPred, 81 bi->lpBranchInfo->loopPredValid, 82 loopPredictor->getLoopUseCounter(), 83 bi->tageBranchInfo->tagePred, bi->tageBranchInfo->altTaken); 84 } 85 86 // record final prediction 87 bi->lpBranchInfo->predTaken = pred_taken; 88 89 return pred_taken; 90} 91
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| 92// PREDICTOR UPDATE
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85void 86LTAGE::update(ThreadID tid, Addr branch_pc, bool taken, void* bp_history, 87 bool squashed, const StaticInstPtr & inst, Addr corrTarget) 88{ 89 assert(bp_history); 90 91 LTageBranchInfo* bi = static_cast<LTageBranchInfo*>(bp_history); 92 93 assert(corrTarget != MaxAddr); 94 95 if (squashed) { 96 if (tage->isSpeculativeUpdateEnabled()) { 97 // This restores the global history, then update it 98 // and recomputes the folded histories. 99 tage->squash(tid, taken, bi->tageBranchInfo, corrTarget); 100 101 if (bi->tageBranchInfo->condBranch) { 102 loopPredictor->squashLoop(bi->lpBranchInfo); 103 } 104 } 105 return; 106 } 107
| 93void 94LTAGE::update(ThreadID tid, Addr branch_pc, bool taken, void* bp_history, 95 bool squashed, const StaticInstPtr & inst, Addr corrTarget) 96{ 97 assert(bp_history); 98 99 LTageBranchInfo* bi = static_cast<LTageBranchInfo*>(bp_history); 100 101 assert(corrTarget != MaxAddr); 102 103 if (squashed) { 104 if (tage->isSpeculativeUpdateEnabled()) { 105 // This restores the global history, then update it 106 // and recomputes the folded histories. 107 tage->squash(tid, taken, bi->tageBranchInfo, corrTarget); 108 109 if (bi->tageBranchInfo->condBranch) { 110 loopPredictor->squashLoop(bi->lpBranchInfo); 111 } 112 } 113 return; 114 } 115
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108 int nrand = TAGEBase::getRandom() & 3;
| 116 int nrand = random_mt.random<int>() & 3;
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109 if (bi->tageBranchInfo->condBranch) { 110 DPRINTF(LTage, "Updating tables for branch:%lx; taken?:%d\n", 111 branch_pc, taken); 112 tage->updateStats(taken, bi->tageBranchInfo); 113 114 loopPredictor->updateStats(taken, bi->lpBranchInfo); 115 116 loopPredictor->condBranchUpdate(tid, branch_pc, taken,
| 117 if (bi->tageBranchInfo->condBranch) { 118 DPRINTF(LTage, "Updating tables for branch:%lx; taken?:%d\n", 119 branch_pc, taken); 120 tage->updateStats(taken, bi->tageBranchInfo); 121 122 loopPredictor->updateStats(taken, bi->lpBranchInfo); 123 124 loopPredictor->condBranchUpdate(tid, branch_pc, taken,
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117 bi->tageBranchInfo->tagePred, bi->lpBranchInfo, instShiftAmt, 118 TAGEBase::getRandom(), TAGEBase::getRandom(), 119 TAGEBase::getRandom());
| 125 bi->tageBranchInfo->tagePred, bi->lpBranchInfo, instShiftAmt);
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120 121 tage->condBranchUpdate(tid, branch_pc, taken, bi->tageBranchInfo,
| 126 127 tage->condBranchUpdate(tid, branch_pc, taken, bi->tageBranchInfo,
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122 nrand, corrTarget);
| 128 nrand, corrTarget, bi->lpBranchInfo->predTaken);
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123 } 124 125 tage->updateHistories(tid, branch_pc, taken, bi->tageBranchInfo, false, 126 inst, corrTarget); 127 128 delete bi; 129} 130 131void 132LTAGE::squash(ThreadID tid, void *bp_history) 133{ 134 LTageBranchInfo* bi = (LTageBranchInfo*)(bp_history); 135 136 if (bi->tageBranchInfo->condBranch) { 137 loopPredictor->squash(tid, bi->lpBranchInfo); 138 } 139 140 TAGE::squash(tid, bp_history); 141} 142 143void 144LTAGE::regStats() 145{ 146 TAGE::regStats(); 147} 148 149LTAGE* 150LTAGEParams::create() 151{ 152 return new LTAGE(this); 153}
| 129 } 130 131 tage->updateHistories(tid, branch_pc, taken, bi->tageBranchInfo, false, 132 inst, corrTarget); 133 134 delete bi; 135} 136 137void 138LTAGE::squash(ThreadID tid, void *bp_history) 139{ 140 LTageBranchInfo* bi = (LTageBranchInfo*)(bp_history); 141 142 if (bi->tageBranchInfo->condBranch) { 143 loopPredictor->squash(tid, bi->lpBranchInfo); 144 } 145 146 TAGE::squash(tid, bp_history); 147} 148 149void 150LTAGE::regStats() 151{ 152 TAGE::regStats(); 153} 154 155LTAGE* 156LTAGEParams::create() 157{ 158 return new LTAGE(this); 159}
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