ltage.cc revision 13433
111784Sarthur.perais@inria.fr/* 211784Sarthur.perais@inria.fr * Copyright (c) 2014 The University of Wisconsin 311784Sarthur.perais@inria.fr * 411784Sarthur.perais@inria.fr * Copyright (c) 2006 INRIA (Institut National de Recherche en 511784Sarthur.perais@inria.fr * Informatique et en Automatique / French National Research Institute 611784Sarthur.perais@inria.fr * for Computer Science and Applied Mathematics) 711784Sarthur.perais@inria.fr * 811784Sarthur.perais@inria.fr * All rights reserved. 911784Sarthur.perais@inria.fr * 1011784Sarthur.perais@inria.fr * Redistribution and use in source and binary forms, with or without 1111784Sarthur.perais@inria.fr * modification, are permitted provided that the following conditions are 1211784Sarthur.perais@inria.fr * met: redistributions of source code must retain the above copyright 1311784Sarthur.perais@inria.fr * notice, this list of conditions and the following disclaimer; 1411784Sarthur.perais@inria.fr * redistributions in binary form must reproduce the above copyright 1511784Sarthur.perais@inria.fr * notice, this list of conditions and the following disclaimer in the 1611784Sarthur.perais@inria.fr * documentation and/or other materials provided with the distribution; 1711784Sarthur.perais@inria.fr * neither the name of the copyright holders nor the names of its 1811784Sarthur.perais@inria.fr * contributors may be used to endorse or promote products derived from 1911784Sarthur.perais@inria.fr * this software without specific prior written permission. 2011784Sarthur.perais@inria.fr * 2111784Sarthur.perais@inria.fr * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 2211784Sarthur.perais@inria.fr * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 2311784Sarthur.perais@inria.fr * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 2411784Sarthur.perais@inria.fr * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 2511784Sarthur.perais@inria.fr * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 2611784Sarthur.perais@inria.fr * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 2711784Sarthur.perais@inria.fr * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 2811784Sarthur.perais@inria.fr * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 2911784Sarthur.perais@inria.fr * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 3011784Sarthur.perais@inria.fr * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 3111784Sarthur.perais@inria.fr * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 3211784Sarthur.perais@inria.fr * 3311784Sarthur.perais@inria.fr * Authors: Vignyan Reddy, Dibakar Gope and Arthur Perais, 3411784Sarthur.perais@inria.fr * from André Seznec's code. 3511784Sarthur.perais@inria.fr */ 3611784Sarthur.perais@inria.fr 3711784Sarthur.perais@inria.fr/* @file 3811784Sarthur.perais@inria.fr * Implementation of a L-TAGE branch predictor 3911784Sarthur.perais@inria.fr */ 4011784Sarthur.perais@inria.fr 4111784Sarthur.perais@inria.fr#include "cpu/pred/ltage.hh" 4211784Sarthur.perais@inria.fr 4311784Sarthur.perais@inria.fr#include "base/intmath.hh" 4412334Sgabeblack@google.com#include "base/logging.hh" 4511784Sarthur.perais@inria.fr#include "base/random.hh" 4611784Sarthur.perais@inria.fr#include "base/trace.hh" 4711784Sarthur.perais@inria.fr#include "debug/Fetch.hh" 4811784Sarthur.perais@inria.fr#include "debug/LTage.hh" 4911784Sarthur.perais@inria.fr 5011784Sarthur.perais@inria.frLTAGE::LTAGE(const LTAGEParams *params) 5111784Sarthur.perais@inria.fr : BPredUnit(params), 5211784Sarthur.perais@inria.fr logSizeBiMP(params->logSizeBiMP), 5313420Spau.cabre@metempsy.com logRatioBiModalHystEntries(params->logRatioBiModalHystEntries), 5411784Sarthur.perais@inria.fr logSizeTagTables(params->logSizeTagTables), 5511784Sarthur.perais@inria.fr logSizeLoopPred(params->logSizeLoopPred), 5611784Sarthur.perais@inria.fr nHistoryTables(params->nHistoryTables), 5711784Sarthur.perais@inria.fr tagTableCounterBits(params->tagTableCounterBits), 5811784Sarthur.perais@inria.fr histBufferSize(params->histBufferSize), 5911784Sarthur.perais@inria.fr minHist(params->minHist), 6011784Sarthur.perais@inria.fr maxHist(params->maxHist), 6111784Sarthur.perais@inria.fr minTagWidth(params->minTagWidth), 6211784Sarthur.perais@inria.fr threadHistory(params->numThreads) 6311784Sarthur.perais@inria.fr{ 6411784Sarthur.perais@inria.fr assert(params->histBufferSize > params->maxHist * 2); 6511784Sarthur.perais@inria.fr useAltPredForNewlyAllocated = 0; 6611784Sarthur.perais@inria.fr logTick = 19; 6711784Sarthur.perais@inria.fr tCounter = ULL(1) << (logTick - 1); 6811784Sarthur.perais@inria.fr 6911784Sarthur.perais@inria.fr for (auto& history : threadHistory) { 7011784Sarthur.perais@inria.fr history.pathHist = 0; 7111784Sarthur.perais@inria.fr history.globalHistory = new uint8_t[histBufferSize]; 7211784Sarthur.perais@inria.fr history.gHist = history.globalHistory; 7311784Sarthur.perais@inria.fr memset(history.gHist, 0, histBufferSize); 7411784Sarthur.perais@inria.fr history.ptGhist = 0; 7511784Sarthur.perais@inria.fr } 7611784Sarthur.perais@inria.fr 7711784Sarthur.perais@inria.fr histLengths = new int [nHistoryTables+1]; 7811784Sarthur.perais@inria.fr histLengths[1] = minHist; 7911784Sarthur.perais@inria.fr histLengths[nHistoryTables] = maxHist; 8011784Sarthur.perais@inria.fr 8111784Sarthur.perais@inria.fr for (int i = 2; i <= nHistoryTables; i++) { 8211784Sarthur.perais@inria.fr histLengths[i] = (int) (((double) minHist * 8311784Sarthur.perais@inria.fr pow ((double) (maxHist) / (double) minHist, 8411784Sarthur.perais@inria.fr (double) (i - 1) / (double) ((nHistoryTables- 1)))) 8511784Sarthur.perais@inria.fr + 0.5); 8611784Sarthur.perais@inria.fr } 8711784Sarthur.perais@inria.fr 8811784Sarthur.perais@inria.fr tagWidths[1] = minTagWidth; 8911784Sarthur.perais@inria.fr tagWidths[2] = minTagWidth; 9011784Sarthur.perais@inria.fr tagWidths[3] = minTagWidth + 1; 9111784Sarthur.perais@inria.fr tagWidths[4] = minTagWidth + 1; 9211784Sarthur.perais@inria.fr tagWidths[5] = minTagWidth + 2; 9311784Sarthur.perais@inria.fr tagWidths[6] = minTagWidth + 3; 9411784Sarthur.perais@inria.fr tagWidths[7] = minTagWidth + 4; 9511784Sarthur.perais@inria.fr tagWidths[8] = minTagWidth + 5; 9611784Sarthur.perais@inria.fr tagWidths[9] = minTagWidth + 5; 9711784Sarthur.perais@inria.fr tagWidths[10] = minTagWidth + 6; 9811784Sarthur.perais@inria.fr tagWidths[11] = minTagWidth + 7; 9911784Sarthur.perais@inria.fr tagWidths[12] = minTagWidth + 8; 10011784Sarthur.perais@inria.fr 10111784Sarthur.perais@inria.fr for (int i = 1; i <= 2; i++) 10211784Sarthur.perais@inria.fr tagTableSizes[i] = logSizeTagTables - 1; 10311784Sarthur.perais@inria.fr for (int i = 3; i <= 6; i++) 10411784Sarthur.perais@inria.fr tagTableSizes[i] = logSizeTagTables; 10511784Sarthur.perais@inria.fr for (int i = 7; i <= 10; i++) 10611784Sarthur.perais@inria.fr tagTableSizes[i] = logSizeTagTables - 1; 10711784Sarthur.perais@inria.fr for (int i = 11; i <= 12; i++) 10811784Sarthur.perais@inria.fr tagTableSizes[i] = logSizeTagTables - 2; 10911784Sarthur.perais@inria.fr 11011784Sarthur.perais@inria.fr for (auto& history : threadHistory) { 11111784Sarthur.perais@inria.fr history.computeIndices = new FoldedHistory[nHistoryTables+1]; 11211784Sarthur.perais@inria.fr history.computeTags[0] = new FoldedHistory[nHistoryTables+1]; 11311784Sarthur.perais@inria.fr history.computeTags[1] = new FoldedHistory[nHistoryTables+1]; 11411784Sarthur.perais@inria.fr 11511784Sarthur.perais@inria.fr for (int i = 1; i <= nHistoryTables; i++) { 11611784Sarthur.perais@inria.fr history.computeIndices[i].init(histLengths[i], (tagTableSizes[i])); 11711784Sarthur.perais@inria.fr history.computeTags[0][i].init( 11811784Sarthur.perais@inria.fr history.computeIndices[i].origLength, tagWidths[i]); 11911784Sarthur.perais@inria.fr history.computeTags[1][i].init( 12011784Sarthur.perais@inria.fr history.computeIndices[i].origLength, tagWidths[i] - 1); 12111784Sarthur.perais@inria.fr DPRINTF(LTage, "HistLength:%d, TTSize:%d, TTTWidth:%d\n", 12211784Sarthur.perais@inria.fr histLengths[i], tagTableSizes[i], tagWidths[i]); 12311784Sarthur.perais@inria.fr } 12411784Sarthur.perais@inria.fr } 12511784Sarthur.perais@inria.fr 12613420Spau.cabre@metempsy.com const uint64_t bimodalTableSize = ULL(1) << logSizeBiMP; 12713420Spau.cabre@metempsy.com btablePrediction.resize(bimodalTableSize, false); 12813420Spau.cabre@metempsy.com btableHysteresis.resize(bimodalTableSize >> logRatioBiModalHystEntries, 12913420Spau.cabre@metempsy.com true); 13013420Spau.cabre@metempsy.com 13111784Sarthur.perais@inria.fr ltable = new LoopEntry[ULL(1) << logSizeLoopPred]; 13211784Sarthur.perais@inria.fr gtable = new TageEntry*[nHistoryTables + 1]; 13311784Sarthur.perais@inria.fr for (int i = 1; i <= nHistoryTables; i++) { 13411784Sarthur.perais@inria.fr gtable[i] = new TageEntry[1<<(tagTableSizes[i])]; 13511784Sarthur.perais@inria.fr } 13611784Sarthur.perais@inria.fr 13711784Sarthur.perais@inria.fr tableIndices = new int [nHistoryTables+1]; 13811784Sarthur.perais@inria.fr tableTags = new int [nHistoryTables+1]; 13911784Sarthur.perais@inria.fr 14011784Sarthur.perais@inria.fr loopUseCounter = 0; 14111784Sarthur.perais@inria.fr} 14211784Sarthur.perais@inria.fr 14311784Sarthur.perais@inria.frint 14411784Sarthur.perais@inria.frLTAGE::bindex(Addr pc_in) const 14511784Sarthur.perais@inria.fr{ 14613413Spau.cabre@metempsy.com return ((pc_in >> instShiftAmt) & ((ULL(1) << (logSizeBiMP)) - 1)); 14711784Sarthur.perais@inria.fr} 14811784Sarthur.perais@inria.fr 14911784Sarthur.perais@inria.frint 15011784Sarthur.perais@inria.frLTAGE::lindex(Addr pc_in) const 15111784Sarthur.perais@inria.fr{ 15213413Spau.cabre@metempsy.com return (((pc_in >> instShiftAmt) & 15313413Spau.cabre@metempsy.com ((ULL(1) << (logSizeLoopPred - 2)) - 1)) << 2); 15411784Sarthur.perais@inria.fr} 15511784Sarthur.perais@inria.fr 15611784Sarthur.perais@inria.frint 15711784Sarthur.perais@inria.frLTAGE::F(int A, int size, int bank) const 15811784Sarthur.perais@inria.fr{ 15911784Sarthur.perais@inria.fr int A1, A2; 16011784Sarthur.perais@inria.fr 16111784Sarthur.perais@inria.fr A = A & ((ULL(1) << size) - 1); 16211784Sarthur.perais@inria.fr A1 = (A & ((ULL(1) << tagTableSizes[bank]) - 1)); 16311784Sarthur.perais@inria.fr A2 = (A >> tagTableSizes[bank]); 16411784Sarthur.perais@inria.fr A2 = ((A2 << bank) & ((ULL(1) << tagTableSizes[bank]) - 1)) 16511784Sarthur.perais@inria.fr + (A2 >> (tagTableSizes[bank] - bank)); 16611784Sarthur.perais@inria.fr A = A1 ^ A2; 16711784Sarthur.perais@inria.fr A = ((A << bank) & ((ULL(1) << tagTableSizes[bank]) - 1)) 16811784Sarthur.perais@inria.fr + (A >> (tagTableSizes[bank] - bank)); 16911784Sarthur.perais@inria.fr return (A); 17011784Sarthur.perais@inria.fr} 17111784Sarthur.perais@inria.fr 17211784Sarthur.perais@inria.fr 17311784Sarthur.perais@inria.fr// gindex computes a full hash of pc, ghist and pathHist 17411784Sarthur.perais@inria.frint 17511784Sarthur.perais@inria.frLTAGE::gindex(ThreadID tid, Addr pc, int bank) const 17611784Sarthur.perais@inria.fr{ 17711784Sarthur.perais@inria.fr int index; 17811784Sarthur.perais@inria.fr int hlen = (histLengths[bank] > 16) ? 16 : histLengths[bank]; 17911784Sarthur.perais@inria.fr index = 18013413Spau.cabre@metempsy.com (pc >> instShiftAmt) ^ 18113413Spau.cabre@metempsy.com ((pc >> instShiftAmt) >> ((int) abs(tagTableSizes[bank] - bank) + 1)) ^ 18211784Sarthur.perais@inria.fr threadHistory[tid].computeIndices[bank].comp ^ 18311784Sarthur.perais@inria.fr F(threadHistory[tid].pathHist, hlen, bank); 18411784Sarthur.perais@inria.fr 18511784Sarthur.perais@inria.fr return (index & ((ULL(1) << (tagTableSizes[bank])) - 1)); 18611784Sarthur.perais@inria.fr} 18711784Sarthur.perais@inria.fr 18811784Sarthur.perais@inria.fr 18911784Sarthur.perais@inria.fr// Tag computation 19011784Sarthur.perais@inria.fruint16_t 19111784Sarthur.perais@inria.frLTAGE::gtag(ThreadID tid, Addr pc, int bank) const 19211784Sarthur.perais@inria.fr{ 19313413Spau.cabre@metempsy.com int tag = (pc >> instShiftAmt) ^ 19413413Spau.cabre@metempsy.com threadHistory[tid].computeTags[0][bank].comp ^ 19513413Spau.cabre@metempsy.com (threadHistory[tid].computeTags[1][bank].comp << 1); 19611784Sarthur.perais@inria.fr 19711784Sarthur.perais@inria.fr return (tag & ((ULL(1) << tagWidths[bank]) - 1)); 19811784Sarthur.perais@inria.fr} 19911784Sarthur.perais@inria.fr 20011784Sarthur.perais@inria.fr 20111784Sarthur.perais@inria.fr// Up-down saturating counter 20211784Sarthur.perais@inria.frvoid 20311784Sarthur.perais@inria.frLTAGE::ctrUpdate(int8_t & ctr, bool taken, int nbits) 20411784Sarthur.perais@inria.fr{ 20511784Sarthur.perais@inria.fr assert(nbits <= sizeof(int8_t) << 3); 20611784Sarthur.perais@inria.fr if (taken) { 20711784Sarthur.perais@inria.fr if (ctr < ((1 << (nbits - 1)) - 1)) 20811784Sarthur.perais@inria.fr ctr++; 20911784Sarthur.perais@inria.fr } else { 21011784Sarthur.perais@inria.fr if (ctr > -(1 << (nbits - 1))) 21111784Sarthur.perais@inria.fr ctr--; 21211784Sarthur.perais@inria.fr } 21311784Sarthur.perais@inria.fr} 21411784Sarthur.perais@inria.fr 21511784Sarthur.perais@inria.fr// Bimodal prediction 21611784Sarthur.perais@inria.frbool 21711784Sarthur.perais@inria.frLTAGE::getBimodePred(Addr pc, BranchInfo* bi) const 21811784Sarthur.perais@inria.fr{ 21913420Spau.cabre@metempsy.com return btablePrediction[bi->bimodalIndex]; 22011784Sarthur.perais@inria.fr} 22111784Sarthur.perais@inria.fr 22211784Sarthur.perais@inria.fr 22313420Spau.cabre@metempsy.com// Update the bimodal predictor: a hysteresis bit is shared among N prediction 22413420Spau.cabre@metempsy.com// bits (N = 2 ^ logRatioBiModalHystEntries) 22511784Sarthur.perais@inria.frvoid 22611784Sarthur.perais@inria.frLTAGE::baseUpdate(Addr pc, bool taken, BranchInfo* bi) 22711784Sarthur.perais@inria.fr{ 22813420Spau.cabre@metempsy.com int inter = (btablePrediction[bi->bimodalIndex] << 1) 22913420Spau.cabre@metempsy.com + btableHysteresis[bi->bimodalIndex >> logRatioBiModalHystEntries]; 23011784Sarthur.perais@inria.fr if (taken) { 23111784Sarthur.perais@inria.fr if (inter < 3) 23211784Sarthur.perais@inria.fr inter++; 23311784Sarthur.perais@inria.fr } else if (inter > 0) { 23411784Sarthur.perais@inria.fr inter--; 23511784Sarthur.perais@inria.fr } 23613420Spau.cabre@metempsy.com const bool pred = inter >> 1; 23713420Spau.cabre@metempsy.com const bool hyst = inter & 1; 23813420Spau.cabre@metempsy.com btablePrediction[bi->bimodalIndex] = pred; 23913420Spau.cabre@metempsy.com btableHysteresis[bi->bimodalIndex >> logRatioBiModalHystEntries] = hyst; 24013420Spau.cabre@metempsy.com DPRINTF(LTage, "Updating branch %lx, pred:%d, hyst:%d\n", pc, pred, hyst); 24111784Sarthur.perais@inria.fr} 24211784Sarthur.perais@inria.fr 24311784Sarthur.perais@inria.fr 24411784Sarthur.perais@inria.fr//loop prediction: only used if high confidence 24511784Sarthur.perais@inria.frbool 24611784Sarthur.perais@inria.frLTAGE::getLoop(Addr pc, BranchInfo* bi) const 24711784Sarthur.perais@inria.fr{ 24811784Sarthur.perais@inria.fr bi->loopHit = -1; 24911784Sarthur.perais@inria.fr bi->loopPredValid = false; 25011784Sarthur.perais@inria.fr bi->loopIndex = lindex(pc); 25113413Spau.cabre@metempsy.com bi->loopTag = ((pc) >> (instShiftAmt + logSizeLoopPred - 2)); 25211784Sarthur.perais@inria.fr 25311784Sarthur.perais@inria.fr for (int i = 0; i < 4; i++) { 25411784Sarthur.perais@inria.fr if (ltable[bi->loopIndex + i].tag == bi->loopTag) { 25511784Sarthur.perais@inria.fr bi->loopHit = i; 25611784Sarthur.perais@inria.fr bi->loopPredValid = (ltable[bi->loopIndex + i].confidence >= 3); 25711784Sarthur.perais@inria.fr bi->currentIter = ltable[bi->loopIndex + i].currentIterSpec; 25811784Sarthur.perais@inria.fr if (ltable[bi->loopIndex + i].currentIterSpec + 1 == 25911784Sarthur.perais@inria.fr ltable[bi->loopIndex + i].numIter) { 26011784Sarthur.perais@inria.fr return !(ltable[bi->loopIndex + i].dir); 26111784Sarthur.perais@inria.fr }else { 26211784Sarthur.perais@inria.fr return (ltable[bi->loopIndex + i].dir); 26311784Sarthur.perais@inria.fr } 26411784Sarthur.perais@inria.fr } 26511784Sarthur.perais@inria.fr } 26611784Sarthur.perais@inria.fr return false; 26711784Sarthur.perais@inria.fr} 26811784Sarthur.perais@inria.fr 26911784Sarthur.perais@inria.frvoid 27011784Sarthur.perais@inria.frLTAGE::specLoopUpdate(Addr pc, bool taken, BranchInfo* bi) 27111784Sarthur.perais@inria.fr{ 27211784Sarthur.perais@inria.fr if (bi->loopHit>=0) { 27311784Sarthur.perais@inria.fr int index = lindex(pc); 27411784Sarthur.perais@inria.fr if (taken != ltable[index].dir) { 27511784Sarthur.perais@inria.fr ltable[index].currentIterSpec = 0; 27611784Sarthur.perais@inria.fr } else { 27711784Sarthur.perais@inria.fr ltable[index].currentIterSpec++; 27811784Sarthur.perais@inria.fr } 27911784Sarthur.perais@inria.fr } 28011784Sarthur.perais@inria.fr} 28111784Sarthur.perais@inria.fr 28211784Sarthur.perais@inria.frvoid 28311784Sarthur.perais@inria.frLTAGE::loopUpdate(Addr pc, bool taken, BranchInfo* bi) 28411784Sarthur.perais@inria.fr{ 28511784Sarthur.perais@inria.fr int idx = bi->loopIndex + bi->loopHit; 28611784Sarthur.perais@inria.fr if (bi->loopHit >= 0) { 28711784Sarthur.perais@inria.fr //already a hit 28811784Sarthur.perais@inria.fr if (bi->loopPredValid) { 28911784Sarthur.perais@inria.fr if (taken != bi->loopPred) { 29011784Sarthur.perais@inria.fr // free the entry 29111784Sarthur.perais@inria.fr ltable[idx].numIter = 0; 29211784Sarthur.perais@inria.fr ltable[idx].age = 0; 29311784Sarthur.perais@inria.fr ltable[idx].confidence = 0; 29411784Sarthur.perais@inria.fr ltable[idx].currentIter = 0; 29511784Sarthur.perais@inria.fr return; 29611784Sarthur.perais@inria.fr } else if (bi->loopPred != bi->tagePred) { 29711784Sarthur.perais@inria.fr DPRINTF(LTage, "Loop Prediction success:%lx\n",pc); 29811784Sarthur.perais@inria.fr if (ltable[idx].age < 7) 29911784Sarthur.perais@inria.fr ltable[idx].age++; 30011784Sarthur.perais@inria.fr } 30111784Sarthur.perais@inria.fr } 30211784Sarthur.perais@inria.fr 30311784Sarthur.perais@inria.fr ltable[idx].currentIter++; 30411784Sarthur.perais@inria.fr if (ltable[idx].currentIter > ltable[idx].numIter) { 30511784Sarthur.perais@inria.fr ltable[idx].confidence = 0; 30611784Sarthur.perais@inria.fr if (ltable[idx].numIter != 0) { 30711784Sarthur.perais@inria.fr // free the entry 30811784Sarthur.perais@inria.fr ltable[idx].numIter = 0; 30911784Sarthur.perais@inria.fr ltable[idx].age = 0; 31011784Sarthur.perais@inria.fr ltable[idx].confidence = 0; 31111784Sarthur.perais@inria.fr } 31211784Sarthur.perais@inria.fr } 31311784Sarthur.perais@inria.fr 31411784Sarthur.perais@inria.fr if (taken != ltable[idx].dir) { 31511784Sarthur.perais@inria.fr if (ltable[idx].currentIter == ltable[idx].numIter) { 31611784Sarthur.perais@inria.fr DPRINTF(LTage, "Loop End predicted successfully:%lx\n", pc); 31711784Sarthur.perais@inria.fr 31811784Sarthur.perais@inria.fr if (ltable[idx].confidence < 7) { 31911784Sarthur.perais@inria.fr ltable[idx].confidence++; 32011784Sarthur.perais@inria.fr } 32111784Sarthur.perais@inria.fr //just do not predict when the loop count is 1 or 2 32211784Sarthur.perais@inria.fr if (ltable[idx].numIter < 3) { 32311784Sarthur.perais@inria.fr // free the entry 32411784Sarthur.perais@inria.fr ltable[idx].dir = taken; 32511784Sarthur.perais@inria.fr ltable[idx].numIter = 0; 32611784Sarthur.perais@inria.fr ltable[idx].age = 0; 32711784Sarthur.perais@inria.fr ltable[idx].confidence = 0; 32811784Sarthur.perais@inria.fr } 32911784Sarthur.perais@inria.fr } else { 33011784Sarthur.perais@inria.fr DPRINTF(LTage, "Loop End predicted incorrectly:%lx\n", pc); 33111784Sarthur.perais@inria.fr if (ltable[idx].numIter == 0) { 33211784Sarthur.perais@inria.fr // first complete nest; 33311784Sarthur.perais@inria.fr ltable[idx].confidence = 0; 33411784Sarthur.perais@inria.fr ltable[idx].numIter = ltable[idx].currentIter; 33511784Sarthur.perais@inria.fr } else { 33611784Sarthur.perais@inria.fr //not the same number of iterations as last time: free the 33711784Sarthur.perais@inria.fr //entry 33811784Sarthur.perais@inria.fr ltable[idx].numIter = 0; 33911784Sarthur.perais@inria.fr ltable[idx].age = 0; 34011784Sarthur.perais@inria.fr ltable[idx].confidence = 0; 34111784Sarthur.perais@inria.fr } 34211784Sarthur.perais@inria.fr } 34311784Sarthur.perais@inria.fr ltable[idx].currentIter = 0; 34411784Sarthur.perais@inria.fr } 34511784Sarthur.perais@inria.fr 34611784Sarthur.perais@inria.fr } else if (taken) { 34711784Sarthur.perais@inria.fr //try to allocate an entry on taken branch 34811784Sarthur.perais@inria.fr int nrand = random_mt.random<int>(); 34911784Sarthur.perais@inria.fr for (int i = 0; i < 4; i++) { 35011784Sarthur.perais@inria.fr int loop_hit = (nrand + i) & 3; 35111784Sarthur.perais@inria.fr idx = bi->loopIndex + loop_hit; 35211784Sarthur.perais@inria.fr if (ltable[idx].age == 0) { 35311784Sarthur.perais@inria.fr DPRINTF(LTage, "Allocating loop pred entry for branch %lx\n", 35411784Sarthur.perais@inria.fr pc); 35511784Sarthur.perais@inria.fr ltable[idx].dir = !taken; 35611784Sarthur.perais@inria.fr ltable[idx].tag = bi->loopTag; 35711784Sarthur.perais@inria.fr ltable[idx].numIter = 0; 35811784Sarthur.perais@inria.fr ltable[idx].age = 7; 35911784Sarthur.perais@inria.fr ltable[idx].confidence = 0; 36011784Sarthur.perais@inria.fr ltable[idx].currentIter = 1; 36111784Sarthur.perais@inria.fr break; 36211784Sarthur.perais@inria.fr 36311784Sarthur.perais@inria.fr } 36411784Sarthur.perais@inria.fr else 36511784Sarthur.perais@inria.fr ltable[idx].age--; 36611784Sarthur.perais@inria.fr } 36711784Sarthur.perais@inria.fr } 36811784Sarthur.perais@inria.fr 36911784Sarthur.perais@inria.fr} 37011784Sarthur.perais@inria.fr 37111784Sarthur.perais@inria.fr// shifting the global history: we manage the history in a big table in order 37211784Sarthur.perais@inria.fr// to reduce simulation time 37311784Sarthur.perais@inria.frvoid 37411784Sarthur.perais@inria.frLTAGE::updateGHist(uint8_t * &h, bool dir, uint8_t * tab, int &pt) 37511784Sarthur.perais@inria.fr{ 37611784Sarthur.perais@inria.fr if (pt == 0) { 37711784Sarthur.perais@inria.fr DPRINTF(LTage, "Rolling over the histories\n"); 37811784Sarthur.perais@inria.fr // Copy beginning of globalHistoryBuffer to end, such that 37911784Sarthur.perais@inria.fr // the last maxHist outcomes are still reachable 38011784Sarthur.perais@inria.fr // through pt[0 .. maxHist - 1]. 38111784Sarthur.perais@inria.fr for (int i = 0; i < maxHist; i++) 38211784Sarthur.perais@inria.fr tab[histBufferSize - maxHist + i] = tab[i]; 38311784Sarthur.perais@inria.fr pt = histBufferSize - maxHist; 38411784Sarthur.perais@inria.fr h = &tab[pt]; 38511784Sarthur.perais@inria.fr } 38611784Sarthur.perais@inria.fr pt--; 38711784Sarthur.perais@inria.fr h--; 38811784Sarthur.perais@inria.fr h[0] = (dir) ? 1 : 0; 38911784Sarthur.perais@inria.fr} 39011784Sarthur.perais@inria.fr 39111784Sarthur.perais@inria.fr// Get GHR for hashing indirect predictor 39211784Sarthur.perais@inria.fr// Build history backwards from pointer in 39311784Sarthur.perais@inria.fr// bp_history. 39411784Sarthur.perais@inria.frunsigned 39511784Sarthur.perais@inria.frLTAGE::getGHR(ThreadID tid, void *bp_history) const 39611784Sarthur.perais@inria.fr{ 39711784Sarthur.perais@inria.fr BranchInfo* bi = static_cast<BranchInfo*>(bp_history); 39811784Sarthur.perais@inria.fr unsigned val = 0; 39911784Sarthur.perais@inria.fr for (unsigned i = 0; i < 32; i++) { 40011784Sarthur.perais@inria.fr // Make sure we don't go out of bounds 40111784Sarthur.perais@inria.fr int gh_offset = bi->ptGhist + i; 40211784Sarthur.perais@inria.fr assert(&(threadHistory[tid].globalHistory[gh_offset]) < 40311784Sarthur.perais@inria.fr threadHistory[tid].globalHistory + histBufferSize); 40411784Sarthur.perais@inria.fr val |= ((threadHistory[tid].globalHistory[gh_offset] & 0x1) << i); 40511784Sarthur.perais@inria.fr } 40611784Sarthur.perais@inria.fr 40711784Sarthur.perais@inria.fr return val; 40811784Sarthur.perais@inria.fr} 40911784Sarthur.perais@inria.fr 41011784Sarthur.perais@inria.fr//prediction 41111784Sarthur.perais@inria.frbool 41211784Sarthur.perais@inria.frLTAGE::predict(ThreadID tid, Addr branch_pc, bool cond_branch, void* &b) 41311784Sarthur.perais@inria.fr{ 41411784Sarthur.perais@inria.fr BranchInfo *bi = new BranchInfo(nHistoryTables+1); 41511784Sarthur.perais@inria.fr b = (void*)(bi); 41611784Sarthur.perais@inria.fr Addr pc = branch_pc; 41711784Sarthur.perais@inria.fr bool pred_taken = true; 41811784Sarthur.perais@inria.fr bi->loopHit = -1; 41911784Sarthur.perais@inria.fr 42011784Sarthur.perais@inria.fr if (cond_branch) { 42111784Sarthur.perais@inria.fr // TAGE prediction 42211784Sarthur.perais@inria.fr 42311784Sarthur.perais@inria.fr // computes the table addresses and the partial tags 42411784Sarthur.perais@inria.fr for (int i = 1; i <= nHistoryTables; i++) { 42511784Sarthur.perais@inria.fr tableIndices[i] = gindex(tid, pc, i); 42611784Sarthur.perais@inria.fr bi->tableIndices[i] = tableIndices[i]; 42711784Sarthur.perais@inria.fr tableTags[i] = gtag(tid, pc, i); 42811784Sarthur.perais@inria.fr bi->tableTags[i] = tableTags[i]; 42911784Sarthur.perais@inria.fr } 43011784Sarthur.perais@inria.fr 43111784Sarthur.perais@inria.fr bi->bimodalIndex = bindex(pc); 43211784Sarthur.perais@inria.fr 43311784Sarthur.perais@inria.fr bi->hitBank = 0; 43411784Sarthur.perais@inria.fr bi->altBank = 0; 43511784Sarthur.perais@inria.fr //Look for the bank with longest matching history 43611784Sarthur.perais@inria.fr for (int i = nHistoryTables; i > 0; i--) { 43711784Sarthur.perais@inria.fr if (gtable[i][tableIndices[i]].tag == tableTags[i]) { 43811784Sarthur.perais@inria.fr bi->hitBank = i; 43911784Sarthur.perais@inria.fr bi->hitBankIndex = tableIndices[bi->hitBank]; 44011784Sarthur.perais@inria.fr break; 44111784Sarthur.perais@inria.fr } 44211784Sarthur.perais@inria.fr } 44311784Sarthur.perais@inria.fr //Look for the alternate bank 44411784Sarthur.perais@inria.fr for (int i = bi->hitBank - 1; i > 0; i--) { 44511784Sarthur.perais@inria.fr if (gtable[i][tableIndices[i]].tag == tableTags[i]) { 44611784Sarthur.perais@inria.fr bi->altBank = i; 44711784Sarthur.perais@inria.fr bi->altBankIndex = tableIndices[bi->altBank]; 44811784Sarthur.perais@inria.fr break; 44911784Sarthur.perais@inria.fr } 45011784Sarthur.perais@inria.fr } 45111784Sarthur.perais@inria.fr //computes the prediction and the alternate prediction 45211784Sarthur.perais@inria.fr if (bi->hitBank > 0) { 45311784Sarthur.perais@inria.fr if (bi->altBank > 0) { 45411784Sarthur.perais@inria.fr bi->altTaken = 45511784Sarthur.perais@inria.fr gtable[bi->altBank][tableIndices[bi->altBank]].ctr >= 0; 45611784Sarthur.perais@inria.fr }else { 45711784Sarthur.perais@inria.fr bi->altTaken = getBimodePred(pc, bi); 45811784Sarthur.perais@inria.fr } 45911784Sarthur.perais@inria.fr 46011784Sarthur.perais@inria.fr bi->longestMatchPred = 46111784Sarthur.perais@inria.fr gtable[bi->hitBank][tableIndices[bi->hitBank]].ctr >= 0; 46211784Sarthur.perais@inria.fr bi->pseudoNewAlloc = 46311784Sarthur.perais@inria.fr abs(2 * gtable[bi->hitBank][bi->hitBankIndex].ctr + 1) <= 1; 46411784Sarthur.perais@inria.fr 46511784Sarthur.perais@inria.fr //if the entry is recognized as a newly allocated entry and 46611784Sarthur.perais@inria.fr //useAltPredForNewlyAllocated is positive use the alternate 46711784Sarthur.perais@inria.fr //prediction 46811784Sarthur.perais@inria.fr if ((useAltPredForNewlyAllocated < 0) 46911784Sarthur.perais@inria.fr || abs(2 * 47011784Sarthur.perais@inria.fr gtable[bi->hitBank][tableIndices[bi->hitBank]].ctr + 1) > 1) 47111784Sarthur.perais@inria.fr bi->tagePred = bi->longestMatchPred; 47211784Sarthur.perais@inria.fr else 47311784Sarthur.perais@inria.fr bi->tagePred = bi->altTaken; 47411784Sarthur.perais@inria.fr } else { 47511784Sarthur.perais@inria.fr bi->altTaken = getBimodePred(pc, bi); 47611784Sarthur.perais@inria.fr bi->tagePred = bi->altTaken; 47711784Sarthur.perais@inria.fr bi->longestMatchPred = bi->altTaken; 47811784Sarthur.perais@inria.fr } 47911784Sarthur.perais@inria.fr //end TAGE prediction 48011784Sarthur.perais@inria.fr 48111784Sarthur.perais@inria.fr bi->loopPred = getLoop(pc, bi); // loop prediction 48211784Sarthur.perais@inria.fr 48311784Sarthur.perais@inria.fr pred_taken = (((loopUseCounter >= 0) && bi->loopPredValid)) ? 48411784Sarthur.perais@inria.fr (bi->loopPred): (bi->tagePred); 48511784Sarthur.perais@inria.fr DPRINTF(LTage, "Predict for %lx: taken?:%d, loopTaken?:%d, " 48611784Sarthur.perais@inria.fr "loopValid?:%d, loopUseCounter:%d, tagePred:%d, altPred:%d\n", 48711784Sarthur.perais@inria.fr branch_pc, pred_taken, bi->loopPred, bi->loopPredValid, 48811784Sarthur.perais@inria.fr loopUseCounter, bi->tagePred, bi->altTaken); 48911784Sarthur.perais@inria.fr } 49011784Sarthur.perais@inria.fr bi->branchPC = branch_pc; 49111784Sarthur.perais@inria.fr bi->condBranch = cond_branch; 49211784Sarthur.perais@inria.fr specLoopUpdate(branch_pc, pred_taken, bi); 49311784Sarthur.perais@inria.fr return pred_taken; 49411784Sarthur.perais@inria.fr} 49511784Sarthur.perais@inria.fr 49611784Sarthur.perais@inria.fr// PREDICTOR UPDATE 49711784Sarthur.perais@inria.frvoid 49811784Sarthur.perais@inria.frLTAGE::update(ThreadID tid, Addr branch_pc, bool taken, void* bp_history, 49911784Sarthur.perais@inria.fr bool squashed) 50011784Sarthur.perais@inria.fr{ 50111784Sarthur.perais@inria.fr assert(bp_history); 50211784Sarthur.perais@inria.fr 50311784Sarthur.perais@inria.fr BranchInfo *bi = static_cast<BranchInfo*>(bp_history); 50411784Sarthur.perais@inria.fr 50511784Sarthur.perais@inria.fr if (squashed) { 50611784Sarthur.perais@inria.fr // This restores the global history, then update it 50711784Sarthur.perais@inria.fr // and recomputes the folded histories. 50811784Sarthur.perais@inria.fr squash(tid, taken, bp_history); 50911784Sarthur.perais@inria.fr return; 51011784Sarthur.perais@inria.fr } 51111784Sarthur.perais@inria.fr 51211784Sarthur.perais@inria.fr int nrand = random_mt.random<int>(0,3); 51311784Sarthur.perais@inria.fr Addr pc = branch_pc; 51411784Sarthur.perais@inria.fr if (bi->condBranch) { 51511784Sarthur.perais@inria.fr DPRINTF(LTage, "Updating tables for branch:%lx; taken?:%d\n", 51611784Sarthur.perais@inria.fr branch_pc, taken); 51711784Sarthur.perais@inria.fr // first update the loop predictor 51811784Sarthur.perais@inria.fr loopUpdate(pc, taken, bi); 51911784Sarthur.perais@inria.fr 52011784Sarthur.perais@inria.fr if (bi->loopPredValid) { 52111784Sarthur.perais@inria.fr if (bi->tagePred != bi->loopPred) { 52211784Sarthur.perais@inria.fr ctrUpdate(loopUseCounter, (bi->loopPred== taken), 7); 52311784Sarthur.perais@inria.fr } 52411784Sarthur.perais@inria.fr } 52511784Sarthur.perais@inria.fr 52611784Sarthur.perais@inria.fr // TAGE UPDATE 52711784Sarthur.perais@inria.fr // try to allocate a new entries only if prediction was wrong 52811784Sarthur.perais@inria.fr bool longest_match_pred = false; 52911784Sarthur.perais@inria.fr bool alloc = (bi->tagePred != taken) && (bi->hitBank < nHistoryTables); 53011784Sarthur.perais@inria.fr if (bi->hitBank > 0) { 53111784Sarthur.perais@inria.fr // Manage the selection between longest matching and alternate 53211784Sarthur.perais@inria.fr // matching for "pseudo"-newly allocated longest matching entry 53311784Sarthur.perais@inria.fr longest_match_pred = bi->longestMatchPred; 53411784Sarthur.perais@inria.fr bool PseudoNewAlloc = bi->pseudoNewAlloc; 53511784Sarthur.perais@inria.fr // an entry is considered as newly allocated if its prediction 53611784Sarthur.perais@inria.fr // counter is weak 53711784Sarthur.perais@inria.fr if (PseudoNewAlloc) { 53811784Sarthur.perais@inria.fr if (longest_match_pred == taken) { 53911784Sarthur.perais@inria.fr alloc = false; 54011784Sarthur.perais@inria.fr } 54111784Sarthur.perais@inria.fr // if it was delivering the correct prediction, no need to 54211784Sarthur.perais@inria.fr // allocate new entry even if the overall prediction was false 54311784Sarthur.perais@inria.fr if (longest_match_pred != bi->altTaken) { 54411784Sarthur.perais@inria.fr ctrUpdate(useAltPredForNewlyAllocated, 54511784Sarthur.perais@inria.fr bi->altTaken == taken, 4); 54611784Sarthur.perais@inria.fr } 54711784Sarthur.perais@inria.fr } 54811784Sarthur.perais@inria.fr } 54911784Sarthur.perais@inria.fr 55011784Sarthur.perais@inria.fr if (alloc) { 55111784Sarthur.perais@inria.fr // is there some "unuseful" entry to allocate 55211784Sarthur.perais@inria.fr int8_t min = 1; 55311784Sarthur.perais@inria.fr for (int i = nHistoryTables; i > bi->hitBank; i--) { 55411784Sarthur.perais@inria.fr if (gtable[i][bi->tableIndices[i]].u < min) { 55511784Sarthur.perais@inria.fr min = gtable[i][bi->tableIndices[i]].u; 55611784Sarthur.perais@inria.fr } 55711784Sarthur.perais@inria.fr } 55811784Sarthur.perais@inria.fr 55911784Sarthur.perais@inria.fr // we allocate an entry with a longer history 56011784Sarthur.perais@inria.fr // to avoid ping-pong, we do not choose systematically the next 56111784Sarthur.perais@inria.fr // entry, but among the 3 next entries 56211784Sarthur.perais@inria.fr int Y = nrand & 56311784Sarthur.perais@inria.fr ((ULL(1) << (nHistoryTables - bi->hitBank - 1)) - 1); 56411784Sarthur.perais@inria.fr int X = bi->hitBank + 1; 56511784Sarthur.perais@inria.fr if (Y & 1) { 56611784Sarthur.perais@inria.fr X++; 56711784Sarthur.perais@inria.fr if (Y & 2) 56811784Sarthur.perais@inria.fr X++; 56911784Sarthur.perais@inria.fr } 57011784Sarthur.perais@inria.fr // No entry available, forces one to be available 57111784Sarthur.perais@inria.fr if (min > 0) { 57211784Sarthur.perais@inria.fr gtable[X][bi->tableIndices[X]].u = 0; 57311784Sarthur.perais@inria.fr } 57411784Sarthur.perais@inria.fr 57511784Sarthur.perais@inria.fr 57611784Sarthur.perais@inria.fr //Allocate only one entry 57711784Sarthur.perais@inria.fr for (int i = X; i <= nHistoryTables; i++) { 57811784Sarthur.perais@inria.fr if ((gtable[i][bi->tableIndices[i]].u == 0)) { 57911784Sarthur.perais@inria.fr gtable[i][bi->tableIndices[i]].tag = bi->tableTags[i]; 58011784Sarthur.perais@inria.fr gtable[i][bi->tableIndices[i]].ctr = (taken) ? 0 : -1; 58111784Sarthur.perais@inria.fr gtable[i][bi->tableIndices[i]].u = 0; //? 58213433Spau.cabre@metempsy.com break; 58311784Sarthur.perais@inria.fr } 58411784Sarthur.perais@inria.fr } 58511784Sarthur.perais@inria.fr } 58611784Sarthur.perais@inria.fr //periodic reset of u: reset is not complete but bit by bit 58711784Sarthur.perais@inria.fr tCounter++; 58811784Sarthur.perais@inria.fr if ((tCounter & ((ULL(1) << logTick) - 1)) == 0) { 58911784Sarthur.perais@inria.fr // reset least significant bit 59011784Sarthur.perais@inria.fr // most significant bit becomes least significant bit 59111784Sarthur.perais@inria.fr for (int i = 1; i <= nHistoryTables; i++) { 59211784Sarthur.perais@inria.fr for (int j = 0; j < (ULL(1) << tagTableSizes[i]); j++) { 59311784Sarthur.perais@inria.fr gtable[i][j].u = gtable[i][j].u >> 1; 59411784Sarthur.perais@inria.fr } 59511784Sarthur.perais@inria.fr } 59611784Sarthur.perais@inria.fr } 59711784Sarthur.perais@inria.fr 59811784Sarthur.perais@inria.fr if (bi->hitBank > 0) { 59911784Sarthur.perais@inria.fr DPRINTF(LTage, "Updating tag table entry (%d,%d) for branch %lx\n", 60011784Sarthur.perais@inria.fr bi->hitBank, bi->hitBankIndex, branch_pc); 60111784Sarthur.perais@inria.fr ctrUpdate(gtable[bi->hitBank][bi->hitBankIndex].ctr, taken, 60211784Sarthur.perais@inria.fr tagTableCounterBits); 60311784Sarthur.perais@inria.fr // if the provider entry is not certified to be useful also update 60411784Sarthur.perais@inria.fr // the alternate prediction 60511784Sarthur.perais@inria.fr if (gtable[bi->hitBank][bi->hitBankIndex].u == 0) { 60611784Sarthur.perais@inria.fr if (bi->altBank > 0) { 60711784Sarthur.perais@inria.fr ctrUpdate(gtable[bi->altBank][bi->altBankIndex].ctr, taken, 60811784Sarthur.perais@inria.fr tagTableCounterBits); 60911784Sarthur.perais@inria.fr DPRINTF(LTage, "Updating tag table entry (%d,%d) for" 61011784Sarthur.perais@inria.fr " branch %lx\n", bi->hitBank, bi->hitBankIndex, 61111784Sarthur.perais@inria.fr branch_pc); 61211784Sarthur.perais@inria.fr } 61311784Sarthur.perais@inria.fr if (bi->altBank == 0) { 61411784Sarthur.perais@inria.fr baseUpdate(pc, taken, bi); 61511784Sarthur.perais@inria.fr } 61611784Sarthur.perais@inria.fr } 61711784Sarthur.perais@inria.fr 61811784Sarthur.perais@inria.fr // update the u counter 61911784Sarthur.perais@inria.fr if (longest_match_pred != bi->altTaken) { 62011784Sarthur.perais@inria.fr if (longest_match_pred == taken) { 62111784Sarthur.perais@inria.fr if (gtable[bi->hitBank][bi->hitBankIndex].u < 1) { 62211784Sarthur.perais@inria.fr gtable[bi->hitBank][bi->hitBankIndex].u++; 62311784Sarthur.perais@inria.fr } 62411784Sarthur.perais@inria.fr } 62511784Sarthur.perais@inria.fr } 62611784Sarthur.perais@inria.fr } else { 62711784Sarthur.perais@inria.fr baseUpdate(pc, taken, bi); 62811784Sarthur.perais@inria.fr } 62911784Sarthur.perais@inria.fr 63011784Sarthur.perais@inria.fr //END PREDICTOR UPDATE 63111784Sarthur.perais@inria.fr } 63211784Sarthur.perais@inria.fr if (!squashed) { 63311784Sarthur.perais@inria.fr delete bi; 63411784Sarthur.perais@inria.fr } 63511784Sarthur.perais@inria.fr} 63611784Sarthur.perais@inria.fr 63711784Sarthur.perais@inria.frvoid 63811784Sarthur.perais@inria.frLTAGE::updateHistories(ThreadID tid, Addr branch_pc, bool taken, void* b) 63911784Sarthur.perais@inria.fr{ 64011784Sarthur.perais@inria.fr BranchInfo* bi = (BranchInfo*)(b); 64111784Sarthur.perais@inria.fr ThreadHistory& tHist = threadHistory[tid]; 64211784Sarthur.perais@inria.fr // UPDATE HISTORIES 64313413Spau.cabre@metempsy.com bool pathbit = ((branch_pc >> instShiftAmt) & 1); 64411784Sarthur.perais@inria.fr //on a squash, return pointers to this and recompute indices. 64511784Sarthur.perais@inria.fr //update user history 64611784Sarthur.perais@inria.fr updateGHist(tHist.gHist, taken, tHist.globalHistory, tHist.ptGhist); 64711784Sarthur.perais@inria.fr tHist.pathHist = (tHist.pathHist << 1) + pathbit; 64811784Sarthur.perais@inria.fr tHist.pathHist = (tHist.pathHist & ((ULL(1) << 16) - 1)); 64911784Sarthur.perais@inria.fr 65011784Sarthur.perais@inria.fr bi->ptGhist = tHist.ptGhist; 65111784Sarthur.perais@inria.fr bi->pathHist = tHist.pathHist; 65211784Sarthur.perais@inria.fr //prepare next index and tag computations for user branchs 65311784Sarthur.perais@inria.fr for (int i = 1; i <= nHistoryTables; i++) 65411784Sarthur.perais@inria.fr { 65511784Sarthur.perais@inria.fr bi->ci[i] = tHist.computeIndices[i].comp; 65611784Sarthur.perais@inria.fr bi->ct0[i] = tHist.computeTags[0][i].comp; 65711784Sarthur.perais@inria.fr bi->ct1[i] = tHist.computeTags[1][i].comp; 65811784Sarthur.perais@inria.fr tHist.computeIndices[i].update(tHist.gHist); 65911784Sarthur.perais@inria.fr tHist.computeTags[0][i].update(tHist.gHist); 66011784Sarthur.perais@inria.fr tHist.computeTags[1][i].update(tHist.gHist); 66111784Sarthur.perais@inria.fr } 66211784Sarthur.perais@inria.fr DPRINTF(LTage, "Updating global histories with branch:%lx; taken?:%d, " 66311784Sarthur.perais@inria.fr "path Hist: %x; pointer:%d\n", branch_pc, taken, tHist.pathHist, 66411784Sarthur.perais@inria.fr tHist.ptGhist); 66511784Sarthur.perais@inria.fr} 66611784Sarthur.perais@inria.fr 66711784Sarthur.perais@inria.frvoid 66811784Sarthur.perais@inria.frLTAGE::squash(ThreadID tid, bool taken, void *bp_history) 66911784Sarthur.perais@inria.fr{ 67011784Sarthur.perais@inria.fr BranchInfo* bi = (BranchInfo*)(bp_history); 67111784Sarthur.perais@inria.fr ThreadHistory& tHist = threadHistory[tid]; 67211784Sarthur.perais@inria.fr DPRINTF(LTage, "Restoring branch info: %lx; taken? %d; PathHistory:%x, " 67311784Sarthur.perais@inria.fr "pointer:%d\n", bi->branchPC,taken, bi->pathHist, bi->ptGhist); 67411784Sarthur.perais@inria.fr tHist.pathHist = bi->pathHist; 67511784Sarthur.perais@inria.fr tHist.ptGhist = bi->ptGhist; 67611784Sarthur.perais@inria.fr tHist.gHist = &(tHist.globalHistory[tHist.ptGhist]); 67711784Sarthur.perais@inria.fr tHist.gHist[0] = (taken ? 1 : 0); 67811784Sarthur.perais@inria.fr for (int i = 1; i <= nHistoryTables; i++) { 67911784Sarthur.perais@inria.fr tHist.computeIndices[i].comp = bi->ci[i]; 68011784Sarthur.perais@inria.fr tHist.computeTags[0][i].comp = bi->ct0[i]; 68111784Sarthur.perais@inria.fr tHist.computeTags[1][i].comp = bi->ct1[i]; 68211784Sarthur.perais@inria.fr tHist.computeIndices[i].update(tHist.gHist); 68311784Sarthur.perais@inria.fr tHist.computeTags[0][i].update(tHist.gHist); 68411784Sarthur.perais@inria.fr tHist.computeTags[1][i].update(tHist.gHist); 68511784Sarthur.perais@inria.fr } 68611784Sarthur.perais@inria.fr 68711784Sarthur.perais@inria.fr if (bi->condBranch) { 68811784Sarthur.perais@inria.fr if (bi->loopHit >= 0) { 68911784Sarthur.perais@inria.fr int idx = bi->loopIndex + bi->loopHit; 69011784Sarthur.perais@inria.fr ltable[idx].currentIterSpec = bi->currentIter; 69111784Sarthur.perais@inria.fr } 69211784Sarthur.perais@inria.fr } 69311784Sarthur.perais@inria.fr 69411784Sarthur.perais@inria.fr} 69511784Sarthur.perais@inria.fr 69611784Sarthur.perais@inria.frvoid 69711784Sarthur.perais@inria.frLTAGE::squash(ThreadID tid, void *bp_history) 69811784Sarthur.perais@inria.fr{ 69911784Sarthur.perais@inria.fr BranchInfo* bi = (BranchInfo*)(bp_history); 70011784Sarthur.perais@inria.fr DPRINTF(LTage, "Deleting branch info: %lx\n", bi->branchPC); 70111784Sarthur.perais@inria.fr if (bi->condBranch) { 70211784Sarthur.perais@inria.fr if (bi->loopHit >= 0) { 70311784Sarthur.perais@inria.fr int idx = bi->loopIndex + bi->loopHit; 70411784Sarthur.perais@inria.fr ltable[idx].currentIterSpec = bi->currentIter; 70511784Sarthur.perais@inria.fr } 70611784Sarthur.perais@inria.fr } 70711784Sarthur.perais@inria.fr 70811784Sarthur.perais@inria.fr delete bi; 70911784Sarthur.perais@inria.fr} 71011784Sarthur.perais@inria.fr 71111784Sarthur.perais@inria.frbool 71211784Sarthur.perais@inria.frLTAGE::lookup(ThreadID tid, Addr branch_pc, void* &bp_history) 71311784Sarthur.perais@inria.fr{ 71411784Sarthur.perais@inria.fr bool retval = predict(tid, branch_pc, true, bp_history); 71511784Sarthur.perais@inria.fr 71611784Sarthur.perais@inria.fr DPRINTF(LTage, "Lookup branch: %lx; predict:%d\n", branch_pc, retval); 71711784Sarthur.perais@inria.fr updateHistories(tid, branch_pc, retval, bp_history); 71811784Sarthur.perais@inria.fr assert(threadHistory[tid].gHist == 71911784Sarthur.perais@inria.fr &threadHistory[tid].globalHistory[threadHistory[tid].ptGhist]); 72011784Sarthur.perais@inria.fr 72111784Sarthur.perais@inria.fr return retval; 72211784Sarthur.perais@inria.fr} 72311784Sarthur.perais@inria.fr 72411784Sarthur.perais@inria.frvoid 72511784Sarthur.perais@inria.frLTAGE::btbUpdate(ThreadID tid, Addr branch_pc, void* &bp_history) 72611784Sarthur.perais@inria.fr{ 72711784Sarthur.perais@inria.fr BranchInfo* bi = (BranchInfo*) bp_history; 72811784Sarthur.perais@inria.fr ThreadHistory& tHist = threadHistory[tid]; 72911784Sarthur.perais@inria.fr DPRINTF(LTage, "BTB miss resets prediction: %lx\n", branch_pc); 73011784Sarthur.perais@inria.fr assert(tHist.gHist == &tHist.globalHistory[tHist.ptGhist]); 73111784Sarthur.perais@inria.fr tHist.gHist[0] = 0; 73211784Sarthur.perais@inria.fr for (int i = 1; i <= nHistoryTables; i++) { 73311784Sarthur.perais@inria.fr tHist.computeIndices[i].comp = bi->ci[i]; 73411784Sarthur.perais@inria.fr tHist.computeTags[0][i].comp = bi->ct0[i]; 73511784Sarthur.perais@inria.fr tHist.computeTags[1][i].comp = bi->ct1[i]; 73611784Sarthur.perais@inria.fr tHist.computeIndices[i].update(tHist.gHist); 73711784Sarthur.perais@inria.fr tHist.computeTags[0][i].update(tHist.gHist); 73811784Sarthur.perais@inria.fr tHist.computeTags[1][i].update(tHist.gHist); 73911784Sarthur.perais@inria.fr } 74011784Sarthur.perais@inria.fr} 74111784Sarthur.perais@inria.fr 74211784Sarthur.perais@inria.frvoid 74311784Sarthur.perais@inria.frLTAGE::uncondBranch(ThreadID tid, Addr br_pc, void* &bp_history) 74411784Sarthur.perais@inria.fr{ 74511784Sarthur.perais@inria.fr DPRINTF(LTage, "UnConditionalBranch: %lx\n", br_pc); 74611784Sarthur.perais@inria.fr predict(tid, br_pc, false, bp_history); 74711784Sarthur.perais@inria.fr updateHistories(tid, br_pc, true, bp_history); 74811784Sarthur.perais@inria.fr assert(threadHistory[tid].gHist == 74911784Sarthur.perais@inria.fr &threadHistory[tid].globalHistory[threadHistory[tid].ptGhist]); 75011784Sarthur.perais@inria.fr} 75111784Sarthur.perais@inria.fr 75211784Sarthur.perais@inria.frLTAGE* 75311784Sarthur.perais@inria.frLTAGEParams::create() 75411784Sarthur.perais@inria.fr{ 75511784Sarthur.perais@inria.fr return new LTAGE(this); 75611784Sarthur.perais@inria.fr} 757