16184SN/A/* 26184SN/A * Copyright (c) 2004-2006 The Regents of The University of Michigan 36184SN/A * All rights reserved. 46184SN/A * 56184SN/A * Redistribution and use in source and binary forms, with or without 66184SN/A * modification, are permitted provided that the following conditions are 76184SN/A * met: redistributions of source code must retain the above copyright 86184SN/A * notice, this list of conditions and the following disclaimer; 96184SN/A * redistributions in binary form must reproduce the above copyright 106184SN/A * notice, this list of conditions and the following disclaimer in the 116184SN/A * documentation and/or other materials provided with the distribution; 126184SN/A * neither the name of the copyright holders nor the names of its 136184SN/A * contributors may be used to endorse or promote products derived from 146184SN/A * this software without specific prior written permission. 156184SN/A * 166184SN/A * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 176184SN/A * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 186184SN/A * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 196184SN/A * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 206184SN/A * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 216184SN/A * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 226184SN/A * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 236184SN/A * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 246184SN/A * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 256184SN/A * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 266184SN/A * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 276184SN/A * 286184SN/A * Authors: Kevin Lim 296184SN/A */ 306184SN/A 3111793Sbrandon.potter@amd.com#include "cpu/pred/2bit_local.hh" 3211793Sbrandon.potter@amd.com 336184SN/A#include "base/intmath.hh" 3412334Sgabeblack@google.com#include "base/logging.hh" 356184SN/A#include "base/trace.hh" 368232Snate@binkert.org#include "debug/Fetch.hh" 376184SN/A 3810785Sgope@wisc.eduLocalBP::LocalBP(const LocalBPParams *params) 399480Snilay@cs.wisc.edu : BPredUnit(params), 409480Snilay@cs.wisc.edu localPredictorSize(params->localPredictorSize), 4113959Sodanrc@yahoo.com.br localCtrBits(params->localCtrBits), 4213959Sodanrc@yahoo.com.br localPredictorSets(localPredictorSize / localCtrBits), 4313959Sodanrc@yahoo.com.br localCtrs(localPredictorSets, SatCounter(localCtrBits)), 4413959Sodanrc@yahoo.com.br indexMask(localPredictorSets - 1) 456184SN/A{ 466184SN/A if (!isPowerOf2(localPredictorSize)) { 476184SN/A fatal("Invalid local predictor size!\n"); 486184SN/A } 496184SN/A 506184SN/A if (!isPowerOf2(localPredictorSets)) { 516184SN/A fatal("Invalid number of local predictor sets! Check localCtrBits.\n"); 526184SN/A } 536184SN/A 549480Snilay@cs.wisc.edu DPRINTF(Fetch, "index mask: %#x\n", indexMask); 556184SN/A 569480Snilay@cs.wisc.edu DPRINTF(Fetch, "local predictor size: %i\n", 576184SN/A localPredictorSize); 586184SN/A 599480Snilay@cs.wisc.edu DPRINTF(Fetch, "local counter bits: %i\n", localCtrBits); 606184SN/A 619480Snilay@cs.wisc.edu DPRINTF(Fetch, "instruction shift amount: %i\n", 626184SN/A instShiftAmt); 636184SN/A} 646184SN/A 656184SN/Avoid 6611434Smitch.hayenga@arm.comLocalBP::btbUpdate(ThreadID tid, Addr branch_addr, void * &bp_history) 678842Smrinmoy.ghosh@arm.com{ 688842Smrinmoy.ghosh@arm.com// Place holder for a function that is called to update predictor history when 698842Smrinmoy.ghosh@arm.com// a BTB entry is invalid or not found. 708842Smrinmoy.ghosh@arm.com} 718842Smrinmoy.ghosh@arm.com 728842Smrinmoy.ghosh@arm.com 736184SN/Abool 7411434Smitch.hayenga@arm.comLocalBP::lookup(ThreadID tid, Addr branch_addr, void * &bp_history) 756184SN/A{ 766184SN/A bool taken; 776184SN/A unsigned local_predictor_idx = getLocalIndex(branch_addr); 786184SN/A 799480Snilay@cs.wisc.edu DPRINTF(Fetch, "Looking up index %#x\n", 806184SN/A local_predictor_idx); 816184SN/A 8213959Sodanrc@yahoo.com.br uint8_t counter_val = localCtrs[local_predictor_idx]; 836184SN/A 849480Snilay@cs.wisc.edu DPRINTF(Fetch, "prediction is %i.\n", 856184SN/A (int)counter_val); 866184SN/A 876184SN/A taken = getPrediction(counter_val); 886184SN/A 896184SN/A return taken; 906184SN/A} 916184SN/A 926184SN/Avoid 9311434Smitch.hayenga@arm.comLocalBP::update(ThreadID tid, Addr branch_addr, bool taken, void *bp_history, 9413626Sjairo.balart@metempsy.com bool squashed, const StaticInstPtr & inst, Addr corrTarget) 956184SN/A{ 966184SN/A assert(bp_history == NULL); 976184SN/A unsigned local_predictor_idx; 986184SN/A 9911783Sarthur.perais@inria.fr // No state to restore, and we do not update on the wrong 10011783Sarthur.perais@inria.fr // path. 10111783Sarthur.perais@inria.fr if (squashed) { 10211783Sarthur.perais@inria.fr return; 10311783Sarthur.perais@inria.fr } 10411783Sarthur.perais@inria.fr 1056184SN/A // Update the local predictor. 1066184SN/A local_predictor_idx = getLocalIndex(branch_addr); 1076184SN/A 1089480Snilay@cs.wisc.edu DPRINTF(Fetch, "Looking up index %#x\n", local_predictor_idx); 1096184SN/A 1106184SN/A if (taken) { 1119480Snilay@cs.wisc.edu DPRINTF(Fetch, "Branch updated as taken.\n"); 11213959Sodanrc@yahoo.com.br localCtrs[local_predictor_idx]++; 1136184SN/A } else { 1149480Snilay@cs.wisc.edu DPRINTF(Fetch, "Branch updated as not taken.\n"); 11513959Sodanrc@yahoo.com.br localCtrs[local_predictor_idx]--; 1166184SN/A } 1176184SN/A} 1186184SN/A 1196184SN/Ainline 1206184SN/Abool 1216184SN/ALocalBP::getPrediction(uint8_t &count) 1226184SN/A{ 1236184SN/A // Get the MSB of the count 1246184SN/A return (count >> (localCtrBits - 1)); 1256184SN/A} 1266184SN/A 1276184SN/Ainline 1286184SN/Aunsigned 1296184SN/ALocalBP::getLocalIndex(Addr &branch_addr) 1306184SN/A{ 1316184SN/A return (branch_addr >> instShiftAmt) & indexMask; 1326184SN/A} 1339480Snilay@cs.wisc.edu 1349480Snilay@cs.wisc.eduvoid 13511434Smitch.hayenga@arm.comLocalBP::uncondBranch(ThreadID tid, Addr pc, void *&bp_history) 1369480Snilay@cs.wisc.edu{ 1379480Snilay@cs.wisc.edu} 13810785Sgope@wisc.edu 13910785Sgope@wisc.eduLocalBP* 14010785Sgope@wisc.eduLocalBPParams::create() 14110785Sgope@wisc.edu{ 14210785Sgope@wisc.edu return new LocalBP(this); 14310785Sgope@wisc.edu} 144