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/*
* Copyright (c) 2014 The University of Wisconsin
*
* Copyright (c) 2006 INRIA (Institut National de Recherche en
* Informatique et en Automatique / French National Research Institute
* for Computer Science and Applied Mathematics)
*
* 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: Vignyan Reddy, Dibakar Gope and Arthur Perais,
* from André Seznec's code.
*/
/* @file
* Implementation of a L-TAGE branch predictor
*/
#include "cpu/pred/ltage.hh"
#include "base/intmath.hh"
#include "base/logging.hh"
#include "base/random.hh"
#include "base/trace.hh"
#include "debug/Fetch.hh"
#include "debug/LTage.hh"
LTAGE::LTAGE(const LTAGEParams *params)
: TAGE(params), loopPredictor(params->loop_predictor)
{
}
void
LTAGE::init()
{
TAGE::init();
}
//prediction
bool
LTAGE::predict(ThreadID tid, Addr branch_pc, bool cond_branch, void* &b)
{
LTageBranchInfo *bi = new LTageBranchInfo(*tage, *loopPredictor);
b = (void*)(bi);
bool pred_taken = tage->tagePredict(tid, branch_pc, cond_branch,
bi->tageBranchInfo);
pred_taken = loopPredictor->loopPredict(tid, branch_pc, cond_branch,
bi->lpBranchInfo, pred_taken,
instShiftAmt);
if (cond_branch) {
if (bi->lpBranchInfo->loopPredUsed) {
bi->tageBranchInfo->provider = LOOP;
}
DPRINTF(LTage, "Predict for %lx: taken?:%d, loopTaken?:%d, "
"loopValid?:%d, loopUseCounter:%d, tagePred:%d, altPred:%d\n",
branch_pc, pred_taken, bi->lpBranchInfo->loopPred,
bi->lpBranchInfo->loopPredValid,
loopPredictor->getLoopUseCounter(),
bi->tageBranchInfo->tagePred, bi->tageBranchInfo->altTaken);
}
// record final prediction
bi->lpBranchInfo->predTaken = pred_taken;
return pred_taken;
}
// PREDICTOR UPDATE
void
LTAGE::update(ThreadID tid, Addr branch_pc, bool taken, void* bp_history,
bool squashed, const StaticInstPtr & inst, Addr corrTarget)
{
assert(bp_history);
LTageBranchInfo* bi = static_cast<LTageBranchInfo*>(bp_history);
assert(corrTarget != MaxAddr);
if (squashed) {
if (tage->isSpeculativeUpdateEnabled()) {
// This restores the global history, then update it
// and recomputes the folded histories.
tage->squash(tid, taken, bi->tageBranchInfo, corrTarget);
if (bi->tageBranchInfo->condBranch) {
loopPredictor->squashLoop(bi->lpBranchInfo);
}
}
return;
}
int nrand = random_mt.random<int>() & 3;
if (bi->tageBranchInfo->condBranch) {
DPRINTF(LTage, "Updating tables for branch:%lx; taken?:%d\n",
branch_pc, taken);
tage->updateStats(taken, bi->tageBranchInfo);
loopPredictor->updateStats(taken, bi->lpBranchInfo);
loopPredictor->condBranchUpdate(tid, branch_pc, taken,
bi->tageBranchInfo->tagePred, bi->lpBranchInfo, instShiftAmt);
tage->condBranchUpdate(tid, branch_pc, taken, bi->tageBranchInfo,
nrand, corrTarget, bi->lpBranchInfo->predTaken);
}
tage->updateHistories(tid, branch_pc, taken, bi->tageBranchInfo, false,
inst, corrTarget);
delete bi;
}
void
LTAGE::squash(ThreadID tid, void *bp_history)
{
LTageBranchInfo* bi = (LTageBranchInfo*)(bp_history);
if (bi->tageBranchInfo->condBranch) {
loopPredictor->squash(tid, bi->lpBranchInfo);
}
TAGE::squash(tid, bp_history);
}
void
LTAGE::regStats()
{
TAGE::regStats();
}
LTAGE*
LTAGEParams::create()
{
return new LTAGE(this);
}
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