444cbe6250
Encapsulate all branch-prediction-related files in a branch_prediction namespace. This will allow these files to be renamed to drop the BP suffix. Issued-on: https://gem5.atlassian.net/browse/GEM5-982 Change-Id: I640c0caa846a3aade6fae95e9a93e4318ae9fca0 Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br> Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47303 Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu> Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu> Tested-by: kokoro <noreply+kokoro@google.com>
145 lines
4.3 KiB
C++
145 lines
4.3 KiB
C++
/*
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* Copyright (c) 2004-2006 The Regents of The University of Michigan
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are
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* met: redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer;
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* redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution;
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* neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "cpu/pred/2bit_local.hh"
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#include "base/intmath.hh"
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#include "base/logging.hh"
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#include "base/trace.hh"
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#include "debug/Fetch.hh"
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namespace gem5
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{
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namespace branch_prediction
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{
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LocalBP::LocalBP(const LocalBPParams ¶ms)
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: BPredUnit(params),
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localPredictorSize(params.localPredictorSize),
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localCtrBits(params.localCtrBits),
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localPredictorSets(localPredictorSize / localCtrBits),
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localCtrs(localPredictorSets, SatCounter8(localCtrBits)),
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indexMask(localPredictorSets - 1)
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{
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if (!isPowerOf2(localPredictorSize)) {
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fatal("Invalid local predictor size!\n");
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}
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if (!isPowerOf2(localPredictorSets)) {
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fatal("Invalid number of local predictor sets! Check localCtrBits.\n");
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}
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DPRINTF(Fetch, "index mask: %#x\n", indexMask);
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DPRINTF(Fetch, "local predictor size: %i\n",
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localPredictorSize);
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DPRINTF(Fetch, "local counter bits: %i\n", localCtrBits);
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DPRINTF(Fetch, "instruction shift amount: %i\n",
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instShiftAmt);
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}
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void
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LocalBP::btbUpdate(ThreadID tid, Addr branch_addr, void * &bp_history)
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{
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// Place holder for a function that is called to update predictor history when
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// a BTB entry is invalid or not found.
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}
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bool
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LocalBP::lookup(ThreadID tid, Addr branch_addr, void * &bp_history)
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{
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bool taken;
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unsigned local_predictor_idx = getLocalIndex(branch_addr);
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DPRINTF(Fetch, "Looking up index %#x\n",
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local_predictor_idx);
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uint8_t counter_val = localCtrs[local_predictor_idx];
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DPRINTF(Fetch, "prediction is %i.\n",
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(int)counter_val);
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taken = getPrediction(counter_val);
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return taken;
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}
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void
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LocalBP::update(ThreadID tid, Addr branch_addr, bool taken, void *bp_history,
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bool squashed, const StaticInstPtr & inst, Addr corrTarget)
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{
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assert(bp_history == NULL);
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unsigned local_predictor_idx;
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// No state to restore, and we do not update on the wrong
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// path.
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if (squashed) {
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return;
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}
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// Update the local predictor.
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local_predictor_idx = getLocalIndex(branch_addr);
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DPRINTF(Fetch, "Looking up index %#x\n", local_predictor_idx);
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if (taken) {
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DPRINTF(Fetch, "Branch updated as taken.\n");
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localCtrs[local_predictor_idx]++;
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} else {
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DPRINTF(Fetch, "Branch updated as not taken.\n");
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localCtrs[local_predictor_idx]--;
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}
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}
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inline
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bool
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LocalBP::getPrediction(uint8_t &count)
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{
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// Get the MSB of the count
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return (count >> (localCtrBits - 1));
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}
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inline
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unsigned
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LocalBP::getLocalIndex(Addr &branch_addr)
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{
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return (branch_addr >> instShiftAmt) & indexMask;
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}
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void
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LocalBP::uncondBranch(ThreadID tid, Addr pc, void *&bp_history)
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{
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}
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} // namespace branch_prediction
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} // namespace gem5
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