gem5/cpu/o3/tournament_pred.cc
Kevin Lim a8b03e4d01 Updates for O3 model.
arch/alpha/isa/decoder.isa:
    Make IPR accessing instructions serializing so they are not issued incorrectly in the O3 model.
arch/alpha/isa/pal.isa:
    Allow IPR instructions to have flags.
base/traceflags.py:
    Include new trace flags from the two new CPU models.
cpu/SConscript:
    Create the templates for the split mem accessor methods.  Also include the new files from the new models (the Ozone model will be checked in next).
cpu/base_dyn_inst.cc:
cpu/base_dyn_inst.hh:
    Update to the BaseDynInst for the new models.

--HG--
extra : convert_revision : cc82db9c72ec3e29cea4c3fdff74a3843e287a35
2006-04-22 18:26:48 -04:00

255 lines
8.9 KiB
C++

/*
* Copyright (c) 2004-2005 The Regents of The University of Michigan
* 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.
*/
#include "cpu/o3/tournament_pred.hh"
TournamentBP::TournamentBP(unsigned _localPredictorSize,
unsigned _localCtrBits,
unsigned _localHistoryTableSize,
unsigned _localHistoryBits,
unsigned _globalPredictorSize,
unsigned _globalCtrBits,
unsigned _globalHistoryBits,
unsigned _choicePredictorSize,
unsigned _choiceCtrBits,
unsigned _instShiftAmt)
: localPredictorSize(_localPredictorSize),
localCtrBits(_localCtrBits),
localHistoryTableSize(_localHistoryTableSize),
localHistoryBits(_localHistoryBits),
globalPredictorSize(_globalPredictorSize),
globalCtrBits(_globalCtrBits),
globalHistoryBits(_globalHistoryBits),
choicePredictorSize(_globalPredictorSize),
choiceCtrBits(_choiceCtrBits),
instShiftAmt(_instShiftAmt)
{
//Should do checks here to make sure sizes are correct (powers of 2)
//Setup the array of counters for the local predictor
localCtrs.resize(localPredictorSize);
for (int i = 0; i < localPredictorSize; ++i)
localCtrs[i].setBits(localCtrBits);
//Setup the history table for the local table
localHistoryTable.resize(localHistoryTableSize);
for (int i = 0; i < localHistoryTableSize; ++i)
localHistoryTable[i] = 0;
// Setup the local history mask
localHistoryMask = (1 << localHistoryBits) - 1;
//Setup the array of counters for the global predictor
globalCtrs.resize(globalPredictorSize);
for (int i = 0; i < globalPredictorSize; ++i)
globalCtrs[i].setBits(globalCtrBits);
//Clear the global history
globalHistory = 0;
// Setup the global history mask
globalHistoryMask = (1 << globalHistoryBits) - 1;
//Setup the array of counters for the choice predictor
choiceCtrs.resize(choicePredictorSize);
for (int i = 0; i < choicePredictorSize; ++i)
choiceCtrs[i].setBits(choiceCtrBits);
threshold = (1 << (localCtrBits - 1)) - 1;
threshold = threshold / 2;
}
inline
unsigned
TournamentBP::calcLocHistIdx(Addr &branch_addr)
{
return (branch_addr >> instShiftAmt) & (localHistoryTableSize - 1);
}
inline
void
TournamentBP::updateHistoriesTaken(unsigned local_history_idx)
{
globalHistory = (globalHistory << 1) | 1;
globalHistory = globalHistory & globalHistoryMask;
localHistoryTable[local_history_idx] =
(localHistoryTable[local_history_idx] << 1) | 1;
}
inline
void
TournamentBP::updateHistoriesNotTaken(unsigned local_history_idx)
{
globalHistory = (globalHistory << 1);
globalHistory = globalHistory & globalHistoryMask;
localHistoryTable[local_history_idx] =
(localHistoryTable[local_history_idx] << 1);
}
bool
TournamentBP::lookup(Addr &branch_addr)
{
uint8_t local_prediction;
unsigned local_history_idx;
unsigned local_predictor_idx;
uint8_t global_prediction;
uint8_t choice_prediction;
//Lookup in the local predictor to get its branch prediction
local_history_idx = calcLocHistIdx(branch_addr);
local_predictor_idx = localHistoryTable[local_history_idx]
& localHistoryMask;
local_prediction = localCtrs[local_predictor_idx].read();
//Lookup in the global predictor to get its branch prediction
global_prediction = globalCtrs[globalHistory].read();
//Lookup in the choice predictor to see which one to use
choice_prediction = choiceCtrs[globalHistory].read();
//@todo Put a threshold value in for the three predictors that can
// be set through the constructor (so this isn't hard coded).
//Also should put some of this code into functions.
if (choice_prediction > threshold) {
if (global_prediction > threshold) {
updateHistoriesTaken(local_history_idx);
assert(globalHistory < globalPredictorSize &&
local_history_idx < localPredictorSize);
globalCtrs[globalHistory].increment();
localCtrs[local_history_idx].increment();
return true;
} else {
updateHistoriesNotTaken(local_history_idx);
assert(globalHistory < globalPredictorSize &&
local_history_idx < localPredictorSize);
globalCtrs[globalHistory].decrement();
localCtrs[local_history_idx].decrement();
return false;
}
} else {
if (local_prediction > threshold) {
updateHistoriesTaken(local_history_idx);
assert(globalHistory < globalPredictorSize &&
local_history_idx < localPredictorSize);
globalCtrs[globalHistory].increment();
localCtrs[local_history_idx].increment();
return true;
} else {
updateHistoriesNotTaken(local_history_idx);
assert(globalHistory < globalPredictorSize &&
local_history_idx < localPredictorSize);
globalCtrs[globalHistory].decrement();
localCtrs[local_history_idx].decrement();
return false;
}
}
}
// Update the branch predictor if it predicted a branch wrong.
void
TournamentBP::update(Addr &branch_addr, unsigned correct_gh, bool taken)
{
uint8_t local_prediction;
unsigned local_history_idx;
unsigned local_predictor_idx;
bool local_pred_taken;
uint8_t global_prediction;
bool global_pred_taken;
// Load the correct global history into the register.
globalHistory = correct_gh;
// Get the local predictor's current prediction, remove the incorrect
// update, and update the local predictor
local_history_idx = calcLocHistIdx(branch_addr);
local_predictor_idx = localHistoryTable[local_history_idx];
local_predictor_idx = (local_predictor_idx >> 1) & localHistoryMask;
local_prediction = localCtrs[local_predictor_idx].read();
local_pred_taken = local_prediction > threshold;
//Get the global predictor's current prediction, and update the
//global predictor
global_prediction = globalCtrs[globalHistory].read();
global_pred_taken = global_prediction > threshold;
//Update the choice predictor to tell it which one was correct
if (local_pred_taken != global_pred_taken) {
//If the local prediction matches the actual outcome, decerement
//the counter. Otherwise increment the counter.
if (local_pred_taken == taken) {
choiceCtrs[globalHistory].decrement();
} else {
choiceCtrs[globalHistory].increment();
}
}
if (taken) {
assert(globalHistory < globalPredictorSize &&
local_predictor_idx < localPredictorSize);
localCtrs[local_predictor_idx].increment();
globalCtrs[globalHistory].increment();
globalHistory = (globalHistory << 1) | 1;
globalHistory = globalHistory & globalHistoryMask;
localHistoryTable[local_history_idx] |= 1;
} else {
assert(globalHistory < globalPredictorSize &&
local_predictor_idx < localPredictorSize);
localCtrs[local_predictor_idx].decrement();
globalCtrs[globalHistory].decrement();
globalHistory = (globalHistory << 1);
globalHistory = globalHistory & globalHistoryMask;
localHistoryTable[local_history_idx] &= ~1;
}
}