gem5/src/cpu/o3/store_set.cc
Ali Saidi b6203360ef LSQ: Set store predictor to periodically clear itself as recommended in the storesets paper.
This patch improves performance by as much as 10% on some spec benchmarks.
2011-08-19 15:08:07 -05:00

367 lines
9.6 KiB
C++

/*
* Copyright (c) 2004-2006 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
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* redistributions in binary form must reproduce the above copyright
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* 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
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*
* Authors: Kevin Lim
*/
#include "base/intmath.hh"
#include "base/misc.hh"
#include "base/trace.hh"
#include "cpu/o3/store_set.hh"
#include "debug/StoreSet.hh"
StoreSet::StoreSet(uint64_t clear_period, int _SSIT_size, int _LFST_size)
: clearPeriod(clear_period), SSITSize(_SSIT_size), LFSTSize(_LFST_size)
{
DPRINTF(StoreSet, "StoreSet: Creating store set object.\n");
DPRINTF(StoreSet, "StoreSet: SSIT size: %i, LFST size: %i.\n",
SSITSize, LFSTSize);
if (!isPowerOf2(SSITSize)) {
fatal("Invalid SSIT size!\n");
}
SSIT.resize(SSITSize);
validSSIT.resize(SSITSize);
for (int i = 0; i < SSITSize; ++i)
validSSIT[i] = false;
if (!isPowerOf2(LFSTSize)) {
fatal("Invalid LFST size!\n");
}
LFST.resize(LFSTSize);
validLFST.resize(LFSTSize);
for (int i = 0; i < LFSTSize; ++i) {
validLFST[i] = false;
LFST[i] = 0;
}
indexMask = SSITSize - 1;
offsetBits = 2;
memOpsPred = 0;
}
StoreSet::~StoreSet()
{
}
void
StoreSet::init(uint64_t clear_period, int _SSIT_size, int _LFST_size)
{
SSITSize = _SSIT_size;
LFSTSize = _LFST_size;
clearPeriod = clear_period;
DPRINTF(StoreSet, "StoreSet: Creating store set object.\n");
DPRINTF(StoreSet, "StoreSet: SSIT size: %i, LFST size: %i.\n",
SSITSize, LFSTSize);
SSIT.resize(SSITSize);
validSSIT.resize(SSITSize);
for (int i = 0; i < SSITSize; ++i)
validSSIT[i] = false;
LFST.resize(LFSTSize);
validLFST.resize(LFSTSize);
for (int i = 0; i < LFSTSize; ++i) {
validLFST[i] = false;
LFST[i] = 0;
}
indexMask = SSITSize - 1;
offsetBits = 2;
memOpsPred = 0;
}
void
StoreSet::violation(Addr store_PC, Addr load_PC)
{
int load_index = calcIndex(load_PC);
int store_index = calcIndex(store_PC);
assert(load_index < SSITSize && store_index < SSITSize);
bool valid_load_SSID = validSSIT[load_index];
bool valid_store_SSID = validSSIT[store_index];
if (!valid_load_SSID && !valid_store_SSID) {
// Calculate a new SSID here.
SSID new_set = calcSSID(load_PC);
validSSIT[load_index] = true;
SSIT[load_index] = new_set;
validSSIT[store_index] = true;
SSIT[store_index] = new_set;
assert(new_set < LFSTSize);
DPRINTF(StoreSet, "StoreSet: Neither load nor store had a valid "
"storeset, creating a new one: %i for load %#x, store %#x\n",
new_set, load_PC, store_PC);
} else if (valid_load_SSID && !valid_store_SSID) {
SSID load_SSID = SSIT[load_index];
validSSIT[store_index] = true;
SSIT[store_index] = load_SSID;
assert(load_SSID < LFSTSize);
DPRINTF(StoreSet, "StoreSet: Load had a valid store set. Adding "
"store to that set: %i for load %#x, store %#x\n",
load_SSID, load_PC, store_PC);
} else if (!valid_load_SSID && valid_store_SSID) {
SSID store_SSID = SSIT[store_index];
validSSIT[load_index] = true;
SSIT[load_index] = store_SSID;
DPRINTF(StoreSet, "StoreSet: Store had a valid store set: %i for "
"load %#x, store %#x\n",
store_SSID, load_PC, store_PC);
} else {
SSID load_SSID = SSIT[load_index];
SSID store_SSID = SSIT[store_index];
assert(load_SSID < LFSTSize && store_SSID < LFSTSize);
// The store set with the lower number wins
if (store_SSID > load_SSID) {
SSIT[store_index] = load_SSID;
DPRINTF(StoreSet, "StoreSet: Load had smaller store set: %i; "
"for load %#x, store %#x\n",
load_SSID, load_PC, store_PC);
} else {
SSIT[load_index] = store_SSID;
DPRINTF(StoreSet, "StoreSet: Store had smaller store set: %i; "
"for load %#x, store %#x\n",
store_SSID, load_PC, store_PC);
}
}
}
void
StoreSet::checkClear()
{
memOpsPred++;
if (memOpsPred > clearPeriod) {
DPRINTF(StoreSet, "Wiping predictor state beacuse %d ld/st executed\n",
clearPeriod);
memOpsPred = 0;
clear();
}
}
void
StoreSet::insertLoad(Addr load_PC, InstSeqNum load_seq_num)
{
checkClear();
// Does nothing.
return;
}
void
StoreSet::insertStore(Addr store_PC, InstSeqNum store_seq_num, ThreadID tid)
{
int index = calcIndex(store_PC);
int store_SSID;
checkClear();
assert(index < SSITSize);
if (!validSSIT[index]) {
// Do nothing if there's no valid entry.
return;
} else {
store_SSID = SSIT[index];
assert(store_SSID < LFSTSize);
// Update the last store that was fetched with the current one.
LFST[store_SSID] = store_seq_num;
validLFST[store_SSID] = 1;
storeList[store_seq_num] = store_SSID;
DPRINTF(StoreSet, "Store %#x updated the LFST, SSID: %i\n",
store_PC, store_SSID);
}
}
InstSeqNum
StoreSet::checkInst(Addr PC)
{
int index = calcIndex(PC);
int inst_SSID;
assert(index < SSITSize);
if (!validSSIT[index]) {
DPRINTF(StoreSet, "Inst %#x with index %i had no SSID\n",
PC, index);
// Return 0 if there's no valid entry.
return 0;
} else {
inst_SSID = SSIT[index];
assert(inst_SSID < LFSTSize);
if (!validLFST[inst_SSID]) {
DPRINTF(StoreSet, "Inst %#x with index %i and SSID %i had no "
"dependency\n", PC, index, inst_SSID);
return 0;
} else {
DPRINTF(StoreSet, "Inst %#x with index %i and SSID %i had LFST "
"inum of %i\n", PC, index, inst_SSID, LFST[inst_SSID]);
return LFST[inst_SSID];
}
}
}
void
StoreSet::issued(Addr issued_PC, InstSeqNum issued_seq_num, bool is_store)
{
// This only is updated upon a store being issued.
if (!is_store) {
return;
}
int index = calcIndex(issued_PC);
int store_SSID;
assert(index < SSITSize);
SeqNumMapIt store_list_it = storeList.find(issued_seq_num);
if (store_list_it != storeList.end()) {
storeList.erase(store_list_it);
}
// Make sure the SSIT still has a valid entry for the issued store.
if (!validSSIT[index]) {
return;
}
store_SSID = SSIT[index];
assert(store_SSID < LFSTSize);
// If the last fetched store in the store set refers to the store that
// was just issued, then invalidate the entry.
if (validLFST[store_SSID] && LFST[store_SSID] == issued_seq_num) {
DPRINTF(StoreSet, "StoreSet: store invalidated itself in LFST.\n");
validLFST[store_SSID] = false;
}
}
void
StoreSet::squash(InstSeqNum squashed_num, ThreadID tid)
{
DPRINTF(StoreSet, "StoreSet: Squashing until inum %i\n",
squashed_num);
int idx;
SeqNumMapIt store_list_it = storeList.begin();
//@todo:Fix to only delete from correct thread
while (!storeList.empty()) {
idx = (*store_list_it).second;
if ((*store_list_it).first <= squashed_num) {
break;
}
bool younger = LFST[idx] > squashed_num;
if (validLFST[idx] && younger) {
DPRINTF(StoreSet, "Squashed [sn:%lli]\n", LFST[idx]);
validLFST[idx] = false;
storeList.erase(store_list_it++);
} else if (!validLFST[idx] && younger) {
storeList.erase(store_list_it++);
}
}
}
void
StoreSet::clear()
{
for (int i = 0; i < SSITSize; ++i) {
validSSIT[i] = false;
}
for (int i = 0; i < LFSTSize; ++i) {
validLFST[i] = false;
}
storeList.clear();
}
void
StoreSet::dump()
{
cprintf("storeList.size(): %i\n", storeList.size());
SeqNumMapIt store_list_it = storeList.begin();
int num = 0;
while (store_list_it != storeList.end()) {
cprintf("%i: [sn:%lli] SSID:%i\n",
num, (*store_list_it).first, (*store_list_it).second);
num++;
store_list_it++;
}
}