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/*
* Copyright (c) 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.
*
* Authors: Ron Dreslinski
* Steve Reinhardt
*/
/**
* @file
* Stride Prefetcher template instantiations.
*/
#include "base/trace.hh"
#include "mem/cache/prefetch/stride.hh"
void
StridePrefetcher::calculatePrefetch(PacketPtr &pkt, std::list<Addr> &addresses,
std::list<Tick> &delays)
{
if (!pkt->req->hasPC()) {
DPRINTF(HWPrefetch, "ignoring request with no PC");
return;
}
if (useContextId && !pkt->req->hasContextId()) {
DPRINTF(HWPrefetch, "ignoring request with no context ID");
return;
}
Addr blk_addr = pkt->getAddr() & ~(Addr)(blkSize-1);
int ctx_id = useContextId ? pkt->req->contextId() : 0;
Addr pc = pkt->req->getPC();
assert(ctx_id < Max_Contexts);
std::list<StrideEntry*> &tab = table[ctx_id];
/* Scan Table for instAddr Match */
std::list<StrideEntry*>::iterator iter;
for (iter = tab.begin(); iter != tab.end(); iter++) {
if ((*iter)->instAddr == pc)
break;
}
if (iter != tab.end()) {
// Hit in table
int new_stride = blk_addr - (*iter)->missAddr;
bool stride_match = (new_stride == (*iter)->stride);
if (stride_match && new_stride != 0) {
if ((*iter)->confidence < Max_Conf)
(*iter)->confidence++;
} else {
(*iter)->stride = new_stride;
if ((*iter)->confidence > Min_Conf)
(*iter)->confidence = 0;
}
DPRINTF(HWPrefetch, "hit: PC %x blk_addr %x stride %d (%s), conf %d\n",
pc, blk_addr, new_stride, stride_match ? "match" : "change",
(*iter)->confidence);
(*iter)->missAddr = blk_addr;
if ((*iter)->confidence <= 0)
return;
for (int d = 1; d <= degree; d++) {
Addr new_addr = blk_addr + d * new_stride;
if (pageStop && !samePage(blk_addr, new_addr)) {
// Spanned the page, so now stop
pfSpanPage += degree - d + 1;
return;
} else {
DPRINTF(HWPrefetch, " queuing prefetch to %x @ %d\n",
new_addr, latency);
addresses.push_back(new_addr);
delays.push_back(latency);
}
}
} else {
// Miss in table
// Find lowest confidence and replace
DPRINTF(HWPrefetch, "miss: PC %x blk_addr %x\n", pc, blk_addr);
if (tab.size() >= 256) { //set default table size is 256
std::list<StrideEntry*>::iterator min_pos = tab.begin();
int min_conf = (*min_pos)->confidence;
for (iter = min_pos, ++iter; iter != tab.end(); ++iter) {
if ((*iter)->confidence < min_conf){
min_pos = iter;
min_conf = (*iter)->confidence;
}
}
DPRINTF(HWPrefetch, " replacing PC %x\n", (*min_pos)->instAddr);
tab.erase(min_pos);
}
StrideEntry *new_entry = new StrideEntry;
new_entry->instAddr = pc;
new_entry->missAddr = blk_addr;
new_entry->stride = 0;
new_entry->confidence = 0;
tab.push_back(new_entry);
}
}
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