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/*
* Copyright (c) 2003-2005 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: Erik Hallnor
* Ron Dreslinski
*/
/**
* @file
* Declaration of a simple coherence policy.
*/
#ifndef __SIMPLE_COHERENCE_HH__
#define __SIMPLE_COHERENCE_HH__
#include <string>
#include "mem/packet.hh"
#include "mem/cache/cache_blk.hh"
#include "mem/cache/miss/mshr_queue.hh"
#include "mem/cache/coherence/coherence_protocol.hh"
class BaseCache;
/**
* A simple MP coherence policy. This policy assumes an atomic bus and only one
* level of cache.
*/
class SimpleCoherence
{
protected:
/** Pointer to the parent cache. */
BaseCache *cache;
/** Pointer to the coherence protocol. */
CoherenceProtocol *protocol;
public:
/**
* Construct and initialize this coherence policy.
* @param _protocol The coherence protocol to use.
*/
SimpleCoherence(CoherenceProtocol *_protocol)
: protocol(_protocol)
{
}
/**
* Set the pointer to the parent cache.
* @param _cache The parent cache.
*/
void setCache(BaseCache *_cache)
{
cache = _cache;
}
/**
* Register statistics.
* @param name The name to prepend to stat descriptions.
*/
void regStats(const std::string &name)
{
}
/**
* This policy does not forward invalidates, return NULL.
* @return NULL.
*/
Packet * getPacket()
{
return NULL;
}
/**
* Return the proper state given the current state and the bus response.
* @param req The bus response.
* @param current The current block state.
* @return The new state.
*/
CacheBlk::State getNewState(Packet * &pkt, CacheBlk::State current)
{
return protocol->getNewState(pkt, current);
}
/**
* Handle snooped bus requests.
* @param req The snooped bus request.
* @param blk The cache block corresponding to the request, if any.
* @param mshr The MSHR corresponding to the request, if any.
* @param new_state Return the new state for the block.
*/
bool handleBusRequest(Packet * &pkt, CacheBlk *blk, MSHR *mshr,
CacheBlk::State &new_state)
{
// assert(mshr == NULL);
//Got rid of, there could be an MSHR, but it can't be in service
if (blk != NULL)
{
if (pkt->cmd != Packet::Writeback) {
return protocol->handleBusRequest(cache, pkt, blk, mshr,
new_state);
}
else { //It is a writeback, must be ownership protocol, just keep state
new_state = blk->status;
}
}
return false;
}
/**
* Get the proper bus command for the given command and status.
* @param cmd The request's command.
* @param state The current state of the cache block.
* @return The proper bus command, as determined by the protocol.
*/
Packet::Command getBusCmd(Packet::Command &cmd, CacheBlk::State state)
{
if (cmd == Packet::Writeback) return Packet::Writeback;
return protocol->getBusCmd(cmd, state);
}
/**
* Return true if this coherence policy can handle fast cache writes.
*/
bool allowFastWrites() { return false; }
bool hasProtocol() { return true; }
};
#endif //__SIMPLE_COHERENCE_HH__
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