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/*
* Copyright (c) 2011 Google
* 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: Gabe Black
*/
#ifndef __CPU_DECODE_CACHE_HH__
#define __CPU_DECODE_CACHE_HH__
#include <unordered_map>
#include "arch/isa_traits.hh"
#include "arch/types.hh"
#include "config/the_isa.hh"
#include "cpu/static_inst_fwd.hh"
namespace TheISA
{
class Decoder;
}
namespace DecodeCache
{
/// Hash for decoded instructions.
typedef std::unordered_map<TheISA::ExtMachInst, StaticInstPtr> InstMap;
/// A sparse map from an Addr to a Value, stored in page chunks.
template<class Value>
class AddrMap
{
protected:
// A pages worth of cache entries.
struct CachePage {
Value items[TheISA::PageBytes];
};
// A map of cache pages which allows a sparse mapping.
typedef typename std::unordered_map<Addr, CachePage *> PageMap;
typedef typename PageMap::iterator PageIt;
// Mini cache of recent lookups.
PageIt recent[2];
PageMap pageMap;
/// Update the mini cache of recent lookups.
/// @param recentest The most recent result;
void
update(PageIt recentest)
{
recent[1] = recent[0];
recent[0] = recentest;
}
/// Attempt to find the CacheePage which goes with a particular
/// address. First check the small cache of recent results, then
/// actually look in the hash map.
/// @param addr The address to look up.
CachePage *
getPage(Addr addr)
{
Addr page_addr = addr & ~(TheISA::PageBytes - 1);
// Check against recent lookups.
if (recent[0] != pageMap.end()) {
if (recent[0]->first == page_addr)
return recent[0]->second;
if (recent[1] != pageMap.end() &&
recent[1]->first == page_addr) {
update(recent[1]);
// recent[1] has just become recent[0].
return recent[0]->second;
}
}
// Actually look in the has_map.
PageIt it = pageMap.find(page_addr);
if (it != pageMap.end()) {
update(it);
return it->second;
}
// Didn't find an existing page, so add a new one.
CachePage *newPage = new CachePage;
page_addr = page_addr & ~(TheISA::PageBytes - 1);
typename PageMap::value_type to_insert(page_addr, newPage);
update(pageMap.insert(to_insert).first);
return newPage;
}
public:
/// Constructor
AddrMap()
{
recent[0] = recent[1] = pageMap.end();
}
Value &
lookup(Addr addr)
{
CachePage *page = getPage(addr);
return page->items[addr & (TheISA::PageBytes - 1)];
}
};
} // namespace DecodeCache
#endif // __CPU_DECODE_CACHE_HH__
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