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/*
* Copyright (c) 2018-2019 Inria
* 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: Daniel Carvalho
*/
/** @file
* Implementation of a dictionary based cache compressor.
*/
#ifndef __MEM_CACHE_COMPRESSORS_DICTIONARY_COMPRESSOR_IMPL_HH__
#define __MEM_CACHE_COMPRESSORS_DICTIONARY_COMPRESSOR_IMPL_HH__
#include <algorithm>
#include "debug/CacheComp.hh"
#include "mem/cache/compressors/dictionary_compressor.hh"
#include "params/BaseDictionaryCompressor.hh"
template <class T>
DictionaryCompressor<T>::CompData::CompData()
: CompressionData()
{
}
template <class T>
void
DictionaryCompressor<T>::CompData::addEntry(std::unique_ptr<Pattern> pattern)
{
// Increase size
setSizeBits(getSizeBits() + pattern->getSizeBits());
// Push new entry to list
entries.push_back(std::move(pattern));
}
template <class T>
DictionaryCompressor<T>::DictionaryCompressor(const Params *p)
: BaseDictionaryCompressor(p)
{
dictionary.resize(dictionarySize);
resetDictionary();
}
template <class T>
void
DictionaryCompressor<T>::resetDictionary()
{
// Reset number of valid entries
numEntries = 0;
// Set all entries as 0
std::fill(dictionary.begin(), dictionary.end(), toDictionaryEntry(0));
}
template <typename T>
std::unique_ptr<typename DictionaryCompressor<T>::Pattern>
DictionaryCompressor<T>::compressValue(const T data)
{
// Split data in bytes
const DictionaryEntry bytes = toDictionaryEntry(data);
// Start as a no-match pattern. A negative match location is used so that
// patterns that depend on the dictionary entry don't match
std::unique_ptr<Pattern> pattern =
getPattern(bytes, toDictionaryEntry(0), -1);
// Search for word on dictionary
for (std::size_t i = 0; i < numEntries; i++) {
// Try matching input with possible patterns
std::unique_ptr<Pattern> temp_pattern =
getPattern(bytes, dictionary[i], i);
// Check if found pattern is better than previous
if (temp_pattern->getSizeBits() < pattern->getSizeBits()) {
pattern = std::move(temp_pattern);
}
}
// Update stats
patternStats[pattern->getPatternNumber()]++;
// Push into dictionary
if (pattern->shouldAllocate()) {
addToDictionary(bytes);
}
return pattern;
}
template <class T>
std::unique_ptr<BaseCacheCompressor::CompressionData>
DictionaryCompressor<T>::compress(const uint64_t* data)
{
std::unique_ptr<BaseCacheCompressor::CompressionData> comp_data =
std::unique_ptr<CompData>(new CompData());
// Reset dictionary
resetDictionary();
// Compress every value sequentially
CompData* const comp_data_ptr = static_cast<CompData*>(comp_data.get());
const std::vector<T> values((T*)data, (T*)data + blkSize / sizeof(T));
for (const auto& value : values) {
std::unique_ptr<Pattern> pattern = compressValue(value);
DPRINTF(CacheComp, "Compressed %016x to %s\n", value,
pattern->print());
comp_data_ptr->addEntry(std::move(pattern));
}
// Return compressed line
return comp_data;
}
template <class T>
T
DictionaryCompressor<T>::decompressValue(const Pattern* pattern)
{
// Search for matching entry
auto entry_it = dictionary.begin();
std::advance(entry_it, pattern->getMatchLocation());
// Decompress the match. If the decompressed value must be added to
// the dictionary, do it
const DictionaryEntry data = pattern->decompress(*entry_it);
if (pattern->shouldAllocate()) {
addToDictionary(data);
}
// Return value
return fromDictionaryEntry(data);
}
template <class T>
void
DictionaryCompressor<T>::decompress(const CompressionData* comp_data,
uint64_t* data)
{
const CompData* casted_comp_data = static_cast<const CompData*>(comp_data);
// Reset dictionary
resetDictionary();
// Decompress every entry sequentially
std::vector<T> decomp_values;
for (const auto& entry : casted_comp_data->entries) {
const T value = decompressValue(&*entry);
decomp_values.push_back(value);
DPRINTF(CacheComp, "Decompressed %s to %x\n", entry->print(), value);
}
// Concatenate the decompressed values to generate the original data
for (std::size_t i = 0; i < blkSize/8; i++) {
data[i] = 0;
const std::size_t values_per_entry = sizeof(uint64_t)/sizeof(T);
for (int j = values_per_entry - 1; j >= 0; j--) {
data[i] |=
static_cast<uint64_t>(decomp_values[values_per_entry*i+j]) <<
(j*8*sizeof(T));
}
}
}
template <class T>
typename DictionaryCompressor<T>::DictionaryEntry
DictionaryCompressor<T>::toDictionaryEntry(T value)
{
DictionaryEntry entry;
for (int i = 0; i < sizeof(T); i++) {
entry[i] = value & 0xFF;
value >>= 8;
}
return entry;
}
template <class T>
T
DictionaryCompressor<T>::fromDictionaryEntry(const DictionaryEntry& entry)
{
T value = 0;
for (int i = sizeof(T) - 1; i >= 0; i--) {
value <<= 8;
value |= entry[i];
}
return value;
}
#endif //__MEM_CACHE_COMPRESSORS_DICTIONARY_COMPRESSOR_IMPL_HH__
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