| /* |
| * 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 |
| * Definition of a dictionary based cache compressor. Each entry is compared |
| * against a dictionary to search for matches. |
| * |
| * The dictionary is composed of 32-bit entries, and the comparison is done |
| * byte per byte. |
| * |
| * The patterns are implemented as individual classes that have a checking |
| * function isPattern(), to determine if the data fits the pattern, and a |
| * decompress() function, which decompresses the contents of a pattern. |
| * Every new pattern must inherit from the Pattern class and be added to the |
| * patternFactory. |
| */ |
| |
| #ifndef __MEM_CACHE_COMPRESSORS_DICTIONARY_COMPRESSOR_HH__ |
| #define __MEM_CACHE_COMPRESSORS_DICTIONARY_COMPRESSOR_HH__ |
| |
| #include <array> |
| #include <cstdint> |
| #include <map> |
| #include <memory> |
| #include <string> |
| #include <vector> |
| |
| #include "base/types.hh" |
| #include "mem/cache/compressors/base.hh" |
| |
| struct BaseDictionaryCompressorParams; |
| |
| class BaseDictionaryCompressor : public BaseCacheCompressor |
| { |
| protected: |
| /** Dictionary size. */ |
| const std::size_t dictionarySize; |
| |
| /** Number of valid entries in the dictionary. */ |
| std::size_t numEntries; |
| |
| /** |
| * @defgroup CompressionStats Compression specific statistics. |
| * @{ |
| */ |
| |
| /** Number of data entries that were compressed to each pattern. */ |
| Stats::Vector patternStats; |
| |
| /** |
| * @} |
| */ |
| |
| /** |
| * Trick function to get the number of patterns. |
| * |
| * @return The number of defined patterns. |
| */ |
| virtual uint64_t getNumPatterns() const = 0; |
| |
| /** |
| * Get meta-name assigned to the given pattern. |
| * |
| * @param number The number of the pattern. |
| * @return The meta-name of the pattern. |
| */ |
| virtual std::string getName(int number) const = 0; |
| |
| public: |
| typedef BaseDictionaryCompressorParams Params; |
| BaseDictionaryCompressor(const Params *p); |
| ~BaseDictionaryCompressor() = default; |
| |
| void regStats() override; |
| }; |
| |
| /** |
| * A template version of the dictionary compressor that allows to choose the |
| * dictionary size. |
| * |
| * @tparam The type of a dictionary entry (e.g., uint16_t, uint32_t, etc). |
| */ |
| template <class T> |
| class DictionaryCompressor : public BaseDictionaryCompressor |
| { |
| protected: |
| /** |
| * Compression data for the dictionary compressor. It consists of a vector |
| * of patterns. |
| */ |
| class CompData; |
| |
| // Forward declaration of a pattern |
| class Pattern; |
| |
| /** Convenience typedef for a dictionary entry. */ |
| typedef std::array<uint8_t, sizeof(T)> DictionaryEntry; |
| |
| /** |
| * Create a factory to determine if input matches a pattern. The if else |
| * chains are constructed by recursion. The patterns should be explored |
| * sorted by size for correct behaviour. |
| */ |
| template <class Head, class... Tail> |
| struct Factory |
| { |
| static std::unique_ptr<Pattern> getPattern( |
| const DictionaryEntry& bytes, const DictionaryEntry& dict_bytes, |
| const int match_location) |
| { |
| // If match this pattern, instantiate it. If a negative match |
| // location is used, the patterns that use the dictionary bytes |
| // must return false. This is used when there are no dictionary |
| // entries yet |
| if (Head::isPattern(bytes, dict_bytes, match_location)) { |
| return std::unique_ptr<Pattern>( |
| new Head(bytes, match_location)); |
| // Otherwise, go for next pattern |
| } else { |
| return Factory<Tail...>::getPattern(bytes, dict_bytes, |
| match_location); |
| } |
| } |
| }; |
| |
| /** Specialization to end the recursion. */ |
| template <class Head> |
| struct Factory<Head> |
| { |
| static std::unique_ptr<Pattern> |
| getPattern(const DictionaryEntry& bytes, |
| const DictionaryEntry& dict_bytes, const int match_location) |
| { |
| // Instantiate last pattern. Should be the XXXX pattern. |
| return std::unique_ptr<Pattern>(new Head(bytes, match_location)); |
| } |
| }; |
| |
| /** The dictionary. */ |
| std::vector<DictionaryEntry> dictionary; |
| |
| /** |
| * Since the factory cannot be instantiated here, classes that inherit |
| * from this base class have to implement the call to their factory's |
| * getPattern. |
| */ |
| virtual std::unique_ptr<Pattern> |
| getPattern(const DictionaryEntry& bytes, const DictionaryEntry& dict_bytes, |
| const int match_location) const = 0; |
| |
| /** |
| * Compress data. |
| * |
| * @param data Data to be compressed. |
| * @return The pattern this data matches. |
| */ |
| std::unique_ptr<Pattern> compressValue(const T data); |
| |
| /** |
| * Decompress a pattern into a value that fits in a dictionary entry. |
| * |
| * @param pattern The pattern to be decompressed. |
| * @return The decompressed word. |
| */ |
| T decompressValue(const Pattern* pattern); |
| |
| /** Clear all dictionary entries. */ |
| void resetDictionary(); |
| |
| /** |
| * Add an entry to the dictionary. |
| * |
| * @param data The new entry. |
| */ |
| virtual void addToDictionary(const DictionaryEntry data) = 0; |
| |
| /** |
| * Apply compression. |
| * |
| * @param data The cache line to be compressed. |
| * @return Cache line after compression. |
| */ |
| std::unique_ptr<BaseCacheCompressor::CompressionData> compress( |
| const uint64_t* data); |
| |
| /** |
| * Decompress data. |
| * |
| * @param comp_data Compressed cache line. |
| * @param data The cache line to be decompressed. |
| */ |
| void decompress(const CompressionData* comp_data, uint64_t* data) override; |
| |
| /** |
| * Turn a value into a dictionary entry. |
| * |
| * @param value The value to turn. |
| * @return A dictionary entry containing the value. |
| */ |
| static DictionaryEntry toDictionaryEntry(T value); |
| |
| /** |
| * Turn a dictionary entry into a value. |
| * |
| * @param The dictionary entry to turn. |
| * @return The value that the dictionary entry contained. |
| */ |
| static T fromDictionaryEntry(const DictionaryEntry& entry); |
| |
| public: |
| typedef BaseDictionaryCompressorParams Params; |
| DictionaryCompressor(const Params *p); |
| ~DictionaryCompressor() = default; |
| }; |
| |
| /** |
| * The compressed data is composed of multiple pattern entries. To add a new |
| * pattern one should inherit from this class and implement isPattern() and |
| * decompress(). Then the new pattern must be added to the PatternFactory |
| * declaration in crescent order of size (in the DictionaryCompressor class). |
| */ |
| template <class T> |
| class DictionaryCompressor<T>::Pattern |
| { |
| protected: |
| /** Pattern enum number. */ |
| const int patternNumber; |
| |
| /** Code associated to the pattern. */ |
| const uint8_t code; |
| |
| /** Length, in bits, of the code and match location. */ |
| const uint8_t length; |
| |
| /** Number of unmatched bytes. */ |
| const uint8_t numUnmatchedBytes; |
| |
| /** Index representing the the match location. */ |
| const int matchLocation; |
| |
| /** Wether the pattern allocates a dictionary entry or not. */ |
| const bool allocate; |
| |
| public: |
| /** |
| * Default constructor. |
| * |
| * @param number Pattern number. |
| * @param code Code associated to this pattern. |
| * @param metadata_length Length, in bits, of the code and match location. |
| * @param num_unmatched_bytes Number of unmatched bytes. |
| * @param match_location Index of the match location. |
| */ |
| Pattern(const int number, const uint64_t code, |
| const uint64_t metadata_length, const uint64_t num_unmatched_bytes, |
| const int match_location, const bool allocate = true) |
| : patternNumber(number), code(code), length(metadata_length), |
| numUnmatchedBytes(num_unmatched_bytes), |
| matchLocation(match_location), allocate(allocate) |
| { |
| } |
| |
| /** Default destructor. */ |
| virtual ~Pattern() = default; |
| |
| /** |
| * Get enum number associated to this pattern. |
| * |
| * @return The pattern enum number. |
| */ |
| int getPatternNumber() const { return patternNumber; }; |
| |
| /** |
| * Get code of this pattern. |
| * |
| * @return The code. |
| */ |
| uint8_t getCode() const { return code; } |
| |
| /** |
| * Get the index of the dictionary match location. |
| * |
| * @return The index of the match location. |
| */ |
| uint8_t getMatchLocation() const { return matchLocation; } |
| |
| /** |
| * Get size, in bits, of the pattern (excluding prefix). Corresponds to |
| * unmatched_data_size + code_length. |
| * |
| * @return The size. |
| */ |
| std::size_t |
| getSizeBits() const |
| { |
| return numUnmatchedBytes*CHAR_BIT + length; |
| } |
| |
| /** |
| * Determine if pattern allocates a dictionary entry. |
| * |
| * @return True if should allocate a dictionary entry. |
| */ |
| bool shouldAllocate() const { return allocate; } |
| |
| /** |
| * Extract pattern's information to a string. |
| * |
| * @return A string containing the relevant pattern metadata. |
| */ |
| std::string |
| print() const |
| { |
| return csprintf("pattern %s (encoding %x, size %u bits)", |
| getPatternNumber(), getCode(), getSizeBits()); |
| } |
| |
| /** |
| * Decompress the pattern. Each pattern has its own way of interpreting |
| * its data. |
| * |
| * @param dict_bytes The bytes in the corresponding matching entry. |
| * @return The decompressed pattern. |
| */ |
| virtual DictionaryEntry decompress( |
| const DictionaryEntry dict_bytes) const = 0; |
| }; |
| |
| template <class T> |
| class DictionaryCompressor<T>::CompData : public CompressionData |
| { |
| public: |
| /** The patterns matched in the original line. */ |
| std::vector<std::unique_ptr<Pattern>> entries; |
| |
| CompData(); |
| ~CompData() = default; |
| |
| /** |
| * Add a pattern entry to the list of patterns. |
| * |
| * @param entry The new pattern entry. |
| */ |
| virtual void addEntry(std::unique_ptr<Pattern>); |
| }; |
| |
| #endif //__MEM_CACHE_COMPRESSORS_DICTIONARY_COMPRESSOR_HH__ |