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/*
* Copyright (c) 2018 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 CPack compression, from "C-Pack: A High-Performance
* Microprocessor Cache Compression Algorithm".
*
* The dictionary is composed of 32-bit entries.
*
* 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_CPACK_HH__
#define __MEM_CACHE_COMPRESSORS_CPACK_HH__
#include <array>
#include <cstdint>
#include <map>
#include <memory>
#include <vector>
#include "base/types.hh"
#include "mem/cache/compressors/base.hh"
struct CPackParams;
class CPack : public BaseCacheCompressor
{
private:
/**
* Compression data for CPack. It consists of a vector of patterns.
*/
class CompData;
// Forward declaration of all possible patterns
class Pattern;
class PatternZZZZ;
class PatternXXXX;
class PatternMMMM;
class PatternMMXX;
class PatternZZZX;
class PatternMMMX;
/**
* 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 std::array<uint8_t, 4>& bytes,
const std::array<uint8_t, 4>& 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 std::array<uint8_t, 4>& bytes,
const std::array<uint8_t, 4>& dict_bytes, const int match_location)
{
// Instantiate last pattern. Should be the XXXX pattern.
return std::unique_ptr<Pattern>(new Head(bytes, match_location));
}
};
/**
* Convenience factory declaration. The templates must be organized by
* size, with the smallest first, and "no-match" last.
*/
using PatternFactory = Factory<PatternZZZZ, PatternMMMM, PatternZZZX,
PatternMMMX, PatternMMXX, PatternXXXX>;
/**
* The dictionary.
*/
std::vector<std::array<uint8_t, 4>> dictionary;
/**
* 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;
/**
* @}
*/
/**
* Compress data.
*
* @param data Data to be compressed.
* @return The pattern this data matches.
*/
std::unique_ptr<Pattern> compressWord(const uint32_t data);
/**
* Decompress a word.
*
* @param pattern The pattern to be decompressed.
* @return The decompressed word.
*/
uint32_t decompressWord(const Pattern* pattern);
/**
* Clear all dictionary entries.
*/
void resetDictionary();
/**
* Apply compression.
*
* @param data The cache line to be compressed.
* @param comp_lat Compression latency in number of cycles.
* @param decomp_lat Decompression latency in number of cycles.
* @return Cache line after compression.
*/
std::unique_ptr<BaseCacheCompressor::CompressionData> compress(
const uint64_t* data, Cycles& comp_lat, Cycles& decomp_lat) override;
/**
* 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;
public:
/** Convenience typedef. */
typedef CPackParams Params;
/**
* Default constructor.
*/
CPack(const Params *p);
/**
* Default destructor.
*/
~CPack() {};
/**
* Register local statistics.
*/
void regStats() override;
};
/**
* 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 CPack class). The pattern
* must be also added to the Name enum in the CPack::Pattern class before
* NUM_PATTERNS.
*/
class CPack::Pattern
{
protected:
/**
* The patterns proposed in the paper. Each letter represents a byte:
* Z is a null byte, M is a dictionary match, X is a new value.
* These are used as indexes to reference the pattern data. If a new
* pattern is added, it must be done before NUM_PATTERNS.
*/
typedef enum {
ZZZZ, XXXX, MMMM, MMXX, ZZZX, MMMX, NUM_PATTERNS
} PatternNumber;
/**
* Pattern enum number.
*/
const PatternNumber 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;
/**
* Get code of this pattern.
*
* @return The code.
*/
uint8_t getCode() const { return code; }
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 PatternNumber 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;
/**
* Trick function to get the number of patterns.
*
* @return The number of defined patterns.
*/
static uint64_t getNumPatterns() { return NUM_PATTERNS; };
/**
* Get enum number associated to this pattern.
*
* @return The pattern enum number.
*/
PatternNumber getPatternNumber() const { return patternNumber; };
/**
* Get meta-name assigned to the given pattern.
*
* @param number The number of the pattern.
* @return The meta-name of the pattern.
*/
static std::string getName(int number)
{
static std::map<PatternNumber, std::string> patternNames = {
{ZZZZ, "ZZZZ"}, {XXXX, "XXXX"}, {MMMM, "MMMM"},
{MMXX, "MMXX"}, {ZZZX, "ZZZX"}, {MMMX, "MMMX"}
};
return patternNames[(PatternNumber)number];
};
/**
* 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;
}
std::string print() const {
return csprintf("pattern %s (encoding %x, size %u bits)",
getName(patternNumber), 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.
* @param data The decompressed pattern.
* @return Whether entry should be added to dictionary or not.
*/
virtual bool decompress(const std::array<uint8_t, 4> dict_bytes,
std::array<uint8_t, 4>& data) const = 0;
};
class CPack::PatternZZZZ : public Pattern
{
public:
PatternZZZZ(const std::array<uint8_t, 4> bytes, const int match_location)
: Pattern(ZZZZ, 0x0, 2, 0, 0, false) {}
static bool isPattern(const std::array<uint8_t, 4>& bytes,
const std::array<uint8_t, 4>& dict_bytes,
const int match_location)
{
return (bytes[3] == 0) && (bytes[2] == 0) && (bytes[1] == 0) &&
(bytes[0] == 0);
}
bool decompress(const std::array<uint8_t, 4> dict_bytes,
std::array<uint8_t, 4>& data) const override
{
data = {0, 0, 0, 0};
return false;
}
};
class CPack::PatternXXXX : public Pattern
{
private:
/**
* A copy of the word.
*/
const std::array<uint8_t, 4> bytes;
public:
PatternXXXX(const std::array<uint8_t, 4> bytes, const int match_location)
: Pattern(XXXX, 0x1, 2, 4, 0, true), bytes(bytes) {}
static bool isPattern(const std::array<uint8_t, 4>& bytes,
const std::array<uint8_t, 4>& dict_bytes,
const int match_location)
{
// It can always be an unmatch, as it is set to this class when other
// patterns fail
return true;
}
bool decompress(const std::array<uint8_t, 4> dict_bytes,
std::array<uint8_t, 4>& data) const override
{
data = bytes;
return true;
}
};
class CPack::PatternMMMM : public Pattern
{
public:
PatternMMMM(const std::array<uint8_t, 4> bytes, const int match_location)
: Pattern(MMMM, 0x2, 6, 0, match_location, true) {}
static bool isPattern(const std::array<uint8_t, 4>& bytes,
const std::array<uint8_t, 4>& dict_bytes,
const int match_location)
{
return (bytes == dict_bytes) && (match_location >= 0);
}
bool decompress(const std::array<uint8_t, 4> dict_bytes,
std::array<uint8_t, 4>& data) const override
{
data = dict_bytes;
return true;
}
};
class CPack::PatternMMXX : public Pattern
{
private:
/**
* A copy of the unmatched bytes.
*/
const uint8_t byte0;
const uint8_t byte1;
public:
PatternMMXX(const std::array<uint8_t, 4> bytes, const int match_location)
: Pattern(MMXX, 0xC, 8, 2, match_location, true),
byte0(bytes[0]), byte1(bytes[1]) {}
static bool isPattern(const std::array<uint8_t, 4>& bytes,
const std::array<uint8_t, 4>& dict_bytes,
const int match_location)
{
// Notice we don't compare bytes[0], as otherwise we'd be unnecessarily
// discarding MMXM. If that pattern is added this should be modified
return (bytes[3] == dict_bytes[3]) && (bytes[2] == dict_bytes[2]) &&
(bytes[1] != dict_bytes[1]) && (match_location >= 0);
}
bool decompress(const std::array<uint8_t, 4> dict_bytes,
std::array<uint8_t, 4>& data) const override
{
data = {byte0, byte1, dict_bytes[2], dict_bytes[3]};
return true;
}
};
class CPack::PatternZZZX : public Pattern
{
private:
/**
* A copy of the unmatched byte.
*/
const uint8_t byte;
public:
PatternZZZX(const std::array<uint8_t, 4> bytes, const int match_location)
: Pattern(ZZZX, 0xD, 4, 1, 0, false), byte(bytes[0]) {}
static bool isPattern(const std::array<uint8_t, 4>& bytes,
const std::array<uint8_t, 4>& dict_bytes,
const int match_location)
{
return (bytes[3] == 0) && (bytes[2] == 0) && (bytes[1] == 0) &&
(bytes[0] != 0);
}
bool decompress(const std::array<uint8_t, 4> dict_bytes,
std::array<uint8_t, 4>& data) const override
{
data = {byte, 0, 0, 0};
return false;
}
};
class CPack::PatternMMMX : public Pattern
{
private:
/**
* A copy of the unmatched byte.
*/
const uint8_t byte;
public:
PatternMMMX(const std::array<uint8_t, 4> bytes, const int match_location)
: Pattern(MMMX, 0xE, 8, 1, match_location, true),
byte(bytes[0]) {}
static bool isPattern(const std::array<uint8_t, 4>& bytes,
const std::array<uint8_t, 4>& dict_bytes,
const int match_location)
{
return (bytes[3] == dict_bytes[3]) && (bytes[2] == dict_bytes[2]) &&
(bytes[1] == dict_bytes[1]) && (bytes[0] != dict_bytes[0]) &&
(match_location >= 0);
}
bool decompress(const std::array<uint8_t, 4> dict_bytes,
std::array<uint8_t, 4>& data) const override
{
data = {byte, dict_bytes[1], dict_bytes[2], dict_bytes[3]};
return true;
}
};
class CPack::CompData : public CompressionData
{
public:
/**
* The patterns matched in the original line.
*/
std::vector<std::unique_ptr<Pattern>> entries;
/**
* Default constructor.
*
* @param dictionary_size Number of entries in the dictionary.
*/
CompData(const std::size_t dictionary_size);
/**
* Default destructor.
*/
~CompData();
};
#endif //__MEM_CACHE_COMPRESSORS_CPACK_HH__
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