src/mem/cache/compressors/zero.hh

   1 /*
   2  * Copyright (c) 2019 Inria
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  *
  28  * Authors: Daniel Carvalho
  29  */
  30
  31 /** @file
  32  * Definition of a zero compressor, which compressed data if it is entirely
  33  * composed of zero bits.
  34  */
  35
  36 #ifndef __MEM_CACHE_COMPRESSORS_ZERO_HH__
  37 #define __MEM_CACHE_COMPRESSORS_ZERO_HH__
  38
  39 #include <array>
  40 #include <cstdint>
  41 #include <map>
  42 #include <memory>
  43
  44 #include "mem/cache/compressors/dictionary_compressor.hh"
  45
  46 struct ZeroCompressorParams;
  47
  48 class ZeroCompressor : public DictionaryCompressor<uint64_t>
  49 {
  50   protected:
  51     using DictionaryEntry = DictionaryCompressor<uint64_t>::DictionaryEntry;
  52
  53     // Forward declaration of all possible patterns
  54     class PatternX;
  55     class PatternZ;
  56
  57     /**
  58      * The patterns proposed in the paper. Each letter represents a byte:
  59      * Z is a null byte, M is a dictionary match, X is a new value.
  60      * These are used as indexes to reference the pattern data. If a new
  61      * pattern is added, it must be done before NUM_PATTERNS.
  62      */
  63     typedef enum {
  64         X, Z, NUM_PATTERNS
  65     } PatternNumber;
  66
  67     /**
  68      * Convenience factory declaration. The templates must be organized by
  69      * size, with the smallest first, and "no-match" last.
  70      */
  71     using PatternFactory = Factory<PatternZ, PatternX>;
  72
  73     uint64_t getNumPatterns() const override { return NUM_PATTERNS; }
  74
  75     std::string
  76     getName(int number) const override
  77     {
  78         static std::map<int, std::string> pattern_names = {
  79             {X, "X"}, {Z, "Z"}
  80         };
  81
  82         return pattern_names[number];
  83     };
  84
  85     std::unique_ptr<Pattern>
  86     getPattern(const DictionaryEntry& bytes, const DictionaryEntry& dict_bytes,
  87         const int match_location) const override
  88     {
  89         return PatternFactory::getPattern(bytes, dict_bytes, match_location);
  90     }
  91
  92     void addToDictionary(DictionaryEntry data) override;
  93
  94     std::unique_ptr<BaseCacheCompressor::CompressionData> compress(
  95         const uint64_t* data, Cycles& comp_lat, Cycles& decomp_lat) override;
  96
  97   public:
  98     typedef ZeroCompressorParams Params;
  99     ZeroCompressor(const Params *p);
 100     ~ZeroCompressor() = default;
 101 };
 102
 103 class ZeroCompressor::PatternX
 104     : public DictionaryCompressor::UncompressedPattern
 105 {
 106   public:
 107     PatternX(const DictionaryEntry bytes, const int match_location)
 108         : DictionaryCompressor::UncompressedPattern(X, 0, 1, match_location,
 109           bytes)
 110     {
 111     }
 112 };
 113
 114 class ZeroCompressor::PatternZ
 115     : public DictionaryCompressor::MaskedValuePattern<0, 0xFFFFFFFFFFFFFFFF>
 116 {
 117   public:
 118     PatternZ(const DictionaryEntry bytes, const int match_location)
 119         : DictionaryCompressor::MaskedValuePattern<0, 0xFFFFFFFFFFFFFFFF>(
 120           Z, 1, 1, match_location, bytes)
 121     {
 122     }
 123 };
 124
 125 #endif //__MEM_CACHE_COMPRESSORS_ZERO_HH__