src/mem/cache/compressors/repeated_qwords.cc

   1 /*
   2  * Copyright (c) 2019-2020 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
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   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,
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  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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  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
  29 /** @file
  30  * Implementation of a repeated values compressor, which compresses data if
  31  * it is entirely composed of repeated qwords.
  32  */
  33
  34 #include "mem/cache/compressors/repeated_qwords.hh"
  35
  36 #include "base/trace.hh"
  37 #include "debug/CacheComp.hh"
  38 #include "mem/cache/compressors/dictionary_compressor_impl.hh"
  39 #include "params/RepeatedQwordsCompressor.hh"
  40
  41 namespace Compressor {
  42
  43 RepeatedQwords::RepeatedQwords(const Params *p)
  44     : DictionaryCompressor<uint64_t>(p)
  45 {
  46 }
  47
  48 void
  49 RepeatedQwords::addToDictionary(DictionaryEntry data)
  50 {
  51     assert(numEntries < dictionarySize);
  52     dictionary[numEntries++] = data;
  53 }
  54
  55 std::unique_ptr<Base::CompressionData>
  56 RepeatedQwords::compress(const std::vector<Chunk>& chunks,
  57     Cycles& comp_lat, Cycles& decomp_lat)
  58 {
  59     std::unique_ptr<Base::CompressionData> comp_data =
  60         DictionaryCompressor::compress(chunks);
  61
  62     // Since there is a single value repeated over and over, there should be
  63     // a single dictionary entry. If there are more, the compressor failed
  64     assert(numEntries >= 1);
  65     if (numEntries > 1) {
  66         comp_data->setSizeBits(blkSize * 8);
  67         DPRINTF(CacheComp, "Repeated qwords compression failed\n");
  68     }
  69
  70     // Set compression latency
  71     comp_lat = Cycles(1);
  72
  73     // Set decompression latency
  74     decomp_lat = Cycles(1);
  75
  76     // Return compressed line
  77     return comp_data;
  78 }
  79
  80 } // namespace Compressor
  81
  82 Compressor::RepeatedQwords*
  83 RepeatedQwordsCompressorParams::create()
  84 {
  85     return new Compressor::RepeatedQwords(this);
  86 }