src/mem/cache/compressors/zero.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
   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
  29 /** @file
  30  * Implementation of a zero compressor, which compressed data if it is entirely
  31  * composed of zero bits.
  32  */
  33
  34 #include "mem/cache/compressors/zero.hh"
  35
  36 #include "base/trace.hh"
  37 #include "debug/CacheComp.hh"
  38 #include "mem/cache/compressors/dictionary_compressor_impl.hh"
  39 #include "params/ZeroCompressor.hh"
  40
  41 namespace Compressor {
  42
  43 Zero::Zero(const Params *p)
  44     : DictionaryCompressor<uint64_t>(p)
  45 {
  46 }
  47
  48 void
  49 Zero::addToDictionary(DictionaryEntry data)
  50 {
  51     assert(numEntries < dictionarySize);
  52     dictionary[numEntries++] = data;
  53 }
  54
  55 std::unique_ptr<Base::CompressionData>
  56 Zero::compress(const std::vector<Chunk>& chunks, Cycles& comp_lat,
  57     Cycles& decomp_lat)
  58 {
  59     std::unique_ptr<Base::CompressionData> comp_data =
  60         DictionaryCompressor::compress(chunks);
  61
  62     // If there is any non-zero entry, the compressor failed
  63     if (numEntries > 0) {
  64         comp_data->setSizeBits(blkSize * 8);
  65         DPRINTF(CacheComp, "Zero compression failed\n");
  66     }
  67
  68     // Set compression latency (Assumes full line zero comparison)
  69     comp_lat = Cycles(1);
  70
  71     // Set decompression latency
  72     decomp_lat = Cycles(1);
  73
  74     // Return compressed line
  75     return comp_data;
  76 }
  77
  78 } // namespace Compressor
  79
  80 Compressor::Zero*
  81 ZeroCompressorParams::create()
  82 {
  83     return new Compressor::Zero(this);
  84 }