src/mem/cache/compressors/zero.cc

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