src/mem/cache/compressors/perfect.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 perfect compressor, which compresses data to its
  33  * maximum allowed compression ratio.
  34  */
  35
  36 #include "mem/cache/compressors/perfect.hh"
  37
  38 #include <algorithm>
  39
  40 #include "debug/CacheComp.hh"
  41 #include "params/PerfectCompressor.hh"
  42
  43 PerfectCompressor::CompData::CompData(const uint64_t* data,
  44     std::size_t num_entries)
  45     : CompressionData(), entries(data, data + num_entries)
  46 {
  47 }
  48
  49 PerfectCompressor::PerfectCompressor(const Params *p)
  50     : BaseCacheCompressor(p),
  51       compressedSize(8 * blkSize / p->max_compression_ratio),
  52       compressionLatency(p->compression_latency),
  53       decompressionLatency(p->decompression_latency)
  54 {
  55 }
  56
  57 std::unique_ptr<BaseCacheCompressor::CompressionData>
  58 PerfectCompressor::compress(const uint64_t* cache_line, Cycles& comp_lat,
  59     Cycles& decomp_lat)
  60 {
  61     // Compress every word sequentially
  62     std::unique_ptr<BaseCacheCompressor::CompressionData> comp_data(
  63         new CompData(cache_line, blkSize/8));
  64
  65     // Set relevant metadata
  66     comp_data->setSizeBits(compressedSize);
  67     comp_lat = compressionLatency;
  68     decomp_lat = decompressionLatency;
  69
  70     return comp_data;
  71 }
  72
  73 void
  74 PerfectCompressor::decompress(const CompressionData* comp_data,
  75     uint64_t* data)
  76 {
  77     // Decompress every entry sequentially
  78     const std::vector<uint64_t>& entries =
  79         static_cast<const CompData*>(comp_data)->entries;
  80     assert(entries.size() == (blkSize/8));
  81     std::copy(entries.begin(), entries.end(), data);
  82 }
  83
  84 PerfectCompressor*
  85 PerfectCompressorParams::create()
  86 {
  87     return new PerfectCompressor(this);
  88 }