fpcd.cc

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/*
 * Copyright (c) 2019 Inria
 * All rights reserved.
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 * notice, this list of conditions and the following disclaimer in the
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 * neither the name of the copyright holders nor the names of its
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 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * Authors: Daniel Carvalho
 */

#include "mem/cache/compressors/fpcd.hh"

#include "mem/cache/compressors/dictionary_compressor_impl.hh"
#include "params/FPCD.hh"

FPCD::FPCD(const Params *p)
    : DictionaryCompressor<uint32_t>(p)
{
}

void
FPCD::addToDictionary(DictionaryEntry data)
{
    // The dictionary behaves as a table with FIFO as replacement policy
    if (numEntries == 2) {
        dictionary[penultimateIndex] = dictionary[previousIndex];
        dictionary[previousIndex] = data;
    } else {
        dictionary[numEntries++] = data;
    }
}

std::unique_ptr<BaseCacheCompressor::CompressionData>
FPCD::compress(const uint64_t* data, Cycles& comp_lat, Cycles& decomp_lat)
{
    std::unique_ptr<BaseCacheCompressor::CompressionData> comp_data =
        DictionaryCompressor<uint32_t>::compress(data);

    // Set compression latency (Accounts for zero checks, ones check, match
    // previous check, match penultimate check, repeated values check, pattern
    // selection, shifting, at a rate of 16B per cycle)
    comp_lat = Cycles(blkSize/2);

    // Set decompression latency. The original claim of 2 cycles is likely
    // too unrealistic
    decomp_lat = Cycles(4);

    // Return compressed line
    return comp_data;
}

FPCD*
FPCDParams::create()
{
    return new FPCD(this);
}