src/mem/cache/compressors/zero.cc

/*
 * Copyright (c) 2019-2020 Inria
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/** @file
 * Implementation of a zero compressor, which compressed data if it is entirely
 * composed of zero bits.
 */

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

#include "base/trace.hh"
#include "debug/CacheComp.hh"
#include "mem/cache/compressors/dictionary_compressor_impl.hh"
#include "params/ZeroCompressor.hh"

namespace gem5
{

GEM5_DEPRECATED_NAMESPACE(Compressor, compression);
namespace compression
{

Zero::Zero(const Params &p)
    : DictionaryCompressor<uint64_t>(p)
{
}

void
Zero::addToDictionary(DictionaryEntry data)
{
    assert(numEntries < dictionarySize);
    dictionary[numEntries++] = data;
}

std::unique_ptr<Base::CompressionData>
Zero::compress(const std::vector<Chunk>& chunks, Cycles& comp_lat,
    Cycles& decomp_lat)
{
    std::unique_ptr<Base::CompressionData> comp_data =
        DictionaryCompressor::compress(chunks);

    // If there is any non-zero entry, the compressor failed
    if (numEntries > 0) {
        comp_data->setSizeBits(blkSize * 8);
        DPRINTF(CacheComp, "Zero compression failed\n");
    }

    // Set compression latency (Assumes full line zero comparison)
    comp_lat = Cycles(1);

    // Set decompression latency
    decomp_lat = Cycles(1);

    // Return compressed line
    return comp_data;
}

} // namespace compression
} // namespace gem5