src/mem/cache/compressors/perfect.cc

/*
 * Copyright (c) 2019-2020 Inria
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/** @file
 * Implementation of a perfect compressor, which compresses data to its
 * maximum allowed compression ratio.
 */

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

#include <algorithm>

#include "debug/CacheComp.hh"
#include "params/PerfectCompressor.hh"

namespace gem5
{

GEM5_DEPRECATED_NAMESPACE(Compressor, compression);
namespace compression
{

Perfect::Perfect(const Params &p)
  : Base(p), compressedSize(8 * blkSize / p.max_compression_ratio)
{
}

std::unique_ptr<Base::CompressionData>
Perfect::compress(const std::vector<Chunk>& chunks,
    Cycles& comp_lat, Cycles& decomp_lat)
{
    // Compress every word sequentially
    std::unique_ptr<Base::CompressionData> comp_data(new CompData(chunks));

    // Set relevant metadata
    comp_data->setSizeBits(compressedSize);

    // Set latencies based on the degree of parallelization, and any extra
    // latencies due to shifting or packaging
    comp_lat = Cycles((chunks.size() / compChunksPerCycle) + compExtraLatency);
    decomp_lat = Cycles((chunks.size() / decompChunksPerCycle) +
        decompExtraLatency);

    return comp_data;
}

void
Perfect::decompress(const CompressionData* comp_data,
    uint64_t* data)
{
    // Decompress every entry sequentially
    fromChunks(static_cast<const CompData*>(comp_data)->chunks, data);
}

} // namespace compression
} // namespace gem5