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30 * Definition of the a multi compressor that choses the best compression
31 * among multiple compressors.
34 #ifndef __MEM_CACHE_COMPRESSORS_MULTI_HH__
35 #define __MEM_CACHE_COMPRESSORS_MULTI_HH__
40 #include "base/statistics.hh"
41 #include "base/types.hh"
42 #include "mem/cache/compressors/base.hh"
44 struct MultiCompressorParams;
46 namespace Compressor {
48 class Multi : public Base
52 * Compression data for the multi compressor. It contains the compression
53 * data of the best compressor, along with its index in the list of
58 /** List of sub-compressors. */
59 std::vector<Base*> compressors;
62 * An encoding is associated to each sub-compressor to inform which
63 * sub-compressor to use when decompressing data. This information can
64 * be added either to the tag entry, in which case no extra bits are
65 * added to the compressed data (numEncodingBits = 0), or to the
66 * compressed data itself.
68 * There is no encoding reserved for the uncompressed case; it is assumed
69 * that an "is compressed" bit is stored in the tags. Therefore, even if
70 * storing the encoding within the compressed data, these extra bits are
71 * not added when the data is uncompressible.
73 * These extra bits are taken into account when thresholding the
74 * compressed data's size.
76 const std::size_t numEncodingBits;
79 * Extra decompression latency to be added to the sub-compressor's
80 * decompression latency. This can different from zero due to decoding,
81 * shifting, or packaging, for example.
83 const Cycles extraDecompressionLatency;
85 struct MultiStats : public Stats::Group
87 const Multi& compressor;
89 MultiStats(BaseStats &base_group, Multi& _compressor);
91 void regStats() override;
94 * Number of times each compressor provided the nth best compression.
96 Stats::Vector2d ranks;
100 typedef MultiCompressorParams Params;
101 Multi(const Params *p);
104 std::unique_ptr<Base::CompressionData> compress(
105 const std::vector<Base::Chunk>& chunks,
106 Cycles& comp_lat, Cycles& decomp_lat) override;
108 void decompress(const CompressionData* comp_data, uint64_t* data) override;
111 class Multi::MultiCompData : public CompressionData
114 /** Index of the compressor that provided these compression results. */
118 /** Compression data of the best compressor. */
119 std::unique_ptr<Base::CompressionData> compData;
122 * Default constructor.
124 * @param index Index of the compressor that provided this compression.
125 * @param comp_data Compression data of the best compressor.
127 MultiCompData(unsigned index,
128 std::unique_ptr<Base::CompressionData> comp_data);
130 /** Default destructor. */
131 ~MultiCompData() = default;
133 /** Get the index of the best compressor. */
134 uint8_t getIndex() const;
137 } // namespace Compressor
139 #endif //__MEM_CACHE_COMPRESSORS_MULTI_HH__