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28 * Authors: Daniel Carvalho
32 * Definition of a basic cache compressor.
35 #include "mem/cache/compressors/base.hh"
41 #include "debug/CacheComp.hh"
42 #include "mem/cache/tags/super_blk.hh"
43 #include "params/BaseCacheCompressor.hh"
45 // Uncomment this line if debugging compression
46 //#define DEBUG_COMPRESSION
48 BaseCacheCompressor::CompressionData::CompressionData()
53 BaseCacheCompressor::CompressionData::~CompressionData()
58 BaseCacheCompressor::CompressionData::setSizeBits(std::size_t size
)
64 BaseCacheCompressor::CompressionData::getSizeBits() const
70 BaseCacheCompressor::CompressionData::getSize() const
72 return std::ceil(_size
/8);
75 BaseCacheCompressor::BaseCacheCompressor(const Params
*p
)
76 : SimObject(p
), blkSize(p
->block_size
)
81 BaseCacheCompressor::compress(const uint64_t* data
, Cycles
& comp_lat
,
82 Cycles
& decomp_lat
, std::size_t& comp_size_bits
)
85 std::unique_ptr
<CompressionData
> comp_data
=
86 compress(data
, comp_lat
, decomp_lat
);
88 // If we are in debug mode apply decompression just after the compression.
89 // If the results do not match, we've got an error
90 #ifdef DEBUG_COMPRESSION
91 uint64_t decomp_data
[blkSize
/8];
93 // Apply decompression
94 decompress(comp_data
.get(), decomp_data
);
96 // Check if decompressed line matches original cache line
97 fatal_if(std::memcmp(data
, decomp_data
, blkSize
),
98 "Decompressed line does not match original line.");
101 // Get compression size
102 comp_size_bits
= comp_data
->getSizeBits();
105 compressionSize
[std::ceil(std::log2(comp_size_bits
))]++;
107 // Print debug information
108 DPRINTF(CacheComp
, "Compressed cache line from %d to %d bits. " \
109 "Compression latency: %llu, decompression latency: %llu\n",
110 blkSize
*8, comp_size_bits
, comp_lat
, decomp_lat
);
114 BaseCacheCompressor::getDecompressionLatency(const CacheBlk
* blk
)
116 const CompressionBlk
* comp_blk
= static_cast<const CompressionBlk
*>(blk
);
118 // If block is compressed, return its decompression latency
119 if (comp_blk
&& comp_blk
->isCompressed()){
120 return comp_blk
->getDecompressionLatency();
123 // Block is not compressed, so there is no decompression latency
128 BaseCacheCompressor::setDecompressionLatency(CacheBlk
* blk
, const Cycles lat
)
131 assert(blk
!= nullptr);
134 static_cast<CompressionBlk
*>(blk
)->setDecompressionLatency(lat
);
138 BaseCacheCompressor::setSizeBits(CacheBlk
* blk
, const std::size_t size_bits
)
141 assert(blk
!= nullptr);
144 static_cast<CompressionBlk
*>(blk
)->setSizeBits(size_bits
);
148 BaseCacheCompressor::regStats()
150 SimObject::regStats();
152 // We also store when compression is bigger than original block size
154 .init(std::log2(blkSize
*8) + 2)
155 .name(name() + ".compression_size")
156 .desc("Number of blocks that were compressed to this power of" \
160 for (unsigned i
= 0; i
<= std::log2(blkSize
*8) + 1; ++i
) {
161 compressionSize
.subname(i
, std::to_string(1 << i
));
162 compressionSize
.subdesc(i
, "Number of blocks that compressed to fit " \
163 "in " + std::to_string(1 << i
) + " bits");