base.cc revision 13942 
1/*
2 * Copyright (c) 2018 Inria
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Daniel Carvalho
29 */
30
31/** @file
32 * Definition of a basic cache compressor.
33 */
34
35#include "mem/cache/compressors/base.hh"
36
37#include <algorithm>
38#include <cstdint>
39
40#include "debug/CacheComp.hh"
41#include "mem/cache/tags/super_blk.hh"
42#include "params/BaseCacheCompressor.hh"
43
44// Uncomment this line if debugging compression
45//#define DEBUG_COMPRESSION
46
47BaseCacheCompressor::CompressionData::CompressionData()
48    : _size(0)
49{
50}
51
52BaseCacheCompressor::CompressionData::~CompressionData()
53{
54}
55
56void
57BaseCacheCompressor::CompressionData::setSizeBits(std::size_t size)
58{
59    _size = size;
60}
61
62std::size_t
63BaseCacheCompressor::CompressionData::getSizeBits() const
64{
65    return _size;
66}
67
68std::size_t
69BaseCacheCompressor::CompressionData::getSize() const
70{
71    return std::ceil(_size/8);
72}
73
74BaseCacheCompressor::BaseCacheCompressor(const Params *p)
75    : SimObject(p), blkSize(p->block_size)
76{
77}
78
79void
80BaseCacheCompressor::compress(const uint64_t* data, Cycles& comp_lat,
81                              Cycles& decomp_lat, std::size_t& comp_size_bits)
82{
83    // Apply compression
84    std::unique_ptr<CompressionData> comp_data =
85        compress(data, comp_lat, decomp_lat);
86
87    // If we are in debug mode apply decompression just after the compression.
88    // If the results do not match, we've got an error
89    #ifdef DEBUG_COMPRESSION
90    uint64_t decomp_data[blkSize/8];
91
92    // Apply decompression
93    decompress(comp_data.get(), decomp_data);
94
95    // Check if decompressed line matches original cache line
96    fatal_if(std::memcmp(data, decomp_data, blkSize),
97             "Decompressed line does not match original line.");
98    #endif
99
100    // Get compression size
101    comp_size_bits = comp_data->getSizeBits();
102
103    // Print debug information
104    DPRINTF(CacheComp, "Compressed cache line from %d to %d bits. " \
105            "Compression latency: %llu, decompression latency: %llu\n",
106            blkSize*8, comp_size_bits, comp_lat, decomp_lat);
107}
108
109Cycles
110BaseCacheCompressor::getDecompressionLatency(const CacheBlk* blk)
111{
112    const CompressionBlk* comp_blk = static_cast<const CompressionBlk*>(blk);
113
114    // If block is compressed, return its decompression latency
115    if (comp_blk && comp_blk->isCompressed()){
116        return comp_blk->getDecompressionLatency();
117    }
118
119    // Block is not compressed, so there is no decompression latency
120    return Cycles(0);
121}
122
123void
124BaseCacheCompressor::setDecompressionLatency(CacheBlk* blk, const Cycles lat)
125{
126    // Sanity check
127    assert(blk != nullptr);
128
129    // Assign latency
130    static_cast<CompressionBlk*>(blk)->setDecompressionLatency(lat);
131}
132
133void
134BaseCacheCompressor::setSizeBits(CacheBlk* blk, const std::size_t size_bits)
135{
136    // Sanity check
137    assert(blk != nullptr);
138
139    // Assign size
140    static_cast<CompressionBlk*>(blk)->setSizeBits(size_bits);
141}
142
143