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 simple superblock class. Each superblock consists of a
33 * number of compressed cache blocks limited by the maximum compression
34 * factor that may or may not be present in the cache.
35 */
36
37#ifndef __MEM_CACHE_TAGS_SUPER_BLK_HH__
38#define __MEM_CACHE_TAGS_SUPER_BLK_HH__
39
40#include "mem/cache/tags/sector_blk.hh"
41
42class SuperBlk;
43
44/**
45 * A superblock is composed of sub-blocks, and each sub-block has information
46 * regarding its superblock and a pointer to its superblock tag. A superblock
47 * can be seen as a variation of a sector block, and therefore we use a sector
48 * nomenclature.
49 */
50class CompressionBlk : public SectorSubBlk
51{
52  private:
53    /**
54     * Set size, in bits, of this compressed block's data.
55     */
56    std::size_t _size;
57
58    /**
59     * Number of cycles needed to decompress this block. We store it to avoid
60     * doing decompressions.
61     */
62    Cycles _decompressionLatency;
63
64  public:
65    CompressionBlk();
66    CompressionBlk(const CompressionBlk&) = delete;
67    CompressionBlk& operator=(const CompressionBlk&) = delete;
68    ~CompressionBlk() {};
69
70    /**
71     * Check if this block holds compressed data.
72     *
73     * @return True if the block holds compressed data.
74     */
75    bool isCompressed() const;
76
77    /**
78     * Set compression bit.
79     */
80    void setCompressed();
81
82    /**
83     * Clear compression bit.
84     */
85    void setUncompressed();
86
87    /*
88     * Get size, in bits, of this compressed block's data.
89     *
90     * @return The compressed size.
91     */
92    std::size_t getSizeBits() const;
93
94    /**
95     * Set size, in bits, of this compressed block's data.
96     *
97     * @param The compressed size.
98     */
99    void setSizeBits(const std::size_t size);
100
101    /**
102     * Get number of cycles needed to decompress this block.
103     *
104     * @return Decompression latency.
105     */
106    Cycles getDecompressionLatency() const;
107
108    /**
109     * Set number of cycles needed to decompress this block.
110     *
111     * @param Decompression latency.
112     */
113    void setDecompressionLatency(const Cycles lat);
114
115    /**
116     * Pretty-print sector offset and other CacheBlk information.
117     *
118     * @return string with basic state information
119     */
120    std::string print() const override;
121};
122
123/**
124 * A basic compression superblock.
125 * Contains the tag and a list of blocks associated to this superblock.
126 */
127class SuperBlk : public SectorBlk
128{
129  protected:
130    /** Block size, in bytes. */
131    std::size_t blkSize;
132
133  public:
134    SuperBlk() : SectorBlk(), blkSize(0) {}
135    SuperBlk(const SuperBlk&) = delete;
136    SuperBlk& operator=(const SuperBlk&) = delete;
137    ~SuperBlk() {};
138
139    /**
140     * Returns whether the superblock contains compressed blocks or not. By
141     * default, if not blocks are valid, the superblock is compressible.
142     *
143     * @param ignored_blk If provided don't consider the given block.
144     * @return The compressibility state of the superblock.
145     */
146    bool isCompressed(const CompressionBlk* ignored_blk = nullptr) const;
147
148    /**
149     * Checks whether a superblock can co-allocate given compressed data block.
150     *
151     * @param compressed_size Size, in bits, of new block to allocate.
152     * @return True if block can be co-allocated in superblock.
153     */
154    bool canCoAllocate(const std::size_t compressed_size) const;
155
156    /**
157     * Set block size. Should be called only once, when initializing blocks.
158     *
159     * @param blk_size The uncompressed block size.
160     */
161    void setBlkSize(const std::size_t blk_size);
162};
163
164#endif //__MEM_CACHE_TAGS_SUPER_BLK_HH__
165