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28 * Authors: Erik Hallnor
33 * Declaration of a LRU tag store.
42 #include "mem/cache/cache_blk.hh" // base class
43 #include "mem/packet.hh" // for inlined functions
45 #include "mem/cache/tags/base_tags.hh"
52 class LRUBlk : public CacheBlk {
54 /** Has this block been touched? Used to aid calculation of warmup time. */
59 * An associative set of cache blocks.
64 /** The associativity of this set. */
67 /** Cache blocks in this set, maintained in LRU order 0 = MRU. */
71 * Find a block matching the tag in this set.
72 * @param asid The address space ID.
73 * @param tag The Tag to find.
74 * @return Pointer to the block if found.
76 LRUBlk* findBlk(Addr tag) const;
79 * Move the given block to the head of the list.
80 * @param blk The block to move.
82 void moveToHead(LRUBlk *blk);
86 * A LRU cache tag store.
88 class LRU : public BaseTags
91 /** Typedef the block type used in this tag store. */
92 typedef LRUBlk BlkType;
93 /** Typedef for a list of pointers to the local block class. */
94 typedef std::list<LRUBlk*> BlkList;
96 /** The number of sets in the cache. */
98 /** The number of bytes in a block. */
100 /** The associativity of the cache. */
102 /** The hit latency. */
103 const int hitLatency;
105 /** The cache sets. */
108 /** The cache blocks. */
110 /** The data blocks, 1 per cache block. */
113 /** The amount to shift the address to get the set. */
115 /** The amount to shift the address to get the tag. */
117 /** Mask out all bits that aren't part of the set index. */
119 /** Mask out all bits that aren't part of the block offset. */
124 * Construct and initialize this tag store.
125 * @param _numSets The number of sets in the cache.
126 * @param _blkSize The number of bytes in a block.
127 * @param _assoc The associativity of the cache.
128 * @param _hit_latency The latency in cycles for a hit.
130 LRU(int _numSets, int _blkSize, int _assoc, int _hit_latency);
138 * Return the block size.
139 * @return the block size.
147 * Return the subblock size. In the case of LRU it is always the block
149 * @return The block size.
151 int getSubBlockSize()
157 * Search for the address in the cache.
158 * @param asid The address space ID.
159 * @param addr The address to find.
160 * @return True if the address is in the cache.
162 bool probe(Addr addr) const;
165 * Invalidate the given block.
166 * @param blk The block to invalidate.
168 void invalidateBlk(BlkType *blk);
171 * Finds the given address in the cache and update replacement data.
172 * Returns the access latency as a side effect.
173 * @param addr The address to find.
174 * @param asid The address space ID.
175 * @param lat The access latency.
176 * @return Pointer to the cache block if found.
178 LRUBlk* findBlock(Addr addr, int &lat);
181 * Finds the given address in the cache, do not update replacement data.
182 * @param addr The address to find.
183 * @param asid The address space ID.
184 * @return Pointer to the cache block if found.
186 LRUBlk* findBlock(Addr addr) const;
189 * Find a replacement block for the address provided.
190 * @param pkt The request to a find a replacement candidate for.
191 * @param writebacks List for any writebacks to be performed.
192 * @param compress_blocks List of blocks to compress, for adaptive comp.
193 * @return The block to place the replacement in.
195 LRUBlk* findReplacement(PacketPtr &pkt, PacketList &writebacks,
196 BlkList &compress_blocks);
199 * Generate the tag from the given address.
200 * @param addr The address to get the tag from.
201 * @return The tag of the address.
203 Addr extractTag(Addr addr) const
205 return (addr >> tagShift);
209 * Generate the tag from the given address.
210 * @param addr The address to get the tag from.
211 * @param blk Ignored.
212 * @return The tag of the address.
214 Addr extractTag(Addr addr, LRUBlk *blk) const
216 return (addr >> tagShift);
220 * Calculate the set index from the address.
221 * @param addr The address to get the set from.
222 * @return The set index of the address.
224 int extractSet(Addr addr) const
226 return ((addr >> setShift) & setMask);
230 * Get the block offset from an address.
231 * @param addr The address to get the offset of.
232 * @return The block offset.
234 int extractBlkOffset(Addr addr) const
236 return (addr & blkMask);
240 * Align an address to the block size.
241 * @param addr the address to align.
242 * @return The block address.
244 Addr blkAlign(Addr addr) const
246 return (addr & ~(Addr)blkMask);
250 * Regenerate the block address from the tag.
251 * @param tag The tag of the block.
252 * @param set The set of the block.
253 * @return The block address.
255 Addr regenerateBlkAddr(Addr tag, unsigned set) const
257 return ((tag << tagShift) | ((Addr)set << setShift));
261 * Return the hit latency.
262 * @return the hit latency.
264 int getHitLatency() const
270 * Read the data out of the internal storage of the given cache block.
271 * @param blk The cache block to read.
272 * @param data The buffer to read the data into.
273 * @return The cache block's data.
275 void readData(LRUBlk *blk, uint8_t *data)
277 std::memcpy(data, blk->data, blk->size);
281 * Write data into the internal storage of the given cache block. Since in
282 * LRU does not store data differently this just needs to update the size.
283 * @param blk The cache block to write.
284 * @param data The data to write.
285 * @param size The number of bytes to write.
286 * @param writebacks A list for any writebacks to be performed. May be
287 * needed when writing to a compressed block.
289 void writeData(LRUBlk *blk, uint8_t *data, int size,
290 PacketList & writebacks)
292 assert(size <= blkSize);
297 * Called at end of simulation to complete average block reference stats.
299 virtual void cleanupRefs();