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28 * Authors: Erik Hallnor
33 * Declaration of a LRU tag store.
36 #ifndef __MEM_CACHE_TAGS_LRU_HH__
37 #define __MEM_CACHE_TAGS_LRU_HH__
43 #include "mem/cache/blk.hh"
44 #include "mem/cache/tags/base.hh"
45 #include "mem/packet.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 * Invalidate the given block.
158 * @param blk The block to invalidate.
160 void invalidateBlk(BlkType *blk);
163 * Access block and update replacement data. May not succeed, in which case
164 * NULL pointer is returned. This has all the implications of a cache
165 * access and should only be used as such. Returns the access latency as a side effect.
166 * @param addr The address to find.
167 * @param asid The address space ID.
168 * @param lat The access latency.
169 * @return Pointer to the cache block if found.
171 LRUBlk* accessBlock(Addr addr, int &lat);
174 * Finds the given address in the cache, do not update replacement data.
175 * i.e. This is a no-side-effect find of a block.
176 * @param addr The address to find.
177 * @param asid The address space ID.
178 * @return Pointer to the cache block if found.
180 LRUBlk* findBlock(Addr addr) const;
183 * Find a block to evict for the address provided.
184 * @param addr The addr to a find a replacement candidate for.
185 * @param writebacks List for any writebacks to be performed.
186 * @return The candidate block.
188 LRUBlk* findVictim(Addr addr, PacketList &writebacks);
191 * Insert the new block into the cache. For LRU this means inserting into
192 * the MRU position of the set.
193 * @param addr The address to update.
194 * @param blk The block to update.
196 void insertBlock(Addr addr, BlkType *blk);
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 * Calculate the set index from the address.
210 * @param addr The address to get the set from.
211 * @return The set index of the address.
213 int extractSet(Addr addr) const
215 return ((addr >> setShift) & setMask);
219 * Get the block offset from an address.
220 * @param addr The address to get the offset of.
221 * @return The block offset.
223 int extractBlkOffset(Addr addr) const
225 return (addr & blkMask);
229 * Align an address to the block size.
230 * @param addr the address to align.
231 * @return The block address.
233 Addr blkAlign(Addr addr) const
235 return (addr & ~(Addr)blkMask);
239 * Regenerate the block address from the tag.
240 * @param tag The tag of the block.
241 * @param set The set of the block.
242 * @return The block address.
244 Addr regenerateBlkAddr(Addr tag, unsigned set) const
246 return ((tag << tagShift) | ((Addr)set << setShift));
250 * Return the hit latency.
251 * @return the hit latency.
253 int getHitLatency() const
259 * Called at end of simulation to complete average block reference stats.
261 virtual void cleanupRefs();
264 #endif // __MEM_CACHE_TAGS_LRU_HH__