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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;
97 /** The number of sets in the cache. */
98 const unsigned numSets;
99 /** The number of bytes in a block. */
100 const unsigned blkSize;
101 /** The associativity of the cache. */
102 const unsigned assoc;
103 /** The hit latency. */
104 const unsigned hitLatency;
106 /** The cache sets. */
109 /** The cache blocks. */
111 /** The data blocks, 1 per cache block. */
114 /** The amount to shift the address to get the set. */
116 /** The amount to shift the address to get the tag. */
118 /** Mask out all bits that aren't part of the set index. */
120 /** Mask out all bits that aren't part of the block offset. */
125 * Construct and initialize this tag store.
126 * @param _numSets The number of sets in the cache.
127 * @param _blkSize The number of bytes in a block.
128 * @param _assoc The associativity of the cache.
129 * @param _hit_latency The latency in cycles for a hit.
131 LRU(unsigned _numSets, unsigned _blkSize, unsigned _assoc,
132 unsigned _hit_latency);
140 * Return the block size.
141 * @return the block size.
150 * Return the subblock size. In the case of LRU it is always the block
152 * @return The block size.
155 getSubBlockSize() const
161 * Invalidate the given block.
162 * @param blk The block to invalidate.
164 void invalidateBlk(BlkType *blk);
167 * Access block and update replacement data. May not succeed, in which case
168 * NULL pointer is returned. This has all the implications of a cache
169 * access and should only be used as such. Returns the access latency as a side effect.
170 * @param addr The address to find.
171 * @param asid The address space ID.
172 * @param lat The access latency.
173 * @return Pointer to the cache block if found.
175 LRUBlk* accessBlock(Addr addr, int &lat, int context_src);
178 * Finds the given address in the cache, do not update replacement data.
179 * i.e. This is a no-side-effect find of a block.
180 * @param addr The address to find.
181 * @param asid The address space ID.
182 * @return Pointer to the cache block if found.
184 LRUBlk* findBlock(Addr addr) const;
187 * Find a block to evict for the address provided.
188 * @param addr The addr to a find a replacement candidate for.
189 * @param writebacks List for any writebacks to be performed.
190 * @return The candidate block.
192 LRUBlk* findVictim(Addr addr, PacketList &writebacks);
195 * Insert the new block into the cache. For LRU this means inserting into
196 * the MRU position of the set.
197 * @param addr The address to update.
198 * @param blk The block to update.
200 void insertBlock(Addr addr, BlkType *blk, int context_src);
203 * Generate the tag from the given address.
204 * @param addr The address to get the tag from.
205 * @return The tag of the address.
207 Addr extractTag(Addr addr) const
209 return (addr >> tagShift);
213 * Calculate the set index from the address.
214 * @param addr The address to get the set from.
215 * @return The set index of the address.
217 int extractSet(Addr addr) const
219 return ((addr >> setShift) & setMask);
223 * Get the block offset from an address.
224 * @param addr The address to get the offset of.
225 * @return The block offset.
227 int extractBlkOffset(Addr addr) const
229 return (addr & blkMask);
233 * Align an address to the block size.
234 * @param addr the address to align.
235 * @return The block address.
237 Addr blkAlign(Addr addr) const
239 return (addr & ~(Addr)blkMask);
243 * Regenerate the block address from the tag.
244 * @param tag The tag of the block.
245 * @param set The set of the block.
246 * @return The block address.
248 Addr regenerateBlkAddr(Addr tag, unsigned set) const
250 return ((tag << tagShift) | ((Addr)set << setShift));
254 * Return the hit latency.
255 * @return the hit latency.
257 int getHitLatency() const
263 * Called at end of simulation to complete average block reference stats.
265 virtual void cleanupRefs();
268 #endif // __MEM_CACHE_TAGS_LRU_HH__