1/*
2 * Copyright (c) 2012-2014,2017 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software

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54
55#include "base/logging.hh"
56#include "base/types.hh"
57#include "debug/CacheRepl.hh"
58#include "mem/cache/base.hh"
59#include "mem/cache/blk.hh"
60#include "mem/cache/replacement_policies/base.hh"
61#include "mem/cache/tags/base.hh"
62#include "params/BaseSetAssoc.hh"
63
64/**
65 * A BaseSetAssoc cache tag store.
66 * @sa \ref gem5MemorySystem "gem5 Memory System"
67 *
68 * The BaseSetAssoc placement policy divides the cache into s sets of w
69 * cache lines (ways). A cache line is mapped onto a set, and can be placed
70 * into any of the ways of this set.
71 */
72class BaseSetAssoc : public BaseTags
73{
74 public:
75 /** Typedef the block type used in this tag store. */
76 typedef CacheBlk BlkType;
77 /** Typedef the set type used in this tag store. */
78 typedef std::vector<CacheBlk*> SetType;
79
80 protected:
81 /** The associativity of the cache. */
82 const unsigned assoc;
83 /** The allocatable associativity of the cache (alloc mask). */
84 unsigned allocAssoc;
85
86 /** The cache blocks. */
87 std::vector<BlkType> blks;
88
89 /** The number of sets in the cache. */
90 const unsigned numSets;
91
92 /** Whether tags and data are accessed sequentially. */
93 const bool sequentialAccess;
94
95 /** The cache sets. */
96 std::vector<SetType> sets;
97
98 /** The amount to shift the address to get the set. */
99 int setShift;
100 /** The amount to shift the address to get the tag. */
101 int tagShift;
102 /** Mask out all bits that aren't part of the set index. */
103 unsigned setMask;
104
105 /** Replacement policy */
106 BaseReplacementPolicy *replacementPolicy;
107
108 /**
109 * Find all possible block locations for insertion and replacement of
110 * an address. Should be called immediately before ReplacementPolicy's
111 * findVictim() not to break cache resizing.
112 * Returns blocks in all ways belonging to the set of the address.
113 *
114 * @param addr The addr to a find possible locations for.
115 * @return The possible locations.
116 */
117 std::vector<ReplaceableEntry*> getPossibleLocations(const Addr addr) const
118 override
119 {
120 std::vector<ReplaceableEntry*> locations;
121 for (const auto& blk : sets[extractSet(addr)]) {
122 locations.push_back(static_cast<ReplaceableEntry*>(blk));
123 }
124 return locations;
125 }
126
127 public:
128 /** Convenience typedef. */
129 typedef BaseSetAssocParams Params;
130
131 /**
132 * Construct and initialize this tag store.
133 */
134 BaseSetAssoc(const Params *p);

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200 // If a cache miss
201 lat = lookupLatency;
202 }
203
204 return blk;
205 }
206
207 /**
208 * Find a block given set and way.
209 *
210 * @param set The set of the block.
211 * @param way The way of the block.
212 * @return The block.
213 */
214 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override;
215
216 /**
217 * Find replacement victim based on address. The list of evicted blocks
218 * only contains the victim.
219 *
220 * @param addr Address to find a victim for.
221 * @param is_secure True if the target memory space is secure.
222 * @param evict_blks Cache blocks to be evicted.
223 * @return Cache block to be replaced.
224 */
225 CacheBlk* findVictim(Addr addr, const bool is_secure,
226 std::vector<CacheBlk*>& evict_blks) const override
227 {
228 // Get possible locations for the victim block
229 std::vector<ReplaceableEntry*> locations = getPossibleLocations(addr);
230
231 // Choose replacement victim from replacement candidates
232 CacheBlk* victim = static_cast<CacheBlk*>(replacementPolicy->getVictim(
233 std::vector<ReplaceableEntry*>(
234 locations.begin(), locations.end())));
235
236 // There is only one eviction for this replacement
237 evict_blks.push_back(victim);
238
239 DPRINTF(CacheRepl, "set %x, way %x: selecting blk for replacement\n",
240 victim->getSet(), victim->getWay());
241
242 return victim;

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280 * @return The maximum number of ways available for replacement.
281 */
282 virtual int getWayAllocationMax() const override
283 {
284 return allocAssoc;
285 }
286
287 /**
288 * Generate the tag from the given address.
289 * @param addr The address to get the tag from.
290 * @return The tag of the address.
291 */
292 Addr extractTag(Addr addr) const override
293 {
294 return (addr >> tagShift);
295 }
296
297 /**
298 * Regenerate the block address from the tag and set.
299 *
300 * @param block The block.
301 * @return the block address.
302 */
303 Addr regenerateBlkAddr(const CacheBlk* blk) const override
304 {
305 const Addr set = blk->getSet() << setShift;
306 return ((blk->tag << tagShift) | set);
307 }
308
309 void forEachBlk(std::function<void(CacheBlk &)> visitor) override {
310 for (CacheBlk& blk : blks) {
311 visitor(blk);
312 }
313 }
314
315 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override {
316 for (CacheBlk& blk : blks) {
317 if (visitor(blk)) {
318 return true;
319 }
320 }
321 return false;
322 }
323
324 private:
325 /**
326 * Calculate the set index from the address.
327 *
328 * @param addr The address to get the set from.
329 * @return The set index of the address.
330 */
331 int extractSet(Addr addr) const
332 {
333 return ((addr >> setShift) & setMask);
334 }
335};
336
337#endif //__MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__