1/*
2 * Copyright (c) 2014 The University of Wisconsin
3 *
4 * Copyright (c) 2006 INRIA (Institut National de Recherche en
5 * Informatique et en Automatique / French National Research Institute
6 * for Computer Science and Applied Mathematics)
7 *
8 * All rights reserved.

--- 62 unchanged lines hidden (view full) ---

71
72 private:
73 // Prediction Structures
74 // Loop Predictor Entry
75 struct LoopEntry
76 {
77 uint16_t numIter;
78 uint16_t currentIter;
79 uint16_t currentIterSpec;
79 uint16_t currentIterSpec; // only for useSpeculation
80 uint8_t confidence;
81 uint16_t tag;
82 uint8_t age;
83 bool dir;
83 bool dir; // only for useDirectionBit
84
85 LoopEntry() : numIter(0), currentIter(0), currentIterSpec(0),
86 confidence(0), tag(0), age(0), dir(0) { }
87 };
88
89 // more provider types
90 enum {
91 LOOP = LAST_TAGE_PROVIDER_TYPE + 1
92 };
93
94 // Primary branch history entry
95 struct LTageBranchInfo : public TageBranchInfo
96 {
97 uint16_t loopTag;
98 uint16_t currentIter;
99
100 bool loopPred;
101 bool loopPredValid;
102 int loopIndex;
103 int loopLowPcBits; // only for useHashing
104 int loopHit;
105
106 LTageBranchInfo(int sz)
107 : TageBranchInfo(sz),
108 loopTag(0), currentIter(0),
109 loopPred(false),
109 loopPredValid(false), loopIndex(0), loopHit(0)
110 loopPredValid(false), loopIndex(0), loopLowPcBits(0), loopHit(0)
111 {}
112 };
113
114 /**
115 * Computes the index used to access the
116 * loop predictor.
117 * @param pc_in The unshifted branch PC.
118 */
119 int lindex(Addr pc_in) const;
120
121 /**
122 * Computes the index used to access the
123 * ltable structures.
124 * It may take hashing into account
125 * @param index Result of lindex function
126 * @param lowPcBits PC bits masked with set size
127 * @param way Way to be used
128 */
129 int finallindex(int lindex, int lowPcBits, int way) const;
130
131 /**
132 * Get a branch prediction from the loop
133 * predictor.
134 * @param pc The unshifted branch PC.
135 * @param bi Pointer to information on the
136 * prediction.
137 * @param speculative Use speculative number of iterations
138 */
127 bool getLoop(Addr pc, LTageBranchInfo* bi) const;
139 bool getLoop(Addr pc, LTageBranchInfo* bi, bool speculative) const;
140
141 /**
142 * Updates the loop predictor.
143 * @param pc The unshifted branch PC.
144 * @param taken The actual branch outcome.
145 * @param bi Pointer to information on the
146 * prediction recorded at prediction time.
147 */
148 void loopUpdate(Addr pc, bool Taken, LTageBranchInfo* bi);
149
150 /**
151 * Speculatively updates the loop predictor
140 * iteration count.
141 * @param pc The unshifted branch PC.
152 * iteration count (only for useSpeculation).
153 * @param taken The predicted branch outcome.
154 * @param bi Pointer to information on the prediction
155 * recorded at prediction time.
156 */
146 void specLoopUpdate(Addr pc, bool taken, LTageBranchInfo* bi);
157 void specLoopUpdate(bool taken, LTageBranchInfo* bi);
158
159 /**
160 * Update LTAGE for conditional branches.
161 * @param branch_pc The unshifted branch PC.
162 * @param taken Actual branch outcome.
163 * @param bi Pointer to information on the prediction
164 * recorded at prediction time.
165 * @nrand Random int number from 0 to 3

--- 41 unchanged lines hidden (view full) ---

207 const unsigned loopTableAgeBits;
208 const unsigned loopTableConfidenceBits;
209 const unsigned loopTableTagBits;
210 const unsigned loopTableIterBits;
211 const unsigned logLoopTableAssoc;
212 const uint8_t confidenceThreshold;
213 const uint16_t loopTagMask;
214 const uint16_t loopNumIterMask;
215 const int loopSetMask;
216
217 LoopEntry *ltable;
218
219 int8_t loopUseCounter;
220 unsigned withLoopBits;
221
222 const bool useDirectionBit;
223 const bool useSpeculation;
224 const bool useHashing;
225
226 // stats
227 Stats::Scalar loopPredictorCorrect;
228 Stats::Scalar loopPredictorWrong;
229};
230
231#endif // __CPU_PRED_LTAGE