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.

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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;
80 uint8_t confidence;
81 uint16_t tag;
82 uint8_t age;
83 bool dir;
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 loopHit;
104
105 LTageBranchInfo(int sz)
106 : TageBranchInfo(sz),
107 loopTag(0), currentIter(0),
108 loopPred(false),
109 loopPredValid(false), loopIndex(0), loopHit(0)
110 {}
111 };
112
113 /**
114 * Computes the index used to access the
115 * loop predictor.
116 * @param pc_in The unshifted branch PC.
117 */
118 int lindex(Addr pc_in) const;
119
120 /**
121 * Get a branch prediction from the loop
122 * predictor.
123 * @param pc The unshifted branch PC.
124 * @param bi Pointer to information on the
125 * prediction.
126 */
127 bool getLoop(Addr pc, LTageBranchInfo* bi) const;
128
129 /**
130 * Updates the loop predictor.
131 * @param pc The unshifted branch PC.
132 * @param taken The actual branch outcome.
133 * @param bi Pointer to information on the
134 * prediction recorded at prediction time.
135 */
136 void loopUpdate(Addr pc, bool Taken, LTageBranchInfo* bi);
137
138 /**
139 * Speculatively updates the loop predictor
140 * iteration count.
141 * @param pc The unshifted branch PC.
142 * @param taken The predicted branch outcome.
143 * @param bi Pointer to information on the prediction
144 * recorded at prediction time.
145 */
146 void specLoopUpdate(Addr pc, bool taken, LTageBranchInfo* bi);
147
148 /**
149 * Update LTAGE for conditional branches.
150 * @param branch_pc The unshifted branch PC.
151 * @param taken Actual branch outcome.
152 * @param bi Pointer to information on the prediction
153 * recorded at prediction time.
154 * @nrand Random int number from 0 to 3

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196 const unsigned loopTableAgeBits;
197 const unsigned loopTableConfidenceBits;
198 const unsigned loopTableTagBits;
199 const unsigned loopTableIterBits;
200 const unsigned logLoopTableAssoc;
201 const uint8_t confidenceThreshold;
202 const uint16_t loopTagMask;
203 const uint16_t loopNumIterMask;
204
205 LoopEntry *ltable;
206
207 int8_t loopUseCounter;
208 unsigned withLoopBits;
209
210 // stats
211 Stats::Scalar loopPredictorCorrect;
212 Stats::Scalar loopPredictorWrong;
213};
214
215#endif // __CPU_PRED_LTAGE