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44 #ifndef __CPU_PRED_2BIT_LOCAL_PRED_HH__
45 #define __CPU_PRED_2BIT_LOCAL_PRED_HH__
49 #include "base/types.hh"
50 #include "cpu/pred/bpred_unit.hh"
51 #include "cpu/pred/sat_counter.hh"
52 #include "params/LocalBP.hh"
55 * Implements a local predictor that uses the PC to index into a table of
56 * counters. Note that any time a pointer to the bp_history is given, it
57 * should be NULL using this predictor because it does not have any branch
58 * predictor state that needs to be recorded or updated; the update can be
59 * determined solely by the branch being taken or not taken.
61 class LocalBP : public BPredUnit
65 * Default branch predictor constructor.
67 LocalBP(const LocalBPParams *params);
69 virtual void uncondBranch(Addr pc, void * &bp_history);
72 * Looks up the given address in the branch predictor and returns
73 * a true/false value as to whether it is taken.
74 * @param branch_addr The address of the branch to look up.
75 * @param bp_history Pointer to any bp history state.
76 * @return Whether or not the branch is taken.
78 bool lookup(Addr branch_addr, void * &bp_history);
81 * Updates the branch predictor to Not Taken if a BTB entry is
82 * invalid or not found.
83 * @param branch_addr The address of the branch to look up.
84 * @param bp_history Pointer to any bp history state.
85 * @return Whether or not the branch is taken.
87 void btbUpdate(Addr branch_addr, void * &bp_history);
90 * Updates the branch predictor with the actual result of a branch.
91 * @param branch_addr The address of the branch to update.
92 * @param taken Whether or not the branch was taken.
94 void update(Addr branch_addr, bool taken, void *bp_history, bool squashed);
96 void retireSquashed(void *bp_history)
97 { assert(bp_history == NULL); }
99 void squash(void *bp_history)
100 { assert(bp_history == NULL); }
106 * Returns the taken/not taken prediction given the value of the
108 * @param count The value of the counter.
109 * @return The prediction based on the counter value.
111 inline bool getPrediction(uint8_t &count);
113 /** Calculates the local index based on the PC. */
114 inline unsigned getLocalIndex(Addr &PC);
116 /** Array of counters that make up the local predictor. */
117 std::vector<SatCounter> localCtrs;
119 /** Size of the local predictor. */
120 unsigned localPredictorSize;
122 /** Number of sets. */
123 unsigned localPredictorSets;
125 /** Number of bits of the local predictor's counters. */
126 unsigned localCtrBits;
128 /** Mask to get index bits. */
132 #endif // __CPU_PRED_2BIT_LOCAL_PRED_HH__