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43 #ifndef __CPU_O3_2BIT_LOCAL_PRED_HH__
44 #define __CPU_O3_2BIT_LOCAL_PRED_HH__
48 #include "base/types.hh"
49 #include "cpu/o3/sat_counter.hh"
52 * Implements a local predictor that uses the PC to index into a table of
53 * counters. Note that any time a pointer to the bp_history is given, it
54 * should be NULL using this predictor because it does not have any branch
55 * predictor state that needs to be recorded or updated; the update can be
56 * determined solely by the branch being taken or not taken.
62 * Default branch predictor constructor.
63 * @param localPredictorSize Size of the local predictor.
64 * @param localCtrBits Number of bits per counter.
65 * @param instShiftAmt Offset amount for instructions to ignore alignment.
67 LocalBP(unsigned localPredictorSize, unsigned localCtrBits,
68 unsigned instShiftAmt);
71 * Looks up the given address in the branch predictor and returns
72 * a true/false value as to whether it is taken.
73 * @param branch_addr The address of the branch to look up.
74 * @param bp_history Pointer to any bp history state.
75 * @return Whether or not the branch is taken.
77 bool lookup(Addr &branch_addr, void * &bp_history);
80 * Updates the branch predictor to Not Taken if a BTB entry is
81 * invalid or not found.
82 * @param branch_addr The address of the branch to look up.
83 * @param bp_history Pointer to any bp history state.
84 * @return Whether or not the branch is taken.
86 void BTBUpdate(Addr &branch_addr, void * &bp_history);
89 * Updates the branch predictor with the actual result of a branch.
90 * @param branch_addr The address of the branch to update.
91 * @param taken Whether or not the branch was taken.
93 void update(Addr &branch_addr, bool taken, void *bp_history);
95 void squash(void *bp_history)
96 { assert(bp_history == NULL); }
102 * Returns the taken/not taken prediction given the value of the
104 * @param count The value of the counter.
105 * @return The prediction based on the counter value.
107 inline bool getPrediction(uint8_t &count);
109 /** Calculates the local index based on the PC. */
110 inline unsigned getLocalIndex(Addr &PC);
112 /** Array of counters that make up the local predictor. */
113 std::vector<SatCounter> localCtrs;
115 /** Size of the local predictor. */
116 unsigned localPredictorSize;
118 /** Number of sets. */
119 unsigned localPredictorSets;
121 /** Number of bits of the local predictor's counters. */
122 unsigned localCtrBits;
124 /** Number of bits to shift the PC when calculating index. */
125 unsigned instShiftAmt;
127 /** Mask to get index bits. */
131 #endif // __CPU_O3_2BIT_LOCAL_PRED_HH__