tournament.hh revision 1684 
1#ifndef __CPU_BETA_CPU_TOURNAMENT_PRED_HH__
2#define __CPU_BETA_CPU_TOURNAMENT_PRED_HH__
3
4// For Addr type.
5#include "arch/alpha/isa_traits.hh"
6#include "cpu/beta_cpu/sat_counter.hh"
7
8class TournamentBP
9{
10  public:
11    /**
12     * Default branch predictor constructor.
13     */
14    TournamentBP(unsigned local_predictor_size,
15                 unsigned local_ctr_bits,
16                 unsigned local_history_table_size,
17                 unsigned local_history_bits,
18                 unsigned global_predictor_size,
19                 unsigned global_history_bits,
20                 unsigned global_ctr_bits,
21                 unsigned choice_predictor_size,
22                 unsigned choice_ctr_bits,
23                 unsigned instShiftAmt);
24
25    /**
26     * Looks up the given address in the branch predictor and returns
27     * a true/false value as to whether it is taken.
28     * @param branch_addr The address of the branch to look up.
29     * @return Whether or not the branch is taken.
30     */
31    bool lookup(Addr &branch_addr);
32
33    /**
34     * Updates the branch predictor with the actual result of a branch.
35     * @param branch_addr The address of the branch to update.
36     * @param taken Whether or not the branch was taken.
37     */
38    void update(Addr &branch_addr, unsigned global_history, bool taken);
39
40    inline unsigned readGlobalHist() { return globalHistory; }
41
42  private:
43
44    inline bool getPrediction(uint8_t &count);
45
46    inline unsigned calcLocHistIdx(Addr &branch_addr);
47
48    inline void updateHistoriesTaken(unsigned local_history_idx);
49
50    inline void updateHistoriesNotTaken(unsigned local_history_idx);
51
52    /** Local counters. */
53    SatCounter *localCtrs;
54
55    /** Size of the local predictor. */
56    unsigned localPredictorSize;
57
58    /** Number of bits of the local predictor's counters. */
59    unsigned localCtrBits;
60
61    /** Array of local history table entries. */
62    unsigned *localHistoryTable;
63
64    /** Size of the local history table. */
65    unsigned localHistoryTableSize;
66
67    /** Number of bits for each entry of the local history table.
68     *  @todo Doesn't this come from the size of the local predictor?
69     */
70    unsigned localHistoryBits;
71
72    /** Mask to get the proper local history. */
73    unsigned localHistoryMask;
74
75
76    /** Array of counters that make up the global predictor. */
77    SatCounter *globalCtrs;
78
79    /** Size of the global predictor. */
80    unsigned globalPredictorSize;
81
82    /** Number of bits of the global predictor's counters. */
83    unsigned globalCtrBits;
84
85    /** Global history register. */
86    unsigned globalHistory;
87
88    /** Number of bits for the global history. */
89    unsigned globalHistoryBits;
90
91    /** Mask to get the proper global history. */
92    unsigned globalHistoryMask;
93
94
95    /** Array of counters that make up the choice predictor. */
96    SatCounter *choiceCtrs;
97
98    /** Size of the choice predictor (identical to the global predictor). */
99    unsigned choicePredictorSize;
100
101    /** Number of bits of the choice predictor's counters. */
102    unsigned choiceCtrBits;
103
104    /** Number of bits to shift the instruction over to get rid of the word
105     *  offset.
106     */
107    unsigned instShiftAmt;
108
109    /** Threshold for the counter value; above the threshold is taken,
110     *  equal to or below the threshold is not taken.
111     */
112    unsigned threshold;
113};
114
115#endif // __CPU_BETA_CPU_TOURNAMENT_PRED_HH__
116