predictorhash.h

   1 #ifndef PREDICTORHASH_H
   2 #define PREDICTORHASH_H
   3
   4
   5
   6 #define PREDICT_TABLE_SIZE 0x1000 // 256 entry table
   7 #define INDEX_MASK 0x00000FFF // 8 bit index in a 256 entry table
   8 #define TAG_MASK   0x00003000 // next 6 bits for tag
   9 #define TAG_SHIFT  12         // shift to bring the tag down for comparison.
  10 #define HASH_SHIFT 5 // shift the prev_hash by this many bits before ORing with last_hash
  11
  12 struct predict_table_entry{
  13 /*Phase prediction paper says that their predictor has
  14 256 entries encompassing less than 500 bytes. This should make each entry of
  15 2 bytes (a little less).  How to divide this between tag and predicted id ?
  16
  17 On-line simpoint says that they have a signature table of 1024 entries. Thus
  18 the phase_id can go up to 10 bits. This leaves only 6 bits for Tag ?  Or did
  19 they use larger table entries ?
  20 */
  21
  22         // limit the size in the light of above discussion?
  23         unsigned int tag;
  24         unsigned int phase_id;
  25 };
  26
  27 struct PredictorHash {
  28
  29 // how much in future we have to predict
  30         unsigned int future_len;
  31
  32         unsigned short * history;
  33         unsigned int hist_head;
  34         unsigned int hist_tail;
  35
  36         /*it shows only the num-entries. size of history = hist_len*2*2 bytes
  37          * if short */
  38         unsigned int history_length;
  39         int largest_center;
  40
  41
  42         // prediction table
  43         // see the size : shall we limit the size ??
  44         struct predict_table_entry predict_table[PREDICT_TABLE_SIZE];
  45         unsigned int prev_hash;       // contains the id and num_occr of
  46                                       // prev (before the last) phase hashed
  47
  48         unsigned int last_phase_predictions; //stats
  49         unsigned int new_phase_predictions;
  50
  51 };
  52
  53 struct PredictorHash * predictor_create(
  54                   unsigned int hist_size
  55                   ,unsigned int futur_len
  56                 );
  57 #endif //PREDICTORHASH_H