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#ifndef __TOURNAMENT_PRED_HH__
#define __TOURNAMENT_PRED_HH__
// For Addr type.
#include "arch/alpha/isa_traits.hh"
class TournamentBP
{
public:
/**
* Default branch predictor constructor.
*/
TournamentBP(unsigned local_predictor_size,
unsigned local_ctr_bits,
unsigned local_history_table_size,
unsigned local_history_bits,
unsigned global_predictor_size,
unsigned global_history_bits,
unsigned global_ctr_bits,
unsigned choice_predictor_size,
unsigned choice_ctr_bits,
unsigned instShiftAmt);
/**
* Looks up the given address in the branch predictor and returns
* a true/false value as to whether it is taken.
* @param branch_addr The address of the branch to look up.
* @return Whether or not the branch is taken.
*/
bool lookup(Addr &branch_addr);
/**
* Updates the branch predictor with the actual result of a branch.
* @param branch_addr The address of the branch to update.
* @param taken Whether or not the branch was taken.
*/
void update(Addr &branch_addr, unsigned global_history, bool taken);
inline unsigned readGlobalHist() { return global_history; }
private:
inline bool getPrediction(uint8_t &count);
inline unsigned calcLocHistIdx(Addr &branch_addr);
inline void updateHistoriesTaken(unsigned local_history_idx);
inline void updateHistoriesNotTaken(unsigned local_history_idx);
/**
* Private counter class for the internal saturating counters.
* Implements an n bit saturating counter and provides methods to
* increment, decrement, and read it.
* @todo Consider making this something that more closely mimics a
* built in class so you can use ++ or --.
*/
class SatCounter
{
public:
/**
* Constructor for the counter.
* @param bits How many bits the counter will have.
*/
SatCounter(unsigned bits);
/**
* Constructor for the counter.
* @param bits How many bits the counter will have.
* @param initial_val Starting value for each counter.
*/
SatCounter(unsigned bits, unsigned initial_val);
/**
* Increments the counter's current value.
*/
void increment();
/**
* Decrements the counter's current value.
*/
void decrement();
/**
* Read the counter's value.
*/
uint8_t read()
{
return counter;
}
private:
uint8_t maxVal;
uint8_t counter;
};
/** Local counters. */
SatCounter *local_ctrs;
/** Size of the local predictor. */
unsigned local_predictor_size;
/** Number of bits of the local predictor's counters. */
unsigned local_ctr_bits;
/** Array of local history table entries. */
unsigned *local_history_table;
/** Size of the local history table. */
unsigned local_history_table_size;
/** Number of bits for each entry of the local history table.
* @todo Doesn't this come from the size of the local predictor?
*/
unsigned local_history_bits;
/** Mask to get the proper local history. */
unsigned localHistoryMask;
/** Array of counters that make up the global predictor. */
SatCounter *global_ctrs;
/** Size of the global predictor. */
unsigned global_predictor_size;
/** Number of bits of the global predictor's counters. */
unsigned global_ctr_bits;
/** Global history register. */
unsigned global_history;
/** Number of bits for the global history. */
unsigned global_history_bits;
/** Mask to get the proper global history. */
unsigned globalHistoryMask;
/** Array of counters that make up the choice predictor. */
SatCounter *choice_ctrs;
/** Size of the choice predictor (identical to the global predictor). */
unsigned choice_predictor_size;
/** Number of bits of the choice predictor's counters. */
unsigned choice_ctr_bits;
/** Number of bits to shift the instruction over to get rid of the word
* offset.
*/
unsigned instShiftAmt;
/** Threshold for the counter value; above the threshold is taken,
* equal to or below the threshold is not taken.
*/
unsigned threshold;
};
#endif // __TOURNAMENT_PRED_HH__
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