Static_branch_prediction_CH32V003

#ifdef BRANCH_PREDICTION

#define ARRAY_SIZE 256
#define MIN   2               //sorted - 0x261a, random - 0x2620
#define MID   ARRAY_SIZE/2    //sorted - 0x2716, random - 0x272c
#define MAX   ARRAY_SIZE-2    //sorted - 0x2812, random - 0x2812


volatile uint32_t time_unsorted;
volatile uint32_t time_sort_min, time_sort_max, time_sort_mid;

volatile uint32_t start_time, end_time;

volatile uint16_t sorted_array[ARRAY_SIZE];
volatile uint16_t unsorted_array[ARRAY_SIZE];
volatile uint32_t cnt_tick;


volatile uint32_t dummy = 0;

void SysTick_Init(void){
   SysTick->SR = 0;
   SysTick->CNT = 0;
   SysTick->CTLR = 5;
}


static uint32_t random_seed = 123456789;

uint16_t rand_xorshift() {
    random_seed ^= random_seed << 13;
    random_seed ^= random_seed >> 17;
    random_seed ^= random_seed << 5;
    return (uint16_t)(random_seed & 0x00FF);
}

uint32_t measure_time(volatile uint16_t *array, uint16_t treshold) {

   start_time = SysTick->CNT;
   for (uint32_t i = 0; i < ARRAY_SIZE; i++) {
        if (array[i] > treshold){
            dummy++;
         } else {
           asm volatile("nop");
           dummy--;
         }
    }
    end_time = SysTick->CNT;
    return end_time - start_time;
}

int main() {

   SysTick_Init();

   for (uint32_t i = 0; i < ARRAY_SIZE; i++) {
        sorted_array[i] = i;
        //unsorted_array[i] = (uint16_t)rand_xorshift();
        unsorted_array[i] = 1;
       }

   while (1){
      time_unsorted = measure_time(unsorted_array,(uint16_t)MID);
      time_sort_min = measure_time(sorted_array,  (uint16_t)MIN);
      time_sort_mid = measure_time(sorted_array,  (uint16_t)MID);
      time_sort_max = measure_time(sorted_array,  (uint16_t)MAX);

      cnt_tick = SysTick->CNT;
      asm("nop");
    }
}
#endif