#include <stm32l1xx.h>

typedef struct {
    unsigned sum;
    unsigned count;
    unsigned avg;
} benchmark_t;

static inline void start_timing()
{
    RCC->APB1ENR |= RCC_APB1ENR_TIM7EN;
    TIM7->CR1 = 1;
    TIM7->ARR = 0xFFFF;
    TIM7->CNT = 0;
}

static inline void end_timing(benchmark_t *b)
{
    b->sum += TIM7->CNT * 2; // APB1 prescaler = 2
    b->count++;
    b->avg = b->sum / b->count;
}