Measure time in milliseconds

Hi

I am a beginner in the AVR world.

I am using Crossworks for AVR with Atmega128.

I want to measure the time execution for a function for example and print the time elapsed, I wrote this code but with 0 result:

void main(void)

{

TCCR0=(1<<WGM01) | (1<<CS01) | (1<<CS00); // start 8 bit clock/64

 #asm("sei")

  start = millis();
  printf("start = %d", start);
 for(i=0;i<100;i++)
 { y=sin(x);}

  finish=millis();

printf("finish = %d", finish);
  elapsed_time =finish-start;
  printf("Elapsed time =");
  printf("%u", elapsed_time);

}

ISR(TIMER1_COMP_vect)
{

   ctl_increment_tick_from_isr();
}

unsigned long millis()
{

    unsigned long m;
  
    m = ctl_current_time;

  
    return m;
 
}

I am getting 0. in the hyperterminal

Can anyone helps me.