Change millis() / micros() to use Systick on Tiva based boards

I want to sugest a change in the milis()/micros() fuctions

I'm realy don't exacly know how to read code in direct access coding but i belive millis() uses micros() to count wich uses TIMER5 right?

Well i think this is a big waste of a timer wich can be used for PWM, pulse measuring or sometigh else since Tiva has a dedicated timer for that, the system tick.

i use this to simulate millis()
void SysTickbegin(){
  SysTickPeriodSet(F_CPU/1000);// for miliseconds, F_CPU/1000000 for microseconds
  SysTickIntRegister(SycTickInt);
  SysTickIntEnable();    
}
void SycTickInt(){
  milis++; //micros++ if period set to  F_CPU/1000000
}