fib-optimized.c

#include <stdio.h>

/**
 * Sequência de Fibonacci otimizada com Inline Assembly
*/
int fib(int n)
{
  register int r = 0;

  __asm__(
    "movl %1, %%ecx\n\t"
    "movl $1, %%ebx\n\t"
    ".lp:\n\t"
    "  xaddl %%ebx, %0\n\t"
    "  loop .lp"

    : "+r" (r)
    : "r"  (n)
  );

  return r;
}

int main(void)
{
  int x;

  scanf("%d", &x);
  printf("fib(%d) = %d\n", x, fib(x));

  return 0;
}