#include <stdint.h>
#include <stdio.h>

typedef enum {
   NEAREST = 0,
   DOWN    = 1,
   UP      = 2,
   TRUNC   = 3
} RoundingMode;

void setRoundMode (RoundingMode mode)
{
   uint16_t ctrl = 0;
   asm ("fstcw %0" : "=m"(ctrl));
   ctrl = (ctrl & 0xF3ff) | (mode << 10);
   asm ("fldcw %0" : : "m"(ctrl));
}

typedef enum {
   PREC_24 = 0,
   PREC_53 = 2,
   PREC_64 = 3
} Precision;

void setPrecision (Precision pres)
{
   uint16_t ctrl = 0;
   asm ("fstcw %0" : "=m"(ctrl));
   ctrl = (ctrl & 0xFCFF) | (pres << 8);
   asm ("fldcw %0" : : "m"(ctrl));
}

int main (void)
{
   double alvo_s = 12345.6789;
   register double alvo_x = 1;
   int i;

   //setRoundMode (TRUNC);
   //setPrecision (PREC_53);

   for (i = 0; i < 100000000; ++i)
      alvo_x = (alvo_s * alvo_x) - (int) (alvo_s * alvo_x);

   printf ("%g\n", alvo_x);

   return 0;
}