Binary rounding problem in 3DNow!

Hello all you happy people :)

I have experience with C, Python and CLisp, but ASM is very new to me.
So I am doing the very-fast-prime-search(which is almost a must when
learning a new language), and I succeeded with a rather slow version
using idivl, at first. I profiled my code and decided that the idivl
could be replaced with the AMD 3DNow! instructions.

The first failure is with %ecx = 3 and %edx=9.
The rounding to int, just before the debug, should round the 1/3*9 to
3, but because of the binary representation of the float, it rounds it
down to 2.
Is there a way around it?

     MOVD    %ecx, %MM0       /* divisor */
     PI2FD   %MM0, %MM0      /* divisor to float */
     MOVQ    %MM0, %MM2     /* copy of divisor */
     PFRCP   %MM0, %MM0    /* 1/divisor */
     MOVD    %edx, %MM1       /* prime candidate */
     PI2FD   %MM1, %MM1      /* prime. to float */
     MOVQ    %MM1, %MM3     /* copy of prime. */
     PFMUL   %MM0, %MM1    /* 1/divisor * prime. */
     PF2ID   %MM1, %MM1      /* answer to int ...*/
     MOVQ    %MM1, %MM4     /* DEBUG for viewing value */
     PI2FD   %MM1, %MM1      /* ... and back to float */
     PFMUL   %MM1, %MM2    /*  int(1/divisor*prime) * divisor */
     PFCMPEQ %MM2, %MM3  /*if the %MM2 and the prime candidate are
equal, then != prime */
     MOVD %MM3, %eax

I know the code is rather ugly, but remember I'm still new, and I am
currently trying to make it work first :)

Every answer(even if it's just for saying "You're fckd!") is
appreciated.

Thanks,
kuratkull