[Bug middle-end/116135] __builtin_mul_overflow inefficient for _BitInt(31) (with widening multiply)

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116135

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Similarly for:
```
int f1(unsigned _BitInt(9) x, unsigned _BitInt(9) y, unsigned _BitInt(9) * res)
{
   return __builtin_mul_overflow(x, y, res);
}

int f2(unsigned _BitInt(9) x, unsigned _BitInt(9) y, unsigned _BitInt(9) * res)
{
  unsigned int xx = x;
  unsigned int yy = y;
  unsigned int t = xx * yy;
  *res = t;
  return (t >> (9)) != 0;
}
```