Resource sharing, implement optimization pass

[JulianKemmerer]

Want to detect and fix things like for ex. below where the same functionality can be done with '1 multiplier and more muxing' instead of '2 multipliers and fewer muxing'.

2 multipliers and fewer muxing

int32_t two_multipliers(uint1_t sel, int32_t a, int32_t b)
{
  int32_t rv;
  if(sel)
  {
    rv = a * a;
  }
  else
  {
    rv = b * b;
  }
  return rv;
}

1 multiplier and more muxing

int32_t one_multiplier(uint1_t sel, int32_t a, int32_t b)
{
  int32_t rv;
  int32_t mult_left;
  int32_t mult_right;
  if(sel)
  {
    mult_left = a;
    mult_right = a;
  }
  else
  {
    mult_left = b;
    mult_right = b;
  }
  rv = mult_left * mult_right;
  return rv;
}