Re: [BusyBox] Re: Long term code compactness regression

[Paolo Carlini <pcarlini at unitus dot it>]

Jan Hubicka wrote:

> > I checked this morning, with last week's gcc-3.1 snapshot.  A few cases
> > with g77 have slowed down in recent weeks.  The worst examples of
> In what testcases g77 slowed down recently?
>
> Honza

Jan, sorry for my pedantry, but I have ready at hand a very short and basic
c++ testcode (reduced from the Haney tests) which today is 2 times (!) slower
than one week ago on i686 (-O2)... Do you have time to look a little bit at
it? Here it is (PR4714 for some more details):

///////////////////////////////////////////////
class RealMatrix {
public:

  float &index(int i, int j)
    {
      return d[i - 1 + n[0] * (j - 1)];
    }
  float index(int i, int j) const
    {
      return d[i - 1 + n[0] * (j - 1)];
    }

  int dim(int i) const { return n[i - 1]; }

private:

  float *d;
  int n[4];
};

void rmatMul(RealMatrix &t, const RealMatrix &a, const RealMatrix &b)
{
  const int M = a.dim(1), N = b.dim(2), K = b.dim(1);

  for (int j = 1; j <= N; j++)
    {
      for (int k = 1; k <= K; k++)
        {
          float temp = b.index(k, j);
          if (temp != 0.0)
            {
              for (int i = 1; i <= M; i++)
                t.index(i, j) += temp * a.index(i, k);
            }
        }
    }
}
/////////////////////////////////////////

Thanks,
Paolo.