[Bug fortran/30609] Calculating masks twice

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=30609

--- Comment #5 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
The problem with the test case is that both sum and count
are transformational functions, i.e. they reduce the
rank.

So, ideally this would be translated into

real sum = 0.;

int count = 0;
for (i=0; i<n; i++)
{
    if (a[i] > 0) {
        count ++;
        sum += a[i];
    }
}

return sum / count;

but the scalarizer does not do that (currently), and neither
does the middle end.  It would require loop fusion.

So, it is probably not useful to do common subexpression
elimination for rank>0 expressions if they are the arguments
of transformational functions.