[Bug middle-end/55814] Missed optimization with short-circuit evaluation of always evaluated comparisons/loads

["tkoenig at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55814

--- Comment #2 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2012-12-27 17:23:54 UTC ---
An even more pronounced test case, where we could sink
a lot more stores, which in fact could lead to moving
a whole loop:

logical function bar(a,b,c)
  logical, intent(in) :: a, b
  logical, intent(in), dimension(3) :: c
  bar = a .and. b .and. any(c)
end

This is translated by the Fortran FE to

bar (logical(kind=4) & restrict a, logical(kind=4) & restrict b,
logical(kind=4)[3] * restrict c)
{
  logical(kind=4) __result_bar;

  {
    logical(kind=4) test.0;

    test.0 = 0;
    {
      integer(kind=8) S.1;

      S.1 = 1;
      while (1)
        {
          if (S.1 > 3) goto L.2;
          if (NON_LVALUE_EXPR <(*c)[S.1 + -1]>)
            {
              test.0 = 1;
              goto L.1;
            }
          S.1 = S.1 + 1;
        }
      L.2:;
    }
    L.1:;
    __result_bar = (*a && *b) && test.0;
  }
  return __result_bar;
}

which the middle-end then doesn't optimize - there would
be no need to evaluate the loop if either a or b were false.