[Bug fortran/50981] New: [4.4/4.5/4.6/4.7 Regression] Wrong-code for scalarizing ELEMENTAL call with absent OPTIONAL argument

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50981

             Bug #: 50981
           Summary: [4.4/4.5/4.6/4.7 Regression] Wrong-code for
                    scalarizing ELEMENTAL call with absent OPTIONAL
                    argument
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org


Created attachment 25705
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25705
test case

As reported by Andriy Kostyuk,
http://gcc.gnu.org/ml/fortran/2011-11/msg00035.html

There is a wrong-code issue with absent OPTIONAL arguments and ELEMENTAL.

It works for me with 4.1, 4.3, and
  4.4.0 20090206 (experimental) [trunk revision 143983] (SUSE Linux)
It fails for me with 4.5, 4.6 and 4.7
  4.4.6 20110219 (prerelease) [gcc-4_4-branch revision 170290]
and was reported to be broken in
  GNU Fortran (Ubuntu/Linaro 4.4.4-14ubuntu5) 4.4.5


If one looks at the dump, one finds:
  ff (real(kind=8) & restrict a, integer(kind=4) * b)
  {
  ...
      integer(kind=4) D.1747;
    D.1747 = *b;
  ...
      while (1)
        {
          if (S.1 > 2) goto L.2;
          val.0 = gg (&ac[S.1 + -1], &D.1747) + val.0;
          S.1 = S.1 + 1;
        }

The "D.1747 = *b;" is a rather bad idea if "b == NULL".