[Fortran] avoid ICE in gfc_omp_check_optional_argument (PR93464)

        PR fortran/93464
        * openmp.c (gfc_omp_check_optional_argument): Avoid ICE when
        DECL_LANG_SPECIFIC and GFC_DESCRIPTOR_TYPE_P but not
        GFC_DECL_SAVED_DESCRIPTOR as for local allocatable character vars.

        PR fortran/93464
        * gfortran.dg/goacc/pr93464.f90: New.

gcc/fortran/ChangeLog

 2020-01-28  Tobias Burnus  <tobias@codesourcery.com>
 
+	PR fortran/93464
+	* openmp.c (gfc_omp_check_optional_argument): Avoid ICE when
+	DECL_LANG_SPECIFIC and GFC_DESCRIPTOR_TYPE_P but not
+	GFC_DECL_SAVED_DESCRIPTOR as for local allocatable character vars.
+
+2020-01-28  Tobias Burnus  <tobias@codesourcery.com>
+
 	* gfortran.texi (Runtime): Remove tailing '.' in @menu.
 
 2020-01-27  Tobias Burnus  <tobias@codesourcery.com>

gcc/fortran/trans-openmp.c

@@ -101,7 +101,8 @@ gfc_omp_check_optional_argument (tree decl, bool for_present_check)
       decl = GFC_DECL_SAVED_DESCRIPTOR (decl);
     }
 
-  if (TREE_CODE (decl) != PARM_DECL
+  if (decl == NULL_TREE
+      || TREE_CODE (decl) != PARM_DECL
       || !DECL_LANG_SPECIFIC (decl)
       || !GFC_DECL_OPTIONAL_ARGUMENT (decl))
     return NULL_TREE;

gcc/testsuite/ChangeLog

+2020-01-28  Tobias Burnus  <tobias@codesourcery.com>
+
+	PR fortran/93464
+	* gfortran.dg/goacc/pr93464.f90: New.
+
 2020-01-28  Richard Sandiford  <richard.sandiford@arm.com>
 
 	PR tree-optimization/93434

gcc/testsuite/gfortran.dg/goacc/pr93464.f90

+! { dg-do compile }
+!
+! PR fortran/93464
+!
+! Contributed by G. Steinmetz
+!
+program p
+   character :: c(2) = 'a'
+   character, allocatable :: z(:)
+   !$acc parallel
+   !$omp target
+   z = c
+   !$acc end parallel
+   !$omp end target
+   print *, z
+end