sanopt: Avoid crash on anonymous parameter [PR93436]

Here we crash when using -fsanitize=address -fdump-tree-sanopt because
the dumping code uses IDENTIFIER_POINTER on a null DECL_NAME.  Instead,
we can print "<anonymous>" in such a case.  Or we could avoid printing
that diagnostic altogether.

2020-01-26  Marek Polacek  <polacek@redhat.com>

	PR tree-optimization/93436
	* sanopt.c (sanitize_rewrite_addressable_params): Avoid crash on
	null DECL_NAME.

gcc/ChangeLog

+2020-01-26  Marek Polacek  <polacek@redhat.com>
+
+	PR tree-optimization/93436
+	* sanopt.c (sanitize_rewrite_addressable_params): Avoid crash on
+	null DECL_NAME.
+
 2020-01-26  Jason Merrill  <jason@redhat.com>
 
 	PR c++/92601

gcc/sanopt.c

@@ -1174,9 +1174,12 @@ sanitize_rewrite_addressable_params (function *fun)
 	    continue;
 
 	  if (dump_file)
-	    fprintf (dump_file,
-		     "Rewriting parameter whose address is taken: %s\n",
-		     IDENTIFIER_POINTER (DECL_NAME (arg)));
+	    {
+	      fprintf (dump_file,
+		       "Rewriting parameter whose address is taken: ");
+	      print_generic_expr (dump_file, arg, dump_flags);
+	      fputc ('\n', dump_file);
+	    }
 
 	  SET_DECL_PT_UID (var, DECL_PT_UID (arg));