PR c++/85240 - LTO ICE with using of undeduced auto fn.

	* cp-gimplify.c (cp_genericize_r): Discard using of undeduced auto.

From-SVN: r259177

gcc/cp/ChangeLog

+2018-04-06  Jason Merrill  <jason@redhat.com>
+
+	PR c++/85240 - LTO ICE with using of undeduced auto fn.
+	* cp-gimplify.c (cp_genericize_r): Discard using of undeduced auto.
+
 2018-04-05  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/85209

gcc/cp/cp-gimplify.c

@@ -1294,17 +1294,21 @@ cp_genericize_r (tree *stmt_p, int *walk_subtrees, void *data)
 	  }
 	if (block)
 	  {
-	    tree using_directive;
-	    gcc_assert (TREE_OPERAND (stmt, 0));
+	    tree decl = TREE_OPERAND (stmt, 0);
+	    gcc_assert (decl);
 
-	    using_directive = make_node (IMPORTED_DECL);
+	    if (undeduced_auto_decl (decl))
+	      /* Omit from the GENERIC, the back-end can't handle it.  */;
+	    else
+	      {
+		tree using_directive = make_node (IMPORTED_DECL);
 		TREE_TYPE (using_directive) = void_type_node;
 
-	    IMPORTED_DECL_ASSOCIATED_DECL (using_directive)
-	      = TREE_OPERAND (stmt, 0);
+		IMPORTED_DECL_ASSOCIATED_DECL (using_directive) = decl;
 		DECL_CHAIN (using_directive) = BLOCK_VARS (block);
 		BLOCK_VARS (block) = using_directive;
 	      }
+	  }
 	/* The USING_STMT won't appear in GENERIC.  */
 	*stmt_p = build1 (NOP_EXPR, void_type_node, integer_zero_node);
 	*walk_subtrees = 0;

gcc/testsuite/g++.dg/cpp1y/auto-fn51.C

+// PR c++/85240
+// { dg-do compile { target c++14 } }
+
+auto foo();
+
+void bar()
+{
+  using ::foo;
+}