--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/torture/pr78684.C	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,20 @@
+// PR middle-end/78684
+// { dg-do compile }
+
+class a {
+public:
+  a(long);
+  void operator<<=(long) {
+    long b;
+    for (unsigned long c; c; c--)
+      d[c + b] = d[c];
+  }
+  a &g();
+  long d[28];
+};
+long e;
+int f;
+void j() {
+  a h(e), i = h;
+  i.g() <<= f;
+}