--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/g++.dg/torture/pr78189.C	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,41 @@
+/* { dg-do run } */
+/* { dg-additional-options "-ftree-slp-vectorize -fno-vect-cost-model" } */
+
+#include <cstddef>
+
+struct A
+{
+  void * a;
+  void * b;
+};
+
+struct alignas(16) B
+{
+  void * pad;
+  void * misaligned;
+  void * pad2;
+
+  A a;
+
+  void Null();
+};
+
+void B::Null()
+{
+  a.a = nullptr;
+  a.b = nullptr;
+}
+
+void __attribute__((noinline,noclone))
+NullB(void * misalignedPtr)
+{
+  B* b = reinterpret_cast<B*>(reinterpret_cast<char *>(misalignedPtr) - offsetof(B, misaligned));
+  b->Null();
+}
+
+int main()
+{
+  B b;
+  NullB(&b.misaligned);
+  return 0;
+}