--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/pr39794.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,33 @@
+/* PR rtl-optimization/39794 */
+/* { dg-do run } */
+/* { dg-options "-O2 -funroll-loops" } */
+
+extern void abort ();
+
+void
+foo (int *a, int n)
+{
+  int i;
+  for (i = 0; i < n; i++)
+    {
+      a[i] *= 2;
+      a[i + 1] = a[i - 1] + a[i - 2];
+    }
+}
+
+int a[16];
+int ref[16] = { 0, 1, 4, 2, 10, 12, 24, 44,
+		72, 136, 232, 416, 736, 1296, 2304, 2032 };
+
+int
+main ()
+{
+  int i;
+  for (i = 0; i < 16; i++)
+    a[i] = i;
+  foo (a + 2, 16 - 3);
+  for (i = 0; i < 16; i++)
+    if (ref[i] != a[i])
+      abort ();
+  return 0;
+}