--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/strlenopt-57.c	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,49 @@
+/* PR tree-optimization/86914 - wrong code with strlen() of poor-man's
+   flexible array member plus offset
+   { dg-do compile }
+   { dg-options "-O2 -Wall -fdump-tree-optimized" } */
+
+#include "strlenopt.h"
+
+struct A0 { char i, a[0]; };
+struct A1 { char i, a[1]; };
+struct A9 { char i, a[9]; };
+struct Ax { char i, a[]; };
+
+extern int a[];
+
+extern struct A0 a0;
+extern struct A1 a1;
+extern struct A9 a9;
+extern struct Ax ax;
+
+void test_var_flexarray_cst_off (void)
+{
+  /* Use arbitrary constants greater than 16 in case GCC ever starts
+     unrolling strlen() calls with small array arguments.  */
+  a[0] = 17 < strlen (a0.a + 1);
+  a[1] = 19 < strlen (a1.a + 1);
+  a[2] = 23 < strlen (a9.a + 9);
+  a[3] = 29 < strlen (ax.a + 3);
+}
+
+void test_ptr_flexarray_cst_off (struct A0 *p0, struct A1 *p1,
+				 struct A9 *p9, struct Ax *px)
+{
+  a[0] = 17 < strlen (p0->a + 1);
+  a[1] = 19 < strlen (p1->a + 1);
+  a[2] = 23 < strlen (p9->a + 9);
+  a[3] = 29 < strlen (px->a + 3);
+}
+
+void test_ptr_flexarray_var_off (struct A0 *p0, struct A1 *p1,
+				 struct A9 *p9, struct Ax *px,
+				 int i)
+{
+  a[0] = 17 < strlen (p0->a + i);
+  a[1] = 19 < strlen (p1->a + i);
+  a[2] = 23 < strlen (p9->a + i);
+  a[3] = 29 < strlen (px->a + i);
+}
+
+/* { dg-final { scan-tree-dump-times "strlen" 12 "optimized" } } */