--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/strlenopt-26.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,25 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#include "strlenopt.h"
+
+__attribute__((noinline, noclone)) size_t
+fn1 (char *p, const char *r)
+{
+  size_t len1 = strlen (r);
+  char *q = strchr (p, '\0');
+  *q = '\0';
+  return len1 - strlen (r); // This strlen should be optimized into len1.
+}
+
+int
+main (void)
+{
+  char p[] = "foobar";
+  const char *volatile q = "xyzzy";
+  fn1 (p, q);
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen" } } */
+/* { dg-final { scan-tree-dump-times "strchr \\(" 0 "strlen" } } */