--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/20050826-1.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,52 @@
+/* Test whether strncmp has not been "optimized" into memcmp
+   nor any code with memcmp semantics.  */
+/* { dg-do run { target mmap } } */
+/* { dg-options "-O2" } */
+#include <stddef.h>
+#include <stdio.h>
+#include <sys/mman.h>
+/* Darwin spells this differently */
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+#ifndef MAP_ANON
+#define MAP_ANON 0
+#endif
+#ifndef MAP_FAILED
+#define MAP_FAILED ((void *)-1)
+#endif
+#include <stdlib.h>
+
+    struct Flags {
+ int filler[18];
+ unsigned int a:14;
+ unsigned int b:14;
+ unsigned int c:1;
+ unsigned int d:1;
+ unsigned int e:1;
+ unsigned int f:1;
+    };
+static void __attribute__((noinline)) set (struct Flags *);
+static void set (struct Flags *fp)
+{
+  fp->b = 5;
+  fp->d = 1;
+}
+
+static int __attribute__((noinline)) bar (int);
+static int bar(int x) { return !(x==1); }
+int main (void)
+{
+  char *p = mmap (NULL, 131072, PROT_READ | PROT_WRITE,
+                  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  struct Flags *fp;
+  if (p == MAP_FAILED)
+    return 0;
+  if (munmap (p + 65536, 65536) < 0)
+    return 0;
+  fp = (struct Flags*)(p + 65536 - sizeof(struct Flags));
+  set(fp);
+  if (fp->b > 0)
+    return (bar(fp->d));
+  return 1;
+}