--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/pr84503-1.c	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,68 @@
+/* PR tree-optimization/84503 */
+/* { dg-do run } */
+/* { dg-options "-O3" } */
+
+typedef __SIZE_TYPE__ size_t;
+typedef __UINTPTR_TYPE__ uintptr_t;
+
+struct S { int a; unsigned short b; int c, d, e; long f, g, h; int i, j; };
+static struct S *k;
+static size_t l = 0;
+int m;
+
+static int
+bar (void)
+{
+  unsigned i;
+  int j;
+  if (k[0].c == 0)
+    {
+      ++m;
+      size_t n = l * 2;
+      struct S *o;
+      o = (struct S *) __builtin_realloc (k, sizeof (struct S) * n);
+      if (!o)
+	__builtin_exit (0);
+      k = o;
+      for (i = l; i < n; i++)
+	{
+	  void *p = (void *) &k[i];
+	  int q = 0;
+	  size_t r = sizeof (struct S);
+	  if ((((uintptr_t) p) % __alignof__ (long)) == 0
+	      && r % sizeof (long) == 0)
+	    {
+	      long __attribute__ ((may_alias)) *s = (long *) p;
+	      long *t = (long *) ((char *) s + r);
+	      while (s < t)
+		*s++ = 0;
+	    }
+	  else
+	    __builtin_memset (p, q, r);
+	  k[i].c = i + 1;
+	  k[i].a = -1;
+	}
+      k[n - 1].c = 0;
+      k[0].c = l;
+      l = n;
+    }
+  j = k[0].c;
+  k[0].c = k[j].c;
+  return j;
+}
+
+int
+main ()
+{
+  k = (struct S *) __builtin_malloc (sizeof (struct S));
+  if (!k)
+    __builtin_exit (0);
+  __builtin_memset (k, '\0', sizeof (struct S));
+  k->a = -1;
+  l = 1;
+  for (int i = 0; i < 15; ++i)
+    bar ();
+  if (m != 4)
+    __builtin_abort ();
+  return 0;
+}