Add a testcase for PR middle-end/87092

	PR middle-end/87092
	* gcc.dg/pr87092.c: New test.

From-SVN: r263837

gcc/testsuite/ChangeLog

+2018-08-24  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR middle-end/87092
+	* gcc.dg/pr87092.c: New test.
+
 2018-08-24  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/67012

gcc/testsuite/gcc.dg/pr87092.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fwrapv" } */
+
+int a, b;
+
+void
+c(void) {
+  if (b)
+    b = a / b;
+}