8298919: Add a regression test for JDK-8298520

Reviewed-by: chagedorn, roland

Author: TobiHartmann

test/hotspot/jtreg/compiler/loopopts/TestUnexpectedOpaque1.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @key stress randomness
+ * @bug 8298520
+ * @requires vm.compiler2.enabled
+ * @summary Dying subgraph confuses logic that tries to find the OpaqueZeroTripGuard.
+ * @run main/othervm -Xcomp -XX:CompileCommand=compileonly,compiler.loopopts.TestUnexpectedOpaque1::* -XX:-TieredCompilation
+ *                   -XX:+UnlockDiagnosticVMOptions -XX:+StressIGVN -XX:StressSeed=1642564308 compiler.loopopts.TestUnexpectedOpaque1
+ * @run main/othervm -Xcomp -XX:CompileCommand=compileonly,compiler.loopopts.TestUnexpectedOpaque1::* -XX:-TieredCompilation
+ *                   -XX:+UnlockDiagnosticVMOptions -XX:+StressIGVN compiler.loopopts.TestUnexpectedOpaque1
+ */
+
+package compiler.loopopts;
+
+public class TestUnexpectedOpaque1 {
+
+    static int cnt = 0;
+
+    static int test() {
+        int res = 42;
+        for (int i = 500; i > 0; --i) {
+            res |= 1;
+            if (res != 0) {
+                return 43;
+            }
+            cnt++;
+        }
+        return Float.floatToIntBits(44F);
+    }
+
+    public static void main(String[] args) {
+        test();
+    }
+}