8080156: Integer.toString(int value) sometimes throws NPE

Summary: Added test to check correctness of type propagation to CmpUNodes.
Reviewed-by: kvn

test/compiler/types/TestTypePropagationToCmpU.java

+/*
+ * Copyright (c) 2015, 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
+ * @bug 8080156 8060036
+ * @summary Test correctness of type propagation to CmpUNodes.
+ * @run main TestTypePropagationToCmpU
+ */
+public class TestTypePropagationToCmpU {
+    public static void main(String[] args) {
+        try {
+            // Trigger compilation
+            for (int i = 0; i < 100_000; ++i) {
+                test();
+            }
+        } catch (NullPointerException e) {
+            // Test should never throw a NullPointerException
+            throw new RuntimeException("Test failed");
+        }
+    }
+
+    static int global = 42;
+
+    public static void test() {
+        int a = Integer.MIN_VALUE;
+        int b = global;
+        char[] buf = { 0 };
+        for (int i = 0; i <= b; ++i) {
+            a = i - b;
+        }
+        // C2 adds a range check and an uncommon trap here to ensure that the array index
+        // is in bounds. If type information is not propagated correctly to the corresponding
+        // CmpUNode, this trap may be always taken. Because C2 also removes the unnecessary
+        // allocation of 'buf', a NullPointerException is thrown in this case.
+        char c = buf[(a * 11) / 2 - a]; // a is 0 here if global >= 0
+        buf[0] = 0;
+    }
+}