changeset 7869:f1b92b73e6aa

8072753: Nondeterministic wrong answer on arithmetic Summary: Check for overflow when inverting the loop during the counted loop conversion Reviewed-by: kvn
author iveresov
date Tue, 17 Feb 2015 11:00:18 -0800
parents 16157f91ff41
children cf7251f51459
files src/share/vm/opto/loopnode.cpp test/compiler/loopopts/CountedLoopProblem.java
diffstat 2 files changed, 67 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- a/src/share/vm/opto/loopnode.cpp	Mon Feb 16 08:47:39 2015 -0800
+++ b/src/share/vm/opto/loopnode.cpp	Tue Feb 17 11:00:18 2015 -0800
@@ -436,6 +436,19 @@
       return false; // cyclic loop or this loop trips only once
   }
 
+  if (phi_incr != NULL) {
+    // check if there is a possiblity of IV overflowing after the first increment
+    if (stride_con > 0) {
+      if (init_t->_hi > max_jint - stride_con) {
+        return false;
+      }
+    } else {
+      if (init_t->_lo < min_jint - stride_con) {
+        return false;
+      }
+    }
+  }
+
   // =================================================
   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
   //
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/compiler/loopopts/CountedLoopProblem.java	Tue Feb 17 11:00:18 2015 -0800
@@ -0,0 +1,54 @@
+/*
+ * 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 8072753
+ * @summary Inner loop induction variable increment occurs before compare which causes integer overflow
+ * @run main/othervm CountedLoopProblem
+ *
+ */
+
+import java.util.*;
+
+public class CountedLoopProblem {
+    public static void main(String[] args) throws Exception {
+        Random r = new Random(42);
+        int x = 0;
+        StringBuilder sb = new StringBuilder();
+        for(int i = 0; i < 1000000; ++i) {
+            int v = Math.abs(r.nextInt());
+            sb.append('+').append(v).append('\n');
+            x += v;
+            // To trigger the problem we must OSR in the following loop
+            // To make the problem 100% reproducible run with -XX:-TieredCompilation -XX:OSROnlyBCI=62
+            while(x < 0) x += 1000000000;
+            sb.append('=').append(x).append('\n');
+        }
+        if (sb.toString().hashCode() != 0xaba94591) {
+            throw new Exception("Unexpected result");
+        }
+    }
+}
+