--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/compiler/loopopts/TestLogSum.java Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2014, 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 8046516
+ * @summary Segmentation fault in JVM (easily reproducible)
+ *
+ * @run main/othervm -XX:-TieredCompilation -Xbatch compiler.loopopts.TestLogSum
+ * @author jackkamm@gmail.com
+ */
+
+package compiler.loopopts;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class TestLogSum {
+ public static void main(String[] args) {
+ double sum;
+
+ for (int i = 0; i < 6; i++) {
+ for (int n = 2; n < 30; n++) {
+ for (int j = 1; j <= n; j++) {
+ for (int k = 1; k <= j; k++) {
+ // System.out.println(computeSum(k, j));
+ sum = computeSum(k, j);
+ }
+ }
+ }
+ }
+ }
+
+ private static Map<List<Integer>, Double> cache = new HashMap<List<Integer>, Double>();
+ public static double computeSum(int x, int y) {
+ List<Integer> key = Arrays.asList(new Integer[] {x, y});
+
+ if (!cache.containsKey(key)) {
+
+ // explicitly creating/updating a double[] array, instead of using the LogSumArray wrapper object, will prevent the error
+ LogSumArray toReturn = new LogSumArray(x);
+
+ // changing loop indices will prevent the error
+ // in particular, for(z=0; z<x-1; z++), and then using z+1 in place of z, will not produce error
+ for (int z = 1; z < x+1; z++) {
+ double logSummand = Math.log(z + x + y);
+ toReturn.addLogSummand(logSummand);
+ }
+
+ // returning the value here without cacheing it will prevent the segfault
+ cache.put(key, toReturn.retrieveLogSum());
+ }
+ return cache.get(key);
+ }
+
+ /*
+ * Given a bunch of logarithms log(X),log(Y),log(Z),...
+ * This class is used to compute the log of the sum, log(X+Y+Z+...)
+ */
+ private static class LogSumArray {
+ private double[] logSummandArray;
+ private int currSize;
+
+ private double maxLogSummand;
+
+ public LogSumArray(int maxEntries) {
+ this.logSummandArray = new double[maxEntries];
+
+ this.currSize = 0;
+ this.maxLogSummand = Double.NEGATIVE_INFINITY;
+ }
+
+ public void addLogSummand(double logSummand) {
+ logSummandArray[currSize] = logSummand;
+ currSize++;
+ // removing this line will prevent the error
+ maxLogSummand = Math.max(maxLogSummand, logSummand);
+ }
+
+ public double retrieveLogSum() {
+ if (maxLogSummand == Double.NEGATIVE_INFINITY) return Double.NEGATIVE_INFINITY;
+
+ assert currSize <= logSummandArray.length;
+
+ double factorSum = 0;
+ for (int i = 0; i < currSize; i++) {
+ factorSum += Math.exp(logSummandArray[i] - maxLogSummand);
+ }
+
+ return Math.log(factorSum) + maxLogSummand;
+ }
+ }
+}