Merge

hotspot/src/share/vm/opto/loopTransform.cpp

@@ -1582,13 +1582,36 @@ void PhaseIdealLoop::mark_reductions(IdealLoopTree *loop) {
           if (opc != ReductionNode::opcode(opc, def_node->bottom_type()->basic_type())) {
             if (!def_node->is_reduction()) { // Not marked yet
               // To be a reduction, the arithmetic node must have the phi as input and provide a def to it
+              bool ok = false;
               for (unsigned j = 1; j < def_node->req(); j++) {
                 Node* in = def_node->in(j);
                 if (in == phi) {
-                  def_node->add_flag(Node::Flag_is_reduction);
+                  ok = true;
                   break;
                 }
               }
+
+              // do nothing if we did not match the initial criteria
+              if (ok == false) {
+                continue;
+              }
+
+              // The result of the reduction must not be used in the loop
+              for (DUIterator_Fast imax, i = def_node->fast_outs(imax); i < imax && ok; i++) {
+                Node* u = def_node->fast_out(i);
+                if (has_ctrl(u) && !loop->is_member(get_loop(get_ctrl(u)))) {
+                  continue;
+                }
+                if (u == phi) {
+                  continue;
+                }
+                ok = false;
+              }
+
+              // iff the uses conform
+              if (ok) {
+                def_node->add_flag(Node::Flag_is_reduction);
+              }
             }
           }
         }

hotspot/test/compiler/loopopts/superword/TestReductionWithLoopVariantUse.java

@@ -0,0 +1,68 @@
+/*
+ * 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 8080976
+ * @summary Loop variant use in reduction should prevent vectorization
+ * @run main/othervm -XX:-BackgroundCompilation -XX:-UseOnStackReplacement TestReductionWithLoopVariantUse
+ *
+ */
+
+public class TestReductionWithLoopVariantUse {
+    static int m(int[] array) {
+        int c = 0;
+        for (int i = 0; i < 256; i++) {
+            c += array[i];
+            array[i] = c;
+        }
+        return c;
+    }
+
+    static public void main(String[] args) {
+        int[] array = new int[256];
+        int[] array2 = new int[256];
+        for (int j = 0; j < 256; j++) {
+            array2[j] = j;
+        }
+        for (int i = 0; i < 20000; i++) {
+            System.arraycopy(array2, 0, array, 0, 256);
+            int res = m(array);
+            boolean success = true;
+            int c = 0;
+            for (int j = 0; j < 256; j++) {
+                c += array2[j];
+                if (array[j] != c) {
+                    System.out.println("Failed for " + j + " : " + array[j] + " != " + c);
+                    success = false;
+                }
+            }
+            if (c != res) {
+                System.out.println("Failed for sum: " + c + " != " + res);
+            }
+            if (!success) {
+                throw new RuntimeException("Test failed");
+            }
+        }
+    }
+}