changeset 51430:e2ced90cbd36

8208275: C2 crash in Node::add_req(Node*) Summary: Split-if optimization should not process (dead) counted loops. Reviewed-by: roland
author thartmann
date Fri, 17 Aug 2018 08:21:20 +0200
parents d9f6e3ee7fcb
children 0bdce38fde83
files src/hotspot/share/opto/ifnode.cpp test/hotspot/jtreg/compiler/loopopts/TestOneIterationStripMined.java
diffstat 2 files changed, 86 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- a/src/hotspot/share/opto/ifnode.cpp	Wed Aug 15 11:19:57 2018 -0700
+++ b/src/hotspot/share/opto/ifnode.cpp	Fri Aug 17 08:21:20 2018 +0200
@@ -267,6 +267,13 @@
   Node* predicate_c = NULL;
   Node* predicate_x = NULL;
   bool counted_loop = r->is_CountedLoop();
+  if (counted_loop) {
+    // Ignore counted loops for now because the split-if logic does not work
+    // in all the cases (for example, with strip mined loops). Also, above
+    // checks only pass for already degraded loops without a tripcount phi
+    // and these are essentially dead and will go away during igvn.
+    return NULL;
+  }
 
   Node *region_c = new RegionNode(req_c + 1);
   Node *phi_c    = con1;
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/compiler/loopopts/TestOneIterationStripMined.java	Fri Aug 17 08:21:20 2018 +0200
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2018, 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 8208275
+ * @summary Test removal of strip mined loop with only one iteration.
+ * @run main/othervm -XX:-TieredCompilation -Xcomp
+ *                   -XX:CompileCommand=compileonly,compiler.loopopts.TestOneIterationStripMined::test*
+ *                   compiler.loopopts.TestOneIterationStripMined
+ */
+
+package compiler.loopopts;
+
+public class TestOneIterationStripMined {
+    static int iField;
+    static volatile Object oField;
+
+    public static void test1(int val) {
+        iField = 0; // Do something
+        // This loop is strip mined and then removed because it has only one iteration.
+        for (int i = 0; i < 1; ++i) {
+            // Trigger split-if optimization
+            if (val == 0) {
+                break;
+            }
+            val = 0;
+        }
+    }
+
+    // Same as test1 but with a volatile Object field
+    // (will trigger a different failure mode)
+    public static void test2(int val) {
+        oField = null;
+        for (int i = 0; i < 1; ++i) {
+            if (val == 0) {
+                break;
+            }
+            val = 0;
+        }
+    }
+
+    // Same as test1 but without any code outside loop body
+    // (will trigger a different failure mode)
+    public static void test3(int val) {
+        for (int i = 0; i < 1; ++i) {
+            if (val == 0) {
+                break;
+            }
+            val = 0;
+        }
+    }
+
+    public static void main(String[] args) {
+        test1(0);
+        test2(0);
+        test3(0);
+    }
+}