8265938: C2's conditional move optimization does not handle top Phi

Reviewed-by: chagedorn, kvn, iignatyev

src/hotspot/share/opto/loopopts.cpp

@@ -718,7 +718,9 @@ Node *PhaseIdealLoop::conditional_move( Node *region ) {
         break;
       }
     }
-    if (phi == NULL)  break;
+    if (phi == NULL || _igvn.type(phi) == Type::TOP) {
+      break;
+    }
     if (PrintOpto && VerifyLoopOptimizations) { tty->print_cr("CMOV"); }
     // Move speculative ops
     wq.push(phi);

test/hotspot/jtreg/compiler/loopopts/TestCMoveWithDeadPhi.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2021, 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 8265938
+ * @summary Test conditional move optimization with a TOP PhiNode.
+ * @library /test/lib
+ * @run main/othervm -XX:CompileCommand=compileonly,compiler.loopopts.TestCMoveWithDeadPhi::test
+ *                   compiler.loopopts.TestCMoveWithDeadPhi
+ */
+
+package compiler.loopopts;
+
+import jdk.test.lib.Utils;
+
+public class TestCMoveWithDeadPhi {
+
+    static void test(boolean b) {
+        if (b) {
+            long l = 42;
+            for (int i = 0; i < 100; i++) {
+                if (i < 10) {
+                    l++;
+                    if (i == 5) {
+                        break;
+                    }
+                }
+            }
+
+            // Infinite loop
+            for (int j = 0; j < 100; j++) {
+                j--;
+            }
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        // Execute test in own thread because it contains an infinite loop
+        Thread thread = new Thread() {
+            public void run() {
+                for (int i = 0; i < 50_000; ++i) {
+                    test((i % 2) == 0);
+                }
+            }
+        };
+        // Give thread some time to trigger compilation
+        thread.setDaemon(true);
+        thread.start();
+        Thread.sleep(Utils.adjustTimeout(4000));
+    }
+}

test/hotspot/jtreg/compiler/loopopts/TestStrangeControl.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2021, 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
@@ -19,20 +19,22 @@
  * 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 8228888
  * @summary Test PhaseIdealLoop::has_local_phi_input() with phi input with non-dominating control.
+ * @library /test/lib
  * @compile StrangeControl.jasm
  * @run main/othervm -Xbatch -XX:CompileCommand=inline,compiler.loopopts.StrangeControl::test
  *                   compiler.loopopts.TestStrangeControl
  */
 
 package compiler.loopopts;
 
+import jdk.test.lib.Utils;
+
 public class TestStrangeControl {
 
     public static void main(String[] args) throws Exception {
@@ -42,8 +44,9 @@ public void run() {
                 StrangeControl.test(42);
             }
         };
+        thread.setDaemon(true);
         thread.start();
         // Give thread executing strange control loop enough time to trigger OSR compilation
-        Thread.sleep(4000);
+        Thread.sleep(Utils.adjustTimeout(4000));
     }
 }