8228888: C2 compilation fails with assert "m has strange control"

Weakened too strong assert.

Reviewed-by: kvn, roland

src/hotspot/share/opto/loopopts.cpp

@@ -324,7 +324,7 @@ Node *PhaseIdealLoop::has_local_phi_input( Node *n ) {
       }
       return NULL;
     }
-    assert(m->is_Phi() || is_dominator(get_ctrl(m), n_ctrl), "m has strange control");
+    assert(n->is_Phi() || m->is_Phi() || is_dominator(get_ctrl(m), n_ctrl), "m has strange control");
   }
 
   return n_ctrl;

test/hotspot/jtreg/compiler/loopopts/StrangeControl.jasm

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2019, 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.
+ *
+ */
+
+super public class compiler/loopopts/StrangeControl
+  version 51:0
+{
+
+static Field field:"I";
+
+public static Method test:"(I)V"
+  stack 2 locals 2
+{
+    iconst_0;
+    istore 1;
+  L1: stack_frame_type append;
+    locals_map int;
+    iinc  1, 1;
+    iload 1;
+    iconst_2;
+    if_icmple L1;
+  L2: stack_frame_type same;
+    iload_0;
+    putstatic Field field:"I";
+    goto L1;
+}
+
+} // end Class StrangeControl

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

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2019, 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 8228888
+ * @summary Test PhaseIdealLoop::has_local_phi_input() with phi input with non-dominating control.
+ * @compile StrangeControl.jasm
+ * @run main/othervm -Xbatch -XX:CompileCommand=inline,compiler.loopopts.StrangeControl::test
+ *                   compiler.loopopts.TestStrangeControl
+ */
+
+package compiler.loopopts;
+
+public class TestStrangeControl {
+
+    public static void main(String[] args) throws Exception {
+        Thread thread = new Thread() {
+            public void run() {
+                // Run this in an own thread because it's basically an endless loop
+                StrangeControl.test(42);
+            }
+        };
+        thread.start();
+        // Give thread executing strange control loop enough time to trigger OSR compilation
+        Thread.sleep(4000);
+    }
+}