8254998: C2: assert(!n->as_Loop()->is_transformed_long_loop()) failure with -XX:StressLongCountedLoop=1

Reviewed-by: vlivanov, kvn, thartmann

src/hotspot/share/opto/compile.cpp

@@ -3428,7 +3428,7 @@ void Compile::final_graph_reshaping_main_switch(Node* n, Final_Reshape_Counts& f
     }
     break;
   case Op_Loop:
-    assert(!n->as_Loop()->is_transformed_long_loop(), "should have been turned into a counted loop");
+    assert(!n->as_Loop()->is_transformed_long_loop() || _loop_opts_cnt == 0, "should have been turned into a counted loop");
   case Op_CountedLoop:
   case Op_OuterStripMinedLoop:
     if (n->as_Loop()->is_inner_loop()) {

test/hotspot/jtreg/compiler/longcountedloops/TestTooManyLoopOpts.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2020, Red Hat, Inc. 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 8254998
+ * @summary C2: assert(!n->as_Loop()->is_transformed_long_loop()) failure with -XX:StressLongCountedLoop=1
+ * @requires vm.compiler2.enabled & vm.gc.Parallel
+ *
+ * @run main/othervm -Xcomp -XX:-TieredCompilation -XX:MaxRecursiveInlineLevel=26 -XX:MaxInlineLevel=26 -XX:LoopOptsCount=41 -XX:+UseParallelGC TestTooManyLoopOpts
+ *
+ */
+
+public class TestTooManyLoopOpts {
+    private static volatile int field;
+
+    public static void main(String[] args) {
+        test(0);
+    }
+
+    private static void test(int stop) {
+        for (long l = 0; l < 10; l++) {
+            test_helper(stop, 26);
+            field = 0x42;
+        }
+    }
+    private static void test_helper(int stop, int rec) {
+        if (rec <= 0) {
+            return;
+        }
+        for (int i = 0; i < stop; i++) {
+            test_helper(stop, rec - 1);
+        }
+    }
+}