8298353: C2 fails with assert(opaq->outcnt() == 1 && opaq->in(1) == limit) failed

Reviewed-by: chagedorn, thartmann, kvn

src/hotspot/share/opto/loopopts.cpp

@@ -1733,7 +1733,7 @@ Node* PhaseIdealLoop::compute_early_ctrl(Node* n, Node* n_ctrl) {
 bool PhaseIdealLoop::ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop) {
   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
     Node* u = n->fast_out(i);
-    if (u->Opcode() == Op_Opaque1) {
+    if (u->is_Opaque1()) {
       return false;  // Found loop limit, bugfix for 4677003
     }
     // We can't reuse tags in PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal() so make sure calls to

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

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2022, 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 8298353
+ * @summary C2 fails with assert(opaq->outcnt() == 1 && opaq->in(1) == limit) failed
+ *
+ * @run main/othervm -XX:-TieredCompilation -XX:-UseOnStackReplacement -XX:-BackgroundCompilation TestBadCountedLoopLimit
+ *
+ */
+
+import java.util.Arrays;
+
+public class TestBadCountedLoopLimit {
+    private static volatile int barrier;
+    private static int field;
+
+    public static void main(String[] args) {
+        boolean[] flag1 = new boolean[100];
+        boolean[] flag2 = new boolean[100];
+        Arrays.fill(flag2, true);
+        for (int i = 0; i < 20_000; i++) {
+            test(0, flag1, flag1);
+            test(0, flag2, flag2);
+            testHelper(true, 0, 0);
+            testHelper(false, 0, 0);
+        }
+    }
+
+    private static int test(int v, boolean[] flag, boolean[] flag2) {
+        int j = testHelper(flag2[0], 0, 1);
+        int i = 1;
+        int limit = 0;
+        for (;;) {
+            synchronized (new Object()) {
+            }
+            limit = j;
+            if (i >= 100) {
+                break;
+            }
+
+            if (flag[i]) {
+                return limit - 3;
+            }
+
+            j = testHelper(flag2[i], 100, 101);
+            i *= 2;
+        };
+        for (int k = 0; k < limit; k++) {
+            barrier = 0x42;
+        }
+        return j;
+    }
+
+    private static int testHelper(boolean flag2, int x, int x1) {
+        return flag2 ? x : x1;
+    }
+}