Backport de826ba18a5e98586029581c2d4bcd27334fbdd1

src/hotspot/share/opto/loopTransform.cpp

@@ -1197,7 +1197,7 @@ Node *PhaseIdealLoop::clone_up_backedge_goo(Node *back_ctrl, Node *preheader_ctr
 }
 
 Node* PhaseIdealLoop::cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop) {
-  Node* castii = new CastIINode(incr, TypeInt::INT, ConstraintCastNode::StrongDependency);
+  Node* castii = new CastIINode(incr, TypeInt::INT, ConstraintCastNode::UnconditionalDependency);
   castii->set_req(0, ctrl);
   register_new_node(castii, ctrl);
   for (DUIterator_Fast imax, i = incr->fast_outs(imax); i < imax; i++) {

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

@@ -0,0 +1,53 @@
+/*
+ * 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 8280600
+ * @summary C2: assert(!had_error) failed: bad dominance
+ * @run main/othervm -Xcomp -XX:CompileOnly=TestCastIIMakesMainLoopPhiDead TestCastIIMakesMainLoopPhiDead
+ */
+
+public class TestCastIIMakesMainLoopPhiDead {
+    int iArr[] = new int[0];
+
+    void test() {
+        int x = 8;
+        try {
+            for (int i = 0; i < 8; i++) {
+                iArr[1] = 9;
+                for (int j = -400; 1 > j; j++) {
+                    iArr[j] = 4;
+                    x -= 2;
+                }
+            }
+        } catch (ArrayIndexOutOfBoundsException e) {
+        }
+    }
+    public static void main(String[] k) {
+        TestCastIIMakesMainLoopPhiDead t = new TestCastIIMakesMainLoopPhiDead();
+        for (int i = 0; i < 3; i++) {
+            t.test();
+        }
+    }
+}