8335708: C2: Compile::verify_graph_edges must start at root and safepoints, just like CCP traversal

Reviewed-by: chagedorn, epeter

Author: marc-chevalier

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

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2025, 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 8335708
+ * @summary Crash Compile::verify_graph_edges with dead code check when safepoints are reachable but not connected back to Root's inputs
+ * @library /test/lib
+ *
+ * @run driver compiler.loopopts.VerifyGraphEdgesWithDeadCodeCheckFromSafepoints
+ * @run main/othervm
+ *       -XX:+IgnoreUnrecognizedVMOptions
+ *       -XX:-TieredCompilation -XX:+VerifyGraphEdges
+ *       -XX:+StressIGVN -Xcomp
+ *       -XX:CompileCommand=compileonly,compiler.loopopts.VerifyGraphEdgesWithDeadCodeCheckFromSafepoints::mainTest
+ *       compiler.loopopts.VerifyGraphEdgesWithDeadCodeCheckFromSafepoints
+ *
+ */
+
+package compiler.loopopts;
+
+import jdk.test.lib.Utils;
+
+public class VerifyGraphEdgesWithDeadCodeCheckFromSafepoints {
+    public static void main(String[] args) throws Exception {
+        Thread thread = new Thread() {
+            public void run() {
+                VerifyGraphEdgesWithDeadCodeCheckFromSafepoints instance = new VerifyGraphEdgesWithDeadCodeCheckFromSafepoints();
+                byte[] a = new byte[997];
+                for (int i = 0; i < 100; ++i) {
+                    instance.mainTest(a, a);
+                }
+            }
+        };
+        // Give thread some time to trigger compilation
+        thread.setDaemon(true);
+        thread.start();
+        Thread.sleep(Utils.adjustTimeout(500));
+    }
+
+    public void mainTest(byte[] a, byte[] b) {
+        int i = 0;
+        while (i < (a.length - 4)) {
+            a[i] = b[i];
+        }
+        while (true) {
+            a[i] = b[i];
+        }
+    }
+}