From 053ff76e14046f796f6e10a9cb2ede1f1ae22ed6 Mon Sep 17 00:00:00 2001
From: Roland Westrelin <roland@openjdk.org>
Date: Tue, 19 Mar 2024 07:57:53 +0000
Subject: [PATCH] 8308660: C2 compilation hits 'node must be dead' assert

Reviewed-by: chagedorn, kvn
---
 src/hotspot/share/opto/ifnode.cpp             |  4 ++
 .../compiler/c2/TestFoldIfRemovesTopNode.java | 69 +++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 test/hotspot/jtreg/compiler/c2/TestFoldIfRemovesTopNode.java

diff --git a/src/hotspot/share/opto/ifnode.cpp b/src/hotspot/share/opto/ifnode.cpp
index 0e21933b6de..9760be95ddd 100644
--- a/src/hotspot/share/opto/ifnode.cpp
+++ b/src/hotspot/share/opto/ifnode.cpp
@@ -1051,6 +1051,10 @@ bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* f
   }
   hook->destruct(igvn);
 
+  if (adjusted_val->is_top() || adjusted_lim->is_top()) {
+    return false;
+  }
+
   if (igvn->type(adjusted_lim)->is_int()->_lo < 0 &&
       !igvn->C->post_loop_opts_phase()) {
     // If range check elimination applies to this comparison, it includes code to protect from overflows that may
diff --git a/test/hotspot/jtreg/compiler/c2/TestFoldIfRemovesTopNode.java b/test/hotspot/jtreg/compiler/c2/TestFoldIfRemovesTopNode.java
new file mode 100644
index 00000000000..e36897aa7d8
--- /dev/null
+++ b/test/hotspot/jtreg/compiler/c2/TestFoldIfRemovesTopNode.java
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2024, 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 8308660
+ * @summary C2 compilation hits 'node must be dead' assert
+ * @requires vm.compiler2.enabled
+ * @run main/othervm -XX:-BackgroundCompilation -XX:-TieredCompilation -XX:-UseOnStackReplacement
+ *                   -XX:+UnlockDiagnosticVMOptions -XX:+StressIGVN -XX:StressSeed=242006623 TestFoldIfRemovesTopNode
+ * @run main/othervm -XX:-BackgroundCompilation -XX:-TieredCompilation -XX:-UseOnStackReplacement
+ *                   -XX:+UnlockDiagnosticVMOptions -XX:+StressIGVN TestFoldIfRemovesTopNode
+ *
+ */
+
+public class TestFoldIfRemovesTopNode {
+
+    public static void main(String[] args) {
+        int[] array = new int[100];
+        for (int i = 0; i < 20_000; i++) {
+            test(false, true, 0, array);
+            test(false, false, 0, array);
+            testHelper2(false, false, 0, array);
+            testHelper(0, true, array);
+        }
+    }
+
+    private static void test(boolean flag, boolean flag2, int k, int[] array) {
+        if (flag2) {
+            testHelper2(flag, flag2, k, array);
+        }
+    }
+
+    private static void testHelper2(boolean flag, boolean flag2, int k, int[] array) {
+        if (flag2) {
+            k = -1;
+        }
+        testHelper(k, flag, array);
+    }
+
+    private static void testHelper(int k, boolean flag, int[] array) {
+        if (flag) {
+            k = new int[k].length;
+            int j = k + 3;
+            if (j >= 0 && j <= array.length) {
+            }
+        }
+    }
+}