From 7c6c34e150cf01cec5d166f6cbb8a649c75b0627 Mon Sep 17 00:00:00 2001
From: Kerem Kat <krk@openjdk.org>
Date: Thu, 29 Jan 2026 13:11:47 +0000
Subject: [PATCH] 8370502: C2: segfault while adding node to IGVN worklist

Reviewed-by: mhaessig, dlong
---
 src/hotspot/share/opto/macro.cpp              | 22 ++++----
 .../c2/TestUnlockNodeNullMemprof.java         | 53 +++++++++++++++++++
 2 files changed, 63 insertions(+), 12 deletions(-)
 create mode 100644 test/hotspot/jtreg/compiler/c2/TestUnlockNodeNullMemprof.java

diff --git a/src/hotspot/share/opto/macro.cpp b/src/hotspot/share/opto/macro.cpp
index 56262d226fc..9470001b2d2 100644
--- a/src/hotspot/share/opto/macro.cpp
+++ b/src/hotspot/share/opto/macro.cpp
@@ -2322,12 +2322,7 @@ void PhaseMacroExpand::expand_unlock_node(UnlockNode *unlock) {
   // No need for a null check on unlock
 
   // Make the merge point
-  Node *region;
-  Node *mem_phi;
-
-  region  = new RegionNode(3);
-  // create a Phi for the memory state
-  mem_phi = new PhiNode( region, Type::MEMORY, TypeRawPtr::BOTTOM);
+  Node* region = new RegionNode(3);
 
   FastUnlockNode *funlock = new FastUnlockNode( ctrl, obj, box );
   funlock = transform_later( funlock )->as_FastUnlock();
@@ -2356,12 +2351,15 @@ void PhaseMacroExpand::expand_unlock_node(UnlockNode *unlock) {
   transform_later(region);
   _igvn.replace_node(_callprojs.fallthrough_proj, region);
 
-  Node *memproj = transform_later(new ProjNode(call, TypeFunc::Memory) );
-  mem_phi->init_req(1, memproj );
-  mem_phi->init_req(2, mem);
-  transform_later(mem_phi);
-
-  _igvn.replace_node(_callprojs.fallthrough_memproj, mem_phi);
+  if (_callprojs.fallthrough_memproj != nullptr) {
+    // create a Phi for the memory state
+    Node* mem_phi = new PhiNode( region, Type::MEMORY, TypeRawPtr::BOTTOM);
+    Node* memproj = transform_later(new ProjNode(call, TypeFunc::Memory));
+    mem_phi->init_req(1, memproj);
+    mem_phi->init_req(2, mem);
+    transform_later(mem_phi);
+    _igvn.replace_node(_callprojs.fallthrough_memproj, mem_phi);
+  }
 }
 
 void PhaseMacroExpand::expand_subtypecheck_node(SubTypeCheckNode *check) {
diff --git a/test/hotspot/jtreg/compiler/c2/TestUnlockNodeNullMemprof.java b/test/hotspot/jtreg/compiler/c2/TestUnlockNodeNullMemprof.java
new file mode 100644
index 00000000000..f86dc495fd2
--- /dev/null
+++ b/test/hotspot/jtreg/compiler/c2/TestUnlockNodeNullMemprof.java
@@ -0,0 +1,53 @@
+/*
+ * 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 8370502
+ * @summary Do not segfault while adding node to IGVN worklist
+ *
+ * @run main/othervm -Xbatch ${test.main.class}
+ */
+
+package compiler.c2;
+
+public class TestUnlockNodeNullMemprof {
+    public static void main(String[] args) {
+        int[] a = new int[0]; // test only valid when size is 0.
+        for (int i = 0; i < Integer.valueOf(10000); i++) // test only valid with boxed loop limit
+            try {
+                test(a);
+            } catch (ArrayIndexOutOfBoundsException e) {
+            }
+    }
+
+    static void test(int[] a) {
+        for (int i = 0; i < 1;) {
+            a[i] = 0;
+            synchronized (TestUnlockNodeNullMemprof.class) {
+            }
+            for (int j = 0; Integer.valueOf(j) < 1;)
+                j = 0;
+        }
+    }
+}