8384202: [lworld] C2: assert(offset == field->offset_in_bytes()) failed: offset mismatch

src/hotspot/share/opto/inlinetypenode.cpp

@@ -230,7 +230,9 @@ Node* InlineTypeNode::field_value_by_offset(int offset, bool recursive) const {
   assert(!field->is_flat() || field->type()->is_inlinetype(), "must be an inline type");
 
   if (!recursive || !field->is_flat() || value->is_top()) {
-    assert(offset == field->offset_in_bytes(), "offset mismatch");
+    // If the graph is dying (value is top), a load may still ask for a nested
+    // field inside a flattened field before the dead load itself is folded away.
+    assert((offset == field->offset_in_bytes()) || (value->is_top() && field->is_flat()), "offset mismatch");
     return value;
   }
 

test/hotspot/jtreg/compiler/valhalla/inlinetypes/TestDeadInlineTypeFieldOffset.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2026, 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.
+ */
+
+package compiler.valhalla.inlinetypes;
+
+import jdk.internal.vm.annotation.LooselyConsistentValue;
+import jdk.internal.vm.annotation.NullRestricted;
+
+/*
+ * @test
+ * @summary Test loads from a dead InlineTypeNode with top field values.
+ * @requires vm.compiler2.enabled
+ * @enablePreview
+ * @modules java.base/jdk.internal.vm.annotation
+ * @run main ${test.main.class}
+ * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:+IgnoreUnrecognizedVMOptions
+ *                   -XX:+StressIGVN -XX:StressSeed=8 -XX:+AlwaysIncrementalInline
+ *                   ${test.main.class}
+ */
+public value class TestDeadInlineTypeFieldOffset {
+    MyValue valueField1;
+    @NullRestricted
+    MyValue valueField2;
+
+    TestDeadInlineTypeFieldOffset(MyValue valueField1, MyValue valueField2) {
+        this.valueField1 = valueField1;
+        this.valueField2 = valueField2;
+    }
+
+    TestDeadInlineTypeFieldOffset test1() {
+        return new TestDeadInlineTypeFieldOffset(null, valueField2);
+    }
+
+    TestDeadInlineTypeFieldOffset test2() {
+        return new TestDeadInlineTypeFieldOffset(valueField1, null);
+    }
+
+    @LooselyConsistentValue
+    static value class NestedValue {
+        int x;
+        int y;
+
+        NestedValue(int x, int y) {
+            this.x = x;
+            this.y = y;
+        }
+    }
+
+    @LooselyConsistentValue
+    static value class MyValue {
+        NestedValue v1;
+        @NullRestricted
+        NestedValue v2;
+
+        MyValue(NestedValue v1, NestedValue v2) {
+            this.v1 = v1;
+            this.v2 = v2;
+        }
+    }
+
+    static TestDeadInlineTypeFieldOffset test(TestDeadInlineTypeFieldOffset vt) {
+        vt = vt.test1();
+        try {
+            vt = vt.test2();
+            throw new RuntimeException();
+        } catch (NullPointerException e) {
+            // Expected.
+        }
+        return vt;
+    }
+
+    public static void main(String[] args) {
+        MyValue val = new MyValue(null, new NestedValue(5, 6));
+        TestDeadInlineTypeFieldOffset vt = new TestDeadInlineTypeFieldOffset(null, val);
+        for (int i = 0; i < 10_000; ++i) {
+            vt = test(vt);
+        }
+    }
+}
+