8347463: jdk/jfr/threading/TestManyVirtualThreads.java crashes with assert(oopDesc::is_oop_or_null(val))

src/hotspot/share/opto/runtime.cpp

@@ -857,8 +857,9 @@ static const TypeFunc* make_jfr_write_checkpoint_Type() {
   const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms, fields);
 
   // create result type (range)
-  fields = TypeTuple::fields(0);
-  const TypeTuple *range = TypeTuple::make(TypeFunc::Parms, fields);
+  fields = TypeTuple::fields(1);
+  fields[TypeFunc::Parms] = TypeInstPtr::BOTTOM;
+  const TypeTuple *range = TypeTuple::make(TypeFunc::Parms + 1, fields);
   return TypeFunc::make(domain, range);
 }
 

src/hotspot/share/opto/runtime.hpp

@@ -48,6 +48,12 @@
 // it calls the C++ code "xxx_C".  The generated nmethod is saved in the
 // CodeCache.  Exception handlers use the nmethod to get the callee-save
 // register OopMaps.
+//
+// Please ensure the return type of the runtime call matches its signature,
+// even if the return value is unused. This is crucial for correct handling
+// of runtime calls that return an oop and may trigger deoptimization
+// on return. See rematerialize_objects() in deoptimization.cpp.
+
 class CallInfo;
 
 //

test/hotspot/jtreg/compiler/intrinsics/TestReturnOopSetForJFRWriteCheckpoint.java

@@ -0,0 +1,67 @@
+/*
+ * 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.
+ */
+
+package compiler.intrinsics;
+
+import compiler.lib.ir_framework.*;
+
+import jdk.jfr.Event;
+import jdk.jfr.Recording;
+
+/**
+ * @test
+ * @summary Tests that the getEventWriter call to write_checkpoint correctly
+ *          reports returning an oop
+ * @bug 8347463
+ * @requires vm.hasJFR
+ * @library /test/lib /
+ * @run driver compiler.intrinsics.TestReturnOopSetForJFRWriteCheckpoint
+ */
+public class TestReturnOopSetForJFRWriteCheckpoint {
+
+    private static class TestEvent extends Event {
+    }
+
+    public static void main(String... args) {
+        TestFramework.run();
+    }
+
+    // Crash was due to the return_oop field not being set
+    // for the write_checkpoint call. Instead of explicitly checking for
+    // it, we look for an non-void return type (which comes hand-in-hand
+    // with the return_oop information).
+    @Test
+    @IR(failOn = { IRNode.STATIC_CALL_OF_METHOD, "write_checkpoint.*void"})
+    public void testWriteCheckpointReturnType() {
+        try (Recording r = new Recording()) {
+            r.start();
+            emitEvent();
+        }
+    }
+
+    @ForceInline
+    public void emitEvent() {
+        TestEvent t = new TestEvent();
+        t.commit();
+    }
+}