[GR-44518] Add possibility to convert object JavaConstant to jobject.

Author: tzezula

src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/hotspot/HotSpotJVMCIRuntime.java

@@ -858,6 +858,26 @@ JavaType lookupTypeInternal(String name, HotSpotResolvedObjectType accessingType
         }
     }
 
+    /**
+     * Gets the {@code jobject} value wrapped by {@code peerObject}. The returned "naked" value is
+     * only valid as long as {@code peerObject} is valid. Note that the latter may be shorter than
+     * the lifetime of {@code peerObject}. As such, this method should only be used to pass an
+     * object parameter across a JNI call from the JVMCI shared library to HotSpot. This method must
+     * only be called from within the JVMCI shared library.
+     *
+     * @param peerObject a reference to an object in the peer runtime
+     * @return the {@code jobject} value wrapped by {@code peerObject}
+     * @throws IllegalArgumentException if the current runtime is not the JVMCI shared library or
+     *             {@code peerObject} is not a peer object reference
+     */
+    public long getJObjectValue(HotSpotObjectConstant peerObject) {
+        if (peerObject instanceof IndirectHotSpotObjectConstantImpl) {
+            IndirectHotSpotObjectConstantImpl remote = (IndirectHotSpotObjectConstantImpl) peerObject;
+            return remote.getHandle();
+        }
+        throw new IllegalArgumentException("Cannot get jobject value for " + peerObject + " (" + peerObject.getClass().getName() + ")");
+    }
+
     @Override
     public JVMCIBackend getHostJVMCIBackend() {
         return hostBackend;