[OFFLOAD] Add missing data fence API for libomptarget migration

offload/liboffload/API/Queue.td

@@ -125,3 +125,12 @@ def olLaunchHostFunction : Function {
   ];
   let returns = [];
 }
+
+def olDataFence : Function {
+    let desc = "Insert a data fence between previous data operations and the following operations if necessary for the device.";
+    let details = [];
+    let params = [
+        Param<"ol_queue_handle_t", "Queue", "handle of the queue", PARAM_IN>
+    ];
+    let returns = [];
+}

offload/liboffload/src/OffloadImpl.cpp

@@ -1214,5 +1214,14 @@ Error olLaunchHostFunction_impl(ol_queue_handle_t Queue,
                                                 Queue->AsyncInfo);
 }
 
+Error olDataFence_impl(ol_queue_handle_t Queue) {
+  if (Queue->AsyncInfo->Queue) {
+    if (auto Err = Queue->Device->Device->dataFence(Queue->AsyncInfo))
+      return Err;
+  }
+
+  return Error::success();
+}
+
 } // namespace offload
 } // namespace llvm