[llvm] [Offload] Don't create events for empty queues (PR #152304)

[Ross Brunton via llvm-commits]

================
@@ -939,6 +939,14 @@ struct GenericDeviceTy : public DeviceAllocatorTy {
   Error printInfo();
   virtual Expected<InfoTreeNode> obtainInfoImpl() = 0;
 
+  /// Return true if the device has work that is either queued or currently
+  /// running
+  ///
+  /// Devices which cannot report this information should always return true
----------------
RossBrunton wrote:

... I wonder if just returning UNSUPPORTED would probably be better.

https://github.com/llvm/llvm-project/pull/152304