[SYCL] Fix depends_on with default-constructed events (#6630)

Using depends_on with default constructed events caused commands to
incorrectly expect the events to have associated PI events. Since
default-constructed events are automatically considered finished, they
can be ignored if they do not have an associated native event.
These changes allows commands to ignore uninitialized events in
dependency events.

Signed-off-by: Larsen, Steffen <steffen.larsen@intel.com>

Author: steffenlarsen

sycl/source/detail/event_impl.hpp

@@ -212,6 +212,15 @@ class event_impl {
   }
   bool needsCleanupAfterWait() { return MNeedsCleanupAfterWait; }
 
+  /// Checks if an event is in a fully intialized state. Default-constructed
+  /// events will return true only after having initialized its native event,
+  /// while other events will assume that they are fully initialized at
+  /// construction, relying on external sources to supply member data.
+  ///
+  /// \return true if the event is considered to be in a fully initialized
+  /// state.
+  bool isInitialized() const noexcept { return MIsInitialized; }
+
 private:
   // When instrumentation is enabled emits trace event for event wait begin and
   // returns the telemetry event generated for the wait

sycl/source/detail/queue_impl.hpp

@@ -530,7 +530,8 @@ class queue_impl {
     // Host and interop tasks, however, are not submitted to low-level runtimes
     // and require separate dependency management.
     const CG::CGTYPE Type = Handler.getType();
-    event Event;
+    event Event = detail::createSyclObjFromImpl<event>(
+        std::make_shared<detail::event_impl>());
 
     if (PostProcess) {
       bool IsKernel = Type == CG::Kernel;

sycl/source/detail/scheduler/commands.cpp

@@ -582,11 +582,12 @@ Command *Command::processDepEvent(EventImplPtr DepEvent, const DepDesc &Dep,
   const ContextImplPtr &WorkerContext = WorkerQueue->getContextImplPtr();
 
   // 1. Async work is not supported for host device.
-  // 2. Some types of commands do not produce PI events after they are enqueued
-  // (e.g. alloca). Note that we can't check the pi event to make that
-  // distinction since the command might still be unenqueued at this point.
-  bool PiEventExpected =
-      !DepEvent->is_host() || getType() == CommandType::HOST_TASK;
+  // 2. Non-host events can be ignored if they are not fully initialized.
+  // 3. Some types of commands do not produce PI events after they are enqueued
+  //    (e.g. alloca). Note that we can't check the pi event to make that
+  //    distinction since the command might still be unenqueued at this point.
+  bool PiEventExpected = (!DepEvent->is_host() && DepEvent->isInitialized()) ||
+                         getType() == CommandType::HOST_TASK;
   if (auto *DepCmd = static_cast<Command *>(DepEvent->getCommand()))
     PiEventExpected &= DepCmd->producesPiEvent();