[SYCL] Move simple event_impl constructor to header (#6611)

On certain systems unittests that uses the event_impl constructor with
no arguments may disagree with the event_impl source file on the layout
of the default std::optional argument. This can cause unexpected memory
accesses when performing operations on the passed argument. This commit
works around this issue by moving the body of the constructor to the
header.

Signed-off-by: Larsen, Steffen <[email protected]>

Author: steffenlarsen

sycl/source/detail/event_impl.cpp

@@ -117,10 +117,6 @@ void event_impl::setContextImpl(const ContextImplPtr &Context) {
   MIsContextInitialized = true;
 }
 
-event_impl::event_impl(std::optional<HostEventState> State)
-    : MIsInitialized(false), MHostEvent(State), MIsFlushed(true),
-      MState(State.value_or(HES_Complete)) {}
-
 event_impl::event_impl(RT::PiEvent Event, const context &SyclContext)
     : MIsContextInitialized(true), MEvent(Event),
       MContext(detail::getSyclObjImpl(SyclContext)), MHostEvent(false),

sycl/source/detail/event_impl.hpp

@@ -46,7 +46,9 @@ class event_impl {
   /// If the constructed SYCL event is waited on it will complete immediately.
   /// Normally constructs a host event, use std::nullopt to instead instantiate
   /// a device event.
-  event_impl(std::optional<HostEventState> State = HES_Complete);
+  event_impl(std::optional<HostEventState> State = HES_Complete)
+      : MIsInitialized(false), MHostEvent(State), MIsFlushed(true),
+        MState(State.value_or(HES_Complete)) {}
 
   /// Constructs an event instance from a plug-in event handle.
   ///