Revert "[SYCL] Reintroduce barrier trivial event for empty in-order queue" (#20535)

Reverts #20263

------

This PR was made as a temporary workaround to unblock the release.
Reverting this workaround so that we can have a proper fix in the next
release.

Author: uditagarwal97

sycl/source/queue.cpp

@@ -366,14 +366,6 @@ event queue::ext_oneapi_submit_barrier(const std::vector<event> &WaitList,
                !EventImpl.hasCommandGraph();
       });
 
-  // If we have an empty in-order queue and no dependencies, we can just return
-  // a trivially finished event.
-  if (is_in_order() && !impl->hasCommandGraph() && !impl->MIsProfilingEnabled &&
-      AllEventsEmptyOrNop && ext_oneapi_empty()) {
-    return detail::createSyclObjFromImpl<event>(
-        detail::event_impl::create_default_event());
-  }
-
   if (WaitList.empty() || AllEventsEmptyOrNop)
     return submit([=](handler &CGH) { CGH.ext_oneapi_barrier(); }, CodeLoc);
   else

sycl/test-e2e/InorderQueue/in_order_ext_oneapi_submit_barrier.cpp

@@ -60,16 +60,6 @@ int main() {
     Q.wait();
     assert(*Res == 10);
   }
-  {
-    // Test cast 3 - empty queue.
-    std::cout << "Test 3" << std::endl;
-    sycl::queue EmptyQ({sycl::property::queue::in_order{}});
-    auto BarrierEvent = EmptyQ.ext_oneapi_submit_barrier();
-    assert(
-        BarrierEvent.get_info<sycl::info::event::command_execution_status>() ==
-        sycl::info::event_command_status::complete);
-    BarrierEvent.wait();
-  }
   {
     // Test cast 4 - graph.
     sycl::queue GQueue{sycl::property::queue::in_order{}};

sycl/unittests/Extensions/ExtOneapiBarrierOpt.cpp

@@ -6,7 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include <detail/queue_impl.hpp>
 #include <gtest/gtest.h>
 #include <helpers/ScopedEnvVar.hpp>
 #include <helpers/UrMock.hpp>
@@ -40,11 +39,6 @@ class ExtOneapiBarrierOptTest : public ::testing::Test {
 TEST_F(ExtOneapiBarrierOptTest, EmptyEventTest) {
   sycl::queue q1{{sycl::property::queue::in_order()}};
 
-  // To avoid current optimizations for empty queues, we trick q1 into thinking
-  // that it isn't empty.
-  int dummyInt = 0;
-  q1.prefetch(&dummyInt, sizeof(int));
-
   mock::getCallbacks().set_after_callback(
       "urEnqueueEventsWaitWithBarrierExt",
       &redefinedEnqueueEventsWaitWithBarrierExt);