[SYCL][L0] Add new environment variable to control the use of copy engine for in-order queues (#4335)

Author: asudarsa

sycl/plugins/level_zero/pi_level_zero.cpp

@@ -60,6 +60,16 @@ static const bool UseCopyEngineForD2DCopy = [] {
   return (CopyEngineForD2DCopy && (std::stoi(CopyEngineForD2DCopy) != 0));
 }();
 
+// This is an experimental option that allows the use of copy engine, if
+// available in the device, in Level Zero plugin for copy operations submitted
+// to an in-order queue. The default is 1.
+static const bool UseCopyEngineForInOrderQueue = [] {
+  const char *CopyEngineForInOrderQueue =
+      std::getenv("SYCL_PI_LEVEL_ZERO_USE_COPY_ENGINE_FOR_IN_ORDER_QUEUE");
+  return (!CopyEngineForInOrderQueue ||
+          (std::stoi(CopyEngineForInOrderQueue) != 0));
+}();
+
 // This class encapsulates actions taken along with a call to Level Zero API.
 class ZeCall {
 private:
@@ -869,7 +879,9 @@ pi_result _pi_context::getAvailableCommandList(
     if (auto Res = Queue->executeOpenCommandList())
       return Res;
   }
-  bool UseCopyEngine = PreferCopyEngine && Queue->Device->hasCopyEngine();
+  bool UseCopyEngine =
+      (!(Queue->isInOrderQueue()) || UseCopyEngineForInOrderQueue) &&
+      PreferCopyEngine && Queue->Device->hasCopyEngine();
 
   // Create/Reuse the command list, because in Level Zero commands are added to
   // the command lists, and later are then added to the command queue.