From be7c202ca19c8be029f437c7fe6456684b170d13 Mon Sep 17 00:00:00 2001
From: Julian Miller <julian.miller@intel.com>
Date: Mon, 26 Jun 2023 15:34:27 +0200
Subject: [PATCH] Merge pull request #237 from
 reble/julianmi/fix-double-root-nodes

Fix adding empty nodes to the graph results in two root nodes
---
 sycl/source/detail/graph_impl.cpp |  3 ---
 sycl/source/detail/graph_impl.hpp |  9 +++------
 sycl/source/handler.cpp           | 13 +++++--------
 3 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/sycl/source/detail/graph_impl.cpp b/sycl/source/detail/graph_impl.cpp
index 9cd1c0d6ab1b6..e0a1b48d9a746 100644
--- a/sycl/source/detail/graph_impl.cpp
+++ b/sycl/source/detail/graph_impl.cpp
@@ -146,9 +146,6 @@ graph_impl::add(const std::shared_ptr<graph_impl> &Impl,
   if (Handler.MSubgraphNode) {
     return Handler.MSubgraphNode;
   }
-  if (Handler.MCGType == sycl::detail::CG::None) {
-    return this->add(Dep);
-  }
   return this->add(Handler.MCGType, std::move(Handler.MGraphNodeCG), Dep);
 }
 
diff --git a/sycl/source/detail/graph_impl.hpp b/sycl/source/detail/graph_impl.hpp
index 8ffa5d047570e..525852290e2cf 100644
--- a/sycl/source/detail/graph_impl.hpp
+++ b/sycl/source/detail/graph_impl.hpp
@@ -43,9 +43,6 @@ class node_impl {
   /// Command group object which stores all args etc needed to enqueue the node
   std::unique_ptr<sycl::detail::CG> MCommandGroup;
 
-  /// True if an empty node, false otherwise.
-  bool MIsEmpty = false;
-
   /// Add successor to the node.
   /// @param Node Node to add as a successor.
   /// @param Prev Predecessor to \p node being added as successor.
@@ -65,7 +62,7 @@ class node_impl {
   }
 
   /// Construct an empty node.
-  node_impl() : MIsEmpty(true) {}
+  node_impl() {}
 
   /// Construct a node representing a command-group.
   /// @param CGType Type of the command-group.
@@ -106,7 +103,7 @@ class node_impl {
 
   /// Query if this is an empty node.
   /// @return True if this is an empty node, false otherwise.
-  bool isEmpty() const { return MIsEmpty; }
+  bool isEmpty() const { return MCGType == sycl::detail::CG::None; }
 
   /// Get a deep copy of this node's command group
   /// @return A unique ptr to the new command group object.
@@ -366,7 +363,7 @@ class exec_graph_impl {
 
   /// Turns the internal graph representation into UR command-buffers for a
   /// device.
-  /// @param D Device to create backend command-buffers for.
+  /// @param Device Device to create backend command-buffers for.
   void createURCommandBuffers(sycl::device Device);
 
   /// Query for the context tied to this graph.
diff --git a/sycl/source/handler.cpp b/sycl/source/handler.cpp
index c72219d1a463d..20905d5d10f2d 100644
--- a/sycl/source/handler.cpp
+++ b/sycl/source/handler.cpp
@@ -380,23 +380,20 @@ event handler::finalize() {
     if (detail::pi::trace(detail::pi::TraceLevel::PI_TRACE_ALL)) {
       std::cout << "WARNING: An empty command group is submitted." << std::endl;
     }
-    std::shared_ptr<ext::oneapi::experimental::detail::graph_impl> GraphImpl;
     if (MGraph) {
-      GraphImpl = MGraph;
+      CommandGroup.reset(
+          new detail::CG(detail::CG::None, std::move(CGData), MCodeLoc));
+      MGraphNodeCG = std::move(CommandGroup);
     } else if (auto QueueGraph = MQueue->getCommandGraph(); QueueGraph) {
-      GraphImpl = QueueGraph;
-    }
-
-    if (GraphImpl) {
       auto EventImpl = std::make_shared<detail::event_impl>();
 
       // Extract relevant data from the handler and pass to graph to create a
       // new node representing this command group.
       std::shared_ptr<ext::oneapi::experimental::detail::node_impl> NodeImpl =
-          GraphImpl->add(CGData.MEvents);
+          QueueGraph->add(CGData.MEvents);
 
       // Associate an event with this new node and return the event.
-      GraphImpl->addEventForNode(EventImpl, NodeImpl);
+      QueueGraph->addEventForNode(EventImpl, NodeImpl);
 
       return detail::createSyclObjFromImpl<event>(EventImpl);
     }