[SYCL][Graph] Throw exception when creating graph for unsupported backend (#280)

* [SYCL][Graph] Throw exception when creating graph for unsupported backend

- Checks backend when creating graphs and throws an exception is the backend is not supported.
- Adds an e2e test to verify this exception throwing.
- Updates some comments
- Improves mock usage in Unitest to avoid having to force emulation mode

---------

Co-authored-by: Pablo Reble <[email protected]>
Co-authored-by: Julian Miller <[email protected]>

Author: 3 people

sycl/source/detail/graph_impl.hpp

@@ -373,6 +373,16 @@ class graph_impl {
     if (PropList.has_property<property::graph::no_cycle_check>()) {
       MSkipCycleChecks = true;
     }
+    if (SyclDevice.get_info<
+            ext::oneapi::experimental::info::device::graph_support>() ==
+        info::graph_support_level::unsupported) {
+      std::stringstream Stream;
+      Stream << SyclDevice.get_backend();
+      std::string BackendString = Stream.str();
+      throw sycl::exception(
+          sycl::make_error_code(errc::invalid),
+          BackendString + " backend is not supported by SYCL Graph extension.");
+    }
   }
 
   /// Remove node from list of root nodes.

sycl/test-e2e/Graph/exception_unsupported_backend.cpp

@@ -0,0 +1,35 @@
+// RUN: %{build} -o %t.out
+// RUN: %{run} %t.out
+
+// Tests the ability to finalize a empty command graph
+// The test checks that invalid exception is thrown
+// when trying to create a graph with an unsupported backend.
+
+#include "graph_common.hpp"
+
+int GetUnsupportedBackend(const sycl::device &Dev) {
+  // Return 1 if the device backend is unsupported or 0 else.
+  // 0 does not prevent another device to be picked as a second choice
+  return Dev.get_info<
+             ext::oneapi::experimental::info::device::graph_support>() ==
+         ext::oneapi::experimental::info::graph_support_level::unsupported;
+}
+
+int main() {
+  sycl::device Dev{GetUnsupportedBackend};
+  queue Queue{Dev};
+
+  if (Dev.get_info<ext::oneapi::experimental::info::device::graph_support>() !=
+      ext::oneapi::experimental::info::graph_support_level::unsupported)
+    return 0;
+
+  std::error_code ExceptionCode = make_error_code(sycl::errc::success);
+  try {
+    exp_ext::command_graph Graph{Queue.get_context(), Dev};
+  } catch (exception &Exception) {
+    ExceptionCode = Exception.code();
+  }
+  assert(ExceptionCode == sycl::errc::invalid);
+
+  return 0;
+}

sycl/unittests/Extensions/CommandGraph.cpp

@@ -474,7 +474,7 @@ TEST_F(CommandGraphTest, Finalize) {
   sycl::buffer<int> Buf(1);
   auto Node1 = Graph.add([&](sycl::handler &cgh) {
     sycl::accessor A(Buf, cgh, sycl::write_only, sycl::no_init);
-    cgh.single_task<class TestKernel1>([=]() { A[0] = 1; });
+    cgh.single_task<TestKernel<>>([]() {});
   });
 
   // Add independent node
@@ -484,7 +484,7 @@ TEST_F(CommandGraphTest, Finalize) {
   // Add a node that depends on Node1 due to the accessor
   auto Node3 = Graph.add([&](sycl::handler &cgh) {
     sycl::accessor A(Buf, cgh, sycl::write_only, sycl::no_init);
-    cgh.single_task<class TestKernel2>([=]() { A[0] = 3; });
+    cgh.single_task<TestKernel<>>([]() {});
   });
 
   // Guarantee order of independent nodes 1 and 2

sycl/unittests/helpers/PiMockPlugin.hpp

@@ -163,7 +163,7 @@ inline pi_result mock_piDeviceGetInfo(pi_device device,
                                       size_t *param_value_size_ret) {
   constexpr char MockDeviceName[] = "Mock device";
   constexpr char MockSupportedExtensions[] =
-      "cl_khr_fp64 cl_khr_fp16 cl_khr_il_program";
+      "cl_khr_fp64 cl_khr_fp16 cl_khr_il_program ur_exp_command_buffer";
   switch (param_name) {
   case PI_DEVICE_INFO_TYPE: {
     // Act like any device is a GPU.