[SYCL] Support sycl_khr_default_context

Spec: KhronosGroup/SYCL-Docs#624
sycl-cts: KhronosGroup/SYCL-CTS#960

This patch is intended to be merged only when there are sycl-cts tests
and the ratified khr extension.

sycl/include/sycl/platform.hpp

@@ -230,6 +230,11 @@ class __SYCL_EXPORT platform : public detail::OwnerLessBase<platform> {
 
   std::vector<device> ext_oneapi_get_composite_devices() const;
 
+  /// Returns a copy of the default context object for this platform.
+  ///
+  /// \return the default context
+  context khr_get_default_context() const;
+
 private:
   ur_native_handle_t getNative() const;
 

sycl/source/detail/queue_impl.hpp

@@ -77,7 +77,7 @@ class queue_impl {
           context{createSyclObjFromImpl<device>(Device), {}, {}});
 
     ContextImplPtr DefaultContext = detail::getSyclObjImpl(
-        Device->get_platform().ext_oneapi_get_default_context());
+        Device->get_platform().khr_get_default_context());
     if (DefaultContext->isDeviceValid(Device))
       return DefaultContext;
     return detail::getSyclObjImpl(

sycl/source/feature_test.hpp.in

@@ -110,6 +110,7 @@ inline namespace _V1 {
 #define SYCL_EXT_ONEAPI_ENQUEUE_NATIVE_COMMAND 1
 // In progress yet
 #define SYCL_EXT_ONEAPI_ATOMIC16 0
+#define SYCL_KHR_DEFAULT_CONTEXT 1
 
 #ifndef __has_include
 #define __has_include(x) 0

sycl/source/platform.cpp

@@ -86,7 +86,7 @@ platform::get_backend_info() const {
 
 #undef __SYCL_PARAM_TRAITS_SPEC
 
-context platform::ext_oneapi_get_default_context() const {
+context platform::khr_get_default_context() const {
   if (!detail::SYCLConfig<detail::SYCL_ENABLE_DEFAULT_CONTEXTS>::get())
     throw std::runtime_error("SYCL default contexts are not enabled");
 
@@ -108,6 +108,10 @@ context platform::ext_oneapi_get_default_context() const {
   return detail::createSyclObjFromImpl<context>(It->second);
 }
 
+context platform::ext_oneapi_get_default_context() const {
+  return khr_get_default_context();
+}
+
 std::vector<device> platform::ext_oneapi_get_composite_devices() const {
   // Only GPU architectures can be composite devices.
   auto GPUDevices = get_devices(info::device_type::gpu);

sycl/test-e2e/Basic/khr_get_default_context.cpp

@@ -0,0 +1,25 @@
+// RUN: %{build} -o %t.out
+// RUN: %{run} %t.out
+
+// Test checks that the default context contains all of the root devices that
+// are associated with this platform.
+
+#include <sycl/detail/core.hpp>
+#include <algorithm>
+
+using namespace sycl;
+
+int main() {
+  auto platforms = platform::get_platforms();
+
+  for (const auto &plt : platforms) {
+    auto def_ctx_devs = plt.khr_get_default_context().get_devices();
+    auto root_devs = plt.get_devices();
+
+    for (const auto &dev : root_devs)
+      if (std::find(def_ctx_devs.begin(), def_ctx_devs.end(), dev) == def_ctx_devs.end())
+        return 1;
+  }
+
+  return 0;
+}

sycl/test/abi/sycl_symbols_linux.dump

@@ -3986,6 +3986,7 @@ _ZNK4sycl3_V18platform13has_extensionENS0_6detail11string_viewE
 _ZNK4sycl3_V18platform16get_backend_infoINS0_4info6device15backend_versionEEENS0_6detail20is_backend_info_descIT_E11return_typeEv
 _ZNK4sycl3_V18platform16get_backend_infoINS0_4info6device7versionEEENS0_6detail20is_backend_info_descIT_E11return_typeEv
 _ZNK4sycl3_V18platform16get_backend_infoINS0_4info8platform7versionEEENS0_6detail20is_backend_info_descIT_E11return_typeEv
+_ZNK4sycl3_V18platform23khr_get_default_contextEv
 _ZNK4sycl3_V18platform30ext_oneapi_get_default_contextEv
 _ZNK4sycl3_V18platform32ext_oneapi_get_composite_devicesEv
 _ZNK4sycl3_V18platform3getEv

sycl/unittests/Extensions/DefaultContext.cpp

@@ -36,6 +36,9 @@ void test_default_context_enabled() {
 
   ASSERT_EQ(Dev1.get_platform().ext_oneapi_get_default_context(),
             Dev2.get_platform().ext_oneapi_get_default_context());
+
+  ASSERT_EQ(Dev1.get_platform().khr_get_default_context(),
+            Dev2.get_platform().khr_get_default_context());
 }
 
 void test_default_context_disabled() {
@@ -51,6 +54,16 @@ void test_default_context_disabled() {
 
   ASSERT_TRUE(catchException)
       << "ext_oneapi_get_default_context did not throw an exception";
+
+  catchException = false;
+  try {
+    (void)Plt.khr_get_default_context();
+  } catch (const std::exception &) {
+    catchException = true;
+  }
+
+  ASSERT_TRUE(catchException)
+      << "khr_get_default_context did not throw an exception";
 }
 
 TEST(DefaultContextTest, DefaultContextTest) {