[SYCL] Specialize errc for backends.

sycl/include/CL/sycl/backend.hpp

@@ -39,6 +39,10 @@ template <backend Backend, typename T> struct BackendReturn {
   // TODO replace usage of interop with specializations.
   using type = typename interop<Backend, T>::type;
 };
+
+// TODO each backend can have its own custom errc enumeration
+// but the details for this are not fully specified yet
+enum class backend_errc : unsigned int {};
 } // namespace detail
 
 template <backend Backend> class backend_traits {
@@ -49,7 +53,7 @@ template <backend Backend> class backend_traits {
   template <class T>
   using return_type = typename detail::BackendReturn<Backend, T>::type;
 
-  // TODO define errc once SYCL2020-style exceptions are supported.
+  using errc = detail::backend_errc;
 };
 
 template <backend Backend, typename SyclType>

sycl/include/CL/sycl/exception.hpp

@@ -10,6 +10,7 @@
 
 // 4.9.2 Exception Class Interface
 
+#include <CL/sycl/backend_types.hpp>
 #include <CL/sycl/detail/common.hpp>
 #include <CL/sycl/detail/export.hpp>
 #include <CL/sycl/detail/pi.h>
@@ -185,6 +186,8 @@ enum class errc : unsigned int {
   backend_mismatch = 13,
 };
 
+template <backend B> using errc_for = typename backend_traits<B>::errc;
+
 /// Constructs an error code using e and sycl_category()
 __SYCL_EXPORT std::error_code make_error_code(sycl::errc E) noexcept;
 

sycl/test/basic_tests/exceptions-SYCL-2020.cpp

@@ -76,6 +76,27 @@ int main() {
   static_assert(std::is_error_code_enum<sycl::errc>::value, "errc enum should identify as error code");
   static_assert(!std::is_error_condition_enum<sycl::errc>::value, "errc enum should not identify as error condition");
 
+  // Test errc_for and backends. Should compile without complaint.
+  constexpr int EC = 1;
+  sycl::backend_traits<sycl::backend::opencl>::errc someOpenCLErrCode{EC};
+  sycl::errc_for<sycl::backend::opencl> anotherOpenCLErrCode{EC};
+  assert(someOpenCLErrCode == anotherOpenCLErrCode);
+  sycl::backend_traits<sycl::backend::level_zero>::errc someL0ErrCode{EC};
+  sycl::errc_for<sycl::backend::level_zero> anotherL0ErrCode{EC};
+  assert(someL0ErrCode == anotherL0ErrCode);
+  sycl::backend_traits<sycl::backend::host>::errc someHOSTErrCode{EC};
+  sycl::errc_for<sycl::backend::host> anotherHOSTErrCode{EC};
+  assert(someHOSTErrCode == anotherHOSTErrCode);
+  sycl::backend_traits<sycl::backend::cuda>::errc someCUDAErrCode{EC};
+  sycl::errc_for<sycl::backend::cuda> anotherCUDAErrCode{EC};
+  assert(someCUDAErrCode == anotherCUDAErrCode);
+  sycl::backend_traits<sycl::backend::esimd_cpu>::errc someESIMDErrCode{EC};
+  sycl::errc_for<sycl::backend::esimd_cpu> anotherESIMDErrCode{EC};
+  assert(someESIMDErrCode == anotherESIMDErrCode);
+  sycl::backend_traits<sycl::backend::rocm>::errc someROCMErrCode{EC};
+  sycl::errc_for<sycl::backend::rocm> anotherROCMErrCode{EC};
+  assert(someROCMErrCode == anotherROCMErrCode);
+
   std::cout << "OK" << std::endl;
   return 0;
 }