[NFCI] More convertToOpenCLType-related simplifications (#12717)

sycl/include/sycl/builtins_preview.hpp

@@ -95,28 +95,13 @@ template <typename T> auto convert_arg(T &&x) {
  __attribute__((ext_vector_type(N)))>;
  // TODO: We should have this bit_cast impl inside vec::convert.
  return bit_cast<result_type>(static_cast<typename no_cv_ref::vector_t>(x));
- } else if constexpr (std::is_same_v<no_cv_ref, half>)
- return static_cast<half_impl::BIsRepresentationT>(x);
- else if constexpr (is_multi_ptr_v<no_cv_ref>) {
- return convert_arg(x.get_decorated());
- } else if constexpr (is_scalar_arithmetic_v<no_cv_ref>) {
- // E.g. on linux: long long -> int64_t (long), or char -> int8_t (signed
- // char) and same for unsigned; Windows has long/long long reversed.
- // TODO: Inline this scalar impl.
- return static_cast<ConvertToOpenCLType_t<no_cv_ref>>(x);
- } else if constexpr (std::is_pointer_v<no_cv_ref>) {
- using elem_type = remove_decoration_t<std::remove_pointer_t<no_cv_ref>>;
- using converted_elem_type =
- decltype(convert_arg(std::declval<elem_type>()));
- using result_type =
- typename DecoratedType<converted_elem_type,
- deduce_AS<no_cv_ref>::value>::type *;
- return reinterpret_cast<result_type>(x);
  } else if constexpr (is_swizzle_v<no_cv_ref>) {
  return convert_arg(simplify_if_swizzle_t<no_cv_ref>{x});
  } else {
- // TODO: should it be unreachable? What can it be?
- return std::forward<T>(x);
+ static_assert(is_scalar_arithmetic_v<no_cv_ref> ||
+ is_multi_ptr_v<no_cv_ref> || std::is_pointer_v<no_cv_ref> ||
+ std::is_same_v<no_cv_ref, half>);
+ return convertToOpenCLType(std::forward<T>(x));
  }
 }