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

Author: aelovikov-intel

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));
   }
 }