[SYCL][NFC] Refactoring of the host side built-in functions

Removed a code duplication.
Moved the common implementation functions to anonymous namespace.

Signed-off-by: Alexey Voronov <[email protected]>

Author: alexeyvoronov-intel

sycl/include/CL/sycl/builtins.hpp

@@ -965,6 +965,8 @@ upsample(T hi, T2 lo) __NOEXC {
       hi, lo);
 }
 
+#undef __invoke_s_upsample
+
 // geninteger popcount (geninteger x)
 template <typename T>
 typename std::enable_if<detail::is_geninteger<T>::value, T>::type

sycl/include/CL/sycl/detail/generic_type_traits.hpp

@@ -1244,6 +1244,10 @@ template <typename T> static constexpr T min_v() {
   return std::numeric_limits<T>::min();
 }
 
+template <typename T> static constexpr T quiet_NaN() {
+  return std::numeric_limits<T>::quiet_NaN();
+}
+
 } // namespace detail
 } // namespace sycl
 } // namespace cl