[ESIMD] Add infra to support half, bfloat, etc, support sycl::half. (#…

…5123)

- implement infrastructure for non-standard element type support
  to support a new type, the following must be implemented:
  * element type traits for the new type
  * scalar and vector conversions to/from selected std C++ type
  * std operations (or default with promotion to std C++ type can be used)
- esimd::simd<sycl::half, N> can now be used on host and device
  * most of the operations, except extended math are supported for half

Signed-off-by: Konstantin S Bobrovsky <konstantin.s.bobrovsky@intel.com>

sycl/include/CL/sycl/half_type.hpp

@@ -35,6 +35,19 @@
 
 __SYCL_INLINE_NAMESPACE(cl) {
 namespace sycl {
+
+namespace ext {
+namespace intel {
+namespace experimental {
+namespace esimd {
+namespace detail {
+class WrapperElementTypeProxy;
+} // namespace detail
+} // namespace esimd
+} // namespace experimental
+} // namespace intel
+} // namespace ext
+
 namespace detail {
 
 inline __SYCL_CONSTEXPR_HALF uint16_t float2Half(const float &Val) {
@@ -255,6 +268,9 @@ class __SYCL_EXPORT half_v2 {
   // Initialize underlying data
   constexpr explicit half_v2(uint16_t x) : Buf(x) {}
 
+  friend class sycl::ext::intel::experimental::esimd::detail::
+      WrapperElementTypeProxy;
+
 private:
   uint16_t Buf;
 };
@@ -391,6 +407,9 @@ class half {
 
   template <typename Key> friend struct std::hash;
 
+  friend class sycl::ext::intel::experimental::esimd::detail::
+      WrapperElementTypeProxy;
+
 private:
   StorageT Data;
 };

sycl/include/sycl/ext/intel/experimental/esimd/common.hpp

@@ -29,6 +29,9 @@
 #define ESIMD_REGISTER(n) __attribute__((register_num(n)))
 
 #define __ESIMD_API ESIMD_NODEBUG ESIMD_INLINE
+
+#define __ESIMD_UNSUPPORTED_ON_HOST
+
 #else // __SYCL_DEVICE_ONLY__
 #define SYCL_ESIMD_KERNEL
 #define SYCL_ESIMD_FUNCTION
@@ -41,6 +44,9 @@
 #define ESIMD_REGISTER(n)
 
 #define __ESIMD_API ESIMD_INLINE
+
+#define __ESIMD_UNSUPPORTED_ON_HOST throw cl::sycl::feature_not_supported()
+
 #endif // __SYCL_DEVICE_ONLY__
 
 // Mark a function being noinline