[SYCL][ESIMD][EMU] Half-type support - __esimd_convertvector_to/from (#6239)

* [SYCL][ESIMD][EMU] Half-type support - __esimd_convertvector_to/from

Author: dongkyunahn-intel

sycl/include/sycl/ext/intel/esimd/detail/elem_type_traits.hpp

@@ -166,8 +166,20 @@ __esimd_convertvector_to(vector_type_t<StdTy, N> Val)
       // element_type_traits<WrapperTy>::use_native_cpp_ops is false.
 #else
 {
-  // TODO implement for host
-  __ESIMD_UNSUPPORTED_ON_HOST;
+  vector_type_t<__raw_t<WrapperTy>, N> Output = 0;
+
+  if constexpr (std::is_same_v<WrapperTy, sycl::half>) {
+    for (int i = 0; i < N; i += 1) {
+      // 1. Convert Val[i] to float (x) using c++ static_cast
+      // 2. Convert x to half (using float2half)
+      // 3. Output[i] = half_of(x)
+      Output[i] = ::sycl::detail::float2Half(static_cast<float>(Val[i]));
+    }
+  } else {
+    __ESIMD_UNSUPPORTED_ON_HOST;
+  }
+
+  return Output;
 }
 #endif // __SYCL_DEVICE_ONLY__
 
@@ -179,8 +191,20 @@ __esimd_convertvector_from(vector_type_t<__raw_t<WrapperTy>, N> Val)
       // element_type_traits<WrapperTy>::use_native_cpp_ops is false.
 #else
 {
-  // TODO implement for host
-  __ESIMD_UNSUPPORTED_ON_HOST;
+  vector_type_t<StdTy, N> Output;
+
+  if constexpr (std::is_same_v<WrapperTy, sycl::half>) {
+    for (int i = 0; i < N; i += 1) {
+      // 1. Convert Val[i] to float y(using half2float)
+      // 2. Convert y to StdTy using c++ static_cast
+      // 3. Store in Output[i]
+      Output[i] = static_cast<StdTy>(::sycl::detail::half2Float(Val[i]));
+    }
+  } else {
+    __ESIMD_UNSUPPORTED_ON_HOST;
+  }
+
+  return Output;
 }
 #endif // __SYCL_DEVICE_ONLY__