refine contiguous gpu implementation

src/targets/gpu/device/contiguous.cpp

 
 #include <migraphx/gpu/device/contiguous.hpp>
 #include <migraphx/gpu/device/nary.hpp>
+#include <hip/hip_fp16.h>
 
 namespace migraphx {
 inline namespace MIGRAPHX_INLINE_NS {
@@ -21,11 +22,31 @@ void contiguous_nonstandard(hipStream_t stream, const argument& result, const ar
 void contiguous_packed(hipStream_t stream, const argument& result, const argument& arg)
 {
     index_int nelements = result.get_shape().elements();
-    visit_all(result, arg)([&](auto output_v, auto input_v) {
-        const auto* input = device_cast(input_v.data());
-        auto* output      = device_cast(output_v.data());
-        gs_launch(stream, nelements)([=](auto i) __device__ { output[i] = input[i]; });
-    });
+    auto type = result.get_shape().type();
+    if (type == shape::half_type)
+    {
+        visit_all(result, arg)([&](auto output_v, auto input_v) {
+            const auto* input = device_cast(input_v.data());
+            auto* output      = device_cast(output_v.data());
+            const __half2* input2 = reinterpret_cast<__half2*>(input_v.data());
+            __half2* output2 = reinterpret_cast<__half2*>(output_v.data());
+            gs_launch(stream, nelements / 2)([=](auto i) __device__ { 
+                output2[i] = input2[i]; 
+                if (i == 0 and (nelements % 2) == 1)
+                {
+                    output[nelements - 1] = input[nelements - 1];
+                }
+            });
+        });
+    }
+    else
+    {
+        visit_all(result, arg)([&](auto output_v, auto input_v) {
+            const auto* input = device_cast(input_v.data());
+            auto* output      = device_cast(output_v.data());
+            gs_launch(stream, nelements)([=](auto i) __device__ { output[i] = input[i]; });
+        });        
+    }
 }
 
 void contiguous(hipStream_t stream, const argument& result, const argument& arg)