Add support for xsimd::widen on PowerPC/VSX

Related to #1179

Author: serge-sans-paille

include/xsimd/arch/xsimd_vsx.hpp

@@ -873,6 +873,13 @@ namespace xsimd
             return vec_trunc(self.data);
         }
 
+        // widen
+        template <class A, class T>
+        XSIMD_INLINE std::array<batch<double, A>, 2> widen(batch<float, A> const& x, requires_arch<vsx>) noexcept
+        {
+            return { batch<double, A>(vec_doublel(x)), batch<double, A>(vec_doubleh(x)) };
+        }
+
         // zip_hi
         template <class A, class T, class = typename std::enable_if<std::is_scalar<T>::value>::type>
         XSIMD_INLINE batch<T, A> zip_hi(batch<T, A> const& self, batch<T, A> const& other, requires_arch<vsx>) noexcept