Remove guards in TrailingZeroCountOperator<T>.Invoke for Vector256 and Vector512 paths (#116721)

Co-authored-by: Alex Covington (Advanced Micro Devices Inc) <[email protected]>

Author: alexcovington

src/libraries/System.Numerics.Tensors/src/System/Numerics/Tensors/netcore/TensorPrimitives.TrailingZeroCount.cs

@@ -48,23 +48,15 @@ public static Vector128<T> Invoke(Vector128<T> x)
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             public static Vector256<T> Invoke(Vector256<T> x)
             {
-                if (PopCountOperator<T>.Vectorizable)
-                {
-                    return PopCountOperator<T>.Invoke(~x & (x - Vector256<T>.One));
-                }
-
-                return Vector256.Create(Invoke(x.GetLower()), Invoke(x.GetUpper()));
+                Debug.Assert(PopCountOperator<T>.Vectorizable);
+                return PopCountOperator<T>.Invoke(~x & (x - Vector256<T>.One));
             }
 
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
             public static Vector512<T> Invoke(Vector512<T> x)
             {
-                if (PopCountOperator<T>.Vectorizable)
-                {
-                    return PopCountOperator<T>.Invoke(~x & (x - Vector512<T>.One));
-                }
-
-                return Vector512.Create(Invoke(x.GetLower()), Invoke(x.GetUpper()));
+                Debug.Assert(PopCountOperator<T>.Vectorizable);
+                return PopCountOperator<T>.Invoke(~x & (x - Vector512<T>.One));
             }
         }
     }