Woops! I tried it but compile error.
I'm sure in http://www.nada.kth.se/~tomaso/Stream2008/M3.pdf in Swizzle page there stating:
– Use Swizzle to mask elements in output – Use Swizzle to mask elements in output
e.g. output.xw = input.x;
I think this is changed after strong type checking in brcc. Both LHS and RHS have to have the same number of components and data type.