Define vwadd/vwaddu/vwsub/vwsubu intrinsics and lower to V instructions.
In this patch, it demonstrates how to model widening vector instructions.
We work with @rogfer01 from BSC to come out this patch.
Authored-by: Roger Ferrer Ibanez <rofirrim@gmail.com>
Co-Authored-by: Hsiangkai Wang <kai.wang@sifive.com>
Widenable is probably better than Wideable.