We previously had lowering for:
vecreduce.add(zext(X)) to vecreduce.add(UDOT(zero, X, one))
This extends that to also handle:
vecreduce.add(mul(zext(X), zext(Y)) to vecreduce.add(UDOT(zero, X, Y))
It extends the existing code to optionally handle a mul with equal extends.
Nit: can we not do:
to avoid creating As and Bs?