This revision adds support for specifying operands or results as "optional". This is a special case of variadic where the number of elements is either 0 or 1. Operands and results of this kind will have accessors generated using Value instead of the range types, making it more natural to interface with.
Nice! Thnks River!
nit: space before (
Also mention AttrSizedOperandSegments?
Nit: else would be better here. We don't have a large body of code following this anyway.
remove trailing s