Tradeoffs around Node::Opcode()?

[Peter B. Kessler]

A lot of things in class Node are organized around having a dense integer range to identify the Node.  That's Node::Opcode().

I'm wondering about the engineering around that method.  Node::Opcode() is a virtual call, to get from a Node instance to a piece of data on the Node subclass of the instance.  An alternative would be to add a data field in Node to hold the opcode, and replace the virtual Node::Opcode() calls with an inline method to return the contents of that slot.  That trades the virtual dispatch cost for each call with a space cost in each instance.

Does anyone have any feeling about whether that's a good tradeoff?  How often is Node::Opcode() called?  What effect would it have to make it run faster?  How important is it to minimize the size of Node instances?  (There are other places where effort is expended to keep Node's small.)

Thanks for any opinions on this.

			... peter