I didn't say I'd used it.
Okay, okay, I did! It's definitely more useful for looking at small sections of the HAL.
The whole thing is a little too much for the tool, but if there's a subset that you're trying to understand better, it's definitely useful.
Thanks for writing it -- I found it because I was setting out to do the exact same thing, also using graphviz, but decided I should look around to see what was already available. You saved me a bunch of work!
paul