[antlr-interest] holy crap! optimization from allah!

[Terence Parr]

You know how somedays things just go right?  Well I have been trying  
to solve a problem with the ASN grammar as submitted to me by Magne  
Rasmussen...at first I thought it was a bug but now I think it is  
just hitting an exponentiality in the algorithm.  So I started  
thinking again about how to speed the analysis up...I have spent  
hours thinking and thinking about how the algorithm works, which is  
how I decided it was still solid.  I did think of one minor  
optimization...when I added it (1 IF statement!), analysis dropped by  
90% or so!!!  Hooray!  Analysis is now down to about 10% of total  
time from 1/3. :)

The optimization avoid computing the closure operation on states that  
are only capable of predicting a single alternative (as analysis will  
stop with that state); no point in computing closure, which is very  
expensive.

Magne: still hitting landmines in the grammar, but I am still working  
on it!

Ter