Request for Reviews(M): 7092905: C2: Keep track of the number of dead nodes

[Bharadwaj Yadavalli]

I'd like to get a code review of the changes at 
http://cr.openjdk.java.net/~bharadwaj/7092905/webrev_01/

These changes are made to keep an (almost) accurate running count of the 
reachable (live) flow graph nodes. This will result in a more realistic 
node count for various phases of C2 to decide on whether to proceed with 
optimizations or not. Prior to these changes, C2 bails out of 
compilation based on the number of nodes created which typically larger 
than the number of reachable (live) nodes.

I observed no significant degradation in C2 compilation time of all 
classes in rt.jar time due to these changes.

Thanks,

Bharadwaj