RFR(XS): 8149543: range check CastII nodes should not be split through Phi

[Roland Westrelin]

Thanks for looking at this, Vladimir.

> It would be nice if we could narrow this bailout only for loops. I mean when Phi's control is loop's head.
> If it is an ordinary merge region splitting through it may help to improve performance. What do you think?
> Could you run some performance tests to effects. If ordinary region cases are rare then you current fix is good enough.

What about this?
http://cr.openjdk.java.net/~roland/8149543/webrev.01/

Tobias’ performance runs when he added the range check CastII found no regressions so I suppose test runs where I tweak how much split thru phi we do for CastII nodes are unlikely to show anything either. What do you think?

Roland.