8066103: C2's range check smearing allows out of bound array accesses

[Roland Westrelin]

>>> That's good; let's do it that way!
>>> 
>>> Final suggestion (really):  Add some more test cases, containing duplicate array indexes, to exercise the "local" logic. 
>> 
>> Thanks John. I’ll add some test cases. Do you want to see another webrev with test cases?
> 
> I'd like to look at it, so please update the webrev, but you can proceed with a thumbs up from me as a reviewer no matter what.

Here is a new webrev for the change I intend to push today:

http://cr.openjdk.java.net/~roland/8066103/webrev.04/

It has more test cases and the previous change had some leftover code:

 939           if (rc0.ctl->in(0)->in(1) == in(1)) {
 940             // If we match the test exactly, then the top test covers

 941             // both our lower and upper bounds. Valid only if there's no
 942             // other range check between us and the top test: for all we
 943             // know this range check was widened and accesses that
 944             // depend on it also depend on the previous range checks to
 945             // be correct.

 946             prev_dom = rc0.ctl;
 947           } else {

Roland.