RFR: 8069016: Add BarrierSet downcast support

[Kim Barrett]

On Feb 18, 2015, at 3:01 PM, Jon Masamitsu <jon.masamitsu at oracle.com> wrote:
> 
> 
> On 2/16/2015 3:16 PM, Kim Barrett wrote:
>> Please review this change that ensures all barrier set downcasts are
>> checked when running in debug mode. This is a step toward some
>> cleanups and changes to the barrier set class hierarchy, improving
>> error checking and making it easier to find places where assumptions
>> are being made that would be invalidated by changes.
>> 
>> I will need a sponsor for this change.
>> 
>> CR:
>> https://bugs.openjdk.java.net/browse/JDK-8069016
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~kbarrett/8069016/webrev.00
>> 
>> Changeset includes
>> 
>> * New FakeRttiSupport utility class template.  This provides some
> 
> Kim,
> 
> Just starting on this but an up front question.  Do you have a
> particular preference for having "Fake" in the class name?  As
> opposed to just RTTISupport?  It feels a little funny and adds
> (unnecessary?) length to the name.

I don’t feel strongly about the name, but “RTTISupport” to me indicates something
related to “real” RTTI, which we don’t have.  I used “fake” because of the use of that
terminology in several existing comments referring the mechanisms I’m replacing or
hope to replace in the future.