Request for reviews (S): 7190310: Inlining WeakReference.get(), and hoisting $referent may lead to non-terminating loops

[Vladimir Kozlov]

http://cr.openjdk.java.net/~kvn/7190310/webrev

7190310: Inlining WeakReference.get(), and hoisting $referent may lead to 
non-terminating loops

Add acquire membar after load from Reference.referent field to prevent commoning 
of loads across safepoint since GC can change its value.

Thanks,
Vladimir