Request for reviews (XS): 7170145: C1 doesn't respect the JMM with volatile field loads

[Christian Thalinger]

http://cr.openjdk.java.net/~twisti/7170145

7170145: C1 doesn't respect the JMM with volatile field loads
Reviewed-by:

ValueNumberingVisitor::do_LoadField does not include logic for
volatile fields which allows CSE of normal field loads across volatile
field loads.  That's explicitly prohibited by the JMM.

This patch also kills the memory across volatile field stores even it
is too strict for now because of volatile field stores and possible
future optimizations.

src/share/vm/c1/c1_ValueMap.hpp