review request (S): 7129034: VM crash with a field setter method with a filterArguments

[John Rose]

http://cr.openjdk.java.net/~jrose/7129034/webrev.00/

7129034: VM crash with a field setter method with a filterArguments
Summary: add null checks before unsafe calls that take a variable base reference; update unit tests

This is a point fix for JDK 8, and will also be back-ported to JDK 7u.

— John

Note:  This class is part of JSR 292.  Therefore the review comments will be collected in mlvm-dev.