RFR (XS): 8025566: EXCEPTION_ACCESS_VIOLATION in compiled by C1 String.valueOf method

[Christian Thalinger]

https://bugs.openjdk.java.net/browse/JDK-8025566
http://cr.openjdk.java.net/~twisti/8025566

8025566: EXCEPTION_ACCESS_VIOLATION in compiled by C1 String.valueOf method
Reviewed-by:

The problem is in ciMethod::ensure_method_data().  The call to ciMethodData::load_data() can fail when the backing metadata pointer is null and return with a still empty method data.  So we have to check here for non-emptiness.

I also removed ciMethodData::set_mature().  This method was only used with the old JSR 292 implementation.