C2 support for reference fields in value types

[Roland Westrelin]

> here's the newest version that solves all previous problems:
> http://cr.openjdk.java.net/~thartmann/valhalla/vt_prototype/webrev.16/

sharedRuntime_x86_64.cpp, that comment:

720       __ mov(r10, r13); // Cannot use r10 above because it's trashed by movptr()

is confusing. r10 is trashed but used anyway?

1154     // TODO is 256 enough? Can we determine the required length?

Shouldn't you add an assert to verify we don't overflow the array?

Other than, that looks good to me.

Roland.