RFR: Fix full-gc matrix updates

[Roman Kennke]

Am 17.03.2017 um 22:02 schrieb Roman Kennke:
> When running the adjust-pointers pass in full-gc, we're also updating
> the matrix. We're using the current oop* for from-region, and the new
> location of the object for to-region. However, the from-object is also
> going to move! We need to take this into account.
>
> It's fixed by computing the offset of the from-object and its new
> location, and subtracting this from the from-pointer in the closure.
>
> I also snuck in two minor improvements:
> - Remove some old redundant code (from last patch)
> - use encode_store_heap_oop_not_null() instead of encode_store_heap_oop().
>
> http://cr.openjdk.java.net/~rkennke/partial-fixfullgc/webrev.00/
> <http://cr.openjdk.java.net/%7Erkennke/partial-fixfullgc/webrev.00/>
>
> Ok?
>
> Roman
>
>
Two little changes:
- Use size_t instead of int, in case we need to address large memory.
- Don't cast HeapWord* to oop, just to cast it back to HeapWord*. ;-)

http://cr.openjdk.java.net/~rkennke/partial-fixfullgc/webrev.01/
<http://cr.openjdk.java.net/%7Erkennke/partial-fixfullgc/webrev.01/>

Roman