LRB midpath code quality

[Roman Kennke]

>>> Well yes, an implicit null-check would be good. It would never fire,
>>> because if the value is null, it would blow up earlier in the cset
>>> check. Or am I missing something?
>>
>> I suppose PhaseCFG::implicit_null_check() doesn't recognize the barrier
>> load as a candidate for implicit null checks for some reason.
> 
> Uhhh. I think I may have removed the -8 handling from 
> MacroAssembler::needs_explicit_null_check() path in original LRB patch :-)
> 
> Let me try to put that back...

Hmm, no. That path looks ok.

I changed the fwdptr load to be raw access. Might that cause problems?

Roman