RFR (S): JDK-6991197 G1: specialize deal_with_reference() for narrowOop*

[Thomas Schatzl]

Hi Tony,

  thanks for the review :)

On Wed, 2014-01-29 at 15:34 -0500, Tony Printezis wrote:
> Thomas,
> 
> (if you need one more opinion) The latest webrev also looks good to me 
> and I found it a nice improvement over the first one.
> 
> Can I take it a step (OK: two steps!) further, if you're interested (and 
> feel free to ignore this)?
> 
> Why is clear_partial_array_mask() a template given that it should only 
> work on oops*'s? (correct?)

Cannot do that right away, since the compiler always instantiates
G1ParScanPartialArrayClosure::do_oop_nv() with both narrowOop and oop*.
It does not detect at parse time that has_partial_array_mask() always
returns false for narrowOop*.

> Then, why is G1ParScanPartialArrayClosure::do_oop_nv(T* p) a template 
> too (should only be called for T == oop). In fact, why is it a closure 
> at all? Would it make sense to just move its body to a method with an 
> oop* parameter and just call it directly from deal_with_reference()?

I am currently working on JDK-8027547 to change the array chunk
iteration code to something like you suggest. Is it okay for you to
defer these cleanup changes for that CR (or another CR)?

Thanks for the information,
  Thomas