RFR (S): 8035326: Assume non-NULL references in G1CollectedHeap::in_cset_fast_test

Mikael Gerdin mikael.gerdin at oracle.com
Thu Feb 20 04:06:01 PST 2014


Thomas,

On Thursday 20 February 2014 11.17.39 Thomas Schatzl wrote:
> Hi Jon,
> 
>   thanks for the review.
> 
> On Wed, 2014-02-19 at 17:18 -0800, Jon Masamitsu wrote:
> > Thomas,
> > 
> > Changes look good.
> > 
> > Is there really nothing you would put into the assert string?
> > 
> > http://cr.openjdk.java.net/~tschatzl/8035326/webrev/src/share/vm/gc_implem
> > entation/g1/g1CollectedHeap.hpp.udiff.html
> > 
> > +    assert(_g1_committed.contains((HeapWord*) obj), "");
> 
> Fixed in http://cr.openjdk.java.net/~tschatzl/8035326/webrev.1 along
> with other suggestions from Stefan.

in g1CollectedHeap.cpp

4792   T heap_oop = oopDesc::load_heap_oop(p);
4793 
4794   // Filter out all NULL references up front avoiding checking this again
4795   // over and over.
4796   if (oopDesc::is_null(heap_oop)) {
4797     return;
4798   }
4799 
4800   oop obj = oopDesc::load_decode_heap_oop_not_null(p);

Why do you dereference p again after the null check? You could just have:
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop)

Otherwise the changes look good.

/Mikael

> 
> Thanks,
>   Thomas



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