RFR: 8229258: Make markOopDesc AllStatic

[Roman Kennke]

Am 14.08.19 um 01:26 schrieb Kim Barrett:
>> On Aug 12, 2019, at 12:19 PM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
>>
>> Hi Roman,
>>
>> Kim helped me figuring out how to get past the volatile issues I had with the class markWord { uintptr_t value; ... } version. So, I've created a version with that:
>>
>> https://cr.openjdk.java.net/~stefank/8229258/webrev.valueMarkWord.01/
>>
>> I can go with either approach, so let me now what you all think.
> 
> I've finally had time to look at the first proposed change.
> 
> Comparing the first approach (an AllStatic MarkWord class and markWord
> typedef'd to uintptr_t) vs the second approach (markWord is a thin
> class wrapping around uintptr_t), I prefer the second.
> 
> * I think the markWord class provides better type safety. It still
> involves too many casts sprinkled over the code base, but I think it
> also provides a better basis for further cast reduction and
> prevention.
> 
> * I think having one markWord class for the data and behavior is
> better / more natural than having a markWord typedef for the data and
> a MarkWord AllStatic class for the behaviour.
> 
> * I like that the markWord class eliminates the markWord vs MarkWord
> homonyms, which I think will be annoying.
> 
> * The markWord class is a trivially copyable class, allowing it to be
> efficiently passed around by value, so no disadvantage there.
> 
> I haven't found anything that I think argues for the first over the
> second. Other folks might have different priorities or taste. I think
> either is better than the status quo.
> 
> I'm still reviewing webrev.valueMarkWord.02, but so far haven't found
> anything that makes me want to suggest backing off from that direction.
> 
> Note that the bug summary doesn't describe the second approach.

+1 :-)

Roman