RFR: JDK-8211241: Missing obj equals in TemplateTable::fast_aldc

[coleen.phillimore at oracle.com]

On 10/1/18 7:18 AM, Roman Kennke wrote:
> Hi Coleen,
>
> thanks for looking at this.
>
> I've combed the interpreter code for similar occurances, but haven't
> found any.
>
> Extra verification in cmpptr could be done but it's probably not worth.?
> It'll not be a small effort...

I agree.
Thanks,
Coleen
>
> Roman
>
>
>> This looks good. Did you search for other cmpptr() to see if they should
>> be cmpoop?  Wonder if you can do a negative verify_oop in cmpptr.
>> Probably not.
>>
>> Lots of people look at the interpreter code, but they're on
>> hotspot-runtime.
>>
>> Thanks,
>> Coleen
>>
>>
>> On 9/27/18 4:33 PM, Roman Kennke wrote:
>>> Included hotspot-runtime-dev because it's an interpreter bug, excluded
>>> hotspot-compiler dev, and also here's all the links:
>>>
>>> Bug:
>>> https://bugs.openjdk.java.net/browse/JDK-8211241
>>> Webrev:
>>> http://cr.openjdk.java.net/~rkennke/JDK-8211241/webrev.00/
>>>
>>> It's never been quite clear to me where to put interpreter bugs.
>>> hotspot/runtime in Jira and hotspot-runtime-dev on mailing lists? Is
>>> that right?
>>>
>>> Thanks, Roman
>>>
>>>
>>>
>>>> TemplateTable::fast_aldc compares the just-loaded reference with
>>>> Universe::the_null_sentinel. If it really is that null-sentinel, we may
>>>> get a false negative (with GCs like Shenandoah that allow both
>>>> from-space and to-space copies of an object to be around), and thus skip
>>>> NULL-ing the ref. In other words, it would allow to get
>>>> the-null-sentinel out into the wild as oop which can cause subtle and
>>>> not-so-subtle bugs.
>>>>
>>>> Fix is easy, call cmpoop() which re-routes through GC-interface for GCs
>>>> that need it:
>>>>
>>>> http://cr.openjdk.java.net/~rkennke/JDK-8211241/webrev.00/
>>>>
>>>> Testing: hotspot/jtreg:tier1
>>>>
>>>> Ok?
>>>>
>>>> Roman
>>>>