RFR(M): 8141551: C2 can not handle returns with incompatible interface arrays

[Vladimir Kozlov]

So what happens to my next question?:

 >> In type.cpp you need to check that ftp != NULL && ftp->isa_instptr() in case
 >> of number of dimensions are different.
 >> In cfgnode.cpp you need check jtp.
 >>
 >
 > Your right.

get_arrays_base_elements() code is good. You just need to check all its results.

Thanks,
Vladimir

On 11/12/15 10:11 AM, Volker Simonis wrote:
> Hi John, Andrew,
>
> thanks for the nice references and history behind the implementation
> (altough two of the bugs are not visible :(
>
> But the link to 8028165 was especially helpful. I think it describes a
> similar problem. I've just managed to reproduce it and I'm now testing
> if my fix also helps there. While doing the tests I've also discovered
> a problem with my fix which I've addressed in this new version of the
> webrev:
>
> http://cr.openjdk.java.net/~simonis/webrevs/2015/8141551.v2/
>
> The problem was that I casted the class-array to an interface instead
> of casting it to an array of interface in Parse::return_current()
>
> -        value = _gvn.transform(new CheckCastPPNode(0,value,tr));
> +          value = _gvn.transform(new CheckCastPPNode(0, value,
> phi->bottom_type()));
>
> And I've also put the whole new part which handles oop-arrays vs.
> arrays-of-interface into an else branch because it is mutually
> exclusive with the existing part which handles returning oops to an
> interface-return.
>
> Regards,
> Volker
>
>
> On Thu, Nov 12, 2015 at 11:27 AM, Andrew Dinn <adinn at redhat.com> wrote:
>> On 12/11/15 01:33, John Rose wrote:
>>> Ughh, that again.  This is 15-year-old technical debt in the C2 type system.
>>> It has almost earned VP-level recognition as an organizational cost center.
>>>
>>> Here is some of the trail of tears:
>>> https://bugs.openjdk.java.net/browse/JDK-6312651
>>> https://bugs.openjdk.java.net/browse/JDK-4641534
>>> https://bugs.openjdk.java.net/browse/JDK-6837094
>>> https://bugs.openjdk.java.net/browse/JDK-8028165?focusedCommentId=13614504&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13614504
>>
>> A shame that the first two links seem not to be traversable (from
>> outside of Oracle at least). The final link is well worth a visit, not
>> just to the referenced comment but also to the opener -- which is not
>> afraid to name names.
>>
>> I think I resolved the references correctly as follows:
>>
>> Davey/Priestley to
>>
>>
>> http://www.cambridge.org/gb/academic/subjects/mathematics/algebra/introduction-lattices-and-order-2nd-edition
>>
>> and Nielson/Nielson/Hankin to
>>
>>    http://www.springer.com/us/book/9783540654100
>>
>> Hecht to
>>
>>    http://dl.acm.org/citation.cfm?id=540175
>>
>> The first one looks like it is just basic lattice theory whereas the
>> second one looks to apply that theory to the compilation task and seems
>> to be highly relevant to what C2 does (1999 pub date :-). The third text
>> also seems to be about applications of lattices to compiler analysis but
>> dates back to the 70s. I assume it is one of those 'seminal works'. A
>> reference to the 2nd text in type.hpp would probably have helped me a
>> lot about 2 years ago.
>>
>> A Happy Christmas (or alter/non-denominational festive vacation) to all
>> our readers.
>>
>> regards,
>>
>>
>> Andrew Dinn
>> -----------
>>