[14] RFR(S): 8233656: assert(d->is_CFG() && n->is_CFG()) failed: must have CFG nodes

[Tobias Hartmann]

Thanks Vladimir.

Best regards,
Tobias

On 08.11.19 17:50, Vladimir Kozlov wrote:
> Good.
> 
> thanks,
> Vladimir
> 
> On 11/8/19 1:46 AM, Tobias Hartmann wrote:
>> Hi,
>>
>> please review the following patch:
>> https://bugs.openjdk.java.net/browse/JDK-8233656
>> http://cr.openjdk.java.net/~thartmann/8233656/webrev.00/
>>
>> During IGVN, we process a CastII node that carries a non-zero dependency from
>> GraphKit::cast_not_null [1]. ConstraintCastNode::dominating_cast then finds another CastII and
>> checks if it's dominating. We assert in PhaseGVN::is_dominator_helper because the other CastII has a
>> ProjNode as control input that has !is_CFG() because it's input is TOP [2]. The input has been
>> replaced in the same round of IGVN and the projection is already on the IGVN worklist but hasn't
>> been processed yet (it will go away).
>>
>> I propose to simply check the control inputs for is_CFG().
>>
>> I can reproduce the issue with a complex Javafuzzer generated test (attached to the bug) but minimal
>> changes/simplifications to the test cause the issue to not reproduce anymore because it depends on
>> the order in which nodes are processed by IGVN. So I don't think it makes sense to include that
>> fragile test.
>>
>> This has been triggered by my fix for 8229496 [3] which added additional Cast nodes but I believe it
>> can also happen without these changes.
>>
>> Thanks,
>> Tobias
>>
>> [1] https://hg.openjdk.java.net/jdk/jdk/rev/86b95fc6ca32#l12.40
>> [2] https://hg.openjdk.java.net/jdk/jdk/file/47c20fc6a517/src/hotspot/share/opto/multnode.cpp#l83
>> [3] https://bugs.openjdk.java.net/browse/JDK-8229496
>>