RFR(XS) 8027388: JVM crashes with SIGSEGV (0xb) at pc=0x00000001077cbbf6

[Igor Veresov]

Thanks, Vladimir!

igor

On Dec 21, 2013, at 1:06 AM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:

> Looks good.
> 
> Thanks,
> Vladimir
> 
> On 12/21/13 12:53 AM, Igor Veresov wrote:
>> Given the following graph, escape analysis currently fails to track the fact that we can load from null.
>> 
>>  Allocate A <-- ...---------- StoreP
>>  Allocate B <-- ... - AddP <--/
>>           \
>>            Phi <--- ... -- AddP <--- LoadP
>>  null <-- /
>> 
>> The AddPs may refer to the same field of B, however, B could be null so we cannot assume that the result of the LoadP is
>> the the argument of the StoreP.
>> We don't want to add edges to null_obj for performance reasons, so we handle this case by faking the effect of storing a
>> null to this field, which will force a potential non-escaping object (that is also stored to this field) to be marked as
>> not scalarizable. The end result is the same -- we cannot predict that value of the field. Notice that if B is
>> non-escaping it will be made non-scalarizable as well because the field has two bases.
>> 
>> Webrev: http://cr.openjdk.java.net/~iveresov/8027388/webrev.00/
>> Testing: jtreg, ctw
>> 
>> Huge thanks to Vladimir for discussions and helping me out with this problem!
>> 
>> igor