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

[Igor Veresov]

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/attachments/20131221/ab48efca/attachment.html