[13] RFR(S): 8219807: C2 crash in IfNode::up_one_dom(Node*, bool)

[Vladimir Kozlov]

Please, add comment. Otherwise it is good.

Thanks,
Vladimir

On 4/29/19 6:24 AM, Tobias Hartmann wrote:
> Hi,
> 
> please review the following patch:
> https://bugs.openjdk.java.net/browse/JDK-8219807
> http://cr.openjdk.java.net/~thartmann/8219807/webrev.00/
> 
> We crash in IfNode::up_one_dom() while walking up the dominator tree because two regions (din3 and
> din4) are degraded to copies (for details see the bug comments). The control inputs of these regions
> were set to NULL in RegionNode::Ideal() but the nodes were not removed because we were still parsing.
> 
> Both regions are on the igvn worklist and will be replaced but the IfNode is processed first and
> therefore encounters the NULL control inputs. I think the code should guard against that. The bug is
> very old and reproduces since JDK 8 with the regression test.
> 
> I will run extended testing as soon as Mach5 is up again.
> 
> Thanks,
> Tobias
>