RFR(S): 8219448: split-if update_uses accesses stale idom data

[Vladimir Kozlov]

Hi Nils,

You are updating map so that next code in idom_no_update() works for you:
http://hg.openjdk.java.net/jdk/jdk/file/196ab0abc685/src/hotspot/share/opto/loopnode.hpp#l928
Which seems a hack to me. I think we should fix spinup() method to skip old region when looking for idom (I assume that 
is where you have the problem).

Thanks,
Vladimir

On 2/28/19 5:18 AM, Nils Eliasson wrote:
> Hi,
> 
> This patch fixes some of the idom updates in split-if. The updates are there, but at the end, which is to late. They 
> need to be correct when handling the uses of the region being split. When the stale idom is seen we end up asserting or 
> crashing.
> 
> https://bugs.openjdk.java.net/browse/JDK-8219448
> 
> http://cr.openjdk.java.net/~neliasso/8219448/webrev.01/
> 
> Please review,
> 
> Nils Eliasson
>