Request for reviews (S): 6877254: Server vm crashes with "no branches off of store slice" when run with CMS and UseSuperWord (default)

[Tom Rodriguez]

On Sep 8, 2009, at 6:30 PM, Vladimir Kozlov wrote:

> I have concerns about StoreCMNode::Ideal(aidx) implementation.
>
> The result of memory_at() is never the same mergemem node.
> I either mergemem->base_memory() or mergemem->in(aidx)
> so your check will be always true.

You're right but i think that just means we can drop that test.

>
> Also mergemem nodes could be chained when the result of memory_at()
> is also mergemem.

I figured Ideal would be called again if there was more work to do and  
it should be a rare case anyway.  The mem of a StoreCM should only be  
something besides a Store if the StoreCM is dead or if something weird  
has gone on with cloning.  These changes are pretty conservative since  
we don't have a clear set of rules for when a StoreCM is dead though I  
think we could if we wanted to.

tom

>
> You can look on methods in memnode.cpp which search through
> mergemem for stores: step_through_mergemem(), find_previous_store().
>
> Thanks,
> Vladimir
>
> Changpeng Fang wrote:
>> Need additional reviews (Tom (never) proposed the implementation,  
>> so I assume he is oked )!
>> Comments are in the webrev.
>> On 09/01/09 11:07, Changpeng Fang wrote:
>>> http://cr.openjdk.java.net/~cfang/6877254/webrev.00/
>>>
>>> Thanks,
>>>
>>> Changpeng
>> Thanks,
>> Changpeng