Request for reviews (XS): 6866651: Regression: simple int sum crashes jvm (build 1.6.0_14-b08 and 1.7.0-ea-b59)

[changpeng fang - Sun Microsystems - Santa Clara United States]

On 08/14/09 16:19, Tom Rodriguez wrote:
> My understanding is that this would only occur for nodes that are dead 
> because of CCP.  A dead node can only have dead users so doesn't 
> calling add_users_to worklist on a dead node seem like a bad idea? 
Do you mean we should not see a LIVE singleton (but !n->is_Con()) there?
If it is the case, then we should not add the code.

Thanks,

Changpeng


>
> tom
>
> On Aug 14, 2009, at 3:46 PM, Vladimir Kozlov wrote:
>
>> I asked for it to short cut transformations when node's type is known
>> const or top. Yes, it is not needed for the bug fix but it could
>> reduce time spent in igvn.optimize().
>>
>> Vladimir
>>
>> Tom Rodriguez wrote:
>>> Why are you including the first part in this fix?  I don't see the 
>>> motivation for that change.
>>> tom
>>> On Aug 14, 2009, at 2:50 PM, changpeng fang - Sun Microsystems - 
>>> Santa Clara United States wrote:
>>>> http://cr.openjdk.java.net/~cfang/6866651/webrev.00/
>>>>
>>>> Fixed 6866651: Regression: simple int sum crashes jvm (build 
>>>> 1.6.0_14-b08 and 1.7.0-ea-b59)
>>>>
>>>> Problem:
>>>> set_req_X will do dead code elimination if the original input has 
>>>> no other use. However, it is possible to
>>>> have the current node (this) removed if a dead loop exists.  So,  
>>>> dead code elimination in set_req_X is not
>>>> safe, and may  cause undesired consequences (like the segfault in 
>>>> 6866651)
>>>>
>>>> Solution:
>>>> Instead of doing dead code elimination immediately in set_req_X, we 
>>>> put the dead node (original input) into
>>>> the worklist, and the dead node will eventually be eliminated when 
>>>> it is its turn to be processed.
>>>>
>>>> In addition,  before ideal transformations, we replace a node with 
>>>> a constant if we know it computes a constant
>>>> to skip unneeded optimizations on this node. Tests: JPRT, 
>>>> CompileTheWorld, Test case in bug report (Test.java in webrev)
>>>>
>>>> Thanks,
>>>>
>>>> Changpeng
>