[8u20, 9] RFR(S): 8011646 : SEGV in compiled code with loop predication

[Albert]

John, Vladimir, thanks for your comments.

How shall we proceed with this bug? Is it OK to push this change?
Shall I file an RFE that suggests to further investigate possible issues
at the places that Vladimir mentioned?

Best,
Albert


On 05/29/2014 03:29 AM, Vladimir Kozlov wrote:
> On 5/28/14 4:42 PM, John Rose wrote:
>> On May 28, 2014, at 2:53 PM, Albert <albert.noll at oracle.com
>> <mailto:albert.noll at oracle.com>> wrote:
>>
>>>> It is only 'Node *' to 'Node* ' change. 'udiffs' show that cleanly.
>>>>
>>> Yes, I just put the '*' uniformly to the left side.
>>
>> (Which is fine BTW, since the majority usage is "T* x" not "T *x";
>> https://wiki.openjdk.java.net/display/HotSpot/StyleGuide points out we
>> do such adjustments.)
>>
>> Are there any other places where C2 uses normal IR to access the mark
>> word of an object, and if so, is a similar bug fix needed there?  If so,
>> the tricky logic for building the free-standing LoadXNode needs to be
>> factored into a subroutine.
>
> There are several places in macro.cpp in expand_lock_node() and 
> expand_unlock_node() which takes control. Note, LockNode is call node 
> and always has control. I thought about this part yesterday but said 
> nothing because we did not have any problems with that code before. 
> And we need more testing if we remove these control edges.
>
> Originally these loads were RAW memory operations and required to have 
> control to prevent skipping safepoints.
>
> Vladimir
>
>>
>> — John