[ping] RFR(S): 8156992: [ppc] Implement template interpreter stack overflow checks as on x86/sparc.

[David Holmes]

On 30/05/2016 5:28 PM, Lindenmaier, Goetz wrote:
> Hi David,
>
>> -----Original Message-----
>> From: David Holmes [mailto:david.holmes at oracle.com]
>> Sent: Samstag, 28. Mai 2016 00:10
>> To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; hotspot-runtime-
>> dev at openjdk.java.net; Frederic Parain <frederic.parain at oracle.com>
>> Subject: Re: [ping] RFR(S): 8156992: [ppc] Implement template interpreter
>> stack overflow checks as on x86/sparc.
>>
>> On 28/05/2016 1:35 AM, Lindenmaier, Goetz wrote:
>>> Hi David,
>>>
>>> well, yes, Dean had similar questions.
>>> X86/sparc load stack_base and stack_size, compute stack_end and then
>> add the
>>> Max(shadow, quard). All in assembly in the template interpreter prolog.
>> On ppc,
>>> we load it from the precomputed field stackoverflow_limit.  The value in
>> that field
>>> differed from what x86/sparc computed, which is the error I want to fix
>> here.
>>
>> That all sounds a bit broken. :(
> Broken as far as my change is concerned, or broken wrt. to the existing
> implementation?

The existing implementation.

>>> I adapted the drawing to the change of that field.
>> I still don't see how the drawing matches the code given the MAX usage.
> If guard_zones > shadow zone, stack_overflow_limit points to stack_reserved_zone_base().
> If guard_zones < shadow zone, stack_overflow_limit points to somewhere in the shadow zone.

Ah! I was using frames view on the webrev and the "somewhere in here" 
comment was off the page.

Thanks,
David

> Best regards,
>   Goetz.
>
>> I can't convince myself that any of this stuff is correct. Given
>> Frederic was working in this area most recently I wonder if he can
>> comment (but I know he may not be around at the moment).
>>
>> Thanks,
>> David
>>
>>> Best regards,
>>>   Goetz
>>>
>>>
>>>
>>>> -----Original Message-----
>>>> From: David Holmes [mailto:david.holmes at oracle.com]
>>>> Sent: Donnerstag, 26. Mai 2016 00:36
>>>> To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>; hotspot-runtime-
>>>> dev at openjdk.java.net
>>>> Subject: Re: [ping] RFR(S): 8156992: [ppc] Implement template interpreter
>>>> stack overflow checks as on x86/sparc.
>>>>
>>>> Hi Goetz,
>>>>
>>>> I know you were having discussions with Dean in relation to this but I
>>>> really don't understand the change to the diagram in thread.hpp nor the
>>>> change to the definition of stackoverflow_limit. To me the limit has to
>>>> be the sum of the guard zone and shadow zone. With your MAX change
>> the
>>>> diagram doesn't even make sense AFAICS.
>>>>
>>>> ??
>>>>
>>>> David
>>>>
>>>> On 25/05/2016 6:07 PM, Lindenmaier, Goetz wrote:
>>>>> Hi,
>>>>>
>>>>> could someone else have a look at this change?  I need a reviewer,
>> please.
>>>>> I also please need a sponsor.
>>>>>
>>>>> Best regards,
>>>>>   Goetz.
>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Lindenmaier, Goetz
>>>>>> Sent: Mittwoch, 18. Mai 2016 12:02
>>>>>> To: hotspot-runtime-dev at openjdk.java.net
>>>>>> Subject: RFR(S): 8156992: [ppc] Implement template interpreter stack
>>>>>> overflow checks as on x86/sparc.
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> When porting the template interpreter, we implemented a different
>>>>>> approach to
>>>>>> Stack overflow handling.  See also the detailed description in the Jira
>> bug.
>>>>>>
>>>>>> This change implements the stack overflow check as on x86/sparc.
>>>>>> It requires simple shared changes, but only to code only used on ppc.
>>>>>> The changes should not affect the other platforms.
>>>>>>
>>>>>> Please review this change. I please need a sponsor.
>>>>>> http://cr.openjdk.java.net/~goetz/wr16/8156922-
>>>> ppcStackFix/webrev.01/
>>>>>>
>>>>>> Best regards,
>>>>>>   Goetz.
>>>>>