RFR: 8214936: assert(_needs_refill == 0) failed: Forgot to handle a failed IC transition requiring IC stubs

[Erik Osterlund]

Hi Tobias,

Thanks for the review.

/Erik

> On 7 Dec 2018, at 11:20, Tobias Hartmann <tobias.hartmann at oracle.com> wrote:
> 
> Hi Erik,
> 
> this looks good to me.
> 
> Best regards,
> Tobias
> 
>> On 06.12.18 14:46, Erik Österlund wrote:
>> Hi,
>> 
>> In 8214338 I moved IC stub refilling out from IC stub transitions, making it the responsibility of
>> the caller. To make sure we don't accidentally forget calling IC stub refill and retrying at the
>> call site, I added some verification code that complains if the caller failed to do so.
>> 
>> I have tracked down that what can happen is that we try to make an IC megamorphic, but fail due to
>> requiring IC stubs to do so. In such a failure, we try setting the IC to clean, expecting that would
>> also fail, due to still not having refilled the buffers yet, but actually succeeding.
>> 
>> As a result of this, the assert fails because we did not refill the IC stubs and retry after the
>> transition to megamorphic failed, due to subsequently succeeding to clean the IC.
>> 
>> In this patch, I made sure we refill and retry instead as intended. I have also improved the
>> verification to use a thread-local verification RAII object that makes it easier to not just see
>> that something unexpected happened, but also where it happened.
>> 
>> Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8214936
>> 
>> Webrev:
>> http://cr.openjdk.java.net/~eosterlund/8214936/webrev.00/
>> 
>> Thanks,
>> /Erik