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

[Tobias Hartmann]

Hi Erik,

still looks good to me.

Best regards,
Tobias

On 07.12.18 13:03, Erik Österlund wrote:
> Hi,
> 
> Per requested a trivial change that the verifier types be available as dummies doing nothing in
> product builds so that we don't need to wrap their uses in DEBUG_ONLY, as Per dislikes using
> DEBUG_ONLY.
> 
> Full:
> http://cr.openjdk.java.net/~eosterlund/8214936/webrev.01/
> 
> Incremental:
> http://cr.openjdk.java.net/~eosterlund/8214936/webrev.00_01/
> 
> Thanks,
> /Erik
> 
> On 2018-12-06 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