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

[Vladimir Kozlov]

Nice verification code. Changes are good.

Thanks,
Vladimir

On 12/6/18 5:46 AM, 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