RFR: Support VerifyBeforeGC and VerifyAfterGC VM options

[Zhengyu Gu]

On 10/20/2018 05:13 AM, Aleksey Shipilev wrote:
> On 10/20/2018 02:24 AM, Zhengyu Gu wrote:
>>> But why final-evac? I think should be final-mark.
> 
> When cycle coalesces UR with next cycle mark, the final VMOp is final-evac. But you are right too:
> when cycle shortcuts, the final VMOp is final-mark. The block in op_final_mark does not make it all
> too obvious, I shall fix it up in a follow-up.
> 
>>> Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/verify_before_after_gc/webrev.01/index.html
>>>
>> Passed tier3_gc_shenandoah and  gc/TestVerifySubSet.java
>> (fastdebug and release)
> 
> I still think putting things near ShenandoahVerify is more straightforward. First, we are guaranteed
> to run in the same conditions as Verifier (i.e. at safepoint), and Verifier has a chance to run
> first when all verification is enabled. This also avoids accidentally placing ::verify in concurrent
> ops, as in your patch in op_updaterefs().
> 
> See:
>    http://cr.openjdk.java.net/~shade/shenandoah/verify-beforeafter/webrev.01/
> 
> This passes tier3_gc_shenandoah (fastdebug|release) and gc/TestVerifySubSet.java. I can push it for you.

Good, please push.

Thanks,

-Zhengyu

> 
> Thanks,
> -Aleksey
> 
> 
>