RFR(S) : 8129092 : compiler/intrinsics/classcast/NullCheckDroppingsTest.java testVarClassCast() can fail

[Igor Ignatyev]

thanks Vladimir, pushed.

-- Igor

> On Dec 3, 2019, at 6:41 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
> 
> LGTM
> 
> Thanks,
> Vladimir K
> 
> On 12/3/19 5:49 PM, Igor Ignatyev wrote:
>> http://cr.openjdk.java.net/~iignatyev//8129092/webrev.01
>>> 69 lines changed: 38 ins; 2 del; 29 mod;
>> Hi all,
>> could you please review the small patch which makes the test more robust by using newly introduced JFR Deoptimization event?
>> the test used to use WhiteBox.isMethodCompiled to check if there was deoptimization, which, in case uncommon trap's action is none or maybe_recompile (which has been seen), is incorrect. the patch replaces WhiteBox method call w/ asserting JFR events, and check not only that deoptimization happens, but also check its reason is null_check. testing that, I noticed that 'testVarClassCast' doesn't hit uncommon trap due to null_check, but because of unstable_if in the ternary operator at L#180, so I modified the test to pass an instance of Class, which required some small changes.
>> JBS: https://bugs.openjdk.java.net/browse/JDK-8129092
>> webrev: http://cr.openjdk.java.net/~iignatyev//8129092/webrev.01
>> testing: compiler/intrinsics/classcast/NullCheckDroppingsTest.java
>> Thanks,
>> -- Igor