RFR (XS): 8023472: C2 optimization breaks with G1

[Vladimir Kozlov]

Thanks, Christian

On 8/21/13 4:04 PM, Christian Thalinger wrote:
>
> On Aug 21, 2013, at 3:18 PM, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>
>> http://cr.openjdk.java.net/~kvn/8023472/webrev/
>>
>> The load of previous value in G1 pre-barrier code (method GraphKit::g1_write_barrier_pre()) does not have control. It is from the time when G1 code was merged into Hotspot sources. I can only speculate that it was done to allow commoning with a preceding normal load if it exists and to avoid generation of 2 loads.
>> This problem, I think, only affects loads from an array because a load from a field should be guarded by NULL check of object.
>>
>> The fix is to put control on this load to always generate it after if (marking) check. I doubt it affect performance much. If there was load before the value should be in cache.
>
> The fix looks good.  Can you at least do a refworkload run to do some due diligence?

Will do it tonight.

>>
>> Added regression test.
>
> Could you change the name of the test?  Since we moved away from using bug ids the test name should more or less explain what it tests.  I suppose there will be more G1CrashTest's in the future :-)

It is external test. I don't want to change it much or its name.

Vladimir

>
> -- Chris
>
>>
>> Thanks,
>> Vladimir
>>