[9] RFR(S): 8183103: Post loop vectorization produces incorrect results

[Tobias Hartmann]

Thanks Vladimir. I'll request approval for JDK 9.

Best regards,
Tobias

On 03.07.2017 17:34, Vladimir Kozlov wrote:
> Looks good.
> 
> Thanks,
> Vladimir
> 
> On 7/3/17 1:43 AM, Tobias Hartmann wrote:
>> Hi,
>>
>> please review the following patch:
>> https://bugs.openjdk.java.net/browse/JDK-8183103
>> http://cr.openjdk.java.net/~thartmann/8183103/webrev.00/
>>
>> Post loop vectorization (-XX:+PostLoopMultiversioning) produces incorrect results on machines that have AVX-512 (-XX:UseAVX=3) support. Please find my detailed analysis in the bug comments.
>>
>> Taking into account that we are very late in the JDK 9 release cycle, a full fix being very complex and requiring testing on AVX-512 supporting platforms and also due to other problems with AVX=3 in the past [1], we decided to make PostLoopMultiversioning and UseAVX=3 experimental in JDK 9. It will be disabled by default but still available if the user sets -XX:+UnlockExperimentalVMOptions on the command line.
>>
>> I filed JDK-8183390 to investigate a full fix in JDK 10 (or a JDK 9 update release).
>>
>> Thanks,
>> Tobias
>>
>> [1]
>> https://bugs.openjdk.java.net/browse/JDK-8178800
>> https://bugs.openjdk.java.net/browse/JDK-8178033
>> https://bugs.openjdk.java.net/browse/JDK-8159016
>>