RFR: 8227505: SuperWordLoopUnrollAnalysis may lead to over loop unrolling

[Jie Fu]

Hi all,

With more experiments, the loop's trip_count seems a good feature to 
detect over loop unrolling.
And on some platforms, the branch-miss rate had been observed increasing 
dramatically with small loop trip count.
It seems that we shouldn't unroll if the trip count becomes too small.

I've updated the webrev here: 
http://cr.openjdk.java.net/~jiefu/8227505/webrev.01/

Please review it and give me some advice.

Thanks a lot.
Best regards,
Jie

On 2019/7/10 下午4:38, Jie Fu wrote:
> Hi all,
>
> JBS:    https://bugs.openjdk.java.net/browse/JDK-8227505
> Webrev: http://cr.openjdk.java.net/~jiefu/8227505/webrev.00/
>
> The patch fix the over loop unrolling problem caused by 
> SuperWordLoopUnrollAnalysis.
> For more info., please refer to the JBS.
>
> Could you please review it and give me some advice?
>
> Thanks a lot.
> Best regards,
> Jie
>
>