[9] RFR(XS) 8059780: SPECjvm2008-MPEG performance regressions on x64 platforms

[Vladimir Kozlov]

I forgot to say that lcm.cpp changes were small part of 8052081 changes. 
The rest of changes will stay.

Thanks,
Vladimir

On 10/31/14 5:55 PM, Vladimir Kozlov wrote:
> http://cr.openjdk.java.net/~kvn/8059780/webrev/
> https://bugs.openjdk.java.net/browse/JDK-8059780
>
> We found performance regression (3-5%) on x64 after changes 8052081 [1]
> were pushed. It is caused by changes in lcm.cpp. Those changes were done
> because Atom is in-order cpu and some benchmarks on Atom showed benefit
> from these changes.
>
> But Atom is not our core platform and the regression is big.
>
> Backout changes made in lcm.cpp in jdk9 and 8u40 (8052081 was backported
> to 8u40).
>
> We have RFEs to improve block's instructions order which may help both
> platforms:
>
> https://bugs.openjdk.java.net/browse/JDK-6958833
> https://bugs.openjdk.java.net/browse/JDK-7101232
>
> Tested with SPECjvm2008-mpegaudio.
>
> Thanks,
> Vladimir
>
> [1] https://bugs.openjdk.java.net/browse/JDK-8052081