RFR(S): 8173196: [REDO] C2 does not optimize redundant memory operations with G1

[Tobias Hartmann]

Hi Roland,

this looks good to me. I'll run some extended testing and let you know once it's done.

Thanks,
Tobias

On 22.05.19 11:25, Roland Westrelin wrote:
> 
> http://cr.openjdk.java.net/~roland/8173196/webrev.00/
> 
> Previous attempt at this was discussed here:
> http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2016-January/021014.html
> 
> And the follow up bugs with some comments on a possible fix:
> 
> https://bugs.openjdk.java.net/browse/JDK-8172850
> 
> The new fix is very similar to the previous one. The 2 differences are:
> 
> - aarch64 code shouldn't need any change because of 8209420 ("Track
>   membars for volatile accesses so they can be properly optimized")
> 
> - The membar only affects the raw memory slice which is now properly
>   handled by MachNodes thanks to 8209691 ("Allow MemBar on single memory
>   slice")
> 
> Roland.
>