RFR (S): 8033380: Experimental VM flag to enforce access atomicity

[Dean Long]

It looks to me that C2 will only look at the atomic flag for longs, not 
doubles, so if you need
atomic access to doubles, I think more work needs to be done.

dl

On 2/11/2014 3:02 AM, Aleksey Shipilev wrote:
> Hi,
>
> I understand we are still closed for integration?
>
> Please review this small feature meanwhile:
>    https://bugs.openjdk.java.net/browse/JDK-8033380
>    http://cr.openjdk.java.net/~shade/8033380/webrev.02/
>
> TL;DR: JMM 9 may need to extend the access atomicity over longs and
> doubles. Luckily, our logic in emitting the relevant access-atomic
> instructions is decoupled from memory barriers logic, and so we can
> "just" unconditionally go through needs_atomic_access where appropriate.
>
> Testing:
>   - full cycle JPRT
>   - targeted microbenchmarks on x86/ARM/PPC
>
> Thanks,
> -Aleksey