RFR (M): 8000805: JMM issue: short loads are non-atomic

Vladimir Ivanov vladimir.x.ivanov at oracle.com
Tue Oct 23 06:45:20 PDT 2012


Thanks for the review!

I filed 8001336 [1] to track the enhancement you are suggesting.
If anybody is interested to work on it, feel free to take it.

Best regards,
Vladimir Ivanov

[1] https://jbs.oracle.com/bugs/browse/JDK-8001336

On 10/23/12 01:01, John Rose wrote:
> That's much better, even though it's a little bit weaker.
> In the long term, we should think about adding bitwise liveness analysis into the system, instead of using pattern matching.  If the live bits out of a LoadB are contained in 0xFF, then we can transform to LoadUB.
> Doing this would require a type system that can represent per-bit liveness, and an analysis phase that pushes such types backwards through the graph.  That is a straightforward extension of our existing type system, augmenting the existing arithmetic range endpoints with corresponding bit masks.  Might be a good pet project for someone.
> — John
> On Oct 22, 2012, at 8:09 AM, Vladimir Ivanov wrote:
>> Updated version: http://cr.openjdk.java.net/~vlivanov/8000805/webrev.01/
>> Removed changes in AD files and perform transforms during IGVN phase
>> when Load has a single user.

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