RFR: 8324751: C2 SuperWord: Aliasing Analysis runtime check [v10]

[Emanuel Peter]

On Tue, 19 Aug 2025 16:02:48 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>>> Do you think it is worth it to benchmark now, or should be just rely on @robcasloz 's occasional benchmarking and address the issues if they come up?
>> 
>> I am fine with using Roberto's benchmarking later. Just keep eye on it.
>
>> @vnkozlov I ran some more benchmarks:
> 
> Thank you for running benchmarks. Which one you check first for aliasing code: multiversioning or predicates?
> 
> From this experiments I think the best sequence would be (when both predicates and multiversioning are enabled):
>  - use predicates for aliasing (fast compilation, small code)
>  - if it is deoptimized recompile with multiversioning
>  
>  Is this how it works now?

@vnkozlov I now automatically disable the flag if the others are both off.

I've also investigated the performance issue with the aliasing case that uses multiversioning. And I so far could not figure out the 10% performance regression, see detailed analysis attempt https://github.com/openjdk/jdk/pull/24278#issuecomment-3201092650

-------------

PR Comment: https://git.openjdk.org/jdk/pull/24278#issuecomment-3206104402