RFR: 8356708: C2: loop strip mining expansion doesn't take sunk stores into account

[Roland Westrelin]

On Wed, 11 Jun 2025 11:30:32 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>> Thanks for working on this, Roland. I just submitted some testing, will come back with the results in a day or two.
>> 
>> Generally, I agree with your proposed approach of handling the case at expansion time as a low-risk fix for JDK 25. But as future work, would it be feasible to maintain regular SSA form for outer strip-mined loops (adding memory and data phi nodes at both loop levels) rather than omitting phi nodes for the outer loops and "repairing" SSA on macro expansion, or is there any fundamental obstacle in doing the former? It would have prevented issues like this, and feels like a more principled and robust approach in general.
>
>> Thanks for working on this, Roland. I just submitted some testing, will come back with the results in a day or two.
> 
> Test results (tier1-5 in Oracle's internal test system) look good.

Thanks for the reviews @robcasloz @eme64 
Change is read for another pass.

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PR Comment: https://git.openjdk.org/jdk/pull/25717#issuecomment-2967328929