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

[Emanuel Peter]

On Tue, 10 Jun 2025 18:51:49 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> 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.

@robcasloz That would have also been my question. @rwestrel why did we omit those `Phi`s at the outer strip-mined loop in the first place? Is that not asking for all sorts of trouble and special handling?

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

PR Comment: https://git.openjdk.org/jdk/pull/25717#issuecomment-2966381509