RFR: 8333393: PhaseCFG::insert_anti_dependences can fail to raise LCAs and to add necessary anti-dependence edges [v13]

[Daniel Lundén]

On Tue, 11 Feb 2025 08:17:23 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> Up to you whether to integrate this point fix and continue your investigation separately or wait until you have explored along this line before integration.

I have considered and implemented a couple of alternative fixes today, but they are not really more elegant than the fix in this PR. If I want to fix the memory graph at loop cloning, what I'm really doing is duplicating the Phi idealization that we already have. So, then I think it would make most sense to work out the combinatorial issues with option 2 that I posted above (for making the Phi idealization less restrictive). I'm leaning towards integrating this for now, but will explore a bit further first.

> Right, the details are not obvious to me either, it would probably require some exploration before we can formalize what it is exactly that we want to verify, since there is no specification (as far as I know) of what is expected for the memory subgraph in terms of liveness and interference.

Let's discuss this offline!

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

PR Review Comment: https://git.openjdk.org/jdk/pull/22852#discussion_r1951406631