RFR: 8323582: C2 SuperWord AlignVector: misaligned vector memory access with unaligned native memory [v4]

[Roland Westrelin]

On Wed, 26 Feb 2025 09:59:36 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

> I suppose we could try that. Is it ok to do that in a separate RFE, so we are keeping this here to a more manageable size?

Ok

> And would we not have similar issues with traversing from the loops to their `OpaqueMultiversioningNode`? What if some are not reachable in the meantime? Then we would just lose the `multiversion_if` early, and could not use it any more. So maybe we'd have to do that after the verification: [JDK-8350637](https://bugs.openjdk.org/browse/JDK-8350637): C2: verify that main_loop finds pre_loop and that multiversion loops find the multiversion_if
> 
> I wonder if we do not have similar issues with `PhaseIdealLoop::eliminate_useless_zero_trip_guard()` currently. Maybe it's rare enough we don't notice.

I don't think that's a problem. When that code runs the graph is in a stable shape. There's no dead condition that needs to go through igvn to be cleaned up. We've just run igvn and haven't made any change to the graph yet.

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PR Comment: https://git.openjdk.org/jdk/pull/22016#issuecomment-2684523673