On Mon, 18 Nov 2024 15:00:51 GMT, Roman Kennke <rken...@openjdk.org> wrote:
>>> @rkennke It just will (silently) not vectorize, thus running slower but >>> still correct. >> >> Ok, I think we can live with that for now. >> >> As said elsewhere, we are currently working on 4-byte-headers, which would >> make that problem go away. >> >> The tests need fixing, though. > >> @rkennke >> >> > As said elsewhere, we are currently working on 4-byte-headers, which would >> > make that problem go away. >> >> Ah. So we would eventually have not a `12-byte` but `8-byte` offset from >> base to payload? Would that happen in all cases? And could that happen >> before `UseCompactObjectHeaders` leaves experimental status? Because it is >> going to be a little annoying to adjust all vectorization tests for the >> special case of `UseCompactObjectHeaders + AlignVector`. Though I can surely >> do it. > > I am not sure if and when this is going to happen. When I presented the idea > at JVMLS, I got some resistance. I am also not sure if we first leave > experimental status for UCOH, and then introduce 4-byte headers under a new > flag (or no flag?), or if we first do 4-byte headers and only leave > experimental status once that is done. The latter sounds more reasonable to > me. @rkennke Filed a bug to track this (we may close it as NotAnIssue, but this way people are aware / can find the analysis): [JDK-8344424](https://bugs.openjdk.org/browse/JDK-8344424): C2 SuperWord: mixed type loops do not vectorize with UseCompactObjectHeaders and AlignVector ------------- PR Comment: https://git.openjdk.org/jdk/pull/20677#issuecomment-2483579571
