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The original asahi code assumed a subgroup size of 32 and a workgroup size of 32 * 32 = 1024. This makes doing ctz(ballot(b)) across an entire workgroup an almost trivial operation. On panfrost, we won't be so blessed unless we choose a workgroup size of 16 * 16 = 256. It's also not clear that we want to use workgroups at all and we may better off sticking to just subgroup parallelism and cutting out memory bandwidth by more than half. With the new code, the only requirement should be that the subgroup size is a power of two (this is always true) and that the workgroup size is an even multiple of the subgroup size. Even though the new code looks way more complicated, thanks to the magic of NIR constant folding, it should all fold down to the original code on asahi and something even smaller if one opts to go for a single subgroup. Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@intel.com> Reviewed-by: Mary Guillemard <mary@mary.zone> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38404>
`Mesa <https://mesa3d.org>`_ - The 3D Graphics Library ====================================================== Source ------ This repository lives at https://gitlab.freedesktop.org/mesa/mesa. Other repositories are likely forks, and code found there is not supported. Build & install --------------- You can find more information in our documentation (`docs/install.rst <https://docs.mesa3d.org/install.html>`_), but the recommended way is to use Meson (`docs/meson.rst <https://docs.mesa3d.org/meson.html>`_): .. code-block:: sh $ meson setup build $ ninja -C build/ $ sudo ninja -C build/ install Support ------- Many Mesa devs hang on IRC; if you're not sure which channel is appropriate, you should ask your question on `OFTC's #dri-devel <irc://irc.oftc.net/dri-devel>`_, someone will redirect you if necessary. Remember that not everyone is in the same timezone as you, so it might take a while before someone qualified sees your question. To figure out who you're talking to, or which nick to ping for your question, check out `Who's Who on IRC <https://dri.freedesktop.org/wiki/WhosWho/>`_. The next best option is to ask your question in an email to the mailing lists: `mesa-dev\@lists.freedesktop.org <https://lists.freedesktop.org/mailman/listinfo/mesa-dev>`_ Bug reports ----------- If you think something isn't working properly, please file a bug report (`docs/bugs.rst <https://docs.mesa3d.org/bugs.html>`_). Contributing ------------ Contributions are welcome, and step-by-step instructions can be found in our documentation (`docs/submittingpatches.rst <https://docs.mesa3d.org/submittingpatches.html>`_). Note that Mesa uses gitlab for patches submission, review and discussions.