Kenneth Graunke
c12300844d
In the past, we didn't have a good solution for combining scalar loads with a variable index plus a constant offset. To handle that, we took our load offset and rounded it down to the nearest vec4, loaded an entire vec4, and trusted in the backend CSE pass to detect loads from the same address and remove redundant ones. These days, nir_opt_load_store_vectorize() does a good job of taking those scalar loads and combining them into vector loads for us, so we no longer need to do this trick. In fact, it can be better not to: our offset need only be 4 byte (scalar) aligned, but we were making it 16 byte (vec4) aligned. So if you wanted to load an unaligned vec2, we might actually load two vec4's (___X | Y___) instead of doing a single load at the starting offset. This should also reduce the work the backend CSE pass has to do, since we just emit a single VARYING_PULL_CONSTANT_LOAD instead of 4. shader-db results on Alchemist: - No changes in SEND count or spills/fills - Instructions: helped 95, hurt 100, +/- 1-3 instructions - Cycles: helped 3411 hurt 1868, -0.01% (-0.28% in affected) - SIMD32: gained 5, lost 3 fossil-db results on Alchemist: - Instrs: 161381427 -> 161384130 (+0.00%); split: -0.00%, +0.00% - Cycles: 14258305873 -> 14145884365 (-0.79%); split: -0.95%, +0.16% - SIMD32: Gained 42, lost 26 - Totals from 56285 (8.63% of 652236) affected shaders: - Instrs: 13318308 -> 13321011 (+0.02%); split: -0.01%, +0.03% - Cycles: 7464985282 -> 7352563774 (-1.51%); split: -1.82%, +0.31% From this we can see that we aren't doing more loads than before and the change is pretty inconsequential, but it requires less optimizing to produce similar results. Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27568>
`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://mesa3d.org/install.html>`_), but the recommended way is to use Meson (`docs/meson.rst <https://mesa3d.org/meson.html>`_): .. code-block:: sh $ mkdir build $ cd build $ meson .. $ sudo ninja 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://mesa3d.org/bugs.html>`_). Contributing ------------ Contributions are welcome, and step-by-step instructions can be found in our documentation (`docs/submittingpatches.rst <https://mesa3d.org/submittingpatches.html>`_). Note that Mesa uses gitlab for patches submission, review and discussions.