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The new code splits the work into a few passes instead of trying to do everything with a single pass. This helps to apply the new clarified rules for structured control flow in the SPIR-V specification, in particular the "exit construct" rules. First find an appropriate ordering for the blocks, based on the approach taken by Tint (WebGPU compiler). Then, with those blocks in order, identify the SPIR-V constructs start and end positions. Finally, walk the blocks again to emit NIR for each of them, "opening" and "closing" the necessary NIR constructs as we reach the start and end positions of the SPIR-V constructs. There are a couple of interesting choices when mapping the constructs to NIR: - NIR doesn't have something like a switch, so like the previous code, we lower the switch construct to a series of conditionals for each case. - And, unlike the previous code, when there's a need to perform a break from a construct that NIR doesn't directly support (e.g. inside a case construct, conditionally breaking early from the switch), we now use a combination of a NIR loop and an NIR if. Extra code is added to ensure that loop_break and loop_continues are propagated to the right loop. This should fix various issues with valid SPIR-V that previously resulted in "Invalid back or cross-edge in the CFG" errors. Thanks to Alan Baker and David Neto for their explanations of ordering the blocks, in the Tint code and in presentations to the SPIR-V WG. Thanks to Jack Clark for providing a lot of valuable tests used to validate this MR. Closes: #5973, #6369 Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17922>
`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.