a2a2fbc510
For example, the proof for this pattern
(('bcsel', ('flt', 'a@32', 0), 'b@32', 'c@32'), ('fcsel_ge', a, c, b)),
would be
bcsel(a < 0, b, c)
bcsel(!(a < 0), c, b)
bcsel(a >= 0, c, b)
fcsel_ge(a, c, b)
However, !(a < 0) => (a >= 0) is well known to produce different
results if `a` is NaN.
Instead of that replacement, use this replacement:
bcsel(a < 0, b, c)
bcsel(-0 < -a, b, c)
bcsel(0 < -a, b, c)
fcsel_gt(-a, b, c)
This is NaN-safe and exact.
Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Fixes: 0f5b3c37c5 ("nir: Add opcodes for fused comp + csel and optimizations")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17048>
`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.