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363efc2823
This commit only documents the current behavior, even if that behavior
is not the behavior preferred by the relevant specs.
In SPIR-V, there are two flavors of the sign instruction, and each lives
in an extended instruction set. The GLSL.std.450 FSign instruction is
defined as:
Result is 1.0 if x > 0, 0.0 if x = 0, or -1.0 if x < 0.
This also matches the GLSL 4.60 definition.
However, the OpenCL.ExtendedInstructionSet.100 sign instruction is
defined as:
Returns 1.0 if x > 0, -0.0 if x = -0.0, +0.0 if x = +0.0, or -1.0 if
x < 0. Returns 0.0 if x is a NaN.
There are two differences. Each treats -0.0 differently, and each also
treats NaN differently. Specifically, GLSL.std.450 FSign does not
define any specific behavior for NaN.
There has been some discussion in Khronos about the NaN behavior of
GLSL.std.450 FSign. As part of that discussion, I did some research
into how we treat NaN for nir_op_fsign, and this commit just captures
some of those notes.
v2: Document the expected behavior of nir_op_fsign more thoroughly.
Suggested by Rhys. Note that the current implementation of constant
folding does not produce the expected result for NaN. Suggested by
Caio.
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com> [v1]
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6358>
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| include | ||
| scons | ||
| src | ||
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| .mailmap | ||
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| Android.mk | ||
| appveyor.yml | ||
| CleanSpec.mk | ||
| common.py | ||
| meson.build | ||
| meson_options.txt | ||
| README.rst | ||
| REVIEWERS | ||
| SConstruct | ||
| VERSION | ||
`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 `Freenode's #dri-devel <irc://chat.freenode.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.