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read-only mirror of https://gitlab.freedesktop.org/mesa/mesa
bf2eb3e0ee
This function has code like:
if (0x7FD <= zExp) {
if ((0x7FD < zExp) ||
((zExp == 0x7FD) &&
(0x001FFFFFu == zFrac0 && 0xFFFFFFFFu == zFrac1) &&
increment)) {
...
return ...;
}
if (zExp < 0) {
I saw that, and I thought, "Uh... what? Dead code?" I thought it was a
bit fishy, so I grabbed the Berkeley SoftFloat Library 3e code, and
there is similar code in softfloat_roundPackToF64
(source/s_roundPackToF64.c), but it has an extra (uint16_t) cast in the
first comparison. This is basicially a shortcut for
if (zExp < 0 || zExp >= 0x7FD) {
So, having the nesting kind of makes sense. On a CPU, nesting the flow
control can be an optimization. On a GPU, it's just fail. Split the
block so that we don't need the uint16_t cast magic.
Results on the 308 shaders extracted from the fp64 portion of the OpenGL
CTS:
Tiger Lake and Ice Lake had similar results. (Tiger Lake shown)
total instructions in shared programs: 683638 -> 658127 (-3.73%)
instructions in affected programs: 666839 -> 641328 (-3.83%)
helped: 92
HURT: 0
helped stats (abs) min: 26 max: 2456 x̄: 277.29 x̃: 144
helped stats (rel) min: 3.21% max: 4.22% x̄: 3.79% x̃: 3.90%
95% mean confidence interval for instructions value: -345.84 -208.75
95% mean confidence interval for instructions %-change: -3.86% -3.73%
Instructions are helped.
total cycles in shared programs: 5458858 -> 5344600 (-2.09%)
cycles in affected programs: 5360114 -> 5245856 (-2.13%)
helped: 92
HURT: 0
helped stats (abs) min: 126 max: 10300 x̄: 1241.93 x̃: 655
helped stats (rel) min: 1.71% max: 2.37% x̄: 2.12% x̃: 2.17%
95% mean confidence interval for cycles value: -1539.93 -943.94
95% mean confidence interval for cycles %-change: -2.16% -2.08%
Cycles are helped.
Fixes:
|
||
|---|---|---|
| .appveyor | ||
| .gitlab-ci | ||
| bin | ||
| build-support | ||
| docs | ||
| doxygen | ||
| include | ||
| scons | ||
| src | ||
| subprojects | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .mailmap | ||
| .travis.yml | ||
| Android.common.mk | ||
| 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.html <https://mesa3d.org/install.html>`_), but the recommended way is to use Meson (`docs/meson.html <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.html <https://mesa3d.org/bugs.html>`_). Contributing ------------ Contributions are welcome, and step-by-step instructions can be found in our documentation (`docs/submittingpatches.html <https://mesa3d.org/submittingpatches.html>`_). Note that Mesa uses gitlab for patches submission, review and discussions.