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The most expensive part of register allocation is the ra_simplify step
which is a fixed-point algorithm with a worst-case complexity of O(n^2)
which adds the registers to a stack which we then use later to do the
actual allocation. This commit uses bit sets and changes the core loop
of ra_simplify to first walk 32-node chunks and then walk each chunk.
This lets us skip whole 32-node chunks in one go based on bit operations
and compute the minimum q value potentially 32x as fast. Of course, the
algorithm still has the same fundamental O(n^2) run-time but the
constant is now much lower.
In the nasty Aztec Ruins compute shader, this shaves a full four seconds
off the 30s compile time for a release build of mesa. In a debug build
(needed for accurate stack traces), perf says that ra_select takes 20%
of runtime before this patch and only 5-6% of runtime after this patch.
It also makes shader-db runs faster.
Shader-db results on Kaby Lake:
total instructions in shared programs: 15311100 -> 15311100 (0.00%)
instructions in affected programs: 0 -> 0
helped: 0
HURT: 0
total cycles in shared programs: 355468050 -> 355468050 (0.00%)
cycles in affected programs: 0 -> 0
helped: 0
HURT: 0
Total CPU time (seconds): 2602.37 -> 2524.31 (-3.00%)
Reviewed-by: Eric Anholt <eric@anholt.net>
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| common.py | ||
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| README.rst | ||
| REVIEWERS | ||
| SConstruct | ||
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`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 email mailing-lists for patches submission, review and discussions.