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A break/continue in a loop is typically emitted like this:
if (cond) {
break/continue;
} else {
}
If cond is uniform, we'll emit code for a uniform if statement and
that will emit a branch right before the if to jump directly to the
else (or the block after the else in this case, since the else is
empty) in case cond evaluates to false. This means we end up emitting
two consecutive branch instructions, one before the if and one for the
THEN block right after:
branch(!cond) -> jump to else (or after else) if cond is false
nop
nop
nop
branch -> unconditional jump to break/continue
nop
nop
nop
Instead, if we are in this scenario, we can do better by emitting the
conditional jump directly and avoiding the "jump to else" case:
branch(cond) -> jump to break/continue if cond is true
nop
nop
nop
We need to be careful when emitting the break/continue for the case
where all lanes are disabled to avoid infinite loops: if we have a
break we always want to take the jump, but we don't want to take it
if it is a continue.
total instructions in shared programs: 13563672 -> 13557348 (-0.05%)
instructions in affected programs: 348034 -> 341710 (-1.82%)
helped: 1158
HURT: 10
Instructions are helped.
total uniforms in shared programs: 3779137 -> 3777535 (-0.04%)
uniforms in affected programs: 90583 -> 88981 (-1.77%)
helped: 1169
HURT: 0
Uniforms are helped.
total max-temps in shared programs: 2317670 -> 2317575 (<.01%)
max-temps in affected programs: 1943 -> 1848 (-4.89%)
helped: 85
HURT: 4
Max-temps are helped.
total sfu-stalls in shared programs: 32247 -> 32247 (0.00%)
sfu-stalls in affected programs: 69 -> 69 (0.00%)
helped: 7
HURT: 9
Inconclusive result (value mean confidence interval includes 0).
total inst-and-stalls in shared programs: 13595919 -> 13589595 (-0.05%)
inst-and-stalls in affected programs: 350674 -> 344350 (-1.80%)
helped: 1154
HURT: 11
Inst-and-stalls are helped.
total nops in shared programs: 358202 -> 354325 (-1.08%)
nops in affected programs: 17367 -> 13490 (-22.32%)
helped: 1168
HURT: 1
Nops are helped.
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9948>
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| .gitlab-ci | ||
| bin | ||
| build-support | ||
| docs | ||
| doxygen | ||
| include | ||
| src | ||
| subprojects | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .mailmap | ||
| .travis.yml | ||
| Android.common.mk | ||
| Android.mk | ||
| CleanSpec.mk | ||
| meson.build | ||
| meson_options.txt | ||
| README.rst | ||
| REVIEWERS | ||
| 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.