Alyssa Rosenzweig
41b7891673
According to Dougall's pseudocode, else_icmp operates as:
if r0l == 0:
r0l = n
elif r0l == 1:
if cc.compare(A[thread], B[thread]):
r0l = 0
else:
r0l = 1
exec_mask[thread] = (r0l == 0)
Notice that the comparison only happens when r0l == 1, that is, for threads that
are about to enter the else block. Threads that just executed the if body are
still active (r0l = 0) and skip the comparison. As such, the sources of
else_icmp are only read in the else block, and hence the whole instruction
should be placed in the else block for correctness with respect to live range
splitting.
shader-db is a wash, but shows some improvements due to correctly modelling the
liveness of the condition variable.
total instructions in shared programs: 1778376 -> 1778390 (<.01%)
instructions in affected programs: 14753 -> 14767 (0.09%)
helped: 35
HURT: 39
Inconclusive result (value mean confidence interval includes 0).
total bytes in shared programs: 12185018 -> 12185102 (<.01%)
bytes in affected programs: 101522 -> 101606 (0.08%)
helped: 35
HURT: 39
Inconclusive result (value mean confidence interval includes 0).
total halfregs in shared programs: 531174 -> 531032 (-0.03%)
halfregs in affected programs: 2320 -> 2178 (-6.12%)
helped: 40
HURT: 1
Halfregs are helped.
total threads in shared programs: 18909184 -> 18909440 (<.01%)
threads in affected programs: 1792 -> 2048 (14.29%)
helped: 2
HURT: 0
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24635>
`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.