7dc297cc14
Serious preprocessor voodoo here. There are two tricks here.
1. Iterating only phis. We know that phis come only at the beginning of a block,
so all over the tree, we open-code iteration like:
nir_foreach_instr(instr, block) {
if (instr->type != phi)
break;
/* do stuff */
}
We can express this equivalently as
nir_foreach_instr(instr, block)
if (instr->type != phi)
break;
else {
/* do stuff */
}
So, we can define a macro
#define nir_foreach_phi(instr, block)
if (instr->type != phi)
break;
else
and then
nir_foreach_phi(..)
statement;
and
nir_foreach_phi(..) {
...
}
will expand to the right thing.
2. Automatically getting the phi as a phi. We want the instruction to go to some
hidden variable, and then automatically insert nir_phi_instr *phi =
nir_instr_as_phi(instr_internal); We can't do that directly, since we need to
express the assignment implicitly in the control flow for the above trick to
work. But we can do it indirectly with a loop initializer.
for (nir_phi_instr *phi = nir_instr_as_phi(instr_internal); ...)
That loop needs to break after exactly one iteration. We know that phi
will always be non-null on its first iteration, since the original
instruction is non-null, so we can use phi==NULL as a sentinel and express a
one-iteration loop as for (phi = nonnull; phi != NULL; phi = NULL).
Putting these together gives the macros implemented used.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Konstantin Seurer <konstantin.seurer@gmail.com>
Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22967>
`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.