21cd9b9557
Up to now, ir3 only supported one predicate register (p0.x). However, since a6xx, four predicate registers are available. This patch adds a register allocator for predicate registers that allows all of them to be used. The RA also works for older generations with only one register. The use of p0.x was hard-coded in many places in ir3. This has been replaced by a new flag, IR3_REG_PREDICATE, to indicate that an SSA value should be allocated to a predicate register. The RA uses the standard liveness analysis available in ir3. Using this, registers are allocated in a single pass over all blocks. For each block we keep track of currently live defs in the registers. Predicate destinations allocate a new register and sources take the register from their def. The live defs of a block are initialized with the intersection of the live-out defs of their predecessors: if all predecessors have the same live-out def in the same register, it is used as live-in. However, we only do this for defs that are actually live-in according to the liveness analysis. This doesn't work for loops: since predecessors from back edges are processed after their successors, we don't know their live-out state yet. We solve this by ignoring such predecessors while calculating the live-in state. When this predecessor is later processed, we fix-up its live-out state to match what its successor expects by reloading defs if necessary. Spilling is implemented by reloading, or rematerializing, the instruction that produced the def. Whenever we need a new register while none are available, we simply free one. If the freed def is later needed again, we clone the original instruction in front on the new use. We keep track of the original def the reload is cloned from so that subsequent uses can reuse the reload. Signed-off-by: Job Noorman <jnoorman@igalia.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27411>
`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.