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We lower NIR's load_constant to load_global_constant, which uses A64 bindless messages. As such, we do the following math to produce the address for each load: base_lo@32 <- BRW_SHADER_RELOC_CONST_DATA_ADDR_LOW base_hi@32 <- BRW_SHADER_RELOC_CONST_DATA_ADDR_HIGH base@64 <- pack_64_2x32_split(base_lo, base_hi) addr@64 <- iadd(base@64, u2u64(offset@32)) On platforms that emulate 64-bit math, we have to emit additional code for the 64-bit iadd to handle the possibility of a carry happening and affecting the top bits. However, NIR constant data is always uploaded adjacent to the shader assembly, in the same buffer. These buffers are required to live in a 4GB region of memory starting at Instruction State Base Address. We always place the base address at a 4GB address. So the constant data always lives in a buffer entirely contained within a 4GB region, which means any offsets from the start of the buffer cannot possibly affect the high bits. So instead, we can simply do a 32-bit addition between the low bits of the base and the offset, then pack that with the unchanged high bits. On anv, INSTRUCTION_STATE_POOL_MIN_ADDRESS is 8GB, so the high bits are always 0x2. We don't even need to patch that portion of the address and can just use an immediate value. We do still need to pack, however. fossil-db on Icelake indicates the following for affected shaders: Instrs: 10830023 -> 10750080 (-0.74%) Cycles: 1048521282 -> 1046770379 (-0.17%); split: -0.33%, +0.16% Subgroup size: 103104 -> 103112 (+0.01%) Send messages: 570886 -> 570760 (-0.02%) Loop count: 14428 -> 14429 (+0.01%) Spill count: 14246 -> 14244 (-0.01%); split: -0.06%, +0.04% Fill count: 22802 -> 22794 (-0.04%); split: -0.04%, +0.01% Scratch Memory Size: 654336 -> 662528 (+1.25%) Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20999> |
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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.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.