docs: move gallium specific docs into gallium folder

Reviewed-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5706>

3 files changed, 318 insertions, 0 deletions

diff --git a/docs/gallium/drivers/llvmpipe.rst b/docs/gallium/drivers/llvmpipe.rst
new file mode 100644
index 00000000000..ec8e92dc0a8
--- /dev/null
+++ b/docs/gallium/drivers/llvmpipe.rst
@@ -0,0 +1,284 @@
+Gallium LLVMpipe Driver
+=======================
+
+Introduction
+------------
+
+The Gallium llvmpipe driver is a software rasterizer that uses LLVM to
+do runtime code generation. Shaders, point/line/triangle rasterization
+and vertex processing are implemented with LLVM IR which is translated
+to x86, x86-64, or ppc64le machine code. Also, the driver is
+multithreaded to take advantage of multiple CPU cores (up to 8 at this
+time). It's the fastest software rasterizer for Mesa.
+
+Requirements
+------------
+
+-  For x86 or amd64 processors, 64-bit mode is recommended. Support for
+   SSE2 is strongly encouraged. Support for SSE3 and SSE4.1 will yield
+   the most efficient code. The fewer features the CPU has the more
+   likely it is that you will run into underperforming, buggy, or
+   incomplete code.
+
+   For ppc64le processors, use of the Altivec feature (the Vector
+   Facility) is recommended if supported; use of the VSX feature (the
+   Vector-Scalar Facility) is recommended if supported AND Mesa is built
+   with LLVM version 4.0 or later.
+
+   See ``/proc/cpuinfo`` to know what your CPU supports.
+
+-  Unless otherwise stated, LLVM version 3.4 is recommended; 3.3 or
+   later is required.
+
+   For Linux, on a recent Debian based distribution do:
+
+   .. code-block:: console
+
+      aptitude install llvm-dev
+
+   If you want development snapshot builds of LLVM for Debian and
+   derived distributions like Ubuntu, you can use the APT repository at
+   `apt.llvm.org <https://apt.llvm.org/>`__, which are maintained by
+   Debian's LLVM maintainer.
+
+   For a RPM-based distribution do:
+
+   .. code-block:: console
+
+      yum install llvm-devel
+
+   For Windows you will need to build LLVM from source with MSVC or
+   MINGW (either natively or through cross compilers) and CMake, and set
+   the ``LLVM`` environment variable to the directory you installed it
+   to. LLVM will be statically linked, so when building on MSVC it needs
+   to be built with a matching CRT as Mesa, and you'll need to pass
+   ``-DLLVM_USE_CRT_xxx=yyy`` as described below.
+
+
+   +-----------------+----------------------------------------------------------------+
+   | LLVM build-type | Mesa build-type                                                |
+   |                 +--------------------------------+-------------------------------+
+   |                 | debug,checked                  | release,profile               |
+   +=================+================================+===============================+
+   | Debug           | ``-DLLVM_USE_CRT_DEBUG=MTd``   | ``-DLLVM_USE_CRT_DEBUG=MT``   |
+   +-----------------+--------------------------------+-------------------------------+
+   | Release         | ``-DLLVM_USE_CRT_RELEASE=MTd`` | ``-DLLVM_USE_CRT_RELEASE=MT`` |
+   +-----------------+--------------------------------+-------------------------------+
+
+   You can build only the x86 target by passing
+   ``-DLLVM_TARGETS_TO_BUILD=X86`` to cmake.
+
+-  scons (optional)
+
+Building
+--------
+
+To build everything on Linux invoke scons as:
+
+.. code-block:: console
+
+   scons build=debug libgl-xlib
+
+Alternatively, you can build it with meson with:
+
+.. code-block:: console
+
+   mkdir build
+   cd build
+   meson -D glx=gallium-xlib -D gallium-drivers=swrast
+   ninja
+
+but the rest of these instructions assume that scons is used. For
+Windows the procedure is similar except the target:
+
+.. code-block:: console
+
+   scons platform=windows build=debug libgl-gdi
+
+Using
+-----
+
+Linux
+~~~~~
+
+On Linux, building will create a drop-in alternative for ``libGL.so``
+into
+
+::
+
+   build/foo/gallium/targets/libgl-xlib/libGL.so
+
+or
+
+::
+
+   lib/gallium/libGL.so
+
+To use it set the ``LD_LIBRARY_PATH`` environment variable accordingly.
+
+For performance evaluation pass ``build=release`` to scons, and use the
+corresponding lib directory without the ``-debug`` suffix.
+
+Windows
+~~~~~~~
+
+On Windows, building will create
+``build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll`` which
+is a drop-in alternative for system's ``opengl32.dll``. To use it put it
+in the same directory as your application. It can also be used by
+replacing the native ICD driver, but it's quite an advanced usage, so if
+you need to ask, don't even try it.
+
+There is however an easy way to replace the OpenGL software renderer
+that comes with Microsoft Windows 7 (or later) with llvmpipe (that is,
+on systems without any OpenGL drivers):
+
+-  copy
+   ``build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll`` to
+   ``C:\Windows\SysWOW64\mesadrv.dll``
+
+-  load this registry settings:
+
+   ::
+
+      REGEDIT4
+
+      ; https://technet.microsoft.com/en-us/library/cc749368.aspx
+      ; https://www.msfn.org/board/topic/143241-portable-windows-7-build-from-winpe-30/page-5#entry942596
+      [HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\OpenGLDrivers\MSOGL]
+      "DLL"="mesadrv.dll"
+      "DriverVersion"=dword:00000001
+      "Flags"=dword:00000001
+      "Version"=dword:00000002
+
+-  Ditto for 64 bits drivers if you need them.
+
+Profiling
+---------
+
+To profile llvmpipe you should build as
+
+::
+
+   scons build=profile <same-as-before>
+
+This will ensure that frame pointers are used both in C and JIT
+functions, and that no tail call optimizations are done by gcc.
+
+Linux perf integration
+~~~~~~~~~~~~~~~~~~~~~~
+
+On Linux, it is possible to have symbol resolution of JIT code with
+`Linux perf <https://perf.wiki.kernel.org/>`__:
+
+::
+
+   perf record -g /my/application
+   perf report
+
+When run inside Linux perf, llvmpipe will create a
+``/tmp/perf-XXXXX.map`` file with symbol address table. It also dumps
+assembly code to ``/tmp/perf-XXXXX.map.asm``, which can be used by the
+``bin/perf-annotate-jit.py`` script to produce disassembly of the
+generated code annotated with the samples.
+
+You can obtain a call graph via
+`Gprof2Dot <https://github.com/jrfonseca/gprof2dot#linux-perf>`__.
+
+Unit testing
+------------
+
+Building will also create several unit tests in
+``build/linux-???-debug/gallium/drivers/llvmpipe``:
+
+-  ``lp_test_blend``: blending
+-  ``lp_test_conv``: SIMD vector conversion
+-  ``lp_test_format``: pixel unpacking/packing
+
+Some of these tests can output results and benchmarks to a tab-separated
+file for later analysis, e.g.:
+
+::
+
+   build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
+
+Development Notes
+-----------------
+
+-  When looking at this code for the first time, start in lp_state_fs.c,
+   and then skim through the ``lp_bld_*`` functions called there, and
+   the comments at the top of the ``lp_bld_*.c`` functions.
+-  The driver-independent parts of the LLVM / Gallium code are found in
+   ``src/gallium/auxiliary/gallivm/``. The filenames and function
+   prefixes need to be renamed from ``lp_bld_`` to something else
+   though.
+-  We use LLVM-C bindings for now. They are not documented, but follow
+   the C++ interfaces very closely, and appear to be complete enough for
+   code generation. See `this stand-alone
+   example <https://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html>`__.
+   See the ``llvm-c/Core.h`` file for reference.
+
+.. _recommended_reading:
+
+Recommended Reading
+-------------------
+
+-  Rasterization
+
+   -  `Triangle Scan Conversion using 2D Homogeneous
+      Coordinates <https://www.cs.unc.edu/~olano/papers/2dh-tri/>`__
+   -  `Rasterization on
+      Larrabee <http://www.drdobbs.com/parallel/rasterization-on-larrabee/217200602>`__
+      (`DevMaster
+      copy <http://devmaster.net/posts/2887/rasterization-on-larrabee>`__)
+   -  `Rasterization using half-space
+      functions <http://devmaster.net/posts/6133/rasterization-using-half-space-functions>`__
+   -  `Advanced
+      Rasterization <http://devmaster.net/posts/6145/advanced-rasterization>`__
+   -  `Optimizing Software Occlusion
+      Culling <https://fgiesen.wordpress.com/2013/02/17/optimizing-sw-occlusion-culling-index/>`__
+
+-  Texture sampling
+
+   -  `Perspective Texture
+      Mapping <http://chrishecker.com/Miscellaneous_Technical_Articles#Perspective_Texture_Mapping>`__
+   -  `Texturing As In
+      Unreal <https://www.flipcode.com/archives/Texturing_As_In_Unreal.shtml>`__
+   -  `Run-Time MIP-Map
+      Filtering <http://www.gamasutra.com/view/feature/3301/runtime_mipmap_filtering.php>`__
+   -  `Will "brilinear" filtering
+      persist? <http://alt.3dcenter.org/artikel/2003/10-26_a_english.php>`__
+   -  `Trilinear
+      filtering <http://ixbtlabs.com/articles2/gffx/nv40-rx800-3.html>`__
+   -  `Texture
+      Swizzling <http://devmaster.net/posts/12785/texture-swizzling>`__
+
+-  SIMD
+
+   -  `Whole-Function
+      Vectorization <http://www.cdl.uni-saarland.de/projects/wfv/#header4>`__
+
+-  Optimization
+
+   -  `Optimizing Pixomatic For Modern x86
+      Processors <http://www.drdobbs.com/optimizing-pixomatic-for-modern-x86-proc/184405807>`__
+   -  `Intel 64 and IA-32 Architectures Optimization Reference
+      Manual <http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-optimization-manual.html>`__
+   -  `Software optimization
+      resources <http://www.agner.org/optimize/>`__
+   -  `Intel Intrinsics
+      Guide <https://software.intel.com/en-us/articles/intel-intrinsics-guide>`__
+
+-  LLVM
+
+   -  `LLVM Language Reference
+      Manual <http://llvm.org/docs/LangRef.html>`__
+   -  `The secret of LLVM C
+      bindings <https://npcontemplation.blogspot.co.uk/2008/06/secret-of-llvm-c-bindings.html>`__
+
+-  General
+
+   -  `A trip through the Graphics
+      Pipeline <https://fgiesen.wordpress.com/2011/07/09/a-trip-through-the-graphics-pipeline-2011-index/>`__
+   -  `WARP Architecture and
+      Performance <https://msdn.microsoft.com/en-us/library/gg615082.aspx#architecture>`__
diff --git a/docs/gallium/index.rst b/docs/gallium/index.rst
index 9688afb2215..29fbefa2eb5 100644
--- a/docs/gallium/index.rst
+++ b/docs/gallium/index.rst
@@ -16,6 +16,7 @@ Contents:
    cso
    distro
    drivers
+   postprocess
    glossary
 
 Indices and tables
diff --git a/docs/gallium/postprocess.rst b/docs/gallium/postprocess.rst
new file mode 100644
index 00000000000..276f3863756
--- /dev/null
+++ b/docs/gallium/postprocess.rst
@@ -0,0 +1,33 @@
+Gallium Post-processing
+=======================
+
+The Gallium drivers support user-defined image post-processing. At the
+end of drawing a frame a post-processing filter can be applied to the
+rendered image. Example filters include morphological antialiasing and
+cell shading.
+
+The filters can be toggled per-app via driconf, or per-session via the
+corresponding environment variables.
+
+Multiple filters can be used together.
+
+PP environment variables
+------------------------
+
+-  PP_DEBUG - If defined debug information will be printed to stderr.
+
+Current filters
+---------------
+
+-  pp_nored, pp_nogreen, pp_noblue - set to 1 to remove the
+   corresponding color channel. These are basic filters for easy testing
+   of the PP queue.
+-  pp_jimenezmlaa, pp_jimenezmlaa_color - `Jimenez's
+   MLAA <https://www.iryokufx.com/mlaa/>`__ is a morphological
+   antialiasing filter. The two versions use depth and color data,
+   respectively. Which works better depends on the app - depth will not
+   blur text, but it will miss transparent textures for example. Set to
+   a number from 2 to 32, roughly corresponding to quality. Numbers
+   higher than 8 see minimizing gains.
+-  pp_celshade - set to 1 to enable cell shading (a more complex color
+   filter).