docs: convert articles to reructuredtext

This uses the previously added scripts to convert the documentation to
reStructuredText, which is both easier to read offline, and can be used
to generate modern HTML for online documentation.

No modification to the generated results have been done.

Acked-by: Eric Engestrom <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4630>

1 files changed, 272 insertions, 0 deletions

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+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:
+
+   ::
+
+      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:
+
+   ::
+
+      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
+
+-  scons (optional)
+
+Building
+--------
+
+To build everything on Linux invoke scons as:
+
+::
+
+   scons build=debug libgl-xlib
+
+Alternatively, you can build it with meson with:
+
+::
+
+   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:
+
+::
+
+   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>`__