src/gallium/drivers/llvmpipe/README

   1 LLVMPIPE -- a fork of softpipe that employs LLVM for code generation.
   2
   3
   4 Status
   5 ======
   6
   7 Done so far is:
   8
   9  - the whole fragment pipeline is code generated in a single function
  10
  11    - input interpolation
  12
  13    - depth testing
  14
  15    - texture sampling
  16      - 1D/2D/3D/cube maps supported
  17      - all texture wrap modes supported
  18      - all texture filtering modes supported
  19      - perhaps not all texture formats yet supported
  20
  21    - fragment shader TGSI translation
  22      - same level of support as the TGSI SSE2 exec machine, with the exception
  23        we don't fallback to TGSI interpretation when an unsupported opcode is
  24        found, but just ignore it
  25      - done in SoA layout
  26      - input interpolation also code generated
  27
  28    - alpha testing
  29
  30    - blend (including logic ops)
  31      - both in SoA and AoS layouts, but only the former used for now
  32
  33  - code is generic
  34    - intermediates can be vectors of floats, ubytes, fixed point, etc, and of
  35      any width and length
  36    - not all operations are implemented for these types yet though
  37
  38 Most mesa/progs/demos/* work.
  39
  40 To do (probably by this order):
  41
  42  - code generate stipple and stencil testing
  43
  44  - translate TGSI control flow instructions, and all other remaining opcodes
  45
  46  - integrate with the draw module for VS code generation
  47
  48  - code generate the triangle setup and rasterization
  49
  50
  51 Requirements
  52 ============
  53
  54  - A x86 or amd64 processor.  64bit mode is preferred.
  55
  56    Support for sse2 is strongly encouraged.  Support for ssse3, and sse4.1 will
  57    yield the most efficient code.  The less features the CPU has the more
  58    likely is that you ran into underperforming, buggy, or incomplete code.
  59
  60    See /proc/cpuinfo to know what your CPU supports.
  61
  62  - LLVM 2.6 (or later)
  63
  64    For Linux, on a recent Debian based distribution do:
  65
  66      aptitude install llvm-dev
  67
  68    For Windows download pre-built MSVC 9.0 or MinGW binaries from
  69    http://people.freedesktop.org/~jrfonseca/llvm/ and set the LLVM environment
  70    variable to the extracted path.
  71
  72    The version of LLVM from SVN ("2.7svn") from mid-March 2010 seems pretty
  73    stable and has some features not in version 2.6.
  74
  75  - scons (optional)
  76
  77  - udis86, http://udis86.sourceforge.net/ (optional):
  78
  79      git clone git://udis86.git.sourceforge.net/gitroot/udis86/udis86
  80      cd udis86
  81      ./autogen.sh
  82      ./configure --with-pic
  83      make
  84      sudo make install
  85
  86
  87 Building
  88 ========
  89
  90 To build everything on Linux invoke scons as:
  91
  92   scons debug=yes statetrackers=mesa drivers=llvmpipe winsys=xlib dri=false
  93
  94 Alternatively, you can build it with GNU make, if you prefer, by invoking it as
  95
  96   make linux-llvm
  97
  98 but the rest of these instructions assume that scons is used.
  99
 100 For windows is everything the except except the winsys:
 101
 102   scons debug=yes statetrackers=mesa drivers=llvmpipe winsys=gdi dri=false
 103
 104 Using
 105 =====
 106
 107 On Linux, building will create a drop-in alternative for libGL.so. To use it
 108 set the environment variables:
 109
 110   export LD_LIBRARY_PATH=$PWD/build/linux-x86_64-debug/lib:$LD_LIBRARY_PATH
 111
 112 or
 113
 114   export LD_LIBRARY_PATH=$PWD/build/linux-x86-debug/lib:$LD_LIBRARY_PATH
 115
 116 For performance evaluation pass debug=no to scons, and use the corresponding
 117 lib directory without the "-debug" suffix.
 118
 119 On Windows, building will create a drop-in alternative for opengl32.dll. To use
 120 it put it in the same directory as the application. It can also be used by
 121 replacing the native ICD driver, but it's quite an advanced usage, so if you
 122 need to ask, don't even try it.
 123
 124
 125 Unit testing
 126 ============
 127
 128 Building will also create several unit tests in
 129 build/linux-???-debug/gallium/drivers/llvmpipe:
 130
 131  - lp_test_blend: blending
 132  - lp_test_conv: SIMD vector conversion
 133  - lp_test_format: pixel unpacking/packing
 134
 135 Some of this tests can output results and benchmarks to a tab-separated-file
 136 for posterior analysis, e.g.:
 137
 138   build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
 139
 140
 141 Development Notes
 142 =================
 143
 144 - When looking to this code by the first time start in lp_state_fs.c, and
 145   then skim through the lp_bld_* functions called in there, and the comments
 146   at the top of the lp_bld_*.c functions.
 147
 148 - The driver-independent parts of the LLVM / Gallium code are found in
 149   src/gallium/auxiliary/gallivm/.  The filenames and function prefixes
 150   need to be renamed from "lp_bld_" to something else though.
 151
 152 - We use LLVM-C bindings for now. They are not documented, but follow the C++
 153   interfaces very closely, and appear to be complete enough for code
 154   generation. See
 155   http://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html
 156   for a stand-alone example.
 157   See the llvm-c/Core.h file for reference.