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 (not all state/formats are supported)
  16
  17    - fragment shader TGSI translation
  18      - same level of support as the TGSI SSE2 exec machine, with the exception
  19        we don't fallback to TGSI interpretation when an unsupported opcode is
  20        found, but just ignore it
  21      - done in SoA layout
  22      - input interpolation also code generated
  23
  24    - alpha testing
  25
  26    - blend (including logic ops)
  27      - both in SoA and AoS layouts, but only the former used for now
  28
  29  - code is generic
  30    - intermediates can be vectors of floats, ubytes, fixed point, etc, and of
  31      any width and length
  32    - not all operations are implemented for these types yet though
  33
  34 Most mesa/progs/demos/* work.
  35
  36 To do (probably by this order):
  37
  38  - code generate stipple and stencil testing
  39
  40  - translate the remaining bits of texture sampling state
  41
  42  - translate TGSI control flow instructions, and all other remaining opcodes
  43
  44  - integrate with the draw module for VS code generation
  45
  46  - code generate the triangle setup and rasterization
  47
  48
  49 Requirements
  50 ============
  51
  52  - Linux
  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.
  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  - scons (optional)
  73
  74  - udis86, http://udis86.sourceforge.net/ (optional):
  75
  76      git clone git://udis86.git.sourceforge.net/gitroot/udis86/udis86
  77      cd udis86
  78      ./autogen.sh
  79      ./configure --with-pic
  80      make
  81      sudo make install
  82
  83
  84 Building
  85 ========
  86
  87 To build everything on Linux invoke scons as:
  88
  89   scons debug=yes statetrackers=mesa drivers=trace,llvmpipe winsys=xlib dri=false
  90
  91 Alternatively, you can build it with GNU make, if you prefer, by invoking it as
  92
  93   make linux-llvm
  94
  95 but the rest of these instructions assume that scons is used.
  96
  97 For windows is everything the except except the winsys:
  98
  99   scons debug=yes statetrackers=mesa drivers=trace,llvmpipe winsys=gdi dri=false
 100
 101 Using
 102 =====
 103
 104 On Linux, building will create a drop-in alternative for libGL.so. To use it
 105 set the environment variables:
 106
 107   export LD_LIBRARY_PATH=$PWD/build/linux-x86_64-debug/lib:$LD_LIBRARY_PATH
 108
 109 or
 110
 111   export LD_LIBRARY_PATH=$PWD/build/linux-x86-debug/lib:$LD_LIBRARY_PATH
 112
 113 For performance evaluation pass debug=no to scons, and use the corresponding
 114 lib directory without the "-debug" suffix.
 115
 116 On Windows, building will create a drop-in alternative for opengl32.dll. To use
 117 it put it in the same directory as the application. It can also be used by
 118 replacing the native ICD driver, but it's quite an advanced usage, so if you
 119 need to ask, don't even try it.
 120
 121
 122 Unit testing
 123 ============
 124
 125 Building will also create several unit tests in
 126 build/linux-???-debug/gallium/drivers/llvmpipe:
 127
 128  - lp_test_blend: blending
 129  - lp_test_conv: SIMD vector conversion
 130  - lp_test_format: pixel unpacking/packing
 131
 132 Some of this tests can output results and benchmarks to a tab-separated-file
 133 for posterior analysis, e.g.:
 134
 135   build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
 136
 137
 138 Development Notes
 139 =================
 140
 141 - When looking to this code by the first time start in lp_state_fs.c, and
 142   then skim through the lp_bld_* functions called in there, and the comments
 143   at the top of the lp_bld_*.c functions.
 144
 145 - All lp_bld_*.[ch] are isolated from the rest of the driver, and could/may be
 146   put in a stand-alone Gallium state -> LLVM IR translation module.
 147
 148 - We use LLVM-C bindings for now. They are not documented, but follow the C++
 149   interfaces very closely, and appear to be complete enough for code
 150   generation. See
 151   http://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html
 152   for a stand-alone example.