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  - A x86 or amd64 processor.  64bit mode is preferred.
  53
  54    Support for sse2 is strongly encouraged.  Support for ssse3, and sse4.1 will
  55    yield the most efficient code.  The less features the CPU has the more
  56    likely is that you ran into underperforming, buggy, or incomplete code.
  57
  58    See /proc/cpuinfo to know what your CPU supports.
  59
  60  - LLVM 2.6.
  61
  62    For Linux, on a recent Debian based distribution do:
  63
  64      aptitude install llvm-dev
  65
  66    For Windows download pre-built MSVC 9.0 or MinGW binaries from
  67    http://people.freedesktop.org/~jrfonseca/llvm/ and set the LLVM environment
  68    variable to the extracted path.
  69
  70  - scons (optional)
  71
  72  - udis86, http://udis86.sourceforge.net/ (optional):
  73
  74      git clone git://udis86.git.sourceforge.net/gitroot/udis86/udis86
  75      cd udis86
  76      ./autogen.sh
  77      ./configure --with-pic
  78      make
  79      sudo make install
  80
  81
  82 Building
  83 ========
  84
  85 To build everything on Linux invoke scons as:
  86
  87   scons debug=yes statetrackers=mesa drivers=llvmpipe winsys=xlib dri=false
  88
  89 Alternatively, you can build it with GNU make, if you prefer, by invoking it as
  90
  91   make linux-llvm
  92
  93 but the rest of these instructions assume that scons is used.
  94
  95 For windows is everything the except except the winsys:
  96
  97   scons debug=yes statetrackers=mesa drivers=llvmpipe winsys=gdi dri=false
  98
  99 Using
 100 =====
 101
 102 On Linux, building will create a drop-in alternative for libGL.so. To use it
 103 set the environment variables:
 104
 105   export LD_LIBRARY_PATH=$PWD/build/linux-x86_64-debug/lib:$LD_LIBRARY_PATH
 106
 107 or
 108
 109   export LD_LIBRARY_PATH=$PWD/build/linux-x86-debug/lib:$LD_LIBRARY_PATH
 110
 111 For performance evaluation pass debug=no to scons, and use the corresponding
 112 lib directory without the "-debug" suffix.
 113
 114 On Windows, building will create a drop-in alternative for opengl32.dll. To use
 115 it put it in the same directory as the application. It can also be used by
 116 replacing the native ICD driver, but it's quite an advanced usage, so if you
 117 need to ask, don't even try it.
 118
 119
 120 Unit testing
 121 ============
 122
 123 Building will also create several unit tests in
 124 build/linux-???-debug/gallium/drivers/llvmpipe:
 125
 126  - lp_test_blend: blending
 127  - lp_test_conv: SIMD vector conversion
 128  - lp_test_format: pixel unpacking/packing
 129
 130 Some of this tests can output results and benchmarks to a tab-separated-file
 131 for posterior analysis, e.g.:
 132
 133   build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
 134
 135
 136 Development Notes
 137 =================
 138
 139 - When looking to this code by the first time start in lp_state_fs.c, and
 140   then skim through the lp_bld_* functions called in there, and the comments
 141   at the top of the lp_bld_*.c functions.
 142
 143 - All lp_bld_*.[ch] are isolated from the rest of the driver, and could/may be
 144   put in a stand-alone Gallium state -> LLVM IR translation module.
 145
 146 - We use LLVM-C bindings for now. They are not documented, but follow the C++
 147   interfaces very closely, and appear to be complete enough for code
 148   generation. See
 149   http://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html
 150   for a stand-alone example.