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    For MSVC there are two set of binaries: llvm-x.x-msvc32mt.7z and
  73    llvm-x.x-msvc32mtd.7z .
  74
  75    You have to set the LLVM=/path/to/llvm-x.x-msvc32mtd env var when passing
  76    debug=yes to scons, and LLVM=/path/to/llvm-x.x-msvc32mt when building with
  77    debug=no. This is necessary as LLVM builds as static library so the chosen
  78    MS CRT must match.
  79
  80    The version of LLVM from SVN ("2.7svn") from mid-March 2010 is pretty
  81    stable and has some features not in version 2.6.
  82
  83  - scons (optional)
  84
  85  - udis86, http://udis86.sourceforge.net/ (optional). My personal repository
  86    supports more opcodes which haven't been merged upstream yet:
  87
  88      git clone git://anongit.freedesktop.org/~jrfonseca/udis86
  89      cd udis86
  90      ./autogen.sh
  91      ./configure --with-pic
  92      make
  93      sudo make install
  94
  95
  96 Building
  97 ========
  98
  99 To build everything on Linux invoke scons as:
 100
 101   scons debug=yes statetrackers=mesa drivers=llvmpipe winsys=xlib dri=false
 102
 103 Alternatively, you can build it with GNU make, if you prefer, by invoking it as
 104
 105   make linux-llvm
 106
 107 but the rest of these instructions assume that scons is used.
 108
 109 For windows is everything the except except the winsys:
 110
 111   scons debug=yes statetrackers=mesa drivers=llvmpipe winsys=gdi dri=false
 112
 113 Using
 114 =====
 115
 116 On Linux, building will create a drop-in alternative for libGL.so. To use it
 117 set the environment variables:
 118
 119   export LD_LIBRARY_PATH=$PWD/build/linux-x86_64-debug/lib:$LD_LIBRARY_PATH
 120
 121 or
 122
 123   export LD_LIBRARY_PATH=$PWD/build/linux-x86-debug/lib:$LD_LIBRARY_PATH
 124
 125 For performance evaluation pass debug=no to scons, and use the corresponding
 126 lib directory without the "-debug" suffix.
 127
 128 On Windows, building will create a drop-in alternative for opengl32.dll. To use
 129 it put it in the same directory as the application. It can also be used by
 130 replacing the native ICD driver, but it's quite an advanced usage, so if you
 131 need to ask, don't even try it.
 132
 133
 134 Unit testing
 135 ============
 136
 137 Building will also create several unit tests in
 138 build/linux-???-debug/gallium/drivers/llvmpipe:
 139
 140  - lp_test_blend: blending
 141  - lp_test_conv: SIMD vector conversion
 142  - lp_test_format: pixel unpacking/packing
 143
 144 Some of this tests can output results and benchmarks to a tab-separated-file
 145 for posterior analysis, e.g.:
 146
 147   build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
 148
 149
 150 Development Notes
 151 =================
 152
 153 - When looking to this code by the first time start in lp_state_fs.c, and
 154   then skim through the lp_bld_* functions called in there, and the comments
 155   at the top of the lp_bld_*.c functions.
 156
 157 - The driver-independent parts of the LLVM / Gallium code are found in
 158   src/gallium/auxiliary/gallivm/.  The filenames and function prefixes
 159   need to be renamed from "lp_bld_" to something else though.
 160
 161 - We use LLVM-C bindings for now. They are not documented, but follow the C++
 162   interfaces very closely, and appear to be complete enough for code
 163   generation. See
 164   http://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html
 165   for a stand-alone example.
 166   See the llvm-c/Core.h file for reference.