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  - udis86, http://udis86.sourceforge.net/ . Use my repository, which decodes
  55    opcodes not yet supported by upstream.
  56
  57      git clone git://people.freedesktop.org/~jrfonseca/udis86
  58      cd udis86
  59      ./configure --with-pic
  60      make
  61      sudo make install
  62
  63  - LLVM 2.5. On Debian based distributions do:
  64
  65      aptitude install llvm-dev
  66
  67    There is a typo in one of the llvm-dev 2.5 headers, that causes compilation
  68    errors in the debug build:
  69
  70      --- /usr/include/llvm-c/Core.h.orig        2009-08-10 15:38:54.000000000 +0100
  71      +++ /usr/include/llvm-c/Core.h     2009-08-10 15:38:25.000000000 +0100
  72      @@ -831,7 +831,7 @@
  73         template<typename T>
  74         inline T **unwrap(LLVMValueRef *Vals, unsigned Length) {
  75           #if DEBUG
  76      -    for (LLVMValueRef *I = Vals, E = Vals + Length; I != E; ++I)
  77      +    for (LLVMValueRef *I = Vals, *E = Vals + Length; I != E; ++I)
  78             cast<T>(*I);
  79           #endif
  80           return reinterpret_cast<T**>(Vals);
  81
  82  - A x86 or amd64 processor with support for sse2, sse3, and sse4.1 SIMD
  83    instructions. This is necessary because we emit several SSE intrinsics for
  84    convenience. See /proc/cpuinfo to know what your CPU supports.
  85
  86  - scons
  87
  88
  89 Building
  90 ========
  91
  92 To build everything invoke scons as:
  93
  94   scons debug=yes statetrackers=mesa drivers=llvmpipe winsys=xlib dri=false -k
  95
  96 Alternatively, you can build it with GNU make, if you prefer, by invoking it as
  97
  98   make linux-llvm
  99
 100 but the rest of these instructions assume that scons is used.
 101
 102
 103 Using
 104 =====
 105
 106 Building will create a drop-in alternative for libGL.so. To use it set the
 107 environment variables:
 108
 109   export LD_LIBRARY_PATH=$PWD/build/linux-x86_64-debug/lib:$LD_LIBRARY_PATH
 110
 111 or
 112
 113   export LD_LIBRARY_PATH=$PWD/build/linux-x86-debug/lib:$LD_LIBRARY_PATH
 114
 115 For performance evaluation pass debug=no to scons, and use the corresponding
 116 lib directory without the "-debug" suffix.
 117
 118
 119 Unit testing
 120 ============
 121
 122 Building will also create several unit tests in
 123 build/linux-???-debug/gallium/drivers/llvmpipe:
 124
 125  - lp_test_blend: blending
 126  - lp_test_conv: SIMD vector conversion
 127  - lp_test_format: pixel unpacking/packing
 128
 129 Some of this tests can output results and benchmarks to a tab-separated-file
 130 for posterior analysis, e.g.:
 131
 132   build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv
 133
 134
 135 Development Notes
 136 =================
 137
 138 - When looking to this code by the first time start in lp_state_fs.c, and
 139   then skim through the lp_bld_* functions called in there, and the comments
 140   at the top of the lp_bld_*.c functions.
 141
 142 - All lp_bld_*.[ch] are isolated from the rest of the driver, and could/may be
 143   put in a stand-alone Gallium state -> LLVM IR translation module.
 144
 145 - We use LLVM-C bindings for now. They are not documented, but follow the C++
 146   interfaces very closely, and appear to be complete enough for code
 147   generation. See
 148   http://npcontemplation.blogspot.com/2008/06/secret-of-llvm-c-bindings.html
 149   for a stand-alone example.