The Mesa 3D Graphics Library

Gallium LLVMpipe Driver


The Gallium llvmpipe driver is a software rasterizer that uses LLVM to do runtime code generation. Shaders, point/line/triangle rasterization and vertex processing are implemented with LLVM IR which is translated to x86, x86-64, or ppc64le machine code. Also, the driver is multithreaded to take advantage of multiple CPU cores (up to 8 at this time). It's the fastest software rasterizer for Mesa.



To build everything on Linux invoke scons as:
  scons build=debug libgl-xlib
Alternatively, you can build it with meson with:
  mkdir build
  cd build
  meson -D glx=gallium-xlib -D gallium-drivers=swrast
but the rest of these instructions assume that scons is used. For Windows the procedure is similar except the target:
  scons platform=windows build=debug libgl-gdi



On Linux, building will create a drop-in alternative for into


To use it set the LD_LIBRARY_PATH environment variable accordingly.

For performance evaluation pass build=release to scons, and use the corresponding lib directory without the -debug suffix.


On Windows, building will create build/windows-x86-debug/gallium/targets/libgl-gdi/opengl32.dll which is a drop-in alternative for system's opengl32.dll. To use it put it in the same directory as your application. It can also be used by replacing the native ICD driver, but it's quite an advanced usage, so if you need to ask, don't even try it.

There is however an easy way to replace the OpenGL software renderer that comes with Microsoft Windows 7 (or later) with llvmpipe (that is, on systems without any OpenGL drivers):


To profile llvmpipe you should build as

  scons build=profile <same-as-before>

This will ensure that frame pointers are used both in C and JIT functions, and that no tail call optimizations are done by gcc.

Linux perf integration

On Linux, it is possible to have symbol resolution of JIT code with Linux perf:

	perf record -g /my/application
	perf report

When run inside Linux perf, llvmpipe will create a /tmp/ file with symbol address table. It also dumps assembly code to /tmp/, which can be used by the bin/ script to produce disassembly of the generated code annotated with the samples.

You can obtain a call graph via Gprof2Dot.

Unit testing

Building will also create several unit tests in build/linux-???-debug/gallium/drivers/llvmpipe:

Some of these tests can output results and benchmarks to a tab-separated file for later analysis, e.g.:

  build/linux-x86_64-debug/gallium/drivers/llvmpipe/lp_test_blend -o blend.tsv

Development Notes