The Mesa 3D Graphics Library


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 or x86-64 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 GNU make, if you prefer, by invoking it as
  make linux-llvm
but the rest of these instructions assume that scons is used. For Windows the procedure is similar except the target:
  scons 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 debug=no to scons, and use the corresponding lib directory without the "-debug" suffix. On Windows, building will create a drop-in alternative for opengl32.dll. To use it put it in the same directory as the 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.


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/perf-annotate-jit 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 this tests can output results and benchmarks to a tab-separated-file for posterior analysis, e.g.:

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

Development Notes

Recommended Reading