LLVMpipe Picks Up Support For New GL Extensions
Written by Michael Larabel in Mesa on 25 February 2013 at 05:53 PM EST. 1 Comment
While LLVMpipe is now commonly used as the default software fallback on the Linux desktop in cases where there is no OpenGL hardware driver available, it remains limited to OpenGL 2.1 compliance and doesn't see too much love by developers. Fortunately, VMware developers continue to take some care of this driver and today there's now support for two new OpenGL extensions pertaining to texture buffers.

Roland Scheidegger committed support to the LLVMpipe Gallium3D CPU-based software graphics driver today for GL_ARB_texture_buffer_object and GL_ARB_texture_buffer_range. The first extension, GL_ARB_texture_buffer_object, introduces buffer textures while the latter expands upon it by offering greater performance when the client only needs a sub-range of a texture buffer object. The specification documents on them can be found here and here.

These OpenGL extensions aren't new to Mesa or the common GPU drivers, but is the first time being introduced to LLVMpipe. With this commit, the Piglit regression tests mostly pass for those relevant to ARB_texture_buffer_objects. However, it does require manually overriding the GL Shading Language version to 1.40 and also overriding the advertised OpenGL version to 3.1.

As shown in the Git log search on LLVMpipe, there's been a bit of other driver activity in the past week thanks to VMware. However, the overall progress of the VMware driver continues to be rather slow even as this driver takes on a greater role and is more widely used in cases of no OpenGL hardware acceleration.

Originally this driver was just used as a tool for driver developers in debugging purposes for testing against a vendor/hardware-neutral driver and making a faster software implementation than "swrast" and Gallium3D Softpipe by leveraging LLVM. The last major commits to the LLVMpipe driver were one month ago. IBM is also looking at porting LLVMpipe to PowerPC but so far there haven't been any commits to mainline Mesa for this CPU architecture support.

The most recent extensive LLVMpipe performance benchmarks happened in late November, but new tests are on the way. LLVMpipe did make it as one of the disappointments of Mesa 9.1, which was released last week.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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