FP64 Support Revised For R600g Gallium3D Driver
Written by Michael Larabel in Radeon on 23 August 2017 at 07:22 AM EDT. 27 Comments
While the Radeon HD 5000/6000 series were advertised as supporting up to OpenGL 4.4 and are supported that way by the Catalyst / Radeon Software proprietary driver, the Mesa R600g driver has only exposed OpenGL 3.3 (with the exception of the HD 5800 / 6900 series) due to lacking FP64 support. That emulated FP64 support is now stepping ahead for the R600g driver.

Elie Tournier is the developer who previously worked on a "soft" FP64 implementation for Mesa using pure GLSL. Tournier is now working for Collabora where among his tasks is working on FP64 support that could be used by the R600 Gallium3D driver. If R600g gets FP64 landed, these graphics cards could then be up to OpenGL 4.1 support right now, similar to the HD 5800/6900 series due to their real FP64 hardware.

While not yet ready to be merged, Elie Tournier today sent out the work-in-progress patches for soft FP64 support in R600g. There are some accuracy issues with this double-precision floating point support and some operations crashing the system, among other early shortcomings, but the support is advancing.

There are 47 patches for this soft FP64 support so far, which amounts to over twenty-two thousand lines of code, most of which is in Mesa's GLSL compiler code. With it being in shared code paths, this FP64 support could still be utilized by other drivers/hardware lacking native FP64 support.

Blocking R600g from OpenGL 4.2 support is shader_atomic_counters and shader_image_load_store support while there are more extensions still blocking R600g from seeing OpenGL 4.3+.

Those wanting to check out this latest work can find the patches via Mesa-dev.
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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 20,000 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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