More NIR Optimizations En Route, "Soft FP64" Still Being Worked On
Written by Michael Larabel in Mesa on 22 November 2018 at 07:16 AM EST. 9 Comments
MESA --
When it comes to letdowns for Mesa in 2018, sadly OpenGL 4.6 support didn't reach mainline. Another unfortunate feature not making it into the Mesa 18.x release series is the "soft FP64" support to allow some older GPUs to work with OpenGL 4.x. While we haven't seen any new soft FP64 patches in a while, not all hope is lost.

It's been a while since any exciting soft FP64 work was presented, but this work is notable in it will let AMD Evergreen GPUs expose OpenGL 4.3 with the open-source driver stack. This FP64 emulation support will also help out older Intel and NVIDIA (via Nouveau) GPUs as well that lack native hardware double precision floating point capabilities.

It looks like some work is still quietly progressing on the soft FP64 front. Posted yesterday were a set of seven patches by Intel's Ian Romanick for reducing worst-case memory usage in NIR. These memory usage improvements for NIR were uncovered as part of the soft FP64 work, as mentioned by the patches.

So in the end these patches will help potentially shave off some memory usage by the NIR code employed by multiple Mesa/Gallium drivers and is a win particularly for the soft FP64 code. Now let's just hope that soft FP64 will make it into a Mesa 19.x release. As time presses on though, users are likely abandoning these older GPUs in favor of newer parts.
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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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