More NIR Optimizations En Route, "Soft FP64" Still Being Worked On

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.