Trying Out RadeonSI's Experimental NIR Support

Last week AMD developers landed experimental NIR support inside RadeonSI as ultimately a step towards ARB_gl_spirv support for this OpenGL Gallium3D driver in being able to re-use the NIR/RADV code-paths. I decided to take the experimental NIR support through a spin to see if it impacted various titles at this point.

The experimental NIR code for RadeonSI can be activated by setting the R600_DEBUG=nir environment variable. But your mileage for now will be limited as with the NIR back-end there is only OpenGL 3.1 support currently exposed as only vertex and pixel shaders are supported for now, compared to OpenGL 4.5 by default. In the future, more of the NIR functionality will be implemented and thus raising the OpenGL support.

So for some quick tests of this NIR RadeonSI back-end I had to run some older Linux games that don't require above OpenGL 3.1.

Tests were done on Mesa Git with Linux 4.13 and in conjunction with a Radeon R9 Fury.




Using the experimental NIR code-path does appear to have some benefit for some Linux games while in others it was unchanged; see this result file for more details. With the exception of Portal seeming regressed anyhow on Mesa Git, I didn't notice any graphical problems with the limited game tests. It will be interesting to see this NIR support once stabilized.