RadeonSI NIR Gets Compute Shader Support

Timothy Arceri of Valve's Linux GPU driver team continues getting the RadeonSI NIR support up to scratch.

Timothy spearheaded the work on tessellation shaders for RadeonSI's NIR back-end and also took this experimental code path to GLSL 4.50 support, among other improvements to the open-source Radeon Linux graphics driver.

The latest work is getting OpenGL compute shaders working when using RadeonSI's NIR code-path. Timothy's latest patches get things working for compute shaders on RadeonSI NIR except for shared variable and atomic support, but he intends to address those next.

More details on the Mesa mailing list.

RadeonSI users can experiment with the NIR code via the R600_DEBUG=nir environment variable. This NIR back-end is ultimately needed for SPIR-V ingestion support but further out in the future RadeonSI might default to NIR for their intermediate representation and further avoid TGSI, but that is still a ways out. If trying out the RadeonSI NIR code today, be aware of likely regressions.