Mesa's R600 Driver Nears Feature Complete NIR Support For Radeon HD 5000/6000 Series
Gert Wollny has been near single handedly working on NIR support for the R600g driver to make use of this modern graphics driver intermediate representation as an alternative to the long-standing Gallium3D TGSI IR.
By making use of NIR, R600g can share more potential optimizations in common with RadeonSI and the other NIR-based Mesa drivers. There is also the possibility of more OpenGL capabilities with NIR being the main IR focus among Mesa developers these days. But still there are limitations considering the age of the supported hardware by R600g.
This NIR bring-up has also been only focused on the more recent hardware supported by the R600g driver, namely Evergreen and Northern Islands. Evergreen was the codename for the Radeon HD 5000 series GPUs and Northern Islands for the Radeon HD 6000 series.
Gert Wollny commented this week that the NIR support is now "close to feature complete" for the Radeon HD 5000/6000 series hardware on R600g. But there is scheduler and back-end optimizations still missing. Thus due to those missing bits still, SB is now enabled for NIR and landed today into Mesa 21.1-devel. SB is a long standing R600g shader optimization path that has long been available with this driver but until now not enabled for the NIR code path.
Long story short, the NIR support is getting into good shape for the Radeon HD 5000/6000 series on R600g. But if you are still using such hardware, it may be time to consider an upgrade for the performance and power efficiency benefits as well as then being able to enjoy Vulkan support and other modern GPU features. This experimental path for those interested can be enabled with the R600_DEBUG=nir environment variable.