Mesa's Radeon R600g Driver Adds NIR Support For Pre-Evergreen GPUs

Merged in early July to Mesa 22.2 was the rewritten R600g NIR back-end for improving older AMD Radeon HD 5000/6000 series graphics cards on Linux with this open-source OpenGL driver. That NIR code was limited to "newer" Radeon GPUs supported by the R600g driver while now it's been extended for supporting pre-Evergreen GPUs too.

The Mesa R600g driver goes back to supporting the Radeon HD 2000 "R600" through Radeon HD 6000 series graphics processors, but with the initial NIR hacking the focus has been on the HD 5000/6000 series. Merged overnight to Mesa 22.2 is enabling the NIR code to work for pre-Evergreen GPUs.

More than decade old Radeon GPUs continue to see new open-source driver work on Linux.

Evergreen was the codename for the Radeon HD 5000 series. This pre-Evergreen support has been primarily tested using the Radeon HD 4800 "RV770" series hardware but the new code drops the chip family check entirely so this NIR support may work all the way back to the Radeon HD 2000 series. Those interested in trying out the NIR code path over the conventional Gallium3D TGSI usage can use the "R600_DEBUG=nir" environment variable with Mesa 22.2.

Gert Wollny continues to be the one near single-handedly improving this old ATI/AMD R600g Gallium3D driver. This merge request that landed today has all the details on this pre-HD5000 series NIR support. Some 900 lines of new code and around 600 lines of removed code were needed for getting the older AMD GPUs working with this driver intermediate representation.

Looks like I'll be dusting off some old Radeon graphics cards when the Mesa 22.2 release nears in a few weeks.