Radeon R600g Driver Retires Its SB Optimizer

A decade ago the Radeon R600g SB shader back-end proved useful for boosting gaming performance on pre-GCN graphics cards of the time and proved useful. But in more recent years in the R600g switch to NIR, the SB path hasn't received much attention and its benefits have diminished. The R600g SB code has now been dropped.

Gert Wollny of Collabora is one of the few Mesa developers still working on the R600g driver from time-to-time and he's been responsible for much of the NIR work on this driver for the Radeon HD 6000 series and prior. He's went ahead and retired the SB back-end.

With today's commit to Mesa 23.3, the SB path has been retired from R600g:

r600: retire SB optimizer

The NIR backend is good enough and here is already a long list of reasons why SB should not be called because it doesn't handle certain instructions correctly.

Dropping the SB code lightens the R600 Gallium3D driver size by some 20k lines of code.