RadeonSI Driver Now Defaults to ACO Shader Backend

Marek Olšák, video driver developer from AMD, has made a significant update to the Mesa codebase. This change has established the RadeonSI driver as the default intermediate representation (IR) of shaders through the NIR backend and the ACO shader compilation backend, developed by Valve as an alternative to the LLVM shader compiler.

The ACO backend is specifically designed to optimize code generation for gaming application shaders and achieve remarkably high compilation speed. By implementing ACO, shader compilation speed is increased, memory consumption is reduced, shader binary size is minimized, and code optimization is enhanced.

Comparing ACO to LLVM, it has been found that shader compilation time can be reduced by up to 8 times, resulting in significantly faster program launch times. Additionally, ACO utilizes fewer SGPR/VGPR (Scalar/Vector General Purpose Register) registers, thereby diminishing the necessity for resource-intensive register spilling operations in scenarios where the available registers are insufficient.