In OpenCL Push, AMD Makes Progress With LLVM For Gallium3D

On Sunday there was a new RFC patch-set by Tom Stellard of AMD with a new TGSI to LLVM conversion interface. The AMD R600 Gallium3D driver with its LLVM shader back-end was also updated, which is a prerequisite to OpenCL support.

Sunday began by Christian König making progress with H.264 VDPAU support in Gallium3D, which is one of AMD's top three priorities for their open-source Linux driver. Tom Stellard meanwhile has been working on one of the other priority projects: enabling OpenCL in the open-source driver.

In early December was the unveiling of the initial R600g LLVM back-end that converts TGSI (the common Gallium3D IR) to LLVM IR and provides a supportive LLVM back-end for the R600g driver (the Gallium3D driver supporting from the Radeon HD 2000 "R600" series through the Radeon HD 6900 "Cayman" series).

The LLVM back-end was derived from AMD's AMDIL LLVM back-end for OpenCL, which they decided to open-source last month. As Stellard said in the release announcement, "The main motivation for this LLVM backend is to help bring compute/OpenCL support to r600g by making it easier to support different compiler frontends."

The R600g LLVM back-end wasn't merged for the forthcoming Mesa 8.0 release, but based upon the activity that's been happening and OpenCL being a priority for AMD's open-source graphics team, this should be a feature of Mesa 8.1.

What's new for January is that Stellard has published patches for a new TGSI to LLVM interface to Gallium and makes the changes necessary so that Gallium3D can use the new interface. Tom Stellard has also updated his R600g LLVM shader back-end branch of Mesa so that it's current as of Sunday. The updated Mesa branch of his can be viewed via CGit.

The RFC patch-set for the new TGSI to LLVM conversion interface can be found on the Mesa mailing list, which makes OpenCL-Gallium3D for Radeon hardware being a tiny bit closer to reality.