Ray-Tracing Support For AMDGPU LLVM Back-End Lands For RDNA 2
Written by Michael Larabel in Radeon on 16 September 2020 at 06:38 PM EDT. 30 Comments
AMD previously confirmed it would be supporting real-time ray-tracing with their next-generation GPUs while now one month out from the Radeon RX 6000 series debut are the first signs of the open-source driver work around GPU ray-tracing.

One day after spotting the patches for AV1 video decode with VCN 3.0, the latest open-source Radeon driver work to point out is the fundamentals around their ray-tracing introduction.

Hitting the LLVM 12 development codebase today was [AMDGPU] gfx1030 RT support. While that may not sound all that exciting, that for the shader compiler back-end is the initial ray-tracing support for GFX1030 (GFX10.3 / Navi 2).

That code is adding the compiler back-end LLVM intrinsic for the AMDGCN "intersect ray" operation.

This by itself isn't all that exciting as we knew these upcoming AMD Radeon GPUs would add hardware ray-tracing for taking on NVIDIA RTX, but it does indicate they are working on the Linux/open-source support.

Besides this AMDGPU LLVM commit, the Vulkan ray-tracing needs to be wired up in the AMD Radeon Vulkan driver code. For that AMD is working on their official Vulkan driver that for the open-source form is AMDVLK. We haven't seen AMD pushing AMDVLK Navi 2 / RX 6000 series code yet to their repository so for that we will likely need to wait until after launch before they push out their new support there. On the RADV side it will be left up to the developers at the likes of Google and Valve to get the Vulkan ray-tracing support figured out for this Mesa Radeon Vulkan driver. RADV already has begun adding Navi 2 support including ACO additions albeit so far appears to be untested.

For the open-source driver support baseline outside of using a packaged Radeon Software for Linux driver on supported distributions, Linux 5.9 + LLVM 11 + Mesa 20.2 is looking to be the minimum viable support. However, given that features like ray-tracing are in flux and we are seeing more kernel side work coming for Linux 5.10, as usual it will be a situation with new hardware where using the newer Git support will generally mean better support, more features, and greater performance. In any case once the Radeon RX 6000 series graphics cards launch, we'll be able to do the testing and provide more details as to the Linux support, performance, and versioning recommendations. In any case, great to see this AMDGPU LLVM RT support and other new features continue to land pre-launch.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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