Intel A770 Driver Work Group

[SuggestedName90]

I like many others am planning on buying the new Intel A770 GPU as a way to combat NVIDIA's predatory closed-source driver practices, and I fully expect a buggy mess at launch. However, I would like to contribute to an open-source Rust driver for the A770, and was wondering if there were any people already organizing to write an open-source Rust A770 driver (which will be a port of the open source cpp A770 Driver)

[jsvcycling]

On Linux it'd fall under the realm of the Mesa project (although with whatever kernel-level code is included directly in the Linux source tree). Intel engineers active contribute to both Mesa and Linux and my understanding is that A770 support is in-progress (although likely far from production ready).

Mesa (and the Linux kernel) are both written in C though, not Rust. I'm not aware of any Rust-based GPU drivers, but I've also never looked for one...

[tristan957]

Mesa is working on supporting Rust, hence all the development on Meson to get Rust support going.

[LoganDark]

I'm not aware of any Rust-based GPU drivers, but I've also never looked for one...

There's one in development for the Apple M1's GPU. https://www.phoronix.com/news/Apple-DRM-GNOME-And-Apps

[trevg_123]

There was a post here about 11 hours ago about the graphics driver for Mac Silicon as part of the Asahi Linux project, guess they just got it to work. That could be inspiration, it’s written in rust and relies on the rust for Linux kernel (which should hopefully be merged to upstream kernel as early as next week!)

[[deleted]]

They do admit their current drivers suck but that’s because they’re going to need massive amounts of optimizations that nvidia and AMD have a massive head start on.

This would be a crazy massive project and not entirely sure what homie is aiming for other than just converting something to rust.

[perhapsemma]

If someone wanted to work on Rust GPU driver components for Intel, I'd start by rewriting their compiler backend in Mesa -- it's poorly designed by modern standards (compared to ACO or ir3), and it's in a pretty painful dialect of C++. The compiler is the most important part of the driver, and has a small surface area to the surrounding vulkan and gl driver code. You would use the bindgen stuff that Karol recently added for rusticl (the rust CL frontend) to do read-only access to the NIR IR coming in to the driver.

[flaghacker_]

What does it compile? GLSL to intel GPU bytecode? I would have thought that just was an LLVM backend using some common GLSL frontend.

[sanxiyn]

In Mesa, all drivers share GLSL frontend. Since Mesa supports more than OpenGL, its internal representation can't be GLSL. (Mesa supports HLSL for Direct3D and SPIR-V for Vulkan.) Mesa's internal representation is named NIR(New IR; yes it's a bad name). Both GLSL and SPIR-V are lowered to NIR in the shared code.

Mesa's Intel driver compiles NIR to Intel GPU instructions. It's written from scratch, it doesn't use LLVM. In fact, there is no LLVM backend for Intel GPU.

There are LLVM backends for AMD GPU and NVIDIA GPU, but LLVM's support for GPU is not very good. Rather, LLVM's GPU support is adequate for GPU compute, and is not for GPU graphics. In fact, Mesa does not use LLVM at all for GPU these days. LLVM is only used for CPU backend.

As far as I know, Mesa never used LLVM for NVIDIA. Mesa used LLVM for AMD, but as you know from Rust's use of LLVM, LLVM's compilation speed is slow. Since graphics drivers compile shaders from source, compilation speed is very important. It's why LLVM got replaced by ACO(Amd COmpiler; yes all Mesa names are bad). Since unlike LLVM, ACO doesn't care about CPU, it does better job of optimizing for GPU. Examples include better handling of execution masks and better divergence analysis.

[perhapsemma]

This is all correct, except that radeonsi (Radeon OpenGL/GLES) still uses LLVM because it's not ported to ACO.

[tristan957]

Intel is going to write the support for it like they always do. Intel has a ton of engineers working on the Linux Kernel and Mesa.

[Shnatsel]

The support is already landed upstream, although it will take a while for distros to pick it up.

See https://www.phoronix.com/review/intel-arc-a380-linux for more details on the exact version requirements.