Ahh, that part. Sorry, I did see that but kind of "filtered it out" in my head because I was looking for open source references.
That text is referring to events like AFDS and others, where we expose architectural information to give application and toolchain developers a heads-up. The information we provide at that point doesn't include anything like the level of detail required for driver development, however.
May you say some details about UVD4 and PowerTune support in open source driver now? Or there is still embargo for such information?
I haven't looked much at UVD in the latest GPUs but I thought they were still UVD 3. Can't really talk much about UVD at this point because I don't know what we are going to be able to release, although we are going to take another look in the new year.
I don't think we have looked at PowerTune specifically; my guess is that the first chance to do that will be a few months from now. There are some more fundamental power management improvements I would like to get out first, and they will probably be a pre-requisite for PowerTune anyways.
Thanks for responding.
I'm not sure I follow you. It SEEMS as though you are saying you will use the open sourced compiler for the old r600 while the new diver will switch to the new one. I apologize if I've misunderstood.
Lastly regarding drm I was attempting to give the impression that since hybrid mode will do most of the work through the CUs we could ignore the small bit that the uvd handles and thus not use uvd at all thus ignoring drm:)
Current thinking (if I remember it correctly ;)) is to tweak the pipe driver API to accept different IR formats (ie other than TGSI) then :
For 6xx-NI graphics the Gallium3D pipe driver will receive TGSI shader programs from Mesa then use the existing code which converts vector TGSI operations directly into VLIW GPU operations
For 6xx-NI compute the Gallium3D pipe driver will receive LLVM IR kernel programs from clover (or other compute front ends), then use "part 2" of the newly released code to generate VLIW GPU instructions from the LLVM IR (may not make great use of the VLIW at first)
For GCN graphics the Gallium3D pipe driver will receive TGSI shader programs from Mesa, use "part 1" of the newly released code to convert TGSI to LLVM IR, then use "part 2" to generate GCN GPU instructions from the LLVM IR
For GCN compute the Gallium3D pipe driver will receive LLVM IR kernel programs from clover (or other compute front ends) then use "part 2" of the newly released code to generate GCN GPU instructions from the LLVM IR
I drew a picture on a whiteboard at work of all this yesterday showing Catalyst OpenCL, clover OpenCL and Mesa with all the different code paths and scenarios. Should have taken a picture of it before erasing, sorry.
What you seem to be saying is that <=NI will make good use of the IR->VLIW, which makes sense (also, graphics stays the same).
For >=SI EVERYTHING goes through the new code (which I didn't know, but I also didn't know there were 2 code drops). Again, what surprises me is that the same compiler code used to generate VLIW is also being used to generate the new SIMD code.
Again, if what Anandtech says is accurate it seems like the old compiler was so hideously complex thay you'd want to jettison it as soon as possible instead of making it able to output to yet another kind of architecture (so presumable it now addresses VLIW4/5/SIMD).
It doesn't know anything about the underlying architecture of the code, it's just a front-end to the GLSL language. Much like a GCC frontend for C or C++ would be shared across multiple architectures, and there is a separate backend portion that takes care of all the hardware details.
The new LLVM IR code drop from AMD is that part, and it will completely replace the hardware dependent portion of the compiler in Mesa.
Compilers tend to have 3 parts - the frontend reads the source code and stores an intermediate reprentation of it (IR), and only depends on the language being parsed.
The back end is responsible for converting that IR into something the hardware can understand (typically binary instructions, but you can also have backends that output other languages, such as the emscripten project).
The middle is where optimizations take place, and is typically split between the front and back end. Generic optimizations for the language go in the shared front-end, while hardware specific optimizations go in the backend.
In mesa, the GLSL compiler is the front end. TGSI and LLVM IR are both forms of IR used internally (so is the GLSL IR). The old 600g driver contains one backend, and the new code based on LLVM contains a new backend to be used for new hardware.
This is one of the biggest problems in Linux for both developers and users IMHO. There has to be an easy and safe way for end-users to install/update drivers without having to depend on distributions and wait for months in order for code to be merged into the latest kernel.Quote:
The open-source driver support is not yet available. No patches have magically landed this morning and they haven't released any support work in advance of the hardware's availability.
AMD recently had a developers conference that covered the technology. I believe Phoronix covered it. However I'm not sure if any of that was for open source development. The architecture is such a massive change that I suspect it could be a year or more before we see optimized code for GCN.