This is a port of DOOM that runs (almost) entirely on the GPU using the LLVM C library for GPUs based on the doomgeneric interface.
To try it you will need a WAD file (game data). If you don't own the game, shareware version is freely available (doom1.wad).
This implementation works on NVIDIA as well as AMDGPU. To use the NVIDIA
implementation perform the same steps but with the nvptx loader and make
target.
- A Linux operating system
- An AMDGPU with ROCm support
- SDL2 libraries
- A ROCm or ROCR-Runtime installation
- An LLVM build off of the main branch (LLVM20 as of writing)
Because I can.
The clang compiler can target GPUs directly. We emit a single kernel that
calls the 'main' function. Functions that require the operating system are
handled through the RPC interface. See my LLVM
talk for more information.
This implementation defines the amdgpu-loader utility, which handles launching
the main kernel, setting up the SDL2 window interface, and provides functions
to get the input keys and write the output framebuffer. Okay, it's not
entirely on the GPU, but all the logic and rendering runs on the GPU.
You will need an LLVM installation with the LLVM C library for GPUs enabled. Don't do a shared library build of LLVM it will probably break. See the documentation for how to build it.
Once installed, use the newly built clang compiler to build the libraries.
Make sure that you have include/hsa.h and libhsa-runtime64.so available from
your ROCm installation.
This currently only works with a single block / workgroup on the GPU. Logic is all done singe-threaded but software rendering is distributed amongst the threads.
$ make -C amdgpu_loader/ -j
$ make -C doomgeneric/ -f Makefile.amdgpu -j
$ ./amdgpu-loader/amdgpu-loader --threads 512 ./doomgeneric/doomgeneric -iwad doom1.wad
Video
Thanks to @hardcode84 for porting help.
The system I tested this on has:
- Arch Linux with kernel 6.10.5
- AMD ATI Radeon RX 6950 XT GPU
- ROCm version 6.0