ROCm is an Advanced Micro Devices (AMD) software stack for graphics processing unit (GPU) programming. ROCm spans several domains: general-purpose computing on graphics processing units (GPGPU), high performance computing (HPC), heterogeneous computing. It offers several programming models: HIP (GPU-kernel-based programming), OpenMP/Message Passing Interface (MPI) (directive-based programming), OpenCL.
ROCm is free, libre and open-source software (except the GPU firmware blobs), it is distributed under various licenses. ROCm is short for Radeon Open Compute platform.
The first GPGPU software stack from ATI/AMD was Close to Metal, which became Stream.
ROCm was launched around 2016 with the Boltzmann Initiative. ROCm stack builds upon previous AMD GPU stacks, some tools trace back to GPUOpen, others to the Heterogeneous System Architecture (HSA).
HSAIL was aimed at producing a middle-level, hardware-agnostic intermediate representation, that could be JIT-compiled to the eventual hardware (GPU, FPGA...) using the appropriate finalizer. This approach was dropped for ROCm: now it builds only GPU code, using LLVM, and its AMDGPU backend that was upstreamed, although there is still research on such enhanced modularity with LLVM MLIR.
ROCm as a stack ranges from the kernel driver to the end-user applications.
AMD has introductory videos about AMD GCN hardware, and ROCm programming via its learning portal.
One of the best technical introductions about the stack and ROCm/HIP programming, remains, to date, to be found on Reddit.
ROCm is primarily targeted at discrete professional GPUs, but unofficial support includes Vega-family and RDNA 2 consumer GPUs.
Accelerated Processor Units (APU) are "enabled", but not officially supported. Having ROCm functional there is involved.
List of AMD graphics processing units
AMD Instinct accelerators are the first-class ROCm citizens, alongside the prosumer Radeon Pro GPU series: they mostly see full support.
The only consumer-grade GPU that has relatively equal support is, as of January 2022, the Radeon VII (GCN 5 - Vega).