amdgpocl
OpenCL on amdgpu for Arch, also in the AUR
This package allows the usage of AMD's proprietary user-space OpenCL driver along with the free amdgpu stack. It should work with upstream amdgpu and Mesa. Inspired by this blog post.
Hardware support
This should work with all amdgpu-enabled GCN GPUs. However, I have no hardware to actually test it.
If you are using SI (Southerin Islands) or CIK (Sea Islands GPU), you'll need to enable the amdgpu and disable the radeon kernel module. Check the Arch Wiki for the exact steps.
Currently tested with Kernel 4.13 and Hawaii. Blender Cycles and Luxmark seem to work without any problems.
What this is not
You are not getting Vulkan support, faster 3D rendering or unicorns.
If you are looking for the full amdgpu-pro stack, including proprietary OpenGL and Vulkan implementations, move over to the aur.
Expect maintainance of this package to be dropped when there is free OpenCL support on top of the ROC stack.