Portable OpenCL (pocl) is a MIT-licensed open source implementation of the OpenCL standard which can be easily adapted for new targets and devices, both for homogeneous CPU and heterogenous GPUs/accelerators. pocl uses Clang as an OpenCL C frontend and LLVM for the kernel compiler implementation, and as a portability layer. Thus, if your desired target has an LLVM backend, it should be able to get OpenCL support easily by using pocl.