Portable Computing Language (pocl) aims to become an efficient implementation of the OpenCL standard. In addition to producing an easily-portable Open Source implementation, another major goal of the project is improving performance portability of OpenCL programs with compiler optimizations, reducing the need for target-dependent manual optimizations. At the core of pocl is a set of LLVM passes used to statically parallelize multiple work items with the kernel compiler, even in the presence of work group barriers. This enables parallelization of the fine-grained static concurrency in the work groups in multiple ways (SIMD, VLIW, superscalar, etc.). The code base is modularized to allow easy adding of new "device drivers" in the host-device layer. A generic multithreaded "target driver" is included. It allows running OpenCL applications on a host which supports the pthread library with multithreading at the work group granularity.