Portable OpenCL aims to be an efficient open source (MIT-licensed)
implementation of the OpenCL 1.2 standard.

In addition to producing an easily portable open source OpenCL
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, ...).

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 that supports
the pthread library with multithreading at the work group granularity.