It is possible to run OpenCL programs on the CPU, however you’ll have to install an OpenCL CPU backend / driver, like those from Intel or AMD. NVIDIA does not currently offer a way to run OpenCL kernels on the CPU. That said, running your program on the CPU will not allow you to debug any issues you might currently have with running the OpenCL kernel on the GPU in particular, simply because the OpenCL runtime / compiler is a completely different one then, with completely different bugs :-)
When you say assembly, for which architecture? PTX or x86 assembly? In the latter case, the Intel OpenCL SDK comes with an offline compiler tool. Regarding PTX / NVIDIA GPU assembly, I guess there is no way to generate it without a GPU unless you have a Tesla card and a headless driver.