OpenCL bytecode running on another card

Question

As far as the OpenCL specification is concerned, you only have guarantees that a program binary can be re-used on the same device on which it was created.

In reality, the binaries that are returned by many OpenCL implementations are compatible with a wider range of devices available from that same vendor. For example, NVIDIA return PTX when you request binaries from their implementation, which is a reasonably high level intermediate representation (i.e. not native instructions). This is certainly compatible with other devices using the same architecture on which it was created (e.g. all GK110 devices, or all GF104 devices), and quite likely to be portable across a range of other NVIDIA GPU architectures too. Other vendors also return various types of intermediate representation (usually LLVM IR based) that allow this kind of binary compatibility.

So yes, you can probably re-use binaries across different devices that have the same architecture, but you'll really just have to try it and see. You could always implement a scheme that tries to use the binary and it that fails resort back to the source code.

In the future, we will hopefully see a large number of vendors supporting the recently ratified SPIR specification, which is a platform-portable intermediate representation for OpenCL device programs. This would allow you to generate binaries that are not only compatible with devices from a single vendor's architecture, but also across devices from many other vendors that also support SPIR. There would clearly be some remaining compilation overhead to lower SPIR to the native instruction set, but this should still result in significant speed-ups compared to compiling raw OpenCL C code.