OpenCL - How to I query for a device's SIMD width?

In CUDA, there is a concept of a warp, which is defined as the maximum number of threads that can execute the same instruction simultaneously within a single processing element. For NVIDIA, this warp size is 32 for all of their cards currently on the market.

In ATI cards, there is a similar concept, but the terminology in this context is wavefront. After some hunting around, I found out that the ATI card I have has a wavefront size of 64.

My question is, what can I do to query for this SIMD width at runtime for OpenCL?