This question has arisen in the ODP project and the thought is that a 'best practices' answer would be more likely to be found on this list.  

We have a component that wants to make use of specialized instructions for performing CRC and/or AES computations and was wondering what is the recommended way for an application to determine whether such instructions are available in the toolchain and whether the user has overruled their use?

Thanks for any insight you can provide.

Bill