Q: 

Are the EFM32LIB functions optimized for speed or function?

A:

The EFM32LIB functions included in the energyAware CMSIS package are designed to help you get started quickly with your design, and getting a prototype up and running without hassle. We have tried to optimize for energy, speed and code size where this does not conflict with our goal to make the functions as generic as possible, and not tailored for a specific application. If you need higher optimization in energy/speed/code size, you could use the EFM32LIB functions as a basis to create your own functions, tailored for your application.