Generic instruction sets have been tried many times before. It's better to use C than go down that road. Processors are just too different, which is a big deal if you're going for the utmost in speed. I could elaborate here with lots of examples if you really want them!
It appears to be easy enough to include assembly language functions. There's a sample in the docs.
It appears to be easy enough to include assembly language functions. There's a sample in the docs.