As posted by Jeff Tranter, when Motorola wanted to supply a floating point package for the 6809, they did it as a ROM:
What’s quite nice about this is that the 8k ROM uses position-independent code and uses only stack-relative RAM, so has no fixed resource requirements from the host system. It’s compliant to IEEE spec, then not quite final, and offers floating point operations at 4, 8 and 10 byte precision.
Much more including references at the blog post.