I'm pretty confident about the 8 and 16 bit instructions, so I guess I can't put off checking the 32 bit instructions anymore. At least I can find out where the holes are, and which instructions should be moved to an external library.
logical shift right
The shifts generate functional, if not efficient, code. I think I can get multiply without too much trouble, but divide and mudulus will have to be in an external library. I wrote the divide code earlier, and it requires a function of 25 instructions with lots of loops. I don't see how allowing that to be inlined would be a good idea.