I compiled a section of 2k_chess to exercise the new code and see where things stand. Things went really well except for this:

unrecognizable insn:
(insn 1253 482 483 85 2k_chess.c:111 (set (reg:QI 2 r2)
(mem/s/j:QI (plus:HI (mem/c:HI (plus:HI (reg/f:HI 10 r10)
(const_int 64 [0x40])) [4 %sfp+64 S2 A16])
(symbol_ref:HI ("b") )) [0 b S1 A8])) -1 (nil))

This instruction should result in "movb @b+64(R10), R2".

This should be handled by the code I have now, but for some reason it's not. Maybe I've goofed on the memory constraints and they are too narrow, disallowing "symbol+offset" forms. I guess I've got some research to do.