I'm looking at the crash today. I suspect that this is during the RTL-to-instrcution conversion. I've added a new expression to the mix, so maybe that code can't handle it properly.

Yep, that's the case. GCC dies in final_scan_insn() on the subreg expression I added.

Maybe not, I traced the crash down to a debug statement I put in earlier, apparently there is no debug file for the final pass, and so the debug fprintf's cause a crash. I just keep shooting myself in the foot with this debug output.

There's still a few minor bugs, and the MOVQI pattern needs more work, but I think this has some promise. I may need to rewrite all instructions and redo all testing once MOVQI is working. Oh boy...