Signed arithmetic/control-flow in DCPU-16?

dcpu-16

Solution

The new DCPU spec published by Notch the other day, does have signed arithmetic instructions:

Unsigned  | Signed
==================
MUL       | MLI
DIV       | DVI
SHR       | ASR
IFG       | IFA
IFL       | IFU

Problem

DCPU-16 (the CPU in Notch's new game) doesn't seem to have any signed `IF`/`MUL`/`DIV` instructions. Is there still a way to do signed arithmetic/control-flow that isn't super incredibly painful?

Original source