-assign_reg :: MachRep -> WordOff -> AvailRegs -> (ParamLocation, WordOff, AvailRegs)
-assign_reg I8 off (v:vs, fs, ds, ls) = (RegisterParam $ v, off, (vs, fs, ds, ls))
-assign_reg I16 off (v:vs, fs, ds, ls) = (RegisterParam $ v, off, (vs, fs, ds, ls))
-assign_reg I32 off (v:vs, fs, ds, ls) = (RegisterParam $ v, off, (vs, fs, ds, ls))
-assign_reg I64 off (vs, fs, ds, l:ls) = (RegisterParam $ l, off, (vs, fs, ds, ls))
+assign_reg :: MachRep -> WordOff -> AvailRegs -> (ParamLocation, WordOff, WordOff, AvailRegs)
+assign_reg I8 off (v:vs, fs, ds, ls) = (RegisterParam $ v, off, 0, (vs, fs, ds, ls))
+assign_reg I16 off (v:vs, fs, ds, ls) = (RegisterParam $ v, off, 0, (vs, fs, ds, ls))
+assign_reg I32 off (v:vs, fs, ds, ls) = (RegisterParam $ v, off, 0, (vs, fs, ds, ls))
+assign_reg I64 off (vs, fs, ds, l:ls) = (RegisterParam $ l, off, 0, (vs, fs, ds, ls))