-assign_reg LongArg (vs, fs, ds, l:ls) = Just (LongReg l, (vs, fs, ds, ls))
-assign_reg PtrArg (v:vs, fs, ds, ls) = Just (VanillaReg v, (vs, fs, ds, ls))
-assign_reg NonPtrArg (v:vs, fs, ds, ls) = Just (VanillaReg v, (vs, fs, ds, ls))
+assign_reg LongArg (vs, fs, ds, l:ls) = pprTrace "longArg" (ppr l) $ Just (LongReg l, (vs, fs, ds, ls))
+assign_reg PtrArg (v:vs, fs, ds, ls) = Just (VanillaReg v VGcPtr, (vs, fs, ds, ls))
+assign_reg NonPtrArg (v:vs, fs, ds, ls) = Just (VanillaReg v VNonGcPtr, (vs, fs, ds, ls))