CmmAssign (CmmLocal (LocalReg u' _)) rhs | u' /= u -> True
CmmAssign g@(CmmGlobal _) rhs -> not (g `regUsedIn` expr)
_other -> False
CmmAssign (CmmLocal (LocalReg u' _)) rhs | u' /= u -> True
CmmAssign g@(CmmGlobal _) rhs -> not (g `regUsedIn` expr)
_other -> False