def get_function_type(self, restype, argtypes):
        """
        Get the LLVM IR Function type for *restype* and *argtypes*.
        """
        arginfo = self._get_arg_packer(argtypes)
        argtypes = list(arginfo.argument_types)
        fnty = ir.FunctionType(self.get_return_type(restype), argtypes)
        return fnty

        Get the LLVM IR Function type for *restype* and *argtypes*.
        
numba/cuda/target.py