Question about function inliner on Machine level (not IR level)

Hi all,

At this moment, I need inliner pass on machine level such as function inliner but I can not find these kind of passes in CodeGen. Could someone recommend some passes or codes to support inliner on machine level? If not possible, is it possible to implement it? I will appreciate any comment about this stupid question.

Thanks,
JinGu Kang