[llvm]/lib/CodeGen/PrologEpilogInserter.cpp RestoreCSRegs before epilogue, why?

Hello all!
Does anybody know why “lib/CodeGen/PrologEpilogInserter.cpp” has code:

Why we don't use directly:

Because the world is not that simple. In particular, if you will real
MSP430FrameLowering::emitEpilogue function, you will see that it needs
to insert stuff both *before* and *after* the callee-saved spill /
restore code. In particular, we need to start to set up frame just at
the start of the function, then integrate the callee-saved spill code
as a normal frame setup and continue afterwards.