The DWARF to compact encoding converter assumes that the DW_CFA_def_cfa_offset

comes after the DW_CFA_def_cfa_register, because the CFA is really ESP from the
start of the function and only gets an offset when the "subl $xxx,%esp"
instruction happens, not the other way around.

And reapply r72898:

The DWARF unwind info was incorrect. While compiling with
`-fomit-frame-pointer', we would lack the DW_CFA_advance_loc information for a
lot of function, and then they would be `0'. The linker (at least on Darwin)
needs to encode the stack size. In some cases, the stack size is too large to
directly encode. So the linker checks to see if there is a "subl $xxx,%esp"
instruction at the point where the `DW_CFA_def_cfa_offset' says the pc was. If
so, the compact encoding records the offset in the function to where the stack
size is embedded. But because the `DW_CFA_advance_loc' instructions are missing,
it looks before the function and dies.

So, instead of emitting the EH debug label before the stack adjustment
operations, emit it afterwards, right before the frame move stuff.

llvm-svn: 73465

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