function arguments offset computation with -fomit-frame-pointer

[Bernardo Innocenti <bernie at develer dot com>]

Hello,

I'm trying to track a bug I've added with some changes I'm working on
in the m68k back-end. 

I want to change function prologue and epilogue in ways that alter the
total size of the frame plus the registers being pushed on the stack.

With frame pointer enabled everything is fine, but I still have problems
with -fomit-frame-pointer. It's not yet clear to me how the rest of the
compiler gets to know how much data the prologue has pushed on the stack
to compute the offset to fetch incoming function arguments from.

I also have a more m68k-specific question: the code path for creating
room for the frame when no frame pointer always adds 4 bytes to the
required frame size. Is that done to get the same offset that
link/unlink would have done? Why is that necessary?

-- 
  // Bernardo Innocenti - Develer S.r.l., R&D dept.
\X/  http://www.develer.com/

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