[RFC] frame_id_inner check and -fsplit-stack

[Joel Brobecker]

> > I think we shouldn't add a knob if we don't need to.  So I'd say we
> > defenitely should try (4).  My initial idea for implementing this
> > would be for the unwinder to mark the frames that "split" the stack
> > (i.e. make the not normal), and skip the check for those frames.  I
> > also think the information should be encoded in the debug information
> > instead of magic section names that could be lost during (re)linking.
> 
> Looking at DWARF, I see that there is a calling_convention enum which
> can be added to the DW_TAG_subprogram for a function.  I don't know all
> that much about DWARF; does that seem like the right sort of thing to
> do?

As mentioned to Ian on IRC, the downside of this approach is that
the information would not be available unless the code was compiled
with debugging info. I think that this is a serious enough downside
that we should try to avoid it if possible.

> That wouldn't help with the unwind info, though.  There I think we could
> add a new augmentation code for a split-stack function.

I'm not a specialist of unwind info either.  But I think that this
approach, if implementable, would be more robust.

-- 
Joel