Question on Dwarf2 unwind info and optimized code

[Jim Wilson]

Christophe LYON wrote:
> I have been look at the Dwarf2 frame info generated by GCC, and how it 
> works.
>  From what I can see, only the register saves are recorded, and not the 
> restores. Why?

The frame info is primarily used for C++ EH stack unwinding.  Since you 
can't throw a C++ exception in an epilogue, epilogue frame info isn't 
needed for this, and was never implemented for most targets.  Which is a 
shame.

There is a PR for this, PR 18749, for the x86-64 target.  The lack of 
epilogue unwind info shows up if you run the libunwind testsuite. 
Otherwise, it is really hard to find an example where the missing unwind 
info is a problem.
-- 
Jim Wilson, GNU Tools Support, http://www.specifix.com