Re: [Libunwind-devel] libunwind x86-64 optimisations?

[Lassi Tuura]

Hey,

> This could also be a dynamic stack realignment (for support of
> vectorization).  I didn't think x86-64 needed that, though.

Basically I guess I worry about use of DW_CFA_def_cfa_expression.  
From what I can tell it's little used on x86-64 (linux) except for  
syscall page and a few glibc exceptions.

Does anyone know any real-life uses of these?

I've only tried GCC up to 4.3.2 myself and don't see any use of these  
on systems I tried (readelf --debug-dump=frames {/usr,}/lib64/*.so* |  
grep DW_CFA_def_ | sort | uniq -c | less)

Lassi