[patch] dwarf2out: Drop the size + performance overhead of DW_AT_sibling

[Jan Kratochvil]

On Wed, 12 Oct 2011 16:18:07 +0200, Jan Kratochvil wrote:
> On Wed, 12 Oct 2011 16:07:24 +0200, Tristan Gingold wrote:
> > I fear that this may degrade performance of other debuggers.  What about
> > adding a command line option ?
> 
> I can test idb,

I do not find the difference measurable.  Dropping DW_AT_sibling is 0.25%
performance _improvement_ but I guess it is just less than the measurement
error.

libstdc++ built with gcc -gdwarf-2 as with gcc -gdwarf-4 -fdebug-types-section
it crashes.  i7-920 x86_64 used for testing:
Intel(R) Debugger for applications running on Intel(R) 64, Version 12.1, Build [76.472.14]

with DW_AT_sibling
real    2m34.206s 2m31.822s 2m31.709s 2m32.316s
avg = 152.51325 seconds

patched GCC without DW_AT_sibling
real    2m32.528s 2m30.524s 2m33.767s 2m31.719s
avg = 152.1345 seconds

I do not see a point in keeping DW_AT_sibling there.


Regards,
Jan