Re: [RFC] Proposal for a new DWARF name index section

[Daniel Jacobowitz <drow@false.org>]

On Wed, Dec 02, 2009 at 12:23:25PM -0700, Tom Tromey wrote:
> I do think that slowing down the compiler to speed up the debugger would
> be the wrong tradeoff.  I was hoping we could get this for free in the
> compiler, or nearly so, but now I unfortunately see that I was confused
> on that point :-(.  We could pick a representation close to what gcc
> already emits -- but then that overly constrains gcc in the future.

That's not an option, anyway; the stuff GCC emits is too vague
in some cases (he says unsubstantiatedly).

> Caching is interesting but it comes with other problems.  We have to
> manage the cache somehow.  And, the cache would not be useful when an
> object changes.  So, I'd prefer a direct approach, if one can be made to
> work.

Well, inherent in the cache approach (IMO) is a system-provided cache;
for installed libraries, the cache data could be added to a debuginfo
file.  Of course, that assumes GDB's format stays "relatively stable"
across GDB updates.

>                            warm cache    cold cache
>  without canonicalization:  ~0.5 sec       5 sec
> gdb does canonicalization:  ~1.7 sec       6 sec
>              gdb cvs head:  ~2.4 sec      10 sec

Not bad!

-- 
Daniel Jacobowitz
CodeSourcery