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