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

[Dodji Seketeli <dodji@redhat.com>]

On Tue, Dec 01, 2009 at 12:13:47PM (-0700), Tom Tromey wrote:
> The biggest fixable performance problem in the current reader is
> actually computing the hash codes for the strings from the
> .debug_gnu_index section.  So, I've been thinking about putting the hash
> code directly into the section.

FWIW, from a G++ pov, I think it'd be tempted to say "let's try to
implement this and see how much GDB gains" so that we can have data to make
an educated choice. So I'd be on the "yes, let's try side" of the story
here.

> 
> The other problem I've noticed is name canonicalization.  This past
> year, we changed gdb to canonicalize names in its symbol tables, and to
> canonicalize user input before doing lookups.  This lets gdb return the
> right answer even when the order of modifiers varies.  This change
> slowed down DWARF reading, and it occurred to me that it would also
> substantially slow down index reading.  So, I would also like to change
> the .debug_gnu_index spec to specify how names are to be canonicalized.

Just to be sure I understand. How saying _how_ the strings are to be
canonicalized is going to speed up significantly GDB's processing?
I would have have thought that the killer gain would come from the
producing directly what the consumer expects. I guess I am missing
something.

        Dodji