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Re: [RFC] Symbol table hashing patch
On Mon, Oct 01, 2001 at 07:12:41PM -0400, Elena Zannoni wrote:
>
>
> As a first comment,, I would strongly reccommend that you break the
> ALL_BLOCK_SYMBOLS changes into a separate patch. That way the
> significant changes to the symtab algorithms will become easier to
> review. It seems from you comments that the MINIMAL_SYMBOL_HASH_SIZE
> is also an independent fix. How about the bug in msymtab_hash_iw, can
> that be separated out as well?
>
> What is 113?
>
Yes, msymtab_hash_iw is also independent.
I'll start breaking it up. On the other hand, I can't do all of it until I
get a little feedback - particularly, the sorting issues. So I would
appreciate any comments on the questions asked in the original message.
As for 113, the exact value is up for debate, but it shows a bit of a
problem with the current hash functions: the values of *string are not
evenly distributed. Multiplying by 31 and then adding an ASCII value
of (usually) ~100 doesn't seem very effective. The thing to do would
probably be to take advantage of Zack Weinberg's recent research; he
spent some time finding a good hash function for the set of
identifiers GCC deals with. It's the same one that this patch
introduces:
#define HASHSTEP(r, c) ((r) * 67 + ((c) - 113));
For reference, the post is:
http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer