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Re: PR rtl-optimization/28071
- From: Roger Sayle <roger at eyesopen dot com>
- To: Jan Hubicka <jh at suse dot cz>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Thu, 27 Jul 2006 08:10:47 -0600 (MDT)
- Subject: Re: PR rtl-optimization/28071
On Thu, 27 Jul 2006, Jan Hubicka wrote:
> 2006-07-27 Jan Hubicka <firstname.lastname@example.org>
> PR rtl-optimization/28071
> * cselib.c (cselib_process_insn): Don't remove useless values too
> often for very large hashtables.
This is OK for mainline.
It might be interesting to also instrument this code to check whether
its reasonable to increase MAX_USELESS_VALUES. It is bizarre that we
have quadratic behaviour keeping the hashtable clean, when the overhead
of probing a dirty table is at worst linear, and best case has no/little
performance overhead best if our hashing is working.
I like your approach of testing the fraction of useless values.
I just wonder if the values "32" and "25%" can be improved upon.