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[Bug tree-optimization/28364] poor optimization choices when iterating over a std::string (probably not c++-specific)
- From: "rakdver at atrey dot karlin dot mff dot cuni dot cz" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 13 Jul 2006 08:01:04 -0000
- Subject: [Bug tree-optimization/28364] poor optimization choices when iterating over a std::string (probably not c++-specific)
- References: <bug-28364-37@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #19 from rakdver at atrey dot karlin dot mff dot cuni dot cz 2006-07-13 08:01 -------
Subject: Re: poor optimization choices when iterating over a std::string
(probably not c++-specific)
> > > I-cache.
> > this only matters if this increase in code size will make the code go
> > out of instruction cache.
>
> The real program that this is taken from is a large C++ application
> which is guaranteed to go out of cache - it's got slightly less than
> four megabytes of .text - the actual goal is to make sure all of its
> inner inner inner loops do stay in cache. And this is one of 'em.
on your real program, how much performance do you gain by hand-rewriting
the assembler to look the way you like? Just to make sure there really
is a problem.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28364