Re: GNU C++ 4.0.1/4.1.0 cache misses on MICO sources.

[Mark Mitchell <mark at codesourcery dot com>]

Karel Gardas wrote:
> On Mon, 23 May 2005, Mark Mitchell wrote:
>
> > Mike Stump wrote:
> >
> > > On May 17, 2005, at 3:16 PM, Karel Gardas wrote:
> > >
> > > > 1) the most expensive seems to be comptypes -- at least from data L2
> > > >    refill point of view (~17%)
> > > >
> > > > 2) comptypes is also the most CPU intensive operation since the most
> > > >    of time is spent there
> > >
> > >
> > >
> > > I think comptypes can be sped up by canonicalizing types better, and  
> > > also adding a conservative hash and checking it first.
> >
> >
> > We've researched this in detail.
> >
> > Speeding up comptypes can best be done by calling it less often.  One 
> > of the primary uses is the template machinery, which works very hard 
> > to work out whether it already has an existing specialization.  The 
> > first step is to insert canonicalizations and other speedups there; 
> > that would reduce the number of calls to comptypes dramatically.  
> > There are also places in the front end that make redundant calls to 
> > comptypes; for example, during declaration processing we sometimes 
> > check whether or not two declarations match more than once.
> >
> > The changes you suggest might still be helpful, but I'd prefer to see 
> > the bigger algorithms fixed first, as those changes will have 
> > secondary benefits beyond comptypes as well.
>
>
> Mark,
>
> shall I put some RFE to bugzilla to have it recordered somewhere, or is 
> this already on your company or team TODO list?

It's certainly well-known here -- but that's not to say it shouldn't go 
in some nice FSF-ish place as well in case somebody else wants to work 
on it.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304