Re: [gentoo-dev] -fbranch-probabilities optimisation

[Chris Davies <c.davies@cdavies.org>]

* Paul de Vrieze (pauldv@gentoo.org) wrote:
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> On Saturday 17 May 2003 16:13, Werner Van Belle wrote:
> > On Saturday 17 May 2003 15:57, Sven Vermeulen wrote:
> > > Aah, then I'm completely in favor of adding this to Portage :)
> >
> > Maybe first investigate how good this thing works. I've done a quick check
> > and I suspect this technique doesn't work on multithreaded programs.
> 
> If the profiles can be created correctly there should be nothing stopping this 
> from working. The problem is thought that this not so much has to be 
> implemented by portage as by specific packages that benefit from this.
> 
> Paul
> 

The current release of gcc doesn't contain threadsafe profiling, and indeed may never do. The cfg branch, where this work is being carried out reports that merging threadsafe profiling with main is problematic, and the code may be dropped.

Still, there a whole bunch of single thread programs that can benifit from this stuff, especially on architectures like x86 which have tiny numbers of registers.

Thanks,
C.Davies


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