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Re: using non-standard optflags (-O3, in particular)



On Sat, 2007-02-10 at 09:29 +0100, Till Maas wrote:
> On Friday 09 February 2007 18:24, Ralf Corsepius wrote:
> 
> > There are reasons why certain optimizations are in -O3 and why they are
> > not in -O2, e.g. because some of them do not provide sufficient
> > performance gains, some of them because they are too architecture
> > specific, some of them because they are unsafe, some of them because
> > they are considered unstable/experimental.
> 
> According to the gcc manpage -O3 enables only three more optimizationes 
> than -O3 does:
"Paper has patience" ("Papier ist geduldig"), as we say in German ;)

> -finline-functions
> -funswitch-loops
> -fgcse-after-reload
> 
> Are all of them bad or is there more optimization done than is described 
> there?

No idea, one would have to have a look into the source code.

-OX change widely between GCC releases and also can differ between
different vendors.

Ralf



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