Re: [proaudio] gcc cflags

[Dominique Michel <dominique.michel@xxxxxxxxxxxx>]

It begin to become clearer. I found a good thread at
http://forums.gentoo.org/viewtopic-t-318191-highlight-.html

It seam at -fomit-frame-pointer will speedup the code on x86, because
it is not enable by default (it make debugging impossible).

-momit-leaf-frame-pointer seam to be safe too.

-fno-ident is not an optimisation flag, but it remove some useless
repeated version strings, and it is safe.

-fweb seam to not do much, but doesn't break anything.

-ffast-math can have really good effect on audio/video decoders, but don't use it as global CFLAGS.

-ftracer: I am 100% not sure about it. Seam to be a good thing.

-ftree-vectorize seam to be good too.

So, I thing at I will try with:
CFLAGS="-O2 -march=pentium4 -pipe -fweb -ftracer -ftree-vectorize -fomit-frame-pointer -momit-leaf-frame-pointer -fno-ident"

CXXFLAGS="${CFLAGS}"

LDFLAGS="-Wl,-O1 -Wl,--sort-common"

BTW, gcc-4.1 go stable just now.

Dominique

 Le Thu, 24
Aug 2006 17:17:19 +0200, Dominique Michel
<dominique.michel@xxxxxxxxxxxx> a écrit :

> Thank you,
> The vectorize flags are for loop optimisation. I read on the IBM website
> at they can increase the speed of a program by a factor of 20. But I
> read in another website at all depend of the size of the loop, because
> they append additional structure control to the code, and at in case of
> small loops, those additional structures will do the resulting program
> slower.
> 
> I think at it will be a good flag to have with math intensive programs
> as multimedia programs, but I am not sure at it is a good flag to have
> as a system flag. Do you know something about this issue?
> 
> On Wed, 23 Aug 2006 16:20:18 -0500
> "Reuben Martin" <reuben.m@xxxxxxxxx> wrote:
> 
> > Based on how agressive you seem to want to be, I would recommend:
> > 
> > CFLAGS="-O2 -march=pentium4 -pipe -ftracer -fweb -ftree-vectorize"
> > 
> > The -ftree-vectorize does wonders.
> > 
> > If you are still feeling like you want to push it a little harder you
> > can try changing -O2 to -O3 and adding -ffast-math. Some things don't
> > work well with -O3 though (some of the LADSPA plugins don't work right
> > with -O3) and some programs don't work correctly with -ffast-math.
> > (for instance OpenOffice will fail to compile if Python has been built
> > with -ffast-math turned on)
> > 
> > -Reuben
> > 
> 
> I don't use -ffast-math and don't want it. I have no problem at this
> time with -O3 and -fforce-addr, and that even to compile the LADSPA
> plugin or openoffice. The only problem is at the resulting code is
> bigger as with -O2 alone and at it seam to be not faster. I
> try to remove the -fforce-addr and tested it with the nec2 antenna
> simulation software. It was faster as with -O2 alone, but I get wrong
> simulation results in some cases. So I thing at I will get with -O2 in
> the future, -O3 is not a good option is you have to remove the speed
> benefice of that option in order to get a correct code with all the
> programs. And I don't have the time to test my flags with every one
> program that I want to install.
> 
> Cheers,
> Dominique
>