Re: [proaudio] gcc cflags

[Thomas Kuther <gimpel@xxxxxxxxxxxxxxxx>]

On Mon, 21 Aug 2006 11:15:49 +0200
Dominique Michel <dominique.michel@xxxxxxxxxxxx> wrote:

> I want soon upgrade to gcc 4, but I want to hear about your
> compilation and linking flags.
> 
> I actually have the following flags with gcc 3.4.6:
> 
> CFLAGS="-O3 -march=pentium4 -pipe -msse -msse2 -mmmx -pipe
> -fomit-frame-pointer -fforce-addr -fno-ident -ftracer -fweb"
> 
> CHOST="i686-pc-linux-gnu" 
> CXXFLAGS="${CFLAGS} -fvisibility-inlines-hidden" 
> 
> LDFLAGS="-Wl,-O1 -Wl,--sort-common"
> 
> I am not sure if the -O3 flag is good to have. It will compile faster
> code in a few cases, but the load time of the programs will be bigger.
> And it can compile buggy code in a few cases as programs like the nec2
> antenna simulation, it is why I have the -fforce-addr flag. Look here
> if you want to know about some test I have done:
> http://bugs.gentoo.org/show_bug.cgi?id=135550#c12
> 
> With the nec2 software, the resulting code was bigger with -O3 and
> -fforce-addr as only with -O2, and the execution speed was the same.
> But I have not done the same test with a sound related program, so I
> don't know if I will get a speed improvement with -O3 and
> -fforce-addr. The NEC2 software give the computation time it used to
> compute a simulation, and I have no idea how I can get an equivalent
> result with a sound program.
> 
> Another issue with gcc4 is at I know at it is some new optimisation
> flags that can be useful with multimedia application, but I don't know
> which flags they are. Have you any suggestion about fast and reliable
> flags for gcc 4?
> 
> Cheers,
> Dominique
> 

Salut!

CFLAGS="-march=athlon-xp -O2 -pipe -fomit-frame-pointer"
CXXFLAGS="${CFLAGS}"
LDFLAGS="-Wl,-O1 -Wl,--sort-common"

No -O3 here, that just blows, and all that -msse2 -mmmx and all other
cpu flags are covered by -march, no use to specify them, also not on
gcc-3.4.6 - the compiler knows them from -march

Regards,
Tom

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