Re: [gentoo-user] cpu flags / USE flags / compiler flags

[ellotheth rimmwen <ellotheth@gmail.com>]

Hm. Clear, brief, instructive. Smells a lot like a mini-HOWTO.

On 9/3/05, waltdnes@waltdnes.org <waltdnes@waltdnes.org> wrote:

>   There are CPU flags and there are USE flags.  Some of them have the
> same names, and that may confuse you.  It works like this...
>   1) Get a listing of your cpu's flags in /proc/cpuinfo
>   2) Check against the list of supported flags in gcc for you cpu, and
>      add them to CFLAGS
>   3) Check http://www.gentoo.org/dyn/use-index.xml for a list of valid
>      USE flags, and include any that show up in /proc/cpuinfo
>   4) Repeat step 3) with /usr/portage/profiles/use.local.desc for any
>      programs you're emerging.  There doesn't seem to be anything
>      special on your pentium4, but my AMD64 not only has mmx and 3dnow,
>      it also has mmxext and 3dnowext.  mplayer can take advantage of
>      them.  I include them in the /etc/portage/package.use entry for
>      media-video/mplayer.
> 
>  I'll assume that you're using gcc 3.3.5.  In that case, the place to
> look for CPU flag options is...
> 
> http://gcc.gnu.org/onlinedocs/gcc-3.3.5/gcc/i386-and-x86_002d64-Options.html#i386-and-x86_002d64-Options
> 
>   That list shows pentium4, mmx, sse, and sse2.  Also, if you have *ANY*
> version of sse available, you can improve performance by running floating
> point math via sse, rather than 387 instructions.  I recommend...
> 
> CFLAGS="-O2 -pipe -fomit-frame-pointer -march=pentium4 -mmmx -msse -msse2 -mfpmath=sse"
> 
> http://www.gentoo.org/dyn/use-index.xml shows mmx and sse as valid USE
> flags, so you can include them in USE.
> 
> --
> Walter Dnes <waltdnes@waltdnes.org>
> My musings on technology and security at http://tech_sec.blog.ca
> --
> gentoo-user@gentoo.org mailing list
> 
>

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