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

[Mark Knecht <markknecht@gmail.com>]

Thanks Walter. That description verifies my guess and gives me a
reason to continue looking at the issue.

I appreciate your help.

Cheers,
Mark

On 9/3/05, waltdnes@waltdnes.org <waltdnes@waltdnes.org> wrote:
> On Wed, Aug 31, 2005 at 09:04:21AM -0700, Mark Knecht wrote
> 
> > flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
> > mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe cid
> > xtpr
>   [...deletia...]
> > I then looked for CPU flags that had an equivalent USE flag and that
> > might be of use for faster graphics. On this machine I chose mmx, sse
> > & sse2. Armed with that I changed my make.conf file to look like this:
> 
>   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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