Re: [gentoo-user] Re: Re: Re: Another hardware thread

[Michael Mol]

On Nov 23, 2011 1:50 PM, "Stefan G. Weichinger" <lists@×××××.at> wrote:
>
> Am 23.11.2011 18:05, schrieb Michael Mol:
> > On Wed, Nov 23, 2011 at 11:55 AM, Stefan G. Weichinger <lists@×××××.at>
wrote:
> >>
> >> Ad CFLAGS for i7-2600:
> >>
> >> Is that too much ricer-style?  -->
> >>
> >> ### gcc -march=native -E -v - </dev/null 2>&1 | sed -n 's/.* -v - //p'
> >>
> >> CFLAGS="-O2 -D_FORTIFY_SOURCE=2 -march=core2 -mcx16 -msahf -maes
> >> -mpclmul -mpopcnt -mavx --param l1-cache-size=32 --param
> >> l1-cache-line-size=64 --param l2-cache-size=8192 -mtune=generic"
> >>
> >> gcc-4.5.3-r1 ...
> >
> > That's equivalent to, what, "-O2 -D_FORTIFY_SOURCE=2 -march=native" ?
> > I don't see anything to complain about.
>
> Ok, thanks.
>
> compiled gcc-4.6.2 (hey, it only takes ~16min now!):
>
> # /usr/bin/gcc-4.6.2  -march=native -E -v - </dev/null 2>&1 | sed -n
> 's/.* -v - //p'
> -D_FORTIFY_SOURCE=2 -march=corei7-avx -mcx16 -msahf -mno-movbe -maes
> -mpclmul -mpopcnt -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mno-bmi
> -mno-tbm -mavx -msse4.2 -msse4.1 --param l1-cache-size=32 --param
> l1-cache-line-size=64 --param l2-cache-size=8192 -mtune=corei7-avx
>
> If I am "feeling adventurous" (Neil) I could now try my luck by choosing
> this nice new compiler w/ options. Maybe *after* a nice backup.
>
> > Actually, it's pretty interesting seeing what that processor comes
> > down to for -march=native. I wish there were a database of processors
> > and their decomposed compiler tuning flags for comparison. That would
> > be *very* interesting, from the standpoint of proc shopping and
> > looking at the evolution of CPUs.
>
> Wouldn't a wiki-page do the trick? gentoo-wiki ...
>
> S
>

ISTR gcc's i7 optimizations giving someone in here trouble within the last
couple weeks. As I recall, they dropped back to march and mtune=core2.