[gentoo-dev] Warning about -march=k6*

[gentoo-dev] Warning about -march=k6*

[Mike Frysinger]

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i have seen many bugs where people who have used -march=k6* in their CFLAGS 
experienced segfaults, compile failures, etc...

i'd like to propose adding a warning to make.conf to deter ppl from using 
these flags ... rather i'd suggest they use -mcpu=k6* ...

the bug can be found at http://bugs.gentoo.org/show_bug.cgi?id=24379
i just want to know if anyone out there has had *success* with this flag ...
- -mike
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Re: [gentoo-dev] Warning about -march=k6*

[Tim Ruehsen]

Yes, I had that problem which ceased after changing architecture from i686 to 
i586.

Tim

Am Montag, 14. Juli 2003 08:14 schrieb Mike Frysinger:
> i have seen many bugs where people who have used -march=k6* in their CFLAGS
> experienced segfaults, compile failures, etc...
>
> i'd like to propose adding a warning to make.conf to deter ppl from using
> these flags ... rather i'd suggest they use -mcpu=k6* ...
>
> the bug can be found at http://bugs.gentoo.org/show_bug.cgi?id=24379
> i just want to know if anyone out there has had *success* with this flag
> ... -mike


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Re: [gentoo-dev] Warning about -march=k6*

[Brad Cowan]

On Mon, 14 Jul 2003 02:14:32 -0400
Mike Frysinger <vapier@gentoo.org> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> i have seen many bugs where people who have used -march=k6* in their
> CFLAGS experienced segfaults, compile failures, etc...
> 
> i'd like to propose adding a warning to make.conf to deter ppl from
> using these flags ... rather i'd suggest they use -mcpu=k6* ...
> 

Most all of the problems I've seen are because the user had a CHOST of
i686 instead of i586, or used options like -funroll-loops which break
things on this arch. Also some use the wrong k6 option ie k6-3 when they
have a k6-2 etc.., but I definately would advize at least a big fat
warning. I would say go with -march=i586 instead of -mcpu=k6 if you want
to go that route.

-- 
Brad Cowan <bcowan@gentoo.org>
Developer,
Gentoo Linux	http://www.gentoo.org/~bcowan

Public Key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0xB1F16A56
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Re: [gentoo-dev] Warning about -march=k6*

[C. Brewer]

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On Mon, 14 Jul 2003 02:14:32 -0400
Mike Frysinger <vapier@gentoo.org> wrote:

> the bug can be found at http://bugs.gentoo.org/show_bug.cgi?id=24379
> i just want to know if anyone out there has had *success* with this flag
> ...

I've had much success with this flag, after long trying times with learning
what flags you can get away with in regards to the different packages. I
first started with-
-O3 -march=k6-2 -pipe -funroll-loops -fomit-frame-pointer (continuing list
of -f functions)
and whittled down to-
-O2 -march=k6-2 -pipe -fomit-frame-pointer with these observations-

-O3 and -funroll-loops work together if not appended with -fPIC or any other
-*PIC option by the source.
-O3 and -funroll-loops will build compression packages (bzip2,jpeg,etc) but
will not allow them to execute correctly.
Bottom line is that since gcc 3.x, the difference between -O3 and -O2 on
k6's speedwise is imperceptible to the end user, and I advise really staying
away from -O3 and excessive -f* functions, especially in the loop dept.:)
-- 
Chuck Brewer
Registered Linux User #284015
Get my gpg public key at pgp.mit.edu!! Encrypted e-mail preferred.



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Re: [gentoo-dev] Warning about -march=k6*

[Stewart Honsberger]

Mike Frysinger wrote:
> i have seen many bugs where people who have used -march=k6* in their CFLAGS
> experienced segfaults, compile failures, etc...
> 
> i'd like to propose adding a warning to make.conf to deter ppl from using
> these flags ... rather i'd suggest they use -mcpu=k6* ...
> 
> the bug can be found at http://bugs.gentoo.org/show_bug.cgi?id=24379
> i just want to know if anyone out there has had *success* with this flag ...

My entire server (AMD K62-400) is built around -march=k6; stage1 
ground-up, however I am using the 1.2 profile with GCC 2.95.

Does -march=k6-2 exist for 2.95? I'd hate to destabalize my server to 
test, but I might be able to scrounge up another of the same chip and 
motherboard.

-- 
Stewart Honsberger
Gentoo Developer
http://www.snerk.org/


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Re: [gentoo-dev] Warning about -march=k6*

[Jon Portnoy]

On Mon, Jul 14, 2003 at 02:32:45PM -0400, Stewart Honsberger wrote:
> Mike Frysinger wrote:
> >i have seen many bugs where people who have used -march=k6* in their CFLAGS
> >experienced segfaults, compile failures, etc...
> >
> >i'd like to propose adding a warning to make.conf to deter ppl from using
> >these flags ... rather i'd suggest they use -mcpu=k6* ...
> >
> >the bug can be found at http://bugs.gentoo.org/show_bug.cgi?id=24379
> >i just want to know if anyone out there has had *success* with this flag 
> >...
> 
> My entire server (AMD K62-400) is built around -march=k6; stage1 
> ground-up, however I am using the 1.2 profile with GCC 2.95.
> 
> Does -march=k6-2 exist for 2.95? I'd hate to destabalize my server to 
> test, but I might be able to scrounge up another of the same chip and 
> motherboard.

Not AFAIK.

> 
> -- 
> Stewart Honsberger
> Gentoo Developer
> http://www.snerk.org/
> 
> 
> --
> gentoo-dev@gentoo.org mailing list

-- 
Jon Portnoy
avenj/irc.freenode.net

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Re: [gentoo-dev] Warning about -march=k6*

[Brad Laue]

Mike Frysinger wrote:

> the bug can be found at http://bugs.gentoo.org/show_bug.cgi?id=24379
> i just want to know if anyone out there has had *success* with this flag ...

I'm using a K6-2 3D with the following attributes:

processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 5
model           : 8
model name      : AMD-K6(tm) 3D processor
stepping        : 12

I'm using -march=k6-2 without problems.

Brad


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