[gentoo-dev] auto selection of optimal gcc architecture settings

[gentoo-dev] auto selection of optimal gcc architecture settings

[Padraig Brady]

Eric Ball wrote:
> On Sat, 26 Apr 2003 12:57 am, Padraig Brady wrote:
> 
>>Hi,
>>
>>I've been testing http://www.pixelbeat.org/scripts/gcccpuopt
>>over the last while with good results. Essentially it's
>>a Linux specific script that only helps on x86 at present
>>but can be updated to other architectures easily.
>>
>>It would be beneficial IMHO for gentoo to run it at
>>installation time and update /etc/make.conf appropriately?
>>
>>thanks,
>>Pádraig.
>
> It seems nifty.
> I'd recommend you submit it in Bugzilla at bugs.gentoo.org or in the 
> gentoo-dev list as the powers-that-be might not read this list.


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Re: [gentoo-dev] auto selection of optimal gcc architecture settings

[Mark Gordon]

On Mon, 28 Apr 2003 10:18:54 +0100
Padraig Brady <padraig.brady@corvil.com> wrote:

> Eric Ball wrote:
> > On Sat, 26 Apr 2003 12:57 am, Padraig Brady wrote:
> > 
> >>Hi,
> >>
> >>I've been testing http://www.pixelbeat.org/scripts/gcccpuopt
> >>over the last while with good results. Essentially it's
> >>a Linux specific script that only helps on x86 at present
> >>but can be updated to other architectures easily.
> >>
> >>It would be beneficial IMHO for gentoo to run it at
> >>installation time and update /etc/make.conf appropriately?
> >>
> >>thanks,
> >>Pádraig.
> >
> > It seems nifty.
> > I'd recommend you submit it in Bugzilla at bugs.gentoo.org or in the
> > 
> > gentoo-dev list as the powers-that-be might not read this list.

It needs extending even for the x86 compatible world.

markg@brenda markg $ ./gcccpuopt 
 -march=pentium2 -mmmx
markg@brenda markg $ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineTMx86
cpu family      : 6
model           : 4
model name      : Transmeta(tm) Crusoe(tm) Processor TM5600
stepping        : 3
cpu MHz         : 661.674
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu vme de pse tsc msr cx8 sep cmov mmx longrun lrti
bogomips        : 1307.44

As far as I'm aware the Crusoe emulates a Pentium, not a PII (I've not
seen anything definitive stating otherwise). If someone can confirm that
I'm wrong or tell me a safe way to test then I'll investigate further.

Any other strange processors out there that might have problems?
-- 
Mark Gordon
Paid to be a Geek & a Senior Software Developer
Currently looking for a new job commutable from Slough, Berks, U.K.
Although my email address says spamtrap, it is real and I read it.

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Re: [gentoo-dev] auto selection of optimal gcc architecture settings

[Paul de Vrieze]

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On Monday 28 April 2003 15:30, Mark Gordon wrote:
> On Mon, 28 Apr 2003 10:18:54 +0100
>
> Any other strange processors out there that might have problems?

While I didn't check the program, I think the program could very well just try 
to compile a trivial test program with the flags and check whether it runs 
well. While this is not bulletproof it should get most errors.

Paul

-- 
Paul de Vrieze
Researcher
Mail: pauldv@cs.kun.nl
Homepage: http://www.devrieze.net

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Re: [gentoo-dev] auto selection of optimal gcc architecture settings

[Padraig Brady]

Paul de Vrieze wrote:
> On Monday 28 April 2003 15:30, Mark Gordon wrote:
> 
>>On Mon, 28 Apr 2003 10:18:54 +0100
>>
>>Any other strange processors out there that might have problems?
> 
> 
> While I didn't check the program, I think the program could very well just try 
> to compile a trivial test program with the flags and check whether it runs 
> well. While this is not bulletproof it should get most errors.

this would be quite useless for testing generated code.
It's only useful for testing compiler options and
I do this instead by explicitly using the gcc version.

Pádraig.


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Re: [gentoo-dev] auto selection of optimal gcc architecture settings

[Padraig Brady]

Mark Gordon wrote:
> On Mon, 28 Apr 2003 10:18:54 +0100
> Padraig Brady <padraig.brady@corvil.com> wrote:
> 
> 
>>Eric Ball wrote:
>>
>>>On Sat, 26 Apr 2003 12:57 am, Padraig Brady wrote:
>>>
>>>
>>>>Hi,
>>>>
>>>>I've been testing http://www.pixelbeat.org/scripts/gcccpuopt
>>>>over the last while with good results. Essentially it's
>>>>a Linux specific script that only helps on x86 at present
>>>>but can be updated to other architectures easily.
>>>>
>>>>It would be beneficial IMHO for gentoo to run it at
>>>>installation time and update /etc/make.conf appropriately?
>>>>
>>>>thanks,
>>>>Pádraig.
>>>
>>>It seems nifty.
>>>I'd recommend you submit it in Bugzilla at bugs.gentoo.org or in the
>>>
>>>gentoo-dev list as the powers-that-be might not read this list.
> 
> 
> It needs extending even for the x86 compatible world.
> 
> markg@brenda markg $ ./gcccpuopt 
>  -march=pentium2 -mmmx
> markg@brenda markg $ cat /proc/cpuinfo
> processor       : 0
> vendor_id       : GenuineTMx86
> cpu family      : 6
> model           : 4
> model name      : Transmeta(tm) Crusoe(tm) Processor TM5600
>
> As far as I'm aware the Crusoe emulates a Pentium, not a PII (I've not
> seen anything definitive stating otherwise).

Nah, cpu family = 6 is quite definitive.
This is from /usr/src/linux-2.4/arch/i386/Makefile
ifdef CONFIG_MCRUSOE
CFLAGS += -march=i686
endif

> Any other strange processors out there that might have problems?

the only exception is a gcc bug where is assumes 686 has cmov,
and this is handled explicitly.

Pádraig.


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Re: [gentoo-dev] auto selection of optimal gcc architecture settings

[Mark Gordon]

On Mon, 28 Apr 2003 14:40:10 +0100
Padraig Brady <padraig.brady@corvil.com> wrote:

> Mark Gordon wrote:
> > On Mon, 28 Apr 2003 10:18:54 +0100
> > Padraig Brady <padraig.brady@corvil.com> wrote:
> > 
> > 
> >>Eric Ball wrote:
> >>
> >>>On Sat, 26 Apr 2003 12:57 am, Padraig Brady wrote:
> >>>
> >>>
> >>>>Hi,
> >>>>
> >>>>I've been testing http://www.pixelbeat.org/scripts/gcccpuopt
> >>>>over the last while with good results. Essentially it's
> >>>>a Linux specific script that only helps on x86 at present
> >>>>but can be updated to other architectures easily.
> >>>>
> >>>>It would be beneficial IMHO for gentoo to run it at
> >>>>installation time and update /etc/make.conf appropriately?
> >>>>
> >>>>thanks,
> >>>>Pádraig.
> >>>
> >>>It seems nifty.
> >>>I'd recommend you submit it in Bugzilla at bugs.gentoo.org or in
> >the>>
> >>>gentoo-dev list as the powers-that-be might not read this list.
> > 
> > 
> > It needs extending even for the x86 compatible world.
> > 
> > markg@brenda markg $ ./gcccpuopt 
> >  -march=pentium2 -mmmx
> > markg@brenda markg $ cat /proc/cpuinfo
> > processor       : 0
> > vendor_id       : GenuineTMx86
> > cpu family      : 6
> > model           : 4
> > model name      : Transmeta(tm) Crusoe(tm) Processor TM5600
> >
> > As far as I'm aware the Crusoe emulates a Pentium, not a PII (I've
> > not seen anything definitive stating otherwise).
> 
> Nah, cpu family = 6 is quite definitive.
> This is from /usr/src/linux-2.4/arch/i386/Makefile
> ifdef CONFIG_MCRUSOE
> CFLAGS += -march=i686
> endif
> 
> > Any other strange processors out there that might have problems?
> 
> the only exception is a gcc bug where is assumes 686 has cmov,
> and this is handled explicitly.

OK, I'll up my make.conf to -march=pentium2 and recompile a few things
starting with xfree86. If I find any problems I'll be back.
-- 
Mark Gordon
Paid to be a Geek & a Senior Software Developer
Currently looking for a new job commutable from Slough, Berks, U.K.
Although my email address says spamtrap, it is real and I read it.

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Re: [gentoo-dev] auto selection of optimal gcc architecture settings

[Chris PeBenito]

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On Mon, 2003-04-28 at 08:30, Mark Gordon wrote:
[cut]
> > >>I've been testing http://www.pixelbeat.org/scripts/gcccpuopt
> > >>over the last while with good results. Essentially it's
> > >>a Linux specific script that only helps on x86 at present
> > >>but can be updated to other architectures easily.
[cut]
> > >>It would be beneficial IMHO for gentoo to run it at
> > >>installation time and update /etc/make.conf appropriately?
[cut]
> It needs extending even for the x86 compatible world.
> 
> markg@brenda markg $ ./gcccpuopt 
>  -march=pentium2 -mmmx
[cut]

I think this would probably be more useful if it dumped out the CHOST
line in addition to the optimizations.  This would help with people that
have the more uncommon processors to set the correct CHOST.  I seen more
than a few times K6* users have had CHOST="i686-pc-linux-gnu", when it
should be i586-pc-linux-gnu.

so it'd print this for a K6-2:

$ ./gcccpuopt
CHOST="i586-pc-linux-gnu"
CFLAGS="-march=k6-2"


So it could easily be pasted into make.conf.  (-mmmx is redundant)

-- 
Chris PeBenito
<pebenito@gentoo.org>
Developer, Gentoo Linux
Hardened Gentoo Project
 
"Engineering does not require science. Science helps
a lot, but people built perfectly good brick walls
long before they knew why cement works."-Alan Cox

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Re: [gentoo-dev] auto selection of optimal gcc architecture settings

[Padraig Brady]

Chris PeBenito wrote:
> On Mon, 2003-04-28 at 08:30, Mark Gordon wrote:
> [cut]
> 
>>>>>I've been testing http://www.pixelbeat.org/scripts/gcccpuopt
>>>>>over the last while with good results. Essentially it's
>>>>>a Linux specific script that only helps on x86 at present
>>>>>but can be updated to other architectures easily.
> 
> [cut]
> 
>>>>>It would be beneficial IMHO for gentoo to run it at
>>>>>installation time and update /etc/make.conf appropriately?
> 
> [cut]
> 
>>It needs extending even for the x86 compatible world.
>>
>>markg@brenda markg $ ./gcccpuopt 
>> -march=pentium2 -mmmx
> 
> [cut]
> 
> I think this would probably be more useful if it dumped out the CHOST
> line in addition to the optimizations.  This would help with people that
> have the more uncommon processors to set the correct CHOST.  I seen more
> than a few times K6* users have had CHOST="i686-pc-linux-gnu", when it
> should be i586-pc-linux-gnu.
> 
> so it'd print this for a K6-2:
> 
> $ ./gcccpuopt
> CHOST="i586-pc-linux-gnu"
> CFLAGS="-march=k6-2"
> 
> So it could easily be pasted into make.conf.  (-mmmx is redundant)

I would do that as an explicit option as it's handy (outside
the gentoo context) to do things like:
   export CFLAGS="$CFLAGS `gcccpuopt` -O3 -pipe -fomit-frame-pointer"

Other useful options would be KERNEL which would output the
appropriate kernel config (e.g. CONFIG_MK7), and GCCVER which would
specify which gcc to use rather than the installed one.

so in summary options to gcccpuopt should be:
[-CFLAGS | -CHOST | -KERNEL] [-GCCVER]

Pádraig.


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