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Date: Fri, 26 Oct 2007 11:41:18 +0100
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To: Adrian Bunk <bunk@kernel.org>
CC: Michael Lothian <mike@fireburn.co.uk>, linux-kernel@vger.kernel.org
Subject: Re: Possibility of adding -march=native to x86
References: <0EC33A59AA72084CA28B83816B40929F02682BB3@REEDXCLSXM01V03.rbsres01.net> <fc94aae90710251133j4bada173h6298242ece586b61@mail.gmail.com> <20071025185022.GP30533@stusta.de> <fc94aae90710251209n74e2cffbj2e3cdd321f36da0d@mail.gmail.com> <20071025191723.GQ30533@stusta.de> <fc94aae90710251232m117421e7ref3e5a6270ff25d2@mail.gmail.com> <20071025195020.GS30533@stusta.de> <fc94aae90710251312w2eba46e8h5d4f8715ad0e91b6@mail.gmail.com> <20071025202031.GU30533@stusta.de>
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Adrian Bunk wrote:
> On Thu, Oct 25, 2007 at 09:12:45PM +0100, Michael Lothian wrote:
>>> The MPENTIUM4 option does not only set -march=pentium4, it also enables
>>> several other options in arch/i386/Kconfig.cpu resulting in better
>>> performance.
>> How about an autodetect to set the right options here too using cpuid?
>>
>> With a warning of course that the code produced will be specifically
>> for the native cpu that it's compiled on.
> 
> If you don't know or can figure out yourself the CPU you have, you'd 
> better not compile your own kernel...

There also is the added variable of what your version of gcc supports.
The kernel gcc options would have to be the highest common factor.
See also http://www.pixelbeat.org/scripts/gcccpuopt

Pádraig.