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List:       freebsd-questions
Subject:    Re: Compiler Flags problem with core2 CPU
From:       Paul B Mahol <onemda () gmail ! com>
Date:       2010-02-28 14:39:58
Message-ID: 3a142e751002280639rdb25d3ajd688caecfedfacbb () mail ! gmail ! com
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Do not top post.

On 2/28/10, Aaron Lewis <aaron.lewis1989@gmail.com> wrote:
> Really ? It's bad to use custom flags to compile kernel , why do you
> think so ?
> I'd like to know more about this : )

Use google.
>
> So setting optimize compiler flags is only useful for userland stuff ?
>
> Paul B Mahol wrote:
>> On 2/28/10, Aaron Lewis <aaron.lewis1989@gmail.com> wrote:
>>
>>> Hi,
>>>     I gonna recompile kernel for my core2 CPU , so i'd like to pass some
>>> flags to gcc.
>>>     Kinds of "-march=core2" , i tried to modify /etc/make.conf
>>>
>>>     e.g    CFLAGS += -march=core2 -O20 -ffast-math -mfpmath=sse
>>>     But it fails .. bad arch switch , core2 cpu is not supported ?
>>>
>> It is bad idea to compile kernel with custom flags. And gcc in FreeBSD
>> doesn't know about core2,
>> use 'native' if you must.
>>
>>
>>>     And is that useful to let gcc select cpu specified asm code ?
>>>
>>
>> Only for some userland stuff like openssl.
>>
>
>
> --
> Best Regards,
> Aaron Lewis - PGP: 0xA476D2E9
> irc: A4r0n on freenode
>
>
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