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From: Nikos Chantziaras <realnc@gmail.com>
Subject: [gentoo-user] Re: CFLAGs for kernel compilation
Date: Sat, 02 May 2015 15:06:19 +0300
Organization: Lucas Barks
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On 02/05/15 14:37, Volker Armin Hemmann wrote:
> Am 02.05.2015 um 13:25 schrieb Nikos Chantziaras:
>>>>
>>>> The kernel uses -O2 and several -march variants (e.g. -march=core2).
>>>> Several other options are used to prevent GCC from generating
>>>> unsuitable code.
>>>>
>>>> Specifying another -march variant does not affect the optimizer
>>>> though. It only affects the code generator. If you don't modify the
>>>> other CFLAGS and only change -march, you will not get FP instructions
>>>> unless you use FP in the code.
>>>
>>> http://www.agner.org/optimize/calling_conventions.pdf
>>
>> Not sure what you're trying to say.
>>
>
> that simd is not save in kernel if not carefully guarded.
>
> Really people, just don't fuck around with the cflags.

I still fail to see the relevance. Unless you mean using a different -O 
level. In that case, yes. You shouldn't. But I was talking about -march.