Compiler Flags problem with core2 CPU

illoai at illoai at
Wed Mar 3 04:57:25 UTC 2010

On 28 February 2010 07:38, Aaron Lewis <aaron.lewis1989 at> 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 ?

Just so you know -O20 is the same as saying -O3.

I don't think everything in base is safe for -ffast-math,
but setting it in make.conf will surely test that.

-O2 is already turned on almost everywhere by default,
so also, I believe, with -fomit-frame-pointer.  The only
thing I've ever found to be remotely useful to change
was -Os on an old, space-restricted machine.  But
last time I tried -Os on amd64 it broke.  Badly.


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