Compiler Flags problem with core2 CPU

[Giorgos Keramidas]

On Sun, 28 Feb 2010 20:38:45 +0800, Aaron Lewis <aaron.lewis1989 at 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 ?
>
>    And is that useful to let gcc select cpu specified asm code ?

See the section "3.17.14 Intel 386 and AMD x86-64 Options" in the gcc
Info manual.  It contains a full list of the supported CPU-TYPE values
for the -mtune=CPU-TYPE option.  The -march=CPU-TYPE option accepts the
same CPU types:

    `-march=CPU-TYPE'
         Generate instructions for the machine type CPU-TYPE.  The
         choices for CPU-TYPE are the same as for `-mtune'.  Moreover,
         specifying `-march=CPU-TYPE' implies `-mtune=CPU-TYPE'.