Re: [gentoo-user] CFLAGS for both AMD64 and Intel?

[Mike Gilbert <floppym@gentoo.org>]

On Sun, Dec 3, 2017 at 2:23 AM, Manuel McLure <manuel@mclure.org> wrote:
> Here's the situation. I have a system that's been running for many years
> with an Athlon 5050e processor. The system is built with
>
> CFLAGS="-march=k8-sse3 -O2 -pipe -msse3"
> CPU_FLAGS_X86="3dnow 3dnowext mmx mmxext sse sse2 sse3"
>
> I have the possibility of upgrading the system to a first-generation Intel
> Core i5 which should give a nice speed boost, but of course the Intel chip
> doesn't understand 3dnow or 3dnowext, so I'll have to do a system rebuild
> before I switch out the motherboard/processor. It seems pretty obvious that
> I have to take "3dnow 3dnowext" out of CPU_FLAGS_X86, but what CFLAGS would
> be recommended for a system that will still run with the AMD processor but
> won't fall over when I switch to the Intel processor? Once I have the Intel
> in place I can rebuild with options more suited for that chip, but I want to
> make sure I don't end up in a catch-22 situation.

I would go with just "-O2 -pipe" for maximum compatibility. Remove the
-march option altogether, and add it back once the system is running
on the Intel chip.