Gentoo Archives: gentoo-user

From: Mike Gilbert <floppym@g.o>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] CFLAGS for both AMD64 and Intel?
Date: Sun, 03 Dec 2017 07:40:39
Message-Id: CAJ0EP42CXzaoVWG50J+An_YrxJMaN6fjiaZ62dLhW71VdV0RAQ@mail.gmail.com
In Reply to: [gentoo-user] CFLAGS for both AMD64 and Intel? by Manuel McLure
On Sun, Dec 3, 2017 at 2:23 AM, Manuel McLure <manuel@××××××.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.