optimising for athlon64

[Hamie]

Hi.

I have a setup for xorg that I use on my laptop for passing optimisation 
flags to gcc for building an optimised version of xorg 6.8.2 for a 
pentium-m, but when I set the same flags in host.def to build for an 
athlon64, the parameters get ignored & the defaults are used...

What should I set in host.def for an athlon64 build? The stuff I put 
into it for my laptop is

#define DefaultGcc2i386Opt -O3 -march=pentium3 -msse2 -mmmx -msse 
-mfpmath=sse,387 -maccumulate-outgoing-args -mno-align-stringops 
-fomit-frame-pointer -ffast-math -funroll-all-loops -fsched-spec-load 
-fprefetch-loop-arrays -ftracer -fmove-all-movables --param 
max-gcse-passes=4

But defining

#define DefaultGcc2i386Opt -O3 -march=athlon64 doesn't get used... But 
there's no docs I can find to say what the equiv is for gentoo on an 
amd64... DefaultGcc2amd64opt? DefaultGcc2k8opt? Or somethign else? I did 
try a few things, but the closest I got was gcc using -O2 and -O3 and 
what looked like several conflicting flags at the same time...

TIA

Hamish