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Date: Tue, 21 Apr 2009 10:20:34 +1000
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Subject: [gentoo-user] gcc and -match=native
From: Beau Henderson <beau@thehenderson.com>
To: gentoo-user@lists.gentoo.org
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G'day,

I was playing around with a few non-essential packages the other day
using -march=native -v on my core2 duo ( configured with
CHOST="i686-pc-linux-gnu" ) and noticed that GCC set the -march=core2
rather than what is typically suggested on the 3rd party wiki ( which
is to use prescott ). According to the GCC docs, the core2 option
includes instructions for x86_64 but would this be ultimately ignored
seeing as the CHOST is set to i686 or would these instructions bloat
the  resulting binaries or could they result in conflicts of some sort
down the line ?

on my Athlon64 it uses ( the 3rd party wiki recommended ) k8-sse3 but
I did notice that the option -mtune=k8 ( no -sse3 ) is set.

I'm a little confused as to how the native option selects the best
fit. I know that -march=native is not "supported". I'm just rather
interested in figuring out why these options are selected and if I'm
better off with them in place.

Note, that there have been no issues *noticed* with final results.

-- 
Beau Dylan Henderson

"No human being should be denied the fundamental right to educate
themselves or indulge their curiosities. To deny any person the right
to do so, for whatever reason, is nothing more than the safeguarding
of ignorance to ensure that enlightenment does not become a threat.
For nothing in this world is more dangerous than an open mind." --
Matthew Good