maxim wexler writes:
> --- On Thu, 5/21/09, Alex Schuster <wo...@wonkology.org> wrote:
> > But it suggests using -march=k8 - isn't that a 64-bit-only
> > thing? I'm not
>
> For an 900A w/intel Atom?
No, I have an AMD Athlon(tm) Dual Core Processor 4850e.
> This is what I get:
>
> Warning: Your compiler supports the -march=native option which you may
> prefer Warning: Newer versions of GCC better support your CPU with
> -march=atom -march=core2 -mtune=pentium -mfpmath=sse.
>
> Now I'm confused. It says *my* compiler supports -march=native. Then it
> says "Newer versions". Isn't v4.3.2 new? It was from a new pkg about a
> month ago. Is it giving me a choice here? Can I really declare two -march
> variables? What about mtune and mfpath, are they meant to be "instead of"
> or "in addition to"?
I'm also confused. Multiple -march options make no sense I believe, as does
specifying both -march and -mtune, as -mtune is implied by -march. And the
docs say in the section about
-mfpmath=sse:
For the i386 compiler, you need to use `-march=CPU-TYPE',
`-msse' or `-msse2' switches to enable SSE extensions and
make this option effective. For the x86-64 compiler, these
extensions are enabled by default.
So it seems to me that -mfpmath does not need to be set.
Well, I'd just use -march=native, unless when using distcc. If so, Daniel's
tip about 'gcc -Q --help=target -march=native' will give you the exact
options to use.
Wonko
