Re: [OT] Proper gcc -march for Athlon/Duron CPU?
On Tue, Apr 02, 2002 at 08:43:46AM -0500, Thomas J. Hamman wrote:
> What is the proper -march to use when compiling with gcc and optimizing
> for a Duron or Athlon CPU? What man page lists the available options?
> I search for 'march' in gcc's man page finds nothing.
It's in the man page for gcc-3.0 in testing/unstable:
-mcpu=cpu-type
Assume the defaults for the machine type cpu-type when
scheduling instructions. The choices for cpu-type are
i386, i486, i586, i686, pentium, pentiumpro, k6, and
athlon
While picking a specific cpu-type will schedule things
appropriately for that particular chip, the compiler
will not generate any code that does not run on the
i386 without the -march=cpu-type option being used.
i586 is equivalent to pentium and i686 is equivalent
to pentiumpro. k6 is the AMD chip as opposed to the
Intel ones.
-march=cpu-type
Generate instructions for the machine type cpu-type.
The choices for cpu-type are the same as for -mcpu.
Moreover, specifying -march=cpu-type implies
-mcpu=cpu-type.
For gcc-2.95, you'll have to look at the info documentation. Use Ctrl-S
to search through all nodes - '/' only searches through the current
node, which isn't terribly useful in this case.
> So, I tried googling and several documents suggest '-march=athlon', but
> that doesn't work for me (I've tried in gcc 2.95.4 in sid and 2.95.3 in
> an LFS installation). So I've been using -march=k6 instead; but, then I
> noticed in my latest kernel recompilation that it was compiling with
> i686 when I chose Athlon/Duron in the config. Bah.
You'll need to have gcc-3.0 installed and CC set to that before the
kernel Makefile will use -march=athlon. I'm not sure that gcc-3.0
generates reliable kernels yet, though.
--
Colin Watson [cjwatson@flatline.org.uk]
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