[PLUG] code optimization with gcc

[Paul Heinlein]

On Tue, 4 Jun 2002, Rich Shepard wrote:

> On Tue, 4 Jun 2002, Carla Schroder wrote:
> 
> > Any gcc gurus out there? I'm going around in circles on targeting
> > specific CPUs. For example, optimize for k6 or i686 instead of
> > i386. Is this a compiler option? make/config option? Do you need
> > to wade through manufacturer specs and tailor your code itself?
> 
>   From info gcc:
> 
>               i386 Options
>               -m486 -mno-486 -msoft-float -mno-fp-ret-in-387
> Could probably do -m686, too.
> 
>   Most of the time there's a configure option that's accessed by
> specifying --target=ix86.

Ah, here's the rub. The optimization switches have changed slightly
between gcc 2.x and 3.x (the uniquely Red Hat 2.96 release is a 3.x in
disguise).

The -m486 option has been retired. The new way of doing things is, as 
Felix mentioned, -march=<whatever> or, to a lesser extent, 
-mcpu=<whatever>.

I haven't really looked to see what changes the recently released gcc 
3.1 introduced.

--Paul Heinlein <heinlein at attbi.com>