Changing default CFLAGS on i386

[Adam Conrad]

On Wed, Mar 05, 2014 at 10:16:13AM -0500, Ryan Lortie wrote:
> 
>  1) Use -fexcess-precision=standard and suffer the performance hit in
>  the name of correctness

I wouldn't be entirely against this option, if the performance hit is
measurably not awful in general purpose usage.

>  2) Bite the bullet and use -march=pentium4 -mfpmath=sse (which is what
>  happens for 64bit)

This cuts out support for a lot of i686 processors we currently run on
today, and I'm not sure that's something we want to do.  That said, we
also dropped support for non-PAE in our kernels, and the intersection
of CPUs with PAE and no SSE2 is certainly a smaller set.  I'd still
like to see a comprehensive list (think outside of just Intel here, to
other x86 kit) of which CPUs we'd be dropping support for before we
even considered this.

... Adam