Wednesday, 5 March 2014

Re: Changing default CFLAGS on i386

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

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