amd64 arch and sse optimization

[Jaromír Mikeš]

2014-02-03 Felipe Sateler <fsateler at debian.org>:

> On Mon, Feb 3, 2014 at 1:07 PM, Reinhard Tartler <siretart at gmail.com>
> wrote:
> >
> > Please note that Jaromir proposed to use the following flags:
> >
> > ifeq ($(DEB_HOST_ARCH_CPU),amd64)
> > CFLAGS += -msse -msse2 -mfpmath=sse
> > endif
> >
> >
> > None of them fall in the "mtune" category, that is, none of them are
> > "safe" to use without further precaution measures!
>
> Hmm, I'm now not sure if they help and are harmless. If sse is
> required by the amd64 spec, then gcc should enable it by default (in
> -O2?). I can't say if the previous is true. Perhaps we should take
> this to a more knowledgeable audience? debian-devel or debian-gcc
> lists would be better, perhaps.
>
> The docs do suggest they are redundant in amd64[1]:
>
> [1]
> http://gcc.gnu.org/onlinedocs/gcc-4.4.2/gcc/i386-and-x86_002d64-Options.html
>

Please go ahead ... It looks like debian-devel would be right place.
It sound strange that sse is redundant in amd64.
Some time ago I played with sse optimization flags and packages build with
and without them
got 30-40% difference in performance in my cases.

Would be great to make it clear.

mira
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