Re: [gentoo-amd64] Assembler USE flag unmaskings

[Conway S. Smith]

On Tue, 24 Oct 2006 15:49:31 +0200
Simon Stelling <blubb@g.o> wrote:
> Hi all,
>
> Back in May 2005 we made the decision to not use the assembler USE
> flags because AMD64 was not affected by the "lots of sub-arches"
> problem and instead just enable SIMD code where possible. As a result
> of this, the 3dnow, 3dnowext, mmx, mmxext, sse and sse2 USE flags got
> masked. This decision turned out to be not the best. Intel's EM64T
> processors don't support 3dnow and 3dnowext, there are AMD64s with
> and without SSE3 support. The "one size fits all" idea simply is no
> longer true. Starting with portage 2.1.2_pre3-r4, there is support to
> force USE flags on or off on a per-package basis. This means less
> ebuild hackery for us, and so I went and checked the ~50 packages
> with mentioned USE flags.
>
> The result is that the assembler USE flags convey their actual
> meaning again IF AND ONLY IF you use >=portage-2.1.2_pre3-r4. I
> suggest you to stick at least "mmx mmxext sse sse2" into your USE
> flags, as this is the common denominator of all AMD64s. If your
> processor supports it, 3dnow and 3dnowext might be worth adding too.
>
> *For users of portage versions prior to 2.1.2_pre3-r4 nothing
> changes*, but I'd still recommend to add the USE flags. They will
> become effective as soon as you upgrade portage.
>
> In a nutshell:
>
> 1. add "mmx mmxext sse sse2" to your USE flags
> 2. emerge -u portage
> 3. emerge -NuD world
>
> If you experience any build failures, please file a bug report on
> http://bugs.gentoo.org/
>
> Thank you for your attention, the team wishes you a convenient flight.
>

We should be able to cat /proc/cpuinfo to find out which ones our CPUs
support, right?  Except IIRC SSE3 is called something else in
/proc/cpuinfo... pni, is it?  Any other caveats we should be aware of?


Conway S. Smith