[gentoo-amd64] Assembler USE flag unmaskings

[Simon Stelling]

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.

--
Kind Regards,

Simon Stelling
Gentoo/AMD64 developer
--
gentoo-amd64@gentoo.org mailing list