Re: [gentoo-dev] Replacing cpu-feature USE flags

["Diego 'Flameeyes' Pettenò" <flameeyes@gentoo.org>]

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On Thursday 06 July 2006 19:51, Ciaran McCreesh wrote:
> And for a single compile?
I always leave the two of them in sync, even C++ apps might have parts 
building CFLAGS. In case you know you're going to use only C++ is not 
difficult to use

CFLAGS=${CXXFLAGS} has_cpuset 3dnow

don't you think?

> And your assumption would be wrong. I can assure you that relying upon
> -march doing anything sensible with __MAGIC__ is entirely unsafe. Go
> and look at the VIS handling if you want a perfect example.
Okay, maybe VIS handling is broken. But we can rely pretty safely on x86, 
amd64 and PPC gcc to know the table of arches and extensions supported. 
Remember that I asked to talk with SPARC team for VIS just because I only 
know about the other three arches.

> No no. Where "regain control" means the user has to screw around with
> nasty hacks and pray, rather than setting a well defined, specific
> variable.
Find me a reason to do that, a part for broken MMX code that should be 
disabled on the ebuild itself already.

> Uh. USE flags are available at DEPEND time.
If you talk about the nasm dependency, then it is rare, most of the MMX 
support is inline in C sources anyway.

> And at the metadata phase?
Should be already transparent or something is strange. nasm is simpler to add 
the dependency for x86, there is really few people not enabling mmx already. 
Yes it is a bit of regression, but for a small percentage of users, while 
there's more safety for many other people.

> Er. No. Not at all. The __MAGIC__ isn't guaranteed. Quite the contrary.
This ain't no magic. The magic is in the _CODE_ that GCC creates, but not in 
the _DEFINES_ that GCC emits.

> You're trying to guess what the user wants based upon hairy magic,
No, about their chosen architecture.

> rather than doing what the user says (aren't you always yelling at
> upstreams for doing that?)
The user asks for athlon64 support? They get athlon64 (mmx, 3dnow, 3dnowex, 
sse, sse2)
The user asks for G3 support? They get G3 (nothing)
The user asks for Pentium4 support? They get what they want (mmx, sse, sse2, 
sse3 in case)

-- 
Diego "Flameeyes" Pettenò - http://farragut.flameeyes.is-a-geek.org/
Gentoo/Alt lead, Gentoo/FreeBSD, Video, AMD64, Sound, PAM, KDE

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