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Re: What to do with package that wants to use sse?



2009/10/31 Bruno Wolff III <bruno wolff to>:
> I am working on packaging pagedgeometry and I noticed that when building
> on gcc it passes -msse which I am guessing says to use sse instructions.
> I think that even in F12 we can't assume these instructions are available.
> The package may gain a lot of benefit from using those instructions.
> (I haven't tested that yet as I am still pretty early in the process.)
> Is there some relatively standard way to handle something like this?
-msse is fine for x86_64 and ia64  by default (but not for non-intel arches).
The only way to have sse enabled on ix86 is for a library to be built
twice, the provides the sse version in %{_libdir}/sse2. The linker
will then enable the appropriate library at runtime.
(note that only sse2 wrap exists - not sse{,3,4},atom,i7 )
That's not possible when the optimized code is within a binary.

Now I would really like to promote a comprehensive understanding of that policy.
Because sometimes the application requirements are beyond the entry
point of  sse. There is a package, outside of the Fedora collection,
that might be compiled with sse on ix86.
There is generic code for it, so it will probably works on s390 or
sparc, along with non-sse ix86. But mixing real time multimedia
streams for deejay will then became harder if not sse enabled. So the
application requirement was to be higher than if the app wasn't
compiled with sse.

I also have another case for a package which is an image renderer for blender.
Using such app on computer that doesn't have sse is really a miss
understanding of what your computer is better used at.

Nicolas (kwizart)


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