Re: RFC: Fedora Extras shipping ix86 optimized rpms?

[Jakub Jelinek <jakub redhat com>]

On Tue, Aug 31, 2004 at 05:38:31PM +0200, Matthias Saou wrote:
> Is then having the same library twice, the regular one in /usr/lib and the
> SSE2 optimized one in /usr/lib/sse2, expected to "just work" at runtime? If

Yes, it will just work.
Both the dynamic linker and ldconfig know how to handle it.

> so, I didn't know the existence of this, and will definitely look into it.
> What about MMX? Should one just simplify with SSE vs. non-SSE instead and
> put (non runtime) MMX optimized libs there too?

ATM sse2 is the only "important" feature ld.so on IA-32 handles.
Previously it used to be mmx, but as every added feature slows down
library loading when not using ld.so.cache (e.g. when LD_LIBRARY_PATH
is used or DT_RPATH; every feature doubles the number of stat'ed
directories before the non-existing directory cache is filled),
it was just changed to sse2 instead of adding sse2 to mmx.
SSE2 was chosen because you can get quite a big speedup already
by recompiling with -msse2 -mfpmath=sse.

	Jakub