i686 build of Fedora Core

[H. Peter Anvin]

Alan Cox wrote:
> On Wed, Jul 28, 2004 at 09:50:11PM +0200, Angelo wrote:
> 
>>Sure, but what can do optimization without using the *hardcoded* cpu
>>instructions inserted in the architecture ?
> 
> 
> 90% of the optimisation work is scheduling instructions - picking which one
> to use and how to lay them out. The actual instructions added by 486 and
> later are not much use. Essentially it adds
> 
> 	bswap		- 	which nothing uses except kernel net code
> 	cmov		- 	which is now slower than avoiding it
> 
> and a collection of locked operations that are great for threading and
> are a big reason glibc has a i686 version since it contains all the pthreads
> stuff.
> 

Actually, the big ones are MMX/MMXEXT/SSE-{1,2,3}.  In particular sse2, since 
sse2 can be used for all floating-point (-msse2 -mfpmath=sse), and on some 
CPUs it can be 2x or more faster than using x87.

	-hpa