Re: [PATCH] Re-implemented i586 asm AES (updated)

[Kasper Sandberg]

i dont know anything at all about this, but wouldnt it be possible to
optimize it even more, if there were a version for each cpu, like one
for athlon-xp and one for p4?

On Fri, 2004-08-06 at 09:43 -0700, Linus Torvalds wrote:
> 
> On Fri, 6 Aug 2004, Andi Kleen wrote:
> > 
> > You could use .altinstructions to patch a jump in at runtime
> > based on CPU capabilities. Assuming MMX is really faster of course.
> 
> I seriously doubt that the MMX code could be faster.
> 
> The only MMX code in the original was saving some integer contents to a 
> scratch MMX register rather than saving to memory. There's _no_ way that 
> is faster, especially since in the kernel it would require us much extra 
> work to first check that the FP context is safed. Even _without_ the extra 
> work I simply cannot imagine that a "movd reg,mmx" is faster than a plain 
> "movl reg,stackslot". 
> 
> 		Linus
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