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


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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