lmw and stmw instructions not used copy functions

[Joakim Tjernlund]

> Joakim Tjernlund wrote:
>
> > I noticed that the lmw and stmw instructions are not used in copy_page(), clear_page() etc.
> > Aren't these instructions faster than a bunch of lwz/stw?
>
> Motorola doesn't guarantee these are any faster, and most documentation indicates
> they are likely to be slower.  If you look closely, you may notice that not
> too many places can utilize these instructions, and often the load or store
> is done to take advantages of some pipeline optimizations with comparisons
> to values in well known registers.

Did some crude benchmarking using clear_page() as my test function.
I made a version that uses stmw and compared that with the orginal
clear_page().

Result:
 The stmw version was much slower. When I increased the number of
 bytes to copy per loop to 32, it became as fast as the orginal.

 Jocke


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