[maemo-developers] [maemo-developers] Optimized memory copying functions for Nokia 770

[From: Siarhei Siamashka]

Tomas Frydrych wrote:

>> Like Dirk already replied, the implementation is in macros in the .h
>> file.
> 
> I see. That makes the comparison with memcpy somewhat unfair, since you
> are not actually providing replacement functions, so this would only
> make difference for -O3 type optimatisation (where you trade speed for
> size); it would be interesting to see what the performance difference is
> if you add the C prologue and epilogue.#

Memory bandwidth benchmarking is done on 2MB memory block, so prologue
and epilogue code does not introduce any noticeable difference.

I did not pay much attention on optimizing prologue/epilogue code yet,
it should make difference on smaller buffer sizes, but it is in a TODO
list.

> BTW, you can instruct gcc to use inlined assembler version of its memcpy
> and friends as well, I think -O3 includes this, but if I read
> bits/string.h correctly in my sbox, there are no such inlined functions
> on the arm though, so there is certainly value in doing this.

Well you got the source, so you can do your own benchmarks either with
-O2 or -O3 or even -O9 and post them here :)