Re: [LAD] GCC Vector extensions

Le 21 juil. 2011 à 20:15, Maurizio De Cecco a écrit :

> On Thursday21/7/11 2:22 PM, Stéphane Letz wrote:
>> Or you can use LLVM to *directly* generate vector code, as in the following example, result of some experiments done with Faust and it's LLVM backend:
>
>
> I would love to have enough time to implement this :->

This is not completely trivial... it needs to go inside Faust FIR (Faust Intermediate Representation) and improve it..... Then some new code have to be added in the LLVM backend itself.

>
> Anyway, under clang/Mac OS X, using the vector types reduced the time spent in simple jmax dsp operator and in the general dsp virtual machine execution to be around 15-18% for some "typical"
> jmax patch. By simple operators i intend the basic signal operations, like multiplication, constants and so on.
>
> The rest of the time is spent on complex objects, that implements
> specific dsp algorithms.
>
> This means that the further performance improvements on jmax dsp execution code (other than specific objects), whatever technique used, cannot be higher than around 10%. (OK, as long as this typical patches are really typical, of course).
>
> Anyway, i repeat the tests on clang/gcc on Mac OS X, and i got, for a given example patch, 30Msamples/seconds for clang with vector extensions, 13Msamples/seconds for gcc with normal code, ad 11 Msamples/second with gcc with vector operators (gcc 4.2, latest apple clang).
>
> Using -mss2 or -mss3 on Linux improved the performance of the code using the vector extensions but really marginally, leaving it largely slower of the basic code.
>
> By the way, by vector extensions i intend what is described here:
> http://gcc.gnu.org/onlinedocs/gcc/Vector-Extensions.html
>
> Maurizio

You should really look at the generated SSE code. Can you paste the result of each test on this list?

Thanks.

Stéphane

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Received on Fri Jul 22 00:15:02 2011