Re: [LAD] GCC Vector extensions

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 :->

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
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Received on Fri Jul 22 00:15:02 2011