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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/49363] [feature request] multiple target attribute (and runtime dispatching based on cpuid)
Date: Mon, 26 May 2014 08:22:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49363

--- Comment #24 from rguenther at suse dot de <rguenther at suse dot de> ---
On Mon, 26 May 2014, vincenzo.innocente at cern dot ch wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49363
> 
> --- Comment #23 from vincenzo Innocente <vincenzo.innocente at cern dot ch> ---
> Which Syntax?
> I want to reuse the same code for the various architecture and let gcc deal
> with vectorization details.
> The best I manage to do to share code is something like this
> 
> namespace {
> inline
> float _sum0(float const *  x,
>            float const *  y, float const *  z) {
>   float sum=0;
>   for (int i=0; i!=1024; ++i)
>     sum += z[i]+x[i]*y[i];
>   return sum;
> }
> }
> 
> 
> float  __attribute__ ((__target__ ("arch=haswell")))
> sum1(float const *  x,
>      float const *  y, float const *  z) {
>   return _sum0(x,y,z);
> }
> 
> float  __attribute__ ((__target__ ("arch=nehalem")))
> sum1(float const *  x,
>      float const *  y, float const *  z) {
>   return _sum0(x,y,z);
> }

I think that's the desired interface (it was designed with the
expectation you'd use intrinsics in the special functions, not
simply let the autovectorizer do its work IIRC).