SIMD support...

[Peter Alexander]

On 12/01/12 8:13 PM, Norbert Nemec wrote:
> Considering these hardware details of the SSE architecture alone, I fear
> that portable low-level support for SIMD is very hard to achieve. If you
> want to offer access to the raw power of each architecture, it might be
> simpler to have machine-specific language extensions for SIMD and leave
> the portability for a wrapper library with a common front-end and
> various back-ends for the different architectures.

You are right, but don't forget that the same is true for instructions 
already in the language. For example, (1 << x) is a very slow operation 
on PPUs (it's micro-coded).

It's simply not possible to be portable and achieve maximum performance 
for any language features, not just vectors. Algorithms must be tuned 
for specific architectures in version statements. However, you can get a 
decent baseline by providing the lowest common denominator in 
functionality. This v128 type (or whatever it will be called) does that.