[vsipl++] SIMD threshold with loop fusion

[Assem Salama]

Jules Bergmann wrote:
>
> [1] This looks good.  However, do you think faux-SIMD should have the
> same "API" as the real SIMD functions below?
>
> For example, AltiVec vgt returns 0xFFFFFFFF or 0x00000000 for each
> position.  That can be used as a mask.  (What does SSE do?)
SSE is the same thing because there is a website that has a 
cross-reference for altivec and sse instructions.
>
> Since faux SIMD returns 1 or 0, it can't be used as mask.  A generic
> routine that uses vgt may not work with faux-simd if it expects
> vgt/vlt to return a value valid for a mask.
Why not? I use normal bit operations on the return values. If I and '1' 
with another value, I get the value, right?
>
> [2] Isn't 'Alg_threshold' already checked in?  I'm confused.
I did check in simd.hpp. I will look and see why this is still a change...