std.math performance (SSE vs. real)

[via Digitalmars-d]

On Wednesday, 2 July 2014 at 08:52:25 UTC, Iain Buclaw via 
Digitalmars-d wrote:
> The crucial thing here is that the layout of float/double types 
> are
> IEEE 754 are compatible. :)

That's nice of course, if you import/export, but hardly the only 
crucial thing.

Implied correctness and warnings when assumptions break is also 
important…

> These behaviours you describe only affect the FP control 
> functions in
> std.math, which are the only thing platform specific, and can 
> only be
> written in inline assembly anyway...

It affects the backend.
It affects vectorization. (NEON is not IEEE754 AFAIK)
It affects what a conforming D compiler is allowed to do.
It affects versioning.

E.g. you can have a flags IEEE754_STRICT or IEE754_HAS_NAN etc 
and use versioning that dectects the wrong compiler-mode.